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Indoor Free Flight Forum => No-Cal => Topic started by: piecost on November 26, 2013, 03:09:19 PM



Title: Cassutt NoCal
Post by: piecost on November 26, 2013, 03:09:19 PM
First of all; I would like to thank Frash for posting the Cassutt plan. After dabbling with my own design MB5 I wanted to build a model which was proven as successful. In particular I wanted a comparison between my model and the Cassutt in terms of the latters; larger wing area, larger propeller, shorter nose and longer tail. I also wanted to calibrate against John Barkers Prop_Picker spreadsheet.

I come from more of a scale background and found it interesting to build a model with some features of more advanced indoor duration models. This required the developemnt of new skills and the use of thinner wood sizes. I really struggled with matching the balsa thickness and density as specified on the plan.

I made the following changes to the plan:

I build the tail as specified by found it far too delicate. I therefore built a second example from 0.050" square. I also added provision to make it removable to allow the model to be flat packed for storage and transport. Rather than gluing the tailplane spar to the rudder post I installed a tube with a matching example on the tailplane. a removable balsa dowl allowed the tail to pivot for adjustment and be removed for storage and transport.

I modified the removable canopy to integrate the horizontal joint to be formed by the wing , rather than employing a seperate longeron on the fuselage side. This saved a little weight and has worked well.  I originally planned to glue the canopy to the wing, but decided against it  due to the likelyhook of  damage during transportation. The canopy was therefore attached by peg and tubes at the forward and aft top longerons and a tube fitting to a peg on the wing trailing edge at the bottom aft corner.

The undercarrage was also made removable, with a tube inside the apex of the legs and a tube on the fuselage. It is a little wobbly but works. The undercarrage came out at ouver 0.5g since the plan specified medium wood. It does act as noseweight.

I employed light Jap tissue sprayed shrunk twice with water and held on a frame to dry. It was ironed before mounting on the structure, which had been Spray-mounted. The edges were wrapped round and attached with thinned Ambroid. It was not a neat as I would like.

This was the first model assembled using tissue tubes and I realised that I had should have built the wing mounting in a different order. I first attached the wing mounting pegs to the wing leading and trailing edges and then marked the position of the tissue tubes on the motor tube. I eye-balled the holes in the motor tube to get them vertical. I found that when I mounted the wing the whole thing twisted . I should have left the gluing of the wing pegs last, after jigged the wing correctly in relation to the fuselage. I had to slot the bottom hole for the front wing mounting tube and moving the tissue tube until the wing twist was correct. A doubler plate was added to cover the slot.

I fitted a reverse S hook to the motor tube since I had previously had problems with slack motors coming loose. This worked well, even with the stint. The wound motor simply jumps onto the hook!

The tail boom was formed round a conductors batton and a single thickness of jap tissue reinforced the tubes prior to drilling for the wing and tail mounting tubes.

The tube and boom mounting gussets on my previous models was not as neat as I liked so this time I changed my approach. I cut and sanded the correct sized holes in 1/16 sheet and glued over-sized rectangles onto the tubes, positioned correctly on the fuselage to dry. Glue was applied to the side of the hole facing the fuselage. When dry; the rectangles were cut to leave neat triangular fillets between the tube and the fuselage. By making the holes in oversize rectangles any splitting was prevented.

The propeller bracket was make from hardware store 10mm by 15mm extruded aluminium. An attempt was made to install it with the specified thrustline, but I lacked a good way to measure this. Any ideas anyone? A 2" long plug of solid balsa was installed in the front of the tube instead of a thin web. This prevented it being crushed when pressing plasticine nose weight into place.

The weights were as follows:

                                                               Uncovered      Covered
Fuselage - Tube & Boom                            0.81g             -----
Motor Tube & boom                                   1.14g             -----
Fuselage with Tube & Boom                      1.95g             2.51g   
Wing                                                         0.99g             1.94g
Tailplane                                                   0.17g             0.50g
undercarrage                                            0.45g              ----
Propeller                                                   0.77g              ----
Airframe + Propeller                                  4.33g             6.17g

The model was built to the 6.0g BMFA rules so is a little heavy.


