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Author Topic: Another Gowen LPP  (Read 9519 times)
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piecost
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« 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.
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Another Gowen LPP
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piecost
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« Reply #1 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
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Olbill
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« Reply #2 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.



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piecost
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« Reply #3 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!
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julio
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« Reply #4 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
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« Reply #5 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.
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Tapio Linkosalo
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« Reply #6 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.
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Olbill
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« Reply #7 on: November 07, 2014, 10:12:29 AM »

Tapio
By now it should come as no surprise that I do everything backwards!
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Hepcat
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« Reply #8 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  Smiley!!

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
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« Reply #9 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.



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« Reply #10 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!
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piecost
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« Reply #11 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.

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« Reply #12 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.
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« Reply #13 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.
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piecost
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« Reply #14 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!
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« Reply #15 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.
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« Reply #16 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.
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« Reply #17 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
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piecost
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« Reply #18 on: December 24, 2015, 08:35:26 AM »

Add photos
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Olbill
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« Reply #19 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.
« Last Edit: December 24, 2015, 09:16:29 AM by Olbill » Logged
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« Reply #20 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!
« Last Edit: December 24, 2015, 09:29:48 AM by calgoddard » Logged
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« Reply #21 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.
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« Reply #22 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.......)
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« Reply #23 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. Embarrassed
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« Reply #24 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.
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