Hip Pocket Builders' Forum

Indoor Free Flight Forum => Penny Plane and Limited Penny Plane => Topic started by: piecost on October 31, 2014, 10:57:06 AM



Title: Another Gowen LPP
Post by: piecost on October 31, 2014, 10:57:06 AM
I constructed a Gowen LPP to replace my first LPP Kenny Penny with a competitive model. I had already been using the Gowen flexible carbon hub flaring propeller and am delighted with the results.

I was rather rushed in constructing this model and did not do the plan full justice; the weight control took a hit as I sped up to finish the model on time.

I sourced the same diameter carbon rods as specified and was pleased in not having to strip and stiffness test balsa for these parts.

I diverted from the plan in constructing the winglets from 2 laminations of 0.020 carbon rod. These were stacked horizontally to hold the curvature and eliminate the brace. Whilst not as stiff in bending as per the plan, they proved adequate in practice and I could not see any flexing in flight.

The tailplane Finlets were made out of single 0.010 rods as per plan, but with the bracing rod replaced by 3.4lb monofiliment fishing line.  This was tied to the rod and cyano’d, then the other end tied round the rod and the knot slid along it until the desired curvature was achieved. Further cyano held the line and curvature in place. This worked well and should have given a small weight saving, more so if a thinner line were used. I used a strand of hair to bind the leading edge/tip rod to the trailing edge prior to gluing. I am not sure if it really added strength but was a neat idea.

I was rushing to finish the model in time for the flying session and found the covering to be problematic and the most time consuming part of the build. I did not crinkle the film properly as I was terrified of repeatedly tearing the OS film. I also discovered that the cauterising pen melts carbon rods as well as film! Back to razer blades. On the plus side; I found the 3M77 and Zippo lighter fuel perfect but needed nearer a 50% mix. Perhaps I can thin it further as I gain experience or could the cooler/damper air in the UK require a strong mix?

After covering I used thin, fresh Zap cyano to attach the winglets/finlets and had problems with one joint repeatedly breaking. I did not bother binding with hair when attaching them to the wings, I don’t know if this would have helped. I also found that care was needed in ensuring that the tip plates did not impart load into the tip rib and cause a distorted shape. This is a problem on the RH side of the tailplane.

The stick was made from the stiffest wood I could find, selected by Euler buckling testing in lateral bending (Stiffness coefficient of 106). This was #5lb/ft3 wood and so the dimensions were increased from the plan.

I recall one of Bill’s posts mentioning #18lb/ft3 balsa for the wing/tail posts. I had trouble finding such heavy/stiff wood. 14-16lb/ft3 balsa was substituted and I broke a number of posts during construction. I had recently bought a jewellers drawplate for rounding the sticks and this took the pain out of shaping the posts. This was a task that put me off building so was an excellent investment.

The model was finished the morning of the flying session with many attempts to attach the wing tubes (using cyano) without permanently fixing to the wing posts. Despite carefully making a wing/motor stick jig from foam board I had real problems in setting the washin correctly once the wing tubes were glued with cyno. The tail tubes were attached using thinned Ambroid.

In my rush I had taken too much material off the motorstick and it ended up underweight, needing 0.28g of ballast, positioned on the tailboom to balance the model. The weights came out as:

Motorstick & Boom         0.98
Wing                               0.78
Tailplane                         0.31     
Propeller                         0.85
Ballast                             0.28
Total                                3.20  (In hindsight; I seem to have added too much ballast!)

I had low expectations of the model at the beginning of the flying session due to the rigging problems and the extremely flexible feel of the wing and tail. A glide test without prop proved ok and I was delighted to find that the model performed perfectly under power. Within 8 flights I achieved a personal best:

Jan 2014 Tan Super-Sport
24" Loop, 3.08g, 2.56g/m
Temperature 14ºC
Wind to 2270 turns and 0.76 oz.in torque
Back-off 50 turns to 0.39 oz.in torque
Landing 150 turns & 0.12 oz.in torque
Flight time 11m57s in Cat III site
173rpm average

I was not winding hard, but trying to launch at the top of the cruise part of the rubber torque curve with different g/m and length motors.  I was pleased to find that the model flew on less thickness than needed by my Kenny Penny and I used the thinnest motors I had ready-made. I may try going down in width a little more.

I did not spend any time adjusting the wing/tail settings, both my pennyplanes do not seem too critical in this respect. After the session I calculated the settings as:

Wing relative to stick                0.6º
Tailplane relative to Stick       -6.4º

I am surprised at the lack of downthrust and the large tail setting. I had the CG without motor approximately as per plan and was pleased that the trim did not change with different motor masses. I confirmed the models stability; on hitting a roof truss the model tail slid for a few lengths and recovered quickly. Perhaps the CG could be moved aft a little (by moving the wing further forward) to gain a little efficiency? The relative incidence of 6.4º is double what I might expect (not that I have much experience of indoor models).

I used 10mm boom offset and found that the model performed nice turns for a large site, but was rather cramped for a 4 badminton court leisure centre. The model set-up mades changes to the turning circle difficult during a flying session, without access to building jigs.

A following flying session in a leisure centre was a disaster, the rear tailplane tube had become loose and the right hand tailplane twisted causing a nose dive and knocking the prop carrier loose. The model deserves a careful refurbishment.

I can only compare the Gowen LPP to the Kenny Penny LPP but found the wing and tail of the former very flexible.

I wonder that since I will be flying in Cat III or lower sites on low torque if I can take some of the weight out of the motorstick and stiffen up the wings and tail somewhat. Perhaps the wing/tail tubes and posts are all rather too flexible.

In conclusion; I am delighted with the model and plan to build a couple more for next year’s nationals.


Title: Re: Another Gowen LPP
Post by: piecost on October 31, 2014, 12:47:10 PM
This picture shows the jigging used to glue the wing leading/trailing edges together. I used a steel board with square magnets set against a rule to ensure straightness. Small round 0.5mm thick magnets with bits of broken razer blades over them held the rods flat onto the board. Thinned ambroid was applied sparingly


Title: Re: Another Gowen LPP
Post by: Olbill on October 31, 2014, 03:24:44 PM
Good job! That's about as good a time as I had in my first 10 years of flying LPP.

A few comments:

Two .020 rods for the wing tip plates seems awfully excessive. I use either one half of an .020 rod or two .010 rods.

Your motor is on the heavy side. I'm not knocking heavy rubber but maybe less would have worked better. I've only tried the 11/13 batch of TSS rubber but an 11/13 motor of that length and weight would take around 1.4 in-oz max. If you wind to somewhere near the max torque for your motor I think you would have to back off an awful lot of turns to get down to an acceptable launch torque.

I'm curious about your wing being so flexible. I haven't noticed that in my wings but I haven't built a balsa wing for years so don't have anything to compare with. I would make sure that your tubes are strong enough and are solidly attached to the wing spars. I'm using a small triangle of balsa behind the tubes to strengthen the joint. When I'm attaching tubes I put a tiny bit of thick CA near the middle of the tube in order to keep from gluing the tubes to the posts - either on the airplane or on my tube jig. When the first application is cured I remove the posts and fill in around the tube with thick CA. Thin CA is a recipe for disaster for attaching tubes.

For my LPP's and F1M's I've gone to bass posts. They are much stronger and can be bent to adjust trim.

Your RPM's are on the high side. I think the small number of turns left and the high RPM's probably indicate that your prop pitch was a little low and/or your hub is too stiff. I've removed one of the rods from each side of my hubs. The hub shown in the Wright Stuff thread is made this way.

I wouldn't worry about moving the CG rearward. Currently my CG is about 5 1/2" from the nose with a 2.6g motor.





Title: Re: Another Gowen LPP
Post by: piecost on November 06, 2014, 02:25:55 PM
Bill,

Thanks for the compliment, that really means a lot. I have demonstrated that your LPP design is tolerant to poor build quality and can deliver good endurance without a lot of trimming!  Having said that; I have spent allot of time reading through all the LPP posts and trying to pick up useful advice.

I made an error in describing the winglets as laminated from two rods of 0.020" carbon. It was 0.010" carbon in fact.

Now, I don't want to be presumptuous in suggesting improvements to your design, having only just got an example flying, but I wonder  if an efficiency gain might be had by towing the winglets in by a couple of degrees?  In theory they should carry a similar amount of "lift" to the adjacent wing and might be under-employed at the moment. If I ever get consistent flight times then I may try a wing with this modification.

I believe that my wing flexibility was down to the tubes being insecurely attached. The tubes were made from 3/4" lengths of light Esaki tissue glued with thinned Ambroid round a 1.65mm (0.065") drill bit. They were attached with thinned cyano on the wing and thinned Ambioid on the tail.

I will certainly  apply your recommendations and strengthen these joints. Can you tell me why thin CA is not good? Does the thick CA have more flexibilty and hence resilience to knocks or is it something else?

I did encounter a problem which is worth mentioning to any prospective Gowen LPP builders.  Care is needed when attaching the winglets/finlets to avoid their carbon leading/trailing edges applying any load into the wing/tail. This can act to compress and distort the tip rib. Combined with the loose tube on the tailplane I found that the RH side of the tail  had excessive camber and warped in flight  to 15º of washout causing the model to crash. The photo in post#1 shows the excessive camber on the RH tailplane tip rib.

I carefully build the finlets to plan with the removable parts as shown  and jigged  the tailplane to be the correct height relative to the finlet. But, I should have  adjusted the height of the finlet relaitive to the tail to ensure that the carbon spars just touched before gluing.

I did wonder about using bass for the posts. It seems a more consistent material than balsa, but do I need to still be careful in selecting good bass?

Rubber; I simply took the lighter motors which I had already made for my Kenny Penny. I was shocked that the 24" loop gave the best flight time. I will make up some lighter motors as suggested and try a range of densities and lengths to try and find the optimum. I believe that my TAN SS can withstand about 10% less turns than the good TAN II that you use (I have no idea about the energy) and wonder how I can account for that. I look forward to doing some testing.

My propeller was set with a pitch of 24".  I will remove one of the rods as suggested. This propeller is the best part of the model since it has blades made from a single  wide sheet of fantastic Greenman wood. It doesn't wobble either!


Title: Re: Another Gowen LPP
Post by: julio on November 06, 2014, 05:37:30 PM
Piecost

This thread is a serious work. Thanks for sharing your build with such details. Great job!

Regards.
Julio


Title: Re: Another Gowen LPP
Post by: Olbill on November 06, 2014, 08:27:04 PM

Now, I don't want to be presumptuous in suggesting improvements to your design, having only just got an example flying, but I wonder  if an efficiency gain might be had by towing the winglets in by a couple of degrees?  In theory they should carry a similar amount of "lift" to the adjacent wing and might be under-employed at the moment. If I ever get consistent flight times then I may try a wing with this modification.


Funny you should mention that! I make the LE of the wing 1/8" shorter than the TE so that the winglets are toed in. I thought that my plans showed that but I'll check to make sure. As I've said before, there's no guarantee that this is correct or that it helps but it feels right to me.