Flying

The model was flown under a 20ft ceiling in a small leisure centre with a 40% motor and 60% stint to simulate the 50ft ceiling at Baulby, where the nationals are flown. I initially used a 0.100" motor of 200% of the propeller to stint length, which matches the contest winning setup on the plan (I used Super-Sport rubber, not the same as used in 1988/1989). The motor proved underpowered and  the model did not climb nor turn. It required a huge amount of right thrust to turn within the bounds of the building.  The wash-in on the right wing seemed perfect wand produced a  nice unbanked flight.

The model flew very slowly, as I had trimmed to near stall in an attempt for  maximum duration, but adjusting downthrust and tail setting. It slightly upset a scale supremo who considered it perverse for a racer to fly like a human powered plane.

The flight speed was a marked contrast to my Martin-Baker MB5 which is more fighter like speed. However,  The model kept slowlng down and stalliing. A small tailplane setting adjustment of , say, 1mm gave a too coarse change in flight path. So it was likely that the centre of gravity was too far aft. This was not measured before or during the flying session. Some weight was added to the nose.


The fuselage was held in a jig with the model being wound off the model. Unfortunately, the wing had to be removed to install the motor. This was a faff but luckily the wing and canopy mounting pegs and tubes worked faultlessly. I was delighted that the removable tailplane worked perfectly as I was worried by the rear mount being delicate.

I found that I had split both propeller blades either sides of the propeller spar. I should have added tissue reinforcement

I changed to 0.108" rubber, but the model was still underpowered, landing with lots of turns left. My model is somewhat overweight compared to the original and I am worried about entering a weight spiral where more rubber. I will try next time.

I had used Hepcat's (John Barkers) Prop_Picker spreadsheet for this model. This suggested that the propeller had too high a pitch for the flying speed of the model (assuming that my assumptions were accurate). So, I will construct a second propeller with less pitch as a comparison. This should rev more and require thinner rubber, perhaps, at the detriment to flight times.

From measurement of the CG after the flying session it turned out that I had flown the model with the CG 17mm (11% amc) aft of that specified on the plan. I recon that I will need 1.2g of nose weight to bring the CG forward to the plan position. This suggests that I should move the rear peg forward by nearly 4 inches! I must double check this before making any changes!




Title: Re: Cassutt NoCal
Post by: lincoln on November 27, 2013, 11:20:30 PM
Sounds like a fun project. Also sounds like it may be worthwhile to build a new tail with lighter and/or smaller wood. If you build a few EZB's, .050" square will seem like a 2X4. At least for a tail. Tell that scale guy that the original was test flown to determine stall speed in January in Death Valley when the barometer was high, and that's the flight you're trying to replicate. Back of the envelope calculations suggest that the stall speed will be close to scale anyway.

Your tissue weight sounds a bit high, though I could be wrong. The best Japanese tissue tends to be around 10 grams per square meter.




Title: Re: Cassutt NoCal
Post by: dslusarc on November 27, 2013, 11:31:41 PM
Cassut nocals will require a fair amount or right thrust (as you have found out) also usually some down thrust, how much down depends on how it behaves when torqued up. You basically use the down thrust to try and control any stalls when highly torqued. It will also require some right rudder offset as well to help kick the tail around to circle and a slight amount of right tail tilt at rest. Too much rudder offset and it will wind in to the right when torqued up so I would start with about 1/8" right rudder and you use the vertical piece of wood in the rudder as the hinge point for the rudder. They do fly nose up and slow more like a Pennyplane. The last Cassutt I built before going to a Hosler Fury had the rear hook at the trailing edge of the wing to help get the correct CG as more rubber will be in front of the CG than beyond and it was always a struggle to get the CG right. I think on later versions of the Cassut my dad moved his hook a little forward as well than what he shows on the plan. Also we started running bigger props than on the plan, 10-12" diameter and rubber in the .110-.125 width and the times were then over 7.5 minutes at USIC. My dads highest was a 7:57 if I recall my max was about 7:45 then we went to the Hosler Fury as we were about 15 seconds behind the Hosler.