I did encounter a problem which is worth mentioning to any prospective Gowen LPP builders.  Care is needed when attaching the winglets/finlets to avoid their carbon leading/trailing edges applying any load into the wing/tail. This can act to compress and distort the tip rib. Combined with the loose tube on the tailplane I found that the RH side of the tail  had excessive camber and warped in flight  to 15º of washout causing the model to crash. The photo in post#1 shows the excessive camber on the RH tailplane tip rib.

I carefully build the finlets to plan with the removable parts as shown  and jigged  the tailplane to be the correct height relative to the finlet. But, I should have  adjusted the height of the finlet relaitive to the tail to ensure that the carbon spars just touched before gluing.


Yes the tip ribs can be a problem. My wings generally show increased camber on the tips as they age. This was a big problem on my last trip to Lakehurst. Lately I've been putting carbon on all 4 sides of the tip ribs to help them hold their shape. It could be worthwhile to use a built up rib at the tips. On my last couple of wings I let the spars stick out past the tip rib a few thousandths of an inch and then fit the winglets inside of the spars. This eliminated burning the film off at the contact points like I used to do.

I recommended thick CA for tubes b/c it doesn't run like thin CA. It seems to be inevitable if I use thin CA it will somehow get into the tube and glue it to the post.

I haven't done much comparison on bass. If you have several pieces to choose from then it would make sense to use the lightest ones.


Title: Re: Another Gowen LPP
Post by: Tapio Linkosalo on November 07, 2014, 12:51:36 AM

Now, I don't want to be presumptuous in suggesting improvements to your design, having only just got an example flying, but I wonder  if an efficiency gain might be had by towing the winglets in by a couple of degrees?  In theory they should carry a similar amount of "lift" to the adjacent wing and might be under-employed at the moment. If I ever get consistent flight times then I may try a wing with this modification.

Funny you should mention that! I make the LE of the wing 1/8" shorter than the TE so that the winglets are toed in. I thought that my plans showed that but I'll check to make sure. As I've said before, there's no guarantee that this is correct or that it helps but it feels right to me.

If you check e.g. the chapter about winglets in Simons' "Model aircraft aerodynamics", for instance the Whitcombe winglets (on some MD jets) are the opposite. The theory behind those says that winglets do not create lift, but extract some forward force from the tip vortex. The vortex comes around the tip, from bottom high pressure to the topside lower pressure. As the winglet is rigged tow-out, that is the leading edge is further out from the centerline than the trailing edge, it has positive incidence to the incoming low/vortex, but the lift vector is tilted somewhat forward. The winglet extracts some energy from the vortex, and produces force that counteracts the wing drag, hence improving overall efficiency. As the vortex is strongest close to the wingtip and less further out, the winglet is twisted so that it has more toe-out at the root, and the tip turns to more streamlined attitude. For geometry this means that the winglet is washed-in!

Therefore toe-in on the winglets seems wrong to me. If they are vertical, they produce no vertical forces, but the only force they generate is extra drag. Then again, I think that the flow around the wing on indoor models is probably so slow that full-size aerodynamics does not apply. I recall there are some results that wing planform / tip shape has practically no effect for wing efficiency, whereas for full-size aircraft and even larger/heavier models the planform and tip shape is very important contributor to efficiency.


Title: Re: Another Gowen LPP
Post by: Olbill on November 07, 2014, 10:12:29 AM
Tapio
By now it should come as no surprise that I do everything backwards!


Title: Re: Another Gowen LPP
Post by: Hepcat on November 07, 2014, 08:28:46 PM
OldBill, Piecost and Tapio,
Piecost, A job well done.  No need to say much more.  The stopwatch tells the story and the stopwatch doesn't lie.  A good write up but for Goodness sake tell me where the CG is instead of just intimating it is at the center of the motor.  You must have some more to tell us considering those incidence settings that you imagine you have  :)!!

On the matter of the tip plates I don't think we know enough to toe in or out.  I have appended a simple sketch below.  Air will be flowing from LE to TE due to forward motion.  Air will be flowing inwards on top of the tip as part of the tip vortex so the resultant would appear to be inclined in the direction indicated.  If the tip plate is mounted straight, fore and aft, it will be at an angle of attack to the resultant.  Toe-in will increase A of A and Toe-out will decrease it.  However the angle of the resultant comes from some abstruse calculation of the velocity of the vortex which is far,far outside my capabilities.

John


Title: Re: Another Gowen LPP
Post by: LynnM on November 07, 2014, 11:05:49 PM
I flew my Gowen LLP last weekend,it did 6:45 under a 23' ceiling,many touches! For what it ls worth my wing is square, but the right tip twists to toe in and the left tip toes out, both in the direction of the turn. It flies in a very stable turn with no bank to speak of! The motor is a 20" loop weighing 2.4 grams, lubed with 2 o rings.I will check the CG when I next assemble it.





Title: Re: Another Gowen LPP
Post by: Olbill on November 07, 2014, 11:10:28 PM
I flew my Gowen LLP last weekend,it did 6:45 under a 23' ceiling,many touches! For what it ls worth my wing is square, but the right tip twists to toe in and the left tip toes out, both in the direction of the turn. It flies in a very stable turn with no bank to speak of! The motor is a 20" loop weighing 2.4 grams, lubed with 2 o rings.I will check the CG when I next assemble it.


Excellent job!


Title: Re: Another Gowen LPP
Post by: piecost on February 18, 2015, 07:20:51 PM
I am building a second wing for my LPP. I found on the first example that the tip ribs were deforming to have extra camber, presumably due to the tension in the covering.

So, I substituted composite ribs at the tips and centre and left balsa ribs for the remaining. The composite centre rib was used to help the other flexibility problems I was having. I reduced the thickness of the balsa core to 0.0315 to reduce the width of the 0.004" thick unidirectional carbon caps. The balsa weighs 0.006g and the caps 0.016g for a finished weight of 0.033g. Hair is used in 5 positions to stop the caps delaminating. For comparison, the original balsa ribs weighed 0.011g. So I have a weight increase of 0.066g over the plain balsa ribs. This should greatly improve the resilience of the wing to damage and prevent the warping.



Title: Re: Another Gowen LPP
Post by: piecost on February 18, 2015, 07:23:58 PM
The jig is a tin lid with 1/32" balsa shaped to the camber. Ambriod is applied to the rib and carbon. They are held in the jig using magnets and acetone applied to melt the glue. The caps are added one at a time and the ends carefully trimmed to overhang by about 0.010" to grip the leading edge. The ribs are the same 0.040" depth as the 2 stacked rods of the LE & TE.


Title: Re: Another Gowen LPP
Post by: piecost on February 18, 2015, 07:31:43 PM
The wing was assembled on a steel sheet using 3mm square magnets to hold the parts in place. Some were taped inside Lego blocks to hold the ribs. The 1/4" washin on the RH tip (zero on LH tip - hope that this is correct!) used magnets and broken razor blades to shim to the correct heights at each rib position. The overhanging  composite rib caps really gripped the LE and TE well and made excellent joints. I added 2º toe-in on the tip ribs and allowed some overhang of the LE and TE past the winglets to aid binding with fishing line during assembly.


Title: Re: Another Gowen LPP
Post by: piecost on February 18, 2015, 07:45:39 PM

I have been plotting a graph of my LPP motor winds and comparing them to Bill's data.

I attach a graph of torque coefficient (on the vertical axis) verses turns coefficient (on the horizontal axis). I use coefficients to ensure that differences in loop length and motor densities are allowed for and, in theory, all motors should lie on the same curve of torque/turns as the motor unwinds. That is assuming identical rubber properties. I plotted the unwinding curve of Tan SS 1/14 labeled as "3/16 Jan 2014 B". I cannot include a Tan II 5/99 curve since I have not tested it. I also include horizontal lines at typical (for TAN II) winding and Testing torque levels from advice I was given.

Points are given for winding, launch and landing. Landing torque is not critical and Bill's is guessed.

Bill's data is given in circles containing a "B". His winding points are all to the right (more turns) than mine which confirms your combination of finesse of technique and the best rubber. He also dares to wind to higher torque than me. I am not confident enough to do this yet and will only start pushing my winding when I feel that I have the optimum motor.

Bill also launches at lower torque than me, perfectly at the start of the flat "cruise" part of the torque curve. (I am assuming similar torque at this point for my S-S and Tan II 5/99)

This graph indicates to me that I should thicken my motors so I can reach the ceiling using a similar launch torque (coefficient) and employ the flat part of the curve. So I will use thicker rubber and set the loop length to keep to 2.6g of rubber.

You may have gathered from this that I enjoy plotting graphs!


Title: Re: Another Gowen LPP
Post by: piecost on February 28, 2015, 06:16:11 AM
A picture of my second model. The winglets employ fishing line to retain the curve. Three attempts at laminating the 0.010" rod into the curve, as I had done on the first model, failed. The Polyimide tubes and gussets cured the wing and tail stiffness problems. Carbon caps are employed on the centre ribs and tip ribs on the wings and tails.


Title: Re: Another Gowen LPP
Post by: piecost on March 21, 2015, 09:44:56 AM
I was wondering why I had hit a limit of duration of about 9 minutes with my 3 rod propeller equipped LPP, despite trying many combinations of motors.

So I revisited my propeller jig and compared the angle at 75% radius of 28º and was astonished that I had been using 15 inches of pitch! I thought that I had set around 22 inches.

I used the useful calculator:

http://www.indoorduration.com/PropCalc.asp

So I will re set my propellers to 22, 23 and 24 inches and can't wait to try again.


Title: Re: Another Gowen LPP
Post by: piecost on December 24, 2015, 08:30:57 AM
I have been achieving frustratingly mediocre flight times from my LPP since an encouraging first session. Bill has kindly agreed to look over the data posted here and offer any advice. I attach photos of my surviving two models and propellers. The top two props were formed on a plastic bucket, whilst the lower two used helical pitch jigs.


In response to Bills questions:

Bearing

I use JKM "Pennyplane" Propeller hangers with 2 teflon washers  - I don't apply lubricating oil. The bearing is set with zero down and side thrust to the stick.

Flying with motorstick horizontal?

I think that the motorstick is reasonable horizontal in flight. It does not look excessively nose-up or nose-down in flight compared to other LPP models. I notice that on very high torque it tends to perform a couple of tight left turns, before establishing a normal climb pattern.

Wing & Tail Rigging

The wing is set +0.6º to the motorstick  to give downthrust
The tail is set to about -6.4º to the motorstick (about  -7º relative to the wing)
This seems like a lot of decalage

Both wing posts are on the right of the right of the motor stick; the front wing post is offset 4.5mm to the right and the rear is 11.5mm to the right. This gives 3.2º of left thrust and 10mm offset from the wing centre to the centre of the stick.

I built the wing with 1/8" washin on the RH tip (the RH tip of the front spar is 0.125” higher than the LH tip). The winglets and Finlets have 2º toe in.

Stick & Boom

The sticks were selected from very stiff #7.3 to 8.1 lb/ft3 balsa. It did not test for torsional stiffness. The tailboom is also stiff wood.

The booms were rigged as follows:

Model #3    Boom offset 17mm to the left & 11mm down
      Tail tilt of 22mm – LH tip high      

Model #4   Boom offset 18mm to the left & 9mm down
Tail tilt of 22mm – LH tip high      

I found that I needed a larger tail tilt than the ¼” recommended to get the model to turn within the width of a sport centre (length of a badminton court) and between the beams of the Brabazon hanger.

The wing and tail posts are made from bass.  The earlier problem of lacking wing/tail stiffness and diving in have been cured. I changed from tissue tubes to 0.057" diameter Polymide. I use a 0.015" 5mm x 5mm triangular  gusset between the tube and the wing spars. I used Ambroid to stick the gussets to the polymide (sanded & pre-coated with cyano). The gussets were cyano’d to the spars.

I recently noticed that broken glue joints between the stacked rods making up the wing spars could be seen in flight by the local increase in wing curvature or, even, one wingtip nodding up and down. When a spar was deflected; it could be seen that the upper rod was held in place by the covering and the lower spar bowed forward or aft. A blob of Ambroid sorted it.

Whilst my airframes are not perfect; I am convinced that my propellers are to blame for the poor performance of my models. The attached graph shows the blade pitch angle verses radius for my various propellers.

Propellers


See attach photos and graph

My original propellers used a blade planform taken from the Lakehurst prop with a 2 1/8” max chord. I originally formed the blades on a Vase (the brown curve in the graph). The vase gave a really high camber of about 11% at 75% radius. I also accidentally set the pitch wrong at 15.0” (28º at 75% radius).  I am not sure, but I think that these propellers may have been used for my near 12 minute flight – this was before I kept meticulous records. Forgetting that the pitch was wrong, for a moment, the blade angle for the vase (brown) was within about 5º from a 15” pitch helical twist (light blue). The tips are significantly over pitched.

I later reformed the blades on a household plastic bucket of 8.9" tio12" diameter with the blade set at 20º from vertical. This yielded a camber of  about 4.8% at 75% radius. So, it seems that I got a more sensible camber using the bucket, but the blade twist angle (in green) was about 20º to 30º smaller than the 15” pitch helical (light blue) near the root. The performance with the bucket formed blades was never more than 10 minutes and I needed high launch torques to climb at all.

The darker blue curve in the graph shows a helical twisted blade with 22” (37.9º at 75% radius); this is what I think that the propellers should have been.

It is clear that using the bucket to form the twist gives too low a pitch angle towards the propeller root. I think that my propellers may have been “inverted” stalling near the hub; they were certainly were causing lots of airframe vibration.

But the incorrect pitch on the high chord LPP propeller causes lots of torque, necessitating thicker motors and poorer flight times.

I have re-pitched my propellers with helical twist and 5% camber. Can you offer any advice on twist and camber distributions for flairing props?

I tested my re-pitched propellers and they seem better, but I need more flights to form a firm opinion.

The recent flying session showed that the new helical propellers were better. The propeller with the spar at 75% chord seemed to give better times that that with the spar at 100% (on the trailing edge)

Pitch 22” (37.9º at 75% Radius)
Spar at 75” Chord
Helical Pitch
4 Rods on Blades

Motor: 17.5” Loop of 2.85g/m Tan S-S weighing 2.85g including O-rings
Wind to 1390 & 0.83 oz.in
Back off 170 turns to 0.32 oz.in
Flight Time 8m59s
Turns remaining: out of turns at 25’ 8m30
Temperature 12.5ºC
Average rpm 136


Motor: 22.8” Loop of 2.56g/m Tan S-S weighing 3.03g including O-rings
Wind to 1770 & 0.70 oz.in
Back off 110 turns to 0.35 oz.in
Flight Time: 8m49s
Turns remaining 450
Temperature 12.2ºC
Average rpm 137


Title: Re: Another Gowen LPP
Post by: piecost on December 24, 2015, 08:35:26 AM
Add photos


Title: Re: Another Gowen LPP
Post by: Olbill on December 24, 2015, 09:04:32 AM
What is the ceiling height where you are flying? How close to the ceiling are you getting?

I put the 22.8" x 3.03 g motor into my spreadsheet and came up with 2900 turns max. This is for Tan2 rubber so it may be more than TSS can take but your number looks very low.


Title: Re: Another Gowen LPP
Post by: calgoddard on December 24, 2015, 09:10:54 AM
Bill is the expert, but a couple of things puzzled me.

First, am I understanding correctly that there is no left thrust on the bearing?

Second, it seems as if there is a lot of wash-in on the right wing tip in your two front view photos.

Regardless, your flight times are impressive.

I applaud your effort and dedication. Keep trying!


Title: Re: Another Gowen LPP
Post by: calgoddard on December 24, 2015, 09:21:01 AM
You indicated that some of your prop blades were formed on a vase and others were formed on a bucket.  Later on you indicated you are using helical propellers.  I am pretty sure that Kang Lee forms his blades on a prop form to get a true helical shape.


Title: Re: Another Gowen LPP
Post by: Olbill on December 24, 2015, 09:47:35 AM
I took pictures to post but my SD card failed. Anyway the total decalage on the model I picked up is 3.5 degrees so yes it looks like 7 degrees is a lot. I'm sure you realize that the CG position affects the amount of decalage needed. My stab tilt is a lot less than yours. I probably have more rudder offset than you do.

Your launch torques look low for anything other than Cat 1 which is why I asked about ceiling height.

My right wing washin is less than yours. I didn't measure it.

Cal Goddard
Bearings are straight and right wing is washed in on all my models. (broken record etc.......)


Title: Re: Another Gowen LPP
Post by: Maxout on December 24, 2015, 09:56:15 AM
I'm with Bill. Wind harder!

I desperately wish I could get flight times like those on that tiny portion of the available energy. :-[


Title: Re: Another Gowen LPP
Post by: Olbill on December 24, 2015, 10:07:43 AM
Here are the pics. The right wing washout is close to zero in the pic. It would be adjusted in the field to be slightly more than shown here. The last pic is the same model with a different wing.


Title: Re: Another Gowen LPP
Post by: calgoddard on December 24, 2015, 11:38:12 AM
Got it Bill.  Sorry for the oversight. I assume that the same trim would be advantageous for a Wright Stuff model.  



Title: Re: Another Gowen LPP
Post by: Olbill on December 24, 2015, 11:59:03 AM
I can't guarantee that my methods are advantageous for anything. But they are what I use.


Title: Re: Another Gowen LPP
Post by: Hepcat on December 24, 2015, 06:44:08 PM
response to #17 and #19.

My turns calculator which usually gives reliable figures for Super Sport gives 2750 turns for the 22.8" 3.03g motor. That is Max, no little bits assumed for safety!

John
 


Title: Re: Another Gowen LPP
Post by: piecost on December 26, 2015, 11:15:26 AM
Thanks for the replies Bill & others & thanks to Bill for going to the effort of posting pictures.

In reponse to the questions; the Venue is a CAT III site. The first flight (in my last post) reached about 70' (about 5' above the level of the crane beams) and the second only 40'. I am perhaps guilty of swapping between different motors too readily rather than getting the most from each of them. I also wonder if I am tending to use motors on the heavy side i.e. over 2.6g.

I have been using Jan 2014 Tan Super-Sport and have tested the torque versus turns and maximum turns. I have not tested 5/99 so cannot really compare but I think that my rubber is getting a similar torque unwinding curve but compressed into 17% less turns. I also have max turns of 9% less than Hepcat posted. I am using the best S-S that I could buy in 2013/2014. I test at room temperature whislt flying at around 12.5 deg C; which may be reducing the turns to reach a target torque level further. I really must test at different temperatures so see the effect. I have some data on Tan II with temperature but wonder if S-S has the same sensitivity.

My aim has been to get the model to reach the beams with a launch torque/turns at the knee of the unwinding curve and not employ the rapid kick-up of torque at high turns. Perhaps this strategy is not suitable for a Cat III site? I will certainly wind my motors harder in the January session.

I did think the decalage rather high and suggestive of a forward CG. I don't think that I have excessive downthrust; the models glide OK. I don't think that the wing is over-cambered i.e. requiring more decalage, since the ribs are sandwhich construction and are very stiff. I will move the wings aft if nessesary.

I mentioned that I have made propellers with the same chord distribution but with the spars set at 75% chord rather than at 100% on the blade trailing edge. I understand that flairing props are using such high chords (over 2 inches max) to achieve the flair. So, is there any disadvantage is keeping the spar at the trailing edge and trimming some chord of the leading edge to reduce the flair? These flairing props must be working at a very low local blade lift coefficient which can't be good for efficiency. Is a 5% camber suitable? If the local lift coefficient is low then would less camber be warrented? Am I missing something about the workings of these flairing props?

Is the helical distribution optimal for flairing props or would some washout at the tips likely help?








Title: Re: Another Gowen LPP
Post by: ykleetx on December 26, 2015, 09:49:00 PM
Piecost,

Your flight RPM is very low at 136, and your launch torque is very low for a 70' climb.

You indicated that your flights were made at about 12 C. Were these flights made recently on December 14 at Brabazon? I'm asking just to understand the conditions at the hangar.

I think you can get many more turns out of your motor without winding it too hard. And be sure the motor is well broken in so that you can get more turns.

-Kang



Title: Re: Another Gowen LPP
Post by: piecost on December 27, 2015, 06:13:07 AM
Kang, the flying
session was on december 9.

The repeated advice is to push the motors harder, so i will give that a go.


Title: Re: Another Gowen LPP
Post by: Hepcat on December 27, 2015, 08:11:08 AM
Response to # 29, quote<And be sure the motor is well broken in so that you can get more turns.>.

Kang,  Can you clarify that quote a little?  If a motor is 'used', 'pre-stretched', 'broken in' it will be longer than when it is new and will take more turns, I have no argument with that.  However I have the feeling that a new motor possibly has more energy and I would assert (with no proof) that after 80 years of winding rubber motors that if I keep winding the same motor time after time there will be a loss of power.

I think I have answered myself whilst I have been writing this.  In Indoor flying the turns are more useful than the torque as proved by 'backing off' turns.

John.


Title: Re: Another Gowen LPP
Post by: Olbill on December 27, 2015, 12:34:04 PM
I don't have any data for a 70' climb. At West Baden my launch torque varied from just under to just over .4 in-oz with my last record attempt at .48. This is for a 90' site. At Kent where my usable height is under 50' the launch torques were around .3 in-oz. Kent is a place where repeatedly bumping the ceiling is almost sure disaster.

The other thing to consider is that in my experience the torque for TSS rubber drops off more quickly than for high grade 5/99 Tan2. This would indicate the need for using a higher launch torque than you would use with 5/99.

Whatever rubber you use, if the model isn't climbing high enough, and if you don't see any signs of misbehaving, then it needs more grunt. The limit for most models is the point where the outside wing washes out and the model either races around in circles without climbing or it actually spins in. That limit for my LPP's is usually around .9 in-oz but it varies depending on the stiffness of the particular model.

You mentioned something about downthrust. I have something similar to what people refer to as downthrust because of the incidence setup I use. Normally there is a few degrees of incidence in the wing and the stab is close to flat (all relative to the motorstick). If I have a problem with the right wing washing out at launch then I might try changing the incidence of both surfaces to give a little more nose up attitude. Sometimes pointing the nose up a little will help get thru the high power at the beginning of the flight. Actually the only place I've ever done this is at Lakehurst (app. 180' usable).