It is very easy to make a no cal tail heavy. Those small plug in and such in the stab will require at least twice the weight in the nose to balance out. So .1 grams additional in the tail will need at least .2 grams nose ballast to balance it out based on the distance from the CG so that is why the tails were built light with minimal structure. It is amazing how using a little heavier density wood multiplied by the moment arms starts to add up. I do know on later models we started using thinner wood for the landing gear and lighter wood. The wheels pant part we went to light 1/32 and the gear leg was still something like 6 pound 1/16 tapered to about .045" at the point where it met the wheel. The leg if made too thin would break mainly during handling. So if the undercarriage is .5 grams now, if you make a new one say 0.35 grams then the .15 grams saved can be added to the nose and that .15 has about three times the effect it did located at the landing gear since the distance of the .15gr ballast on the nose is about 3 times the distance that same .15 grams would be at the landing gear. So if you move these small amounts of weight around like that they suddenly add up. I know we also started to remove some of the wood on the nose sheeting area and so the weight saved there could be added to the nose. My dads "medium" balsa would be 5-6 pound density but later ones we used 4-4.5 pound for that sheeting on the nose and also went to thinner about .050". Our "hard" balsa would be wood you would find inside a Comet kit. We use to win kits at indoor contests then take the really hard wood strips in those kits and put them in a box called "hard" for use as prop spars on models like this.

Here is an article I wrote in regards to nocal some time back. You may find some info helpful
http://www.indoorfreeflight.com/nocaltips.htm    

I also attached a photo of my dad's original model the plan is based from. The .100 motor was used with a foam coffee cup prop seen in the photo and the rpm was rather high. That rubber he used was much different than the rubber today. That older Pirelli had much less stretch and would torque up more and you got a longer climb than Tan rubber. The 27" loop of .100 Pirelli would take 2100 turns and a 24" loop on .120 Tan would take 2000 turns, so similar turns but way different thickness.  

The Cassutt will fly well even at 7 grams. The first one per the plan was 7.4 grams. Then got lighter as the building was refined. I would try a shorter heavier motor say a 20" long loop of ~.115-.120 and see how it goes from there. You should not need a lot of tail incidence either, maybe like 1/16" to maybe 1/8". Too much and it will stall about every half circle or too aft cg will do the same and a close CG but not enough rudder can make it stall gently so adding in some rudder will help it groove in the turn and if it still stalls then either CG or incidence needs to be adjusted. I would set the incidence then find the CG that makes it fly, instead of setting CG and finding incidence needed to fly. You want to fly this model with about 3/16-1/4" total incidence so that means ~1/8" incidence in the wing and about 1/16"-1/8" neg incidence in the stab then adjust CG to get it to fly. 

Don


Title: Re: Cassutt NoCal
Post by: piecost on November 28, 2013, 01:41:48 PM
Thanks for the positive comments lincoln and the extensive reply Don. I see this hobby in terms of development projects rather than making a single model and moving on.  So, I will digest your recommendations, check the tissue weight and set about replacing parts with lighter examples. The advice on motor selection was most welcome.

Don, I was aware of your article and tried to understand and follow the guidelines. But, some things only sink-in with experience. Feel free to ignore the following, but I would like to pick your brains about propellers...

So, is there a practical limit to the propeller diameter? I understand that more diameter should give more efficiency but be more prone to damage and may require a thicker motor (assuming similar blade chord). So, I guess that a larger propeller should have a lower blade chord (less solidity) to prevent the motor thickness increasing too much? I guess that the pitch is matched to the flying speed or can I use a higher pitch to get a longer motor run. The limit may be blade stall at high turns? Of coarse, the choice of propeller is intrinsically linked to the motor used. A larger propeller may be more destabilising in pitch and yaw as well (have to be careful about this statement when varying other parameters as well). Was there a reason why the Hosler Fury was used with a larger propeller than a Cassutt?

I am very tempted by the Fury as a next model. I have plenty of red tissue left.

I was even wondering about the Facetmobile. It certainly has lots of wing area and could theoretically lift allot of rubber and have a low sink speed. But I suspect that the wing would be too compromised to have any advantage over conventional models.

The important thing is to make the most of the half dozen indoor flying sessions over the winter and to try something new in each one.

Thanks again for the feedback!


Title: Re: Cassutt NoCal
Post by: lincoln on November 29, 2013, 01:52:51 AM
Don's the expert here. However, I can tell you that I COULD NOT trim my nocal to fly well until I cut down the prop quite a bit. After that, it was quite successful. It's the only one I ever built, but it has a number of canones to its credit. Longest flight was over 4 minutes under what I think was a 35 or 40 foot ceiling. And I think I got about 3:30 under an 18 foot ceiling that was very clean.