I never use down thrust (or side thrust) in the bearing. Side thrust is accomplished by aiming the motorstick to the left.

Are you using sleeves? Is the model coming down with knots gathering around the rear hook? A clump of knots at the rear hook will destroy the cruise and letdown. A clump of knots at the front can end the flight. If you're using my front hook up system then you shouldn't get clumps of knots at the front. If you're using sleeves and you're still getting clumps of knots then you need to shorten the motors a little. The limit for me seems to be around 22". Your 17.5" motor was certainly too short. The longer one should work if it had sleeves.


Title: Re: Another Gowen LPP
Post by: piecost on December 27, 2015, 01:09:37 PM
Thanks Bill. This advice is invaluable. I will do some studying of your torque levels. I will also investigate the models cg to reduce the decalage and and incorporate more downthrust. I use a reverse s-hook on the propeller but don't use sleeves. I have had problems with bunching on longer motors and put this down to lack of finess in winding. Can you elaborate on the use of sleeves please?


Title: Re: Another Gowen LPP
Post by: mkirda on December 27, 2015, 03:19:11 PM
Thanks Bill. This advice is invaluable. I will do some studying of your torque levels. I will also investigate the models cg to reduce the decalage and and incorporate more downthrust. I use a reverse s-hook on the propeller but don't use sleeves. I have had problems with bunching on longer motors and put this down to lack of finess in winding. Can you elaborate on the use of sleeves please?

Experiment with soda straws. You'll find a size that fits onto the front hook and lets the motor mostly unwind. When you find a good source, grab a few extra.

Regards.
Mike Kirda


Title: Re: Another Gowen LPP
Post by: piecost on December 27, 2015, 04:13:29 PM
Thanks for the tip mike, won't the sharp edges of the straws xut the rubber? I was wondering if heatshrink is suitable.


Title: Re: Another Gowen LPP
Post by: Olbill on December 27, 2015, 05:00:43 PM
After an hour looking for the pictures that I was SURE I had posted somewhere I finally gave up and took new ones. Here are the specs for the o-rings, hook and sleeves:

Hook - .018" wire. Outside width of the hook is .160". The turned up end is necessary to keep the sleeve from sliding forward.

Sleeve - app. 1/8" inside dimension black heat shrink tubing. I think I got this from US Plastics.

O-ring - sliced from .155" outside dimension black semi-rigid nylon pressure tubing, also from US Plastics. I use the same size for F1M.

The o-rings, hook and sleeves can be different from this as long as you can slide the sleeve over the o-ring and hook.

For the rear the sleeve is just pushed back against the rear hook. It's held there by the motor knot.

For A6 everything is the same except smaller. For A6 I found plastic straws that were perfect for sleeves. The A6 o-rings are cut from the next size smaller nylon tubing.

For both A6 and LPP the limit on motor length is knotting at the rear hook. I almost never have problems at the prop hook.

For F1M I don't use sleeves. The front hook for F1M is a reverse S.

Now anyone can do it!


Title: Re: Another Gowen LPP
Post by: piecost on December 27, 2015, 05:16:41 PM
Thanks for your continuing efforts bill, it is really appreciated. But, can you tell me if the prop hook is a reverse s or a plain hook?


Title: Re: Another Gowen LPP
Post by: Olbill on December 27, 2015, 05:54:00 PM
It's a plain oval hook. You can't do this kind of hookup with an S hook.


Title: Re: Another Gowen LPP
Post by: mkirda on December 27, 2015, 07:57:01 PM
Thanks for the tip mike, won't the sharp edges of the straws xut the rubber? I was wondering if heatshrink is suitable.

No more so than heat shrink tubing, which would also be suitable.
Bill uses straws on A6 - He gave me a couple for use.

Regards.
Mike Kirda


Title: Re: Another Gowen LPP
Post by: piecost on October 05, 2016, 07:07:43 PM
I thought it a good time to make another post since I am delighted to report that I won the 2016 UK indoor duration LPP class using the Gowen LPP deisgn. Thanks to Bill and others for providing the plan and much advice.

The best two of my four competition flights were 10m08s and 9m47s combined to give a combined score of 19m54s, 7% ahead of the next 3 competators (they were all within 6 seconds of each other). My strategy was to start making competition flights once I had exceeded 9m30s. I was a little disapointed that I didn't manage to push the time up to 11m,  since I had achieved that in a couple of previous sessions. My plans didn't work out when I hung a model up on my second competition flight. Though frustrating, This was not a big problem as I had allready been using two models, to experiement with different motor lengths prior to the competition flights. So I used the remaining model. Once I had a lead I then concentrated on other classes instead of trying to reach my target duration.

Data for the two best competition flights

Prop: 22" pitch x 1.5" chord minimum induced loss planform & twist
Temperature 18.5ºC
Rubber: Tan II May 97, 2.71g/m x 19.25" Loop 2.66g
Wind to 1820 turns & 0.92 oz.in
Back of 130 turns to 0.37 oz.in
Touched light at 2m58s and recovered. Dived in from 20' when out of turns
Landing turns 0
10m07s

Prop: 22" pitch x 1.5" chord minimum induced loss planform & twist
Temperature 18.5ºC
Rubber: Tan II May 97, 2.71g/m x 19.25" Loop 2.66g
Wind to 2050 turns & 0.92 oz.in
Back of 160 turns to 0.33 oz.in
max height 45', no touch
Landing turns 160, torque 0.14 oz.in
9m47s

I used Bill's published wind/launch torque levels as a guide for my own motors (allowing for different mass per length of my motors). I have also been experimenting with my own propeller designs, modifying them to utalise a similar launch torque that Bill uses. I previously found that I could not use the same prop as shown on Bill's plan (Lakehurst planform, with helical twist and 22" to 24" pitch). The propeller required too much launch torque. Even moving the spar to 75% or chord at 75% radius still required a higher launch torque than Bill employed; well into the non-linear torque region. Since, I reasoned, that the  large chord was intended to maximise the flair; moving the spar forward negated this effect and thus the need for such a large chord. So, I next designed a 1.5" chord propeller aiming to keep the distance between the assumed centre of pressure of the propeller and the spar the same. The new propeller had the spar moved to near the trailing edge again and employed a minimum induced loss planform and twist distribution with 22" of pitch (at 75% radius). I achieved similar times with the new propeller as with the 22" Lakehurst prop with a 75% spar position. So, I switched to using the my new propeller, if only for the satisfaction of using an own design. This new propeller required a launch torque much lower than before and approximatly the same as that which Bill employed.
 
I had built 3 new models for the competition and was very pleased that they performed reliably with the minimum of trimming. I was fed-up with the diffculty of attaching wing and tail posts accuratly so employed a jig to assemble the stick, prop hanger, boom and posts. A wing and tail setting jig ensured that the models required the a minimum of trimming.

To achieve the competition win; I have spent 2 years worth of monthly practice (in the competition venue), have built 7 models, 13 propellers and lodged 3 of them in the ceiling. It was worth it!


Title: Re: Another Gowen LPP
Post by: ykleetx on October 05, 2016, 11:46:53 PM
Well done, piecost.


Title: Re: Another Gowen LPP
Post by: OZPAF on October 06, 2016, 03:25:54 AM
Congratulations again Piecost. Winning in 2 classes at your nationals. You were a very busy man! Thanks for your detailed report - your results show the benefit of a methodical careful approach and lots of practice.
I think you should publish a paper on your approach and findings for your FF symposium digest.

John


Title: Re: Another Gowen LPP
Post by: Pete Fardell on October 06, 2016, 07:27:14 AM
Brilliant! Well done! I really enjoyed reading this report, and also the one on your no-cal win.


Title: Re: Another Gowen LPP
Post by: Olbill on October 06, 2016, 08:52:26 AM
Now that you're in the winner's circle I think it's time you started giving me lessons on how to do it. Some of the people I've mentored have started beating up on me every time I fly!


Title: Re: Another Gowen LPP
Post by: frash on October 10, 2016, 10:04:11 PM
piecost, OlBill, and All,

Obviously this design and these flyers win and set records. Congratulations. Attention to construction details, improved methods, and flying strategy is impressive from you folks.

I noticed that piecost used a minimum induced loss platform and twist for the prop blades. This is sometimes called a Larrabee prop since he developed the minimum induced loss methods for human powered flight several years ago. I attempted to code his method into "Larrabee Lazarus Propeller Design" in the HPA Plans Section>Airfoils and Propellers. The source code in Lazarus Pascal is also posted for anyone to edit, modify, improve, repost, or whatever. Lazarus Pascal is a free download from Source Forge, but is unneeded just to try the prop design program.

If someone will enter their inputs from one of these known good designs, the Cl, Cd, and Alpha of the prop blades maybe can be corrected and improved. Form 3 already has provision to move the spar forward or backward on the blade.

Thanks to any and all for suggestions for improvements.

Fred Rash


Title: Re: Another Gowen LPP
Post by: cvasecuk on October 11, 2016, 08:49:15 AM
Fred, form 3 will not accept a change of "flare". I can put in a number greater than zero but I can not input a decimal!!!
Ron


Title: Re: Another Gowen LPP
Post by: frash on October 11, 2016, 02:28:45 PM
Thanks, Ron. You are correct that there is a problem. My local copy also has this problem if I ever delete the decimal. I must try a fresh download since there is no guarantee that the local copy that I tried and the posted one are identical.

My local copy that I tried, if I kept and never deleted the decimal, showed for flare = 1.0, all the blade forward of the spar as expected like you and Bill Gowen probably are using. Entering 0.5 gave the blade symmetrical on the spar, and 0.0 gave all the prop blade behind the spar. This value is  working but never desirable in practice. My default value was 0.72 for flare in earlier versions.

I'll download fresh and try to clean this up. You are very helpful. Finding errors can be hard. Thank you.

Fred Rash


Title: Re: Another Gowen LPP
Post by: frash on October 11, 2016, 09:31:46 PM
Ron,

The "fresh download" from HPA also showed and confirmed the problem that you found. If you can keep your decimal point in the Flare Box in the third screen and not delete it, I think that you can continue. I think that I have fixed the problem, but 1-2 days may be required to post the newer version to the HPA Plans section.

Thanks for finding this. There may be more...

Fred Rash


Title: Re: Another Gowen LPP
Post by: cvasecuk on October 12, 2016, 04:58:02 AM
Thanks, Fred. I have tried it, not deleting the decimal and it works OK.
Ron


Title: Re: Another Gowen LPP
Post by: piecost on October 12, 2016, 06:34:02 PM
Hi Fred,

Thanks for your compliment. I consider the major contribution to my performance was that the venue for the competition was my home site and thus I could practice every month, concentrating on LPP to the exclusion of other classes. This gave me ample time to match the rubber to my propeller, relative to those who could only attend the competition or made ocasional visits.

I enjoyed designing a new propeller but have to admit that the assumptions for the inputs were not well defined and much care was needed to give an output that looked similar to well proven designs. I used Hepcat's Prop Picker with a selected pitch and chord to give the power and rpm and a MIL spreadsheet to derrive the chord and pitch distribution.

Whilst I have a method for determining the MIL propeller shape; I must admit to not seeing the underlying the maths. Can you provide a copy of Dr Larabee's original paper? I would be interested in playing with your propeller design code and seeing what it made of my propeller. Can you prove a more explicit instructions on how to download the Lazarus Pascal? I am rather a dummy at this sort of thing.

I found your May 1999 Rubber Turns, Torque Calculator very interesting and adopted it for my own motors. So, thanks for taking the time to publish such tools.



Title: Re: Another Gowen LPP
Post by: Hepcat on October 13, 2016, 08:14:50 PM
Piecost,
Belated congratulation on your double Nationals win.  That took some dedication.  Also, as so many others have said, thank you for the detailed information you pass onto the rest of us.

Do you have all the Larrabee information that you want?  I have the 1979 NFFS Sympo (16 pages covering the subject in English and French!) which has several descriptive pages and an appendix with 21 numbered calculation steps.
I also have the 1977 Sympo in which Larrabee had an 8 page paper talking about minimum loss propellers in a more general way and, finally: 'Propeller Design for Motor-soarers' which he gave as a NASA Conference report in 1979.  This is an 18 page report covering the subject in a more technical manner.  As a matter of interest I do have a copy of Sydney Goldsteins famous 1929 paper which proved Betz and Prandle were correct but I don't recommend it, I was lost by the end of the first page.

I was very interested when you said that you had a method for designing an MIL propeller but did not see a clear connexion with the underlying maths because that is exactly how I am.  I know my mathematical abilities are slipping away with age.  Not that they were ever more than was needed for basic design engineering but I can look at an expression nowadays and it just appears as a jumble of symbols. It can be very upsetting at times.

Strangely I cannot pass much comment on Larrabee's two Symposium papers because I have never used his approach.  Once, when I changed jobs, I had a long break from modelling, and during that time the Sympos started.  When I eventually saw one I wanted all the others but it took some years to get them second hand.  By the time I saw the Larrabee ones I had other methods I did not want to change.
John



Title: Re: Another Gowen LPP
Post by: frash on October 14, 2016, 08:20:53 AM
Thanks Hepcat and piecost,

I already had the Larrabee paper scanned from the 1979 NFFS International Symposium so I emailed it to piecost yesterday. I have a paper copy of the 1977 Sympo paper somewhere but have not yet found a scanned copy here. Perhaps for John to send the 1977 paper to piecost would help the most. However, this is really not my call.

Interest in Larrabee and most other methods from you two and others is very welcome.

Thanks to you both and to many others for making HPA so strong, particularly to the guys that run HPA. Ratz again properly sorted out my attempts to post corrections and delete old versions.

Fred Rash


Title: Re: Another Gowen LPP
Post by: piecost on October 14, 2016, 10:08:06 AM
Hello John,

Thanks for your congratulations.  By, the way; I also came third with your Bar Fly design in Legal Eagle, see link:

http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=16906.0

Fred kindly sent me the 1979 NFFS Symposium Report, but I will appreciate it if you can send me any others.  I still read your propeller articles from time to time and appreciate their clarity. It is very likely that I will get bogged down with Larrabee's maths as it is a bit too much like work and I'd rather spend my modelling time using my hands rather than my brain. I'd like to have a play with Fred's programme if I can get over the slight hurdle of installing the code and getting it running.

I understand that the Larrabee propellers revolutionised human powered flight, enabling the Gossamer Albatross and the MIT Daedalus to make long distance flights. But, I don't have a feel for its impact on rubber powered duration models. Was it a flash in the pan, fashonable for a while and then only considered by aero/programming enthusiasts? Or has it continued to influenced propeller shapes, even if poeple don't remembering it doing so. A successful concept may be adopted long after the oringal rational is forgotton?

Or do other constraints render it impractical for indoor duration? Such as:
  Only working fully at a design point, not over the motor run; is it still good off-design?
  Useful for variable pitch propellers?
  even such things as a propeller tip radius being too tight to bend the propeller outline around (not a problem for sheet LPP props)
  contraints on pitch distribution such as tip washout to prevent seperation at lauch

I suppose that human powered flight is the ideal application of MIL propellers since the flying speed and power requirements are constant and efficiency is all important.


Title: Re: Another Gowen LPP
Post by: piecost on September 19, 2018, 04:22:04 PM
I am pleased to report that I won gold in LPP in the 2018 UK nationals. After a break of 2 years both models were still in trim! In the single practice session before the competition I employed the same long, heavy motor that I had used in the Brabazon hanger under 56" beams in the Eton sports hall with İts 28' beams:

Jun 16, 2.54g/m x 22" & 2.88g

This was combined with a similar propeller as employed before, but with a 2 Rod Gowen hub and the pitch reduced from 22' to 17.5. The practice session yeilded a near 8 minute flight so I was confident. This was the first time I had steered a model using a roach pole. This was a skill I
not developed in the 300' by 300' floor of the Brabazon hanger.

I spent the first day of the competition becoming very frustrated. I found that the motor bunching badly yielding fluctuating torque levels. More importantly, my digital torque meter was drifting by 0.10g. Since it measures 10 oz.in per gram; the torque levels were varying by a massive 1 oz.in. This was causing my model to have alternate flights refusing to climb or bashing into the roof. Indeed; I lost my best model on top of a roof beam. My trimming flights put up good times but the first two competition flights yielded under 5 minute tines. My third of 6m0s minutes was half way down the field of 11 entries with the best two models reaching around 7 minutes. On the second day I resorted to sharing a torsion wire torque meter and things became more.orderly. It was frustrating having to adjust the length of the winder to meter to match my model prior to each flight and not being able to stretch wind the motor hard tor fear of breaking the shared meter. But I found the 1g.cm scale more conducive to fine adjustments and crucially the reading did not drift.

I changed to a thinner and shorter motor to eliminate the bunching problems:

Super Sport, 2.34g'm x 16 1.97g

This worked well so made up 18', then 20 motors without problems. My third flight gave an improved but uncompetitive 6m0s, whilst the 4th suffered a beam hit,
ollowed by scraping down the net that divided the hall, landing in under 4 minutes.

With 2 lights remaining everything came right. The details are:

Super Sport of unknown vintage 2.12gmx 20 loop & 2.20g
Wind to 2050 turns, 41g.cm
Back off 410 turns, 13.9 g.cm
23 max height no touch
Average pm 161
8m315

I tound a broken slrand on landing. Whilst I had not been winding hard I had nol been resting the motor.

The sum of my best two flights was 14:41 which put me into the lead with 14:01 in second place. I was prepared to use my last competition flight if nessesary, but this was not.needed.

Reviewing the best flight I concluded that even though I had employed a.lighter and shorter motor than usual; I still had not wound it hard. The launch torque was half that I had used with the heavier motor in practice.

I had made a 20" pitch propeller but had not had time to tey it. It will certainly lower the rpm and require a.high launch torque so may yeild higher times.


Title: Re: Another Gowen LPP
Post by: OZPAF on September 19, 2018, 07:18:20 PM
Congratulations and thanks for the report.

John


Title: Re: Another Gowen LPP
Post by: Olbill on September 19, 2018, 11:24:33 PM
Wow! Good job!


Title: Re: Another Gowen LPP
Post by: piecost on March 19, 2019, 04:01:06 PM
I really enjoyed competing in the BMFA North Wast Gala at the Manchester Velodrome on 16 March 2019. 1t was great to be flying under a high ceiling after losing access to the Brabazan hanger. The duration competitions were run to unlirnited number of flights but i was limited by alternating between flying and timing for my mate . we managed a flight every quarter of an hour.

Care was needed to prevent the mcdels climbing above the nettng (to prevent the models escaping and landing on the cyclists) . the top of the net was 40'8", exceeding this which resulted in a disqualified fighl. The white steel roof structure provided the marker for the maximum
height.  Lucky people had models hit the lights or speakers mounted below them losing enough height to remain legal.

It was a close competition with the best time ol 5m08s, 2nd place at 4m58 and 3 place with 3m57s. I must admit being disapointed in achleving 3rd place. I am not being totally conceiled because in Ihe 2018 nats my best flight achiaved 8m30s compared to about 7m for the other competitors. However, my result at the nats was tempored by the fact that I cnly achieved one standout flight with the others being similar to my competitors. This good tlight was late in the day I would not have such tima avalable at the Velodrome.

Problems at the nats with my digital torque meter causng a model lost in the girders result in my being very caurious in progressively increasing launch torque in each flight. It usually takes me into the alternoon of a day's flying to reach the ceiling. I did not have the time lo do this in the velodrome since the flying was limited to three slots of about an hour's length.

The competition limited rubber to 0.75g with 0.75g ballast. I employed a 50% spacer.

I changed trom the 22" pitch with 4 rod Hub Minimum Induced Loss planform and twist propeller that I had employed previously lo 20" piich and 3 carbon rod Hub, I thought that increased fairing and lower pitch might be helpful.

I managed a practice session Under 25' ceiling with a motor and spacer scaled to 62% of the completion setup and found that I needed 1.98gm rubber af 4.75" loop achieve a no touch time of 3m02s. This scaled to 4m53s in the Velodrome ceiing. Not a bad mach to the competition time. In fact. I was not sure of the maximum allowable height in the Velodrome before the event.

I made up a variety of motors for the completion and ended up selecting 1.83g/m, since a thinner motcr worked well on my Legal Eagle model. I had reduced the mass/length by 8% from my practice setup which proved to be too much.

l used 3 identical motors and progressively increased the launch torque in each flight. However, I was not getting over half of the available height with most flights. I kept thinking that in the next flight the model will "light up and reach the caling. I found that I was winding up the peak of the torque curve and any backing off was reducing the torque beyond my target

I found that over 35g.cm the motar stick bends down causing the model to complete a circuit or so fast and flat before climbing as the torque drops. Over 40g.cm the stick twists so much as to cause noticeable warp and an outside banking turn , again before the wing straightens out and the model climbs.i did not notice lhis behaviour when practicing with a short motor under a low ceiling. Iguess that the stick still deforms but the torque draps off quicker and daes not kill the intial climb so much as under full height conditions.

The impact of the increasing the launch torque was being negated by the stick bending, killing the initial climb. Especialy when launch in the non-linear part of the rubber curve where the torque level drops off quickly.

Details ol my best flight:

Propeller Minimum Induced Loss Planform & Twist, 20" pitch, 3 Rod hub
0.75g  x 8" loop of June 2016 Super Sport
Wind to 950 turns, 48g.cm
Back off 50 turns to 37g.cm
Max Height 20' time 4m57s

In hindsight; l should have been more aggressive in increasing the launch torque. Thus discovering that the
motor was too thin earlier and switching lo a more appropriate mctar.

It may also have bean a mistake to use the more flairing lower pitch propeller.  Stick bending may be the limiting
Factor

I think useful to perform a back to back test using tho old propeller and the new one using the same motor.

I look forward to flying in the veledrome again


Title: Re: Another Gowen LPP
Post by: piecost on March 19, 2019, 04:09:58 PM
The velodrome


Title: Re: Another Gowen LPP
Post by: OZPAF on March 19, 2019, 08:21:55 PM
Thanks for another of your very detailed reports - It really highlights the skill required to be competitive in this area.

John


Title: Re: Another Gowen LPP
Post by: LASTWOODSMAN on March 19, 2019, 10:05:11 PM
Hi piecost.  Thanks for explaining all of those details of how those things work - very interesting and all new to me - and thanks for the pic of your flying field "Velodrome".

LASTWOODSMAN
Richard


Title: Re: Another Gowen LPP
Post by: ceandra on April 01, 2019, 10:07:20 PM
My Science Olympiad kids have been really inspired this year, so we decided to plan to visit Round Valley in April (Cannot make the Nats, because SO nats same weekend in Ithaca NY).

Since we were already using Bill's construction techniques, it made sense to build Bill's Carbon LPP. We built 5, one by me and one by each WS kid. We had a very short shared test session a few weeks ago, and got basic trim on all the planes. We struggled with a few things, so had to have another build session to improve our prop hooks and a few rogue joints.

I am pleased to report that ALL of the kids built between 3.1 and 3.2g! Mine was the heaviest at 3.2g.

We have 3 test sessions planned before Round Valley. The kids are really looking forward to this!. They can also fly in F1M with these planes.

Two of my glider kids built Lit-L-Sweeps, as their SO gliders won't go to 100'.

Should be a fun time. Maybe I'll meet some of you there!

Chuck


Title: Re: Another Gowen LPP
Post by: calgoddard on April 02, 2019, 08:17:01 PM
Chuck -

It's great to hear that you and your students will be flying at the Round Valley Dome. It will be an incredible experience for these young people.  I am going to the AMA/NFFS Nats being held from May 29 - June 2, 2019 at the same venue. Sorry I will miss you.

I am taking three LPPs, four A-6 models, two P-18s and one P-24.  My No-Cal and indoor Embryo models just would not be competitive in that venue so I won't be taking them, well maybe one Embryo.

Good for you that you mentored several of your Wright Stuff students in building LPPs.  It is a wonderful indoor class. It's very impressive that they built at or near the minimum weight of 3.1 grams. Your students are probably amazed by the slow turning prop of an LPP model.

I recently built my fourth LPP, based on my own design. I have been flying the same LPP for the past five years and it has performed very well, but my local competition is creeping up on me and therefore I wanted to implement some improvements.  

Josh and Hope Finn of J & H Aerospace have a new LPP kit out. It looks like a very competitive design. I wish I had seen this kit before my latest effort building a new LPP. It would have saved me a lot of time. I used a helical prop form from Mike Kirda to build several LPP props, including two flaring props and one that does not flare.  I think I will probably use the latter at the Round Valley Dome to hopefully get my new LPP near the 104 foot peak.  

I built one of the J & H Aerospace Intruder A-6 models and plan to fly it this Sunday in a local A-6 contest if I can get it trimmed. The J & H Aerospace kit included really nice contest grade balsa wood.  The pre-formed prop hook and rear hook were very nice, as was the polyimide tubing for the wing post sockets.

Let us know how you and your students do at the Round Valley Dome.  Good luck to you and your team at the SO Nationals in the Wright Stuff event.

PS - I coached a Division C team in ELG a few years back.  They flew Stan Buddenbohm's LIT'L SWEEP glider and won the gold medal.  The ceiling height was low (24 feet) but they still beat all the FFM flappers.  Nobody knows more about HLG and CLG than Stan.  Few can beat him, indoors or outdoors.  If you have not seen it, check out Stan's record setting indoor flight (F1N) at Tustin on YouTube. The flight time was one minute and fifty-two seconds. Here is the link:

https://www.youtube.com/watch?v=DWpwLfVqBso


Title: Re: Another Gowen LPP
Post by: ceandra on April 02, 2019, 09:44:45 PM
Cal:

I'll certainly post an update here after Round Valley.

Our team has done well. Last year at Nationals my mid schoolers missed gold by 0.07 seconds, at 2:29.50. Third place was less than 2 minutes. High school took gold in heli at Nationals. This year WS is going very well, good enough that we took the break to do AMA. Gliders is still a challenge. I think they are harder to trim than WS! We are hoping to use the Round Valley experience to test some higher launches, as Nationals will be a 40' ceiling.

This forum (the SO page) has been incredibly helpful in getting us from nothing to contenders.

We have stolen much of Bill's LPP design for our SO planes over the last 3 years, so transition to LPP was not hard. We have early Regionals and States, so we are not able to wait for kits. Much better to have our own design anyway!

I have been watching the videos Josh put out on his new kit. He gives Bill credit, as you can see a lot of influence in the design. A very complete kit! We had already bought all the carbon anticipating, so we built from plans. Just ordered more carbon today. Josh put me on to the poly tubing, and i found some on Ebay which I snagged for about half price.

Chuck


Title: Re: Another Gowen LPP
Post by: ceandra on April 15, 2019, 12:16:40 PM
My Science Olympiad kids went with me to Round Valley Dome this weekend for our first ever indoor contest. Four high school kids (plus me) built Bill Gowen's Carbon Penny and competed in LPP and F1M. Two mid schoolers built Stan's Lit-L-Sweep and competed in Std Catapult Glider.

All of the kids got to around 10 minutes in both LPP and F1M, not bad for our first attempt at a contest like this. They learned to get to the rafters at nearly 100'. We even picked up some thermals, as the dome has skylights.

Josiah Rose came out on top in F1M, taking a new National Record for Youth Sr at 10:15.3. It was very closely competed. He had put his plane away for the day when another team member put up a flight within 2 seconds, and she had one more flight left. So Josiah had to re-assemble the plane and defend his time at the end of the day. All four high schoolers had planes in the air at last call, trying to knock Josiah off the top. They all put in times right at 10 minutes in both LPP and F1M. Josiah had a 10:45 in LPP on Saturday, and I got an 11:45.

I am really proud of my kids, and I had a great time even without flying very much at all!

These kids want to do more testing and flying this week! I think they are hooked!

Chuck


Title: Re: Another Gowen LPP
Post by: piecost on April 15, 2019, 02:27:01 PM
Well done Chuck to you and your team,

Can you post any pictures of the site and the models? I am particularly interested in the propeller as i struggled to get Bills original design working consistently. Any details of motors and torque levels alao gratefully received.


Cheers

Tim


Title: Re: Another Gowen LPP
Post by: ceandra on April 15, 2019, 04:37:27 PM
Tim:

We pretty much built per Bill's plan, except the prop. All 5 planes flew great on Friday, and all very similar, so the plan appears solid. We got a lot of compliments on how well they flew, and especially how resilient they were when pounding the rafters. Unfortunately, two planes were badly damaged when we got in a hurry cleaning up that night. After disassembly and placement in the box, a notebook was dropped into the box. We repaired in the hotel room, but those planes struggled the rest of the weekend (they did gradually get better. One simply could not get to the rafters anymore no matter what we tried. The other as soon as it touched, dove to the ground. It acted like the stability was gone, but we moved CG as much as a cm ahead of plan, and it did not improve. I think we lost stiffness in the stab, but we will try to fix it later. It flew great until a touch. All others flew perfectly with CG on plan.

The props were formed on Don Slusarczyk's 20" prop block from Thingyverse. The blade shape was copied from the Ikara flaring prop (9.5" diameter) blades, but scaled to 12" diameter. Each kid had two props, one with nothing behind the spar, the other with the extended blade behind the spar. @ used the trimmed prop, 3 used the full prop. The spar was a 1/16" square basswood, turned 45 degrees. Each side was sanded to 1/32" thick from about 3mm outside the shaft to the tip. The spar was 6" diameter. Several props were stiffened by adding 1/32" sheet to the sanded portion for the exposed portion, as they were over flaring. The basswood definitely differed plane to plane. The blades were generally set to 40 degrees at 4" radius, or about 21" pitch. However, some were closer to 35 degrees, and two (mine and Josiah's) were increased to 50 degrees. We adjusted pitch by heating the exposed part of the spar with a Monokote heat gun and twisting.

In LPP, we seemed to converge on about 2.3g of rubber, whereas we started testing with 2.5g. Some kids (and I) had issues with bunching at either end around 7 minutes in, even with sleeves. We spent some time improving our winding technique (keep it turning more at the end when coming in fast) and the bunching went away. It was fun to see the kids adapt techniques quickly as we learned. The rubber was 0.054g/in for the heavy props, and 0.049g/in for the lighter props.

For F1M, with 1.5g of rubber (lubed we were around 1.49g), the heavy props were happy at 0.052 to 0.051 g/in. The lightest prop dialed all the way down to 0.039 g/in! She did a lot to adjust here winding style, whereas I thought changing the pitch may have been better. It was late Sunday, so it was quicker to adjust the rubber. She actually got within 2 seconds of the heavy prop kid, sparking a last minute flurry of competition.

The main thing as times increase was to dial in the rubber density for each kid, so that they had only a few turns when they landed, and were not pounding the girders quite so much. Every kid increased time throughout the day. I spent the day processing rubber request slips and cutting rubber for them! You know they are studying the data when they have on 0.052 and want something "maybe just a little larger than 0.051 g/in".

I suspect these numbers may change at lower altitude. I also think we need to try a higher pitch prop block, but it was convenient to use Don's. He has camber built in. We had made a few prop blocks for SO, but they were 14" and 18" and required a camber form to be carved as well. We'll make something around 24 or 26" before we make more props.

Overall, except after the damage, the planes flew very similar, very stable, very consistent. This allowed the kids to focus on the prop/rubber optimization. I gotta hand it to Bill, the plane is easy to build (even 5 at a time in a group), and it is very tough!

Oh, in general the high pitch guys (including me) were launching at 0.52 oz-in or even a bit higher, and the low pitch at perhaps 0.4 to 0.45 oz-in. We were winding generally to 1.2 oz-in (I think the rubber could take more, but we were trying to extend life a bit so I did not have to cut for every flight). At high torque, the planes would climb at maybe a 60-degree angle for a lap or so. Someone commented they thought it looked like F1D. I think this was more pronounced in F1M, in which case some would actually power stall, but then recover and continue climbing. In LPP, with more mass, they just tractored on up. In general they were to the rafters in a minute or so, at least the aggressive winds were.

We did get stuck twice, once on conduit at the top, and once on speaker hanging cables. Both times we got help with a pair of party balloons and recovered the planes without damage.

When the sun hit the floor through the skylights there were some nice thermals to ride. ON Sunday the wind was howling outside, and it made little difference inside. I have heard of issues with wind, but they did not seem to have an issue this weekend. The planes on Sunday would circulate right in the middle, cruising at 95' for 5-7 minutes without moving out of the peak of the dome.

Chuck


Title: Re: Another Gowen LPP
Post by: OZPAF on April 15, 2019, 07:21:40 PM
Well that was a great report Chuck and congratulations! Wish we had something similar here in Oz. Good on you Bill - your design has well and truly proven itself.

John


Title: Re: Another Gowen LPP
Post by: ceandra on April 15, 2019, 07:39:02 PM
Thanks John!

While Science Olympiad got kids to me that were interested, it is limited in that only two kids compete in the flying task, out of 15 on the team. With the success and fun of flying, the flying tasks have become extremely popular, and only a few get to fly. But, with AMA competition, any and all can join in. I am not going to spoon feed, but if the kids are willing and able to do the work, I will bend over backward to help them along. We built the planes less than a month ago, and that was a busy time!

I am finding kids, once exposed, love aviation. While SO may not be down under, perhaps you can start an after-school club at a local high school. If you can interest 2-3 kids, word will get out. This would also give you access to a gymnasium for testing and practice!

If we don't inspire the kids, nobody is going to replace us.

Chuck


Title: Re: Another Gowen LPP
Post by: calgoddard on April 15, 2019, 07:42:01 PM
Chuck -

Thank you for the two reports on your success at the Round Valley Dome.  Congratulations to you and your students.  They will never forget the experience. Kudos to you for mentoring them.

I am going to the AMA Indoor Nats from May 29 - June 2 at the Round Valley Dome.  I will use some of your info to trim my LPPs and make up additional rubber motors as needed. I have very little experience flying LPPs in anything other than a CAT 1 site.

I generally fly my LPPs in a CAT 1 site with a 2.2 gram rubber motor. I was thinking of going to 2.6 gram rubber motors at the Round Valley Dome.  I believe that Bill Gowen and Kang Lee have had success with 2.6 gram motors for their LPPs. I am not in their class.  You saved me a lot of time.  I think I will go with my already made 2.2 gram rubber motors and strip more at the Round Valley Dome as needed.  My two best LPPs are very near the 3.1 gram minimum and I may have to ballast up a tiny bit if they lose weight in the very dry conditions in Eagar, Arizona.

I built three new props for Eager using a 23-inch prop block from Mike Kirda.  Two have all the prop blade area in front of the spars. One of those uses Bill Gowen's design and has four carbon fiber spars so that the blades will flare at high torque. I don't think I will be using it much at Eager as I need to get max climb.  The prop with some blade area behind the spars is supposed to be non-flaring so I can at least get one of my LPPs up to the rafters.

Let us know if your student gets his official AMA record.


Title: Re: Another Gowen LPP
Post by: piecost on April 15, 2019, 08:10:02 PM
Chuck,

Thanks for the comprehensive report! I will be taking a detailed look at your data in due course. I am most impressed with yor teams performance. It is interesting that you found the model easy to build, since I found it rather fiddly and had lots of problems with carvon to carbon tip joints and wing and tail tube stiffness. Rhe latter solved with Bills patient advice. I agree that it is a great model and am convinced it is more efficient than other LPPs Ive seen in the UK.

It is interesting that we are using similar motors with different propellers. Perhaps it is not too sensitive. I am supprised that you mention a steep climb and reaching the ceiling in about a minute. I wonder if your propellers are really flairing much at all. My experience suggests that switching to flairing props delayed the top of climb from approximarely  25% to more like 33% of total duration. I was allways flying under 60' ceiling or less. What do you think?

I would love to watch your high torque launches. I found that launching at higher torque causes the model to perform a fast flat circuit rather than climb, due to the stick bending. My experiment with a bass spar and a flairing blade with the spar at the trailing edge didn't seem to flair at all.

Cheers

Tim



Title: Re: Another Gowen LPP
Post by: Olbill on April 15, 2019, 09:20:46 PM
A few comments:

I've hung on the ceiling at Lakehurst (190') with a flaring prop.

The flat high speed circles at the beginning of a high torque launch will waste a lot of energy and affect the total climb available. On my models the cause of this is usually the right wing washing out. That's one of the main reasons I use washin on the right side.

Both props that I'm flying now have the area behind the spar removed.

I seem to fly the same general weight motors in all different ceiling heights. Motor weights are in the range of 2.4 to 2.8g or so. Test results on motors carry more weight in my decision making than exact weights or lengths.

Due to occasional problems with bunches of knots at the rear hook I've been flying 20" motors more than longer ones. The worst problem with knots at the rear hook is a CG shift messing up the cruise and let down. My sleeve arrangement now is about 3/8" of heat shrink tubing at the front and 3/4" to 1" of a larger diameter plastic straw at the rear. The picture attached shows older rear sleeve from HS tubing. The straw weighs about half as much as the HS tubing.

Since I never have trouble with knots at the prop hook I usually try to move all the knots forward as much as possible before launching.


Title: Re: Another Gowen LPP
Post by: ceandra on April 15, 2019, 09:40:32 PM
The bass spar, sanded to half thickness, flared pretty well. The blades were 1/32" C grain, about 6.5#, sanded to 0.025. We cut blades from two sides of the wood (3" wood), but match pairs from the same side. In retrospect, one side was more C grain than the other, and so there was a distinct difference in flaring stiffness.

We measure flare stiffness by placing the blade against a scale and rotating the prop shaft until the blade flexes to flat. In these cases it was anywhere from 6.5 to about 9 g, the basswood and the blades varied. But each pair was pretty consistent. The props that we stiffened flexed at 10-12 grams. I am thinking this is not a good measure, because some spars may "wind up", especially the Gowen style carbon spars. I need to make a fixture that will measure the flex stiffness for 10 degrees of flare, not 45.

I was more in favor of a slow graceful climb, but the kids loved the rocket climb. They pointed the plane straight ahead, but if immediately rotated to a steep climb, and seemed happy. I am hoping a parent has a video of a launch, then I can post it somewhere and post a link here. I was too busy for photos and videos! I think at 60', we would not have been above 0.5 torque and the climbs may have been more slow.

It was interesting to me that we did not see a huge difference in performance between the full prop and the ones without the trailing edge. Some of us switched because the full prop was not getting us up, and the thinner prop did, but this is probably more a reflection in the various stiffnesses.

We went in planning on 2.5g as a baseline. I had some shorter rubber in the box, and the kids tried it out and it worked better in terms of time. Remember the air is thin, so the weight penalty may be greater than sea level. Another interesting point is that by the end of Sunday (We did F1M exclusively Sunday) they had progressed from 7.5 minutes to over 10 minutes, and had got very close to their LPP scores. I have to wonder if a few more days they could have improved greatly on LPP base don what they learned Sunday. Another flyer (I forget name) slipped in a 13:45 flight, his only flight. So while we were very pleased with our first ever, there is room for more!

On the rubber width, note that the lower pitch props went all the way down to 0.039g/in. But, most were grouped around 0.051g/in (for 1.5g in F1M).

Bill responded while I was typing. We definitely saw better performance with right wing wash in, as suggested by Bill. A few mm is all. On SO planes, the wing has less chord, so the twist form motor stick has less impact (and we launch often with less torque), so we generally run those flat.

I think the main reason we went down to 2.3g is the bunching. However, as the weekend progressed, teh kids got better at controlling the bunching be careful end game on winding. Bunching was eliminated. Since we were running fairly thin rubber, the lengths were getting pretty long, and we tried to cap it at 56cm (22"). But Bill is right, keeping under 20" seemed better. I think if you could pitch up a bit more than we did, go with rubber approaching 0.060 g/in or more, you may be able to carry more mass without bunching.

My 11:45 was with my prop with no TE surface area.

Chuck


Title: Re: Another Gowen LPP
Post by: ceandra on April 15, 2019, 09:44:54 PM
Tim:

We have used Bill's construction techniques for a few years in SO, so it was not hard. When gluing tip plates on, we wrap with a half thread of polyester embroidery thread. That makes it bullet proof. we wrap 2 turns, put a dot of thin CA, all before cutting the bottoms off.

Chuck


Title: Re: Another Gowen LPP
Post by: Olbill on April 15, 2019, 10:12:00 PM
I actually changed the tip plate connection a few years ago. I think Tim was building the earlier version. Now on the LPP and the SO models I just extend the spars a little past the end rib and set the tip plate between the spars.


Title: Re: Another Gowen LPP
Post by: ceandra on April 16, 2019, 12:04:57 AM
OK, yes, we do that and I can see that it would be harder without that extension.

Chuck


Title: Re: Another Gowen LPP
Post by: calgoddard on April 16, 2019, 09:48:52 AM
Chuck -

Can you please give more details about your following comment from Reply #66?

"We spent some time improving our winding technique (keep it turning more at the end when coming in fast) and the bunching went away."

Thank you.


Title: Re: Another Gowen LPP
Post by: ceandra on April 16, 2019, 12:10:13 PM
Cal:

One of my kids was consistently getting a huge wad at the front end about 7 minutes into the flight, which would stop the prop and the plane would come down from 70-80 feet. Several others were getting large wads at the back, not every flight, but often, with or without sleeves. These would cause a CG shift, as well as significant unused turns.

On observing them wind, I saw that they were reaching close to their goal winds while still a foot away from the holder for the winder. If they simply stopped winding here and moved in, they would get obvious large stringers sticking out the side of the rubber, which are hard to get rid of. However, if they walked the rest of the way in with just a turn or two (10:1), they did not get stringers and all looked well, but they would get balled up in flight.

Instead, I got them to either save a few more winds for this last part, or stretch it back out a little and go over budget on winds. This made a more even distribution of medium-large knots, instead of a few larger knots. The few larger knots were not immediately apparent, but would form a nucleation site for a big mess in flight. By focusing on getting more winds in that last foot of walk-in, the bunching was more uniformly distributed, and resulted in no further instances of major bunching, with or without sleeves. Note that we generally went to 2.3g instead of 2.5 as well. But, the one that was bunching at the front also was the one that was using the lightest rubber, and her loop lengths were still at 22".

Chuck


Title: Re: Another Gowen LPP
Post by: ceandra on April 16, 2019, 12:19:53 PM
I have not yet found a video of the high power launches yet.

After thinking overnight, while these launches are certainly better than unwinding at the table, and better than racing in a circle, they are not efficient use of the energy. Ideally, the flare load would be sufficient to slow the plane down and fly more on the wing, without thrashing the air. However, then the flare must relax to the right point for efficient cruise. This probably means some combination of a softer flare, with a lower static pitch, such that the pitch goes way up on launch (but not so far as to stall the blades), and then goes to the right pitch for efficient cruise, not so low as to spin high RPM in cruise and letdown.

At the high altitude, thin air, I am not sure you can load the prop enough at 0.55 oz-in torque to slow the launch. But, we did not explore all variations of pitch and stiffness. The high power launches would last perhaps halfway to the ceiling, then it would settle into a more normal climb. Other methods explored did not get to the ceiling, and resulted in shorter flights. I would love to spend a day or two in the Dome exploring a variety of prop flare and pitch combinations! I am sure there is a more efficient setup. What we found got us very respectable times for a first time team, but in no way is the ultimate solution.

The one guy who out-flew us (perhaps his name was Avery?), my student thinks. was a guy who got it up into the opening at the center. The plane actually disappeared over the railings up there, then came back out. Not certain that was the 13:45 flight, but my student thinks it was. I did not see the climb on his, but believe it was more controlled. If you could convert those rapid turns into a controlled climb on the wing, I think you could gain a minute or more.

Chuck


Title: Re: Another Gowen LPP
Post by: piecost on April 16, 2019, 06:49:36 PM
I am enjoying this revitalised thread. Especially the comments about winding and bunching. I have certanly had terrible looking bunches on my motors, which can't be good, but have not needed to employ sleeves.

I concluded that bunches effectively prevent the rubber within them taking further turns. I believe that this causes a premature torque rise at too low winding turns. Also a lumpy torque delivery as bunches run out. Do you agree?

I like the testing of prop flair and have not quite got round to doing that myself. I have built far too many variations of pitch and number of rods on the hub to ever test. I would be better sticking with a tried and tested setup than fiddling all the time. But this is where the fun is for me. I have not even started to use washout to prevent blade stall at high torque.

I had used the inset tip ribs and binding the tips with fine fishing line before applying freshly opened cyano. I was pleased to find that steering with a roach pole against the side of the.fin did not cause the joint to fail.

I will have to check and reset the twist of my wings to prevent the warp at high torque.


Title: Re: Another Gowen LPP
Post by: ceandra on April 16, 2019, 07:15:54 PM
piecost:

The bunching I am referring to is not necessarily visible during winding, but rather manifests in flight as a big wad, either at the tail hook or at the prop hook. Even with seeming decent looking wound rubber, these occurred and caused loss of several minutes of flight. I am suspecting that even when large unsightly bunches were not visible in the wound motor, the largest knots were unevenly distributed and became bunched enough to hit the motor stick during flight. Careful attention to the last stages of winding seemed to greatly improve the situation.

Chuck


Title: Re: Another Gowen LPP
Post by: Olbill on April 16, 2019, 08:15:31 PM
I haven't seen much effect from winding technique on knot formation but I'm not saying it isn't possible. One thing that makes me dubious is how does that relate to backoff turns. It seems like whatever you did during winding would be wiped out by backoff turns.

Anyway, when I get my launch torque set and put the motor on the model I move as many knots as possible to the front. With a 1" rear sleeve, the knots moved to the front and 20" or so maximum motor length, most of my flights will have an acceptable unwinding of the motor without a cruise killing CG shift.

A6's have a 6" nose to hook maximum and use the same length motors (at least mine do)!


Title: Re: Another Gowen LPP
Post by: ceandra on April 17, 2019, 12:38:23 AM
Bill:

I do see your point. And there were many variables we were playing with. It did seem that we did better after the change in winding, but the majority switched to rubber that was 20" or under, though the one girl with the most struggles was still using 22" rubber.

So much fun learning in all of this, and I really appreciate the feedback we get on this forum.

Tonight we flew in a 20' gym, with walls right at the edge of the single court. Our planes were clearly not ideal for that gym. One student got over 5 minutes twice, and another two would have been if not for late hits on tables, chairs, and walls. We'll play with the flare stiffness before next time! The ceiling took a lot of hits.

Chuck


Title: Re: Another Gowen LPP
Post by: ceandra on May 19, 2019, 06:25:49 PM
Here is Josiah with his official record from AMA. 10:15 for F1M in Cat III, Youth Senior. Flying Bill's Carbon Penny.

Chuck


Title: Re: Another Gowen LPP
Post by: Olbill on May 19, 2019, 06:29:18 PM
Good job!


Title: Re: Another Gowen LPP
Post by: piecost on May 19, 2019, 07:27:30 PM
Well done!


Title: Re: Another Gowen LPP
Post by: OZPAF on May 19, 2019, 08:04:11 PM
Congratulations young man - great effort with a good model from Bill.

John


Title: Re: Another Gowen LPP
Post by: Skymon on May 20, 2019, 08:12:34 AM
Top job, well done!


Title: Re: Another Gowen LPP
Post by: AC01010 on July 13, 2019, 09:40:16 PM
Hi everyone,

I recently built Mr. Gowen's Carbon Penny and I don't know where else to put it so I'm putting it here. I'm just a high school student with limited experience in ELG/Wright Stuff so any advice would be appreciated.

Stab: https://photos.app.goo.gl/u9bRZJGbXr9aZJos8
Propeller: https://photos.app.goo.gl/DVgd3f5Y42apWfWb8

I used 3/32 Tan SS Rubber, 2.62g.

Launched with 1500 winds, dewinded 300.

My flight today (outside!) brought the plane to 15' within less than a minute and it cruised there for about 4 minutes, didn't go any higher. Flight ended after it hit a tree at about 5-6' off the ground. Luckily nothing broke but the final time came to 4 minutes and 31 seconds.

https://photos.app.goo.gl/Lb3RBvzWSDqyVydD7
Video: https://photos.app.goo.gl/4WuBNJt7BR1VXjd5A

Sorry for the terrible video quality. I'll edit this post with specifics on the plane tomorrow when I have time.

-Allen


Title: Re: Another Gowen LPP
Post by: Olbill on July 13, 2019, 11:57:02 PM
Great job Allen and some excellent thinking about how to solve problems! The model looks great and seems to fly very well.


Title: Re: Another Gowen LPP
Post by: OZPAF on July 14, 2019, 04:03:49 AM
Nice effort Allen - good luck with it.

John


Title: Re: Another Gowen LPP
Post by: cvasecuk on July 14, 2019, 05:24:30 AM
Incredible! An LPP flying outdoors. We are lucky if the wind is less than 10mph!
Ron


Title: Re: Another Gowen LPP
Post by: piecost on July 14, 2019, 07:23:29 AM
Great job Allen, please keep us informed of progress with this model.


Title: Re: Another Gowen LPP
Post by: bjt4888 on July 14, 2019, 08:21:03 PM
Allen,

Excellent work. Hopefully, your local school district can get you some gym time to fly indoors.

Brian T


Title: Re: Another Gowen LPP
Post by: AC01010 on July 14, 2019, 09:45:02 PM
Allen,

Excellent work. Hopefully, your local school district can get you some gym time to fly indoors.

Brian T

I will be (hopefully) getting time indoors tomorrow, but it's a small gym that's just under 20'.

As promised, here's some specifics on my plane:

Boom: 0.23g
Stab: 0.46g
Wing: 0.83g
Ballast: 0.03g
Motorstick: 0.82g
Propeller: 0.78g
Total: 3.15g

The first time I made the wing, I had trouble attaching the winglets. I wasn't sure how do attach it, so I ended up ripping the superultrafilm once on both winglets. I redid the wing again with a couple of minor improvements but I ended up only having a minor rip on one of the sides.

Today I flew a few times but I got my best flight with a 5 minute 5 second flight. It got to about 30' but I didn't want it to fly any higher since it would risk hitting a tree from draft. 1600 winds with 200 dewinds, nowhere near the maximum winds the rubber can take. How can I get more winds and torque in while limiting the height?

I used 3/32 Tan rubber, 20 inches, 2.62g. Suggestions for lubricant? I've been using Armorall but there's probably a better alternative.

Images:
Propeller: https://photos.app.goo.gl/gcw1F6HDtiTtK9XB6
Wing: https://photos.app.goo.gl/o3w6MsRpu9h8YjuP9
Stab: https://photos.app.goo.gl/AiuJEznbUmpe38Qj6
Whole plane: https://photos.app.goo.gl/6VfNakKpKiWJi6sY6

The propeller was built with a 3d printed prop block found here: https://www.thingiverse.com/thing:3451441
I used 4 0.01" CF rods as shown in the plan to make the prop hub and I used 0.015" music wire to make the hook.

Regarding the motorstick, it is twisting a little from all of the torque. Any suggestions on how to fix this?
With rubber, what is the best type of rubber I can find? I've been using Tan SS rubber but I'm hoping to get better quality rubber (and a rubber stripper?) next year for Science Olympiad.

Here's part of the flight: (First 2 and a half minutes)
https://photos.app.goo.gl/sszXKSiBx4kfSyX26

I'm clearly still a beginner at this, so any advice would be appreciated!


Title: Re: Another Gowen LPP
Post by: Olbill on July 15, 2019, 01:42:29 AM
Allen
Let me start off with a rule problem - you can't use a MS bracing thread on a LPP if you're flying it in AMA competition.

Now for the rest:

Your weights all look very good and similar to mine.

Your prop is beautiful! It looks like you have balsa between the carbon rods for the full length of the spar. If so, you would get more flare of the blades if you removed most of that.

Armorall is what I use for a lube. Silicon oil is also good.

Your motor might be a little too long for Cat 1 flying. I would try 18" or so. But for higher ceilings you can go to 20", 22", maybe 24" if the need arises. (and use sleeves on all of those)

I don't have a lot of experience with Tan SS but in general you can get more flight time by winding your motor close to the maximum number of turns it will take and then backing off turns to a predetermined launch torque.

The only way to get a motorstick that twists less is just to find a better piece of balsa. When your motorstick twists just enough to be a problem, sometimes you can get a successful launch by twisting the stick in the opposite direction for 15 or 20 seconds before launching. I had to do this at the Kibbie Dome this year in order to launch with enough torque to reach the ceiling. (and the same with my F1L)


Title: Re: Another Gowen LPP
Post by: AC01010 on July 15, 2019, 04:16:26 PM
Allen
Let me start off with a rule problem - you can't use a MS bracing thread on a LPP if you're flying it in AMA competition.

Now for the rest:

Your weights all look very good and similar to mine.

Your prop is beautiful! It looks like you have balsa between the carbon rods for the full length of the spar. If so, you would get more flare of the blades if you removed most of that.

Armorall is what I use for a lube. Silicon oil is also good.

Your motor might be a little too long for Cat 1 flying. I would try 18" or so. But for higher ceilings you can go to 20", 22", maybe 24" if the need arises. (and use sleeves on all of those)

I don't have a lot of experience with Tan SS but in general you can get more flight time by winding your motor close to the maximum number of turns it will take and then backing off turns to a predetermined launch torque.

The only way to get a motorstick that twists less is just to find a better piece of balsa. When your motorstick twists just enough to be a problem, sometimes you can get a successful launch by twisting the stick in the opposite direction for 15 or 20 seconds before launching. I had to do this at the Kibbie Dome this year in order to launch with enough torque to reach the ceiling. (and the same with my F1L)


About the MS bracing thread: yikes. I don't really want to remove it though since there's almost no chance of competing but that's definitely something I'll look out for in the future.

With the prop, I will try to build a second one soon and take off most of the balsa. How many inches should I leave connected to the prop?

Thank you for your advice! Unfortunately I was unable to get gym space today (there was some camp there) but I will try. What do you mean by sleeves on the rubber?

Thanks.

-Allen


Title: Re: Another Gowen LPP
Post by: Olbill on July 15, 2019, 11:49:55 PM
https://www.hippocketaeronautics.com/hpa_forum/index.php?topic=3650.25 for sleeve info. These days I usually put the sleeves on after the motor is tied. I'll post a pic of the tool if I can find it.

Here are pics of the front and rear hookup using sleeves and the hub of one of my props.


Title: Re: Another Gowen LPP
Post by: Olbill on July 16, 2019, 12:00:21 AM
I just found this set of photos that I did for Andrew a few months ago. They show my current sleeves being installed on a motor with a special sleeve tool that takes a couple of minutes to make. The last 4 photos will be in the next reply.


Title: Re: Another Gowen LPP
Post by: Olbill on July 16, 2019, 12:01:26 AM
The rest of the photos.


Title: Re: Another Gowen LPP
Post by: AC01010 on July 16, 2019, 05:03:45 PM
The rest of the photos.

Interesting. I will definitely take a look at this. Thank you!