I could be wrong, but I suspect that a Facetmobile or Hosler Fury only makes sense for a weight limit event. In that case, I wonder if a biplane with a large gap and a low aspect ratio might be better. You'd have to find some way to get around the motor loading problem, but perhaps it would be worth it. Certainly in pennyplane the biplanes have done very well. You may find the following thread amusing:
http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=13645.0
How about the Graham White shown in the above thread? And if you're really good at building ghost ships, how about the Caproni Pensuti?
http://i275.photobucket.com/albums/jj311/aquilius-files/Rumpelkiste/Caproni-Pensuti_Triplan.jpg


Title: Re: Cassutt NoCal
Post by: dslusarc on November 29, 2013, 03:58:51 PM
The largest prop I have ever run on a nocal was 12" diameter. Larger than that does not seem to work as the model can roll over from high launch torque, it may be OK for lower sites but at the time we were really fine tuning our models for Johnson city which was ~116 feet high so 12" worked best. In general I go between 10-12" diameter depending on the subject and weight class but a bigger model like a Cassut or Hosler will handle the larger prop so we run 12" prop and about 20" pitch. My dad always flew larger props than I did on the Cassutt and he always edged me out as well. When we went to the Hosler he went right to a 12" prop and I tried a 10" prop with smaller blade area thinking I could fly on a long thin loop. What I found was my dad was flying on nearly the same size rubber I was but he was doing much more time. I was flying ~.105" rubber and he was flying ~.110-.115 but doing 6 minutes and I was doing 4 and I was climbing up higher and coming down faster, he was just cruising around during his flights so I went to a 12" prop and my times jump up to his.

The reason why the Cassutt plan has a small prop is because that was published early on during our Nocal development. Back then nocals really did not fly over 5 minutes. 3-4 was normal and the foam coffee prop is what my dad used on his Lacey M-10 nocal to break 5 minutes back in 1985 (which we think was the first 5 minute indoor nocal) and that is why the plan has that prop mentioned as that is what he was using initially at the time. It was later that we started making bigger props and then started getting the higher flight times. 5-6 minutes became the norm then with more refinement we went past 7 and then on to pushing 8.   

If you plan on building a Hosler I will tell you that keeping track of the weight is critical as there is so much tissue paper on that model. Since FAC banned gampi tissue making a Hosler to 6.0 gram weight with Esaki tissue is tough. But I will tell you even a 7 gram Hosler will still do 6.5 minutes in about 50 feet of ceiling. The covering method can add lots of weight. I use 3M 77 spray adhesive for my nocals. Too much spray and you add dead weight, too little and the tissue can come off over time. Another alternative which my dad is fond of is white glue and water for tissue adhesion. That is light but will require the use of wax paper and weights to hold parts down when drying. I prefer the spray adhesive as it is fast then if it comes loose in a spot months later, then I just reattach the loose spot with the white glue water mixture (about a 50/50 mixture). Also with spray adhesive once the part is covered and cut out, then I carefully run my finger over all the areas the tissues touches to get the best adhesion to the wood. 

In regards to flying wing nocals like a Facetmobile, they are hard to trim as a flying wing really wants to fly at one speed all the time, so with higher torque they tend to stall when climbing then they may cruise OK but then as power comes off they tend to dive near the end. The net result is a model that does not fly as long as a conventional model as for a large portion of the flight the model is slightly out of trim, at least that was my experience.  I am sure there is one flying wing type where the down thrust is just right etc that it may work out just fine. In regards to a biplane nocal, I only tried on and it did not fly longer than my regular model at the time which was the Cassutt. The biplanes suffered from a flight trim issue I once encountered on an experimental Pennyplane biplane. Most full size planes have the horizontal stabilizer located between the upper and lower wing. When the nose comes up the stab would get blanketed by the lower wing. Indoor pennyplane biplanes do not have this issue as both wings are above the motorstick and the stab below. So if you want to try a biplane nocal, I would take that into consideration. The result I had was the model needed to fly a very forward CG to keep the model flying and try to prevent the nose coming up at all, it had to fly flat all the time, not nose up like an indoor model. Once the nose came up the stab would get blanketed then the model would mush around in a nose high stall like it was very tail heavy. Please don't take my comments as telling you not to try it, I am just saying be prepared for failure but that also can be part of the fun! My dad and I tried many nocals over the years including a Dornier Do-335 with twin motors!


Title: Re: Cassutt NoCal
Post by: piecost on November 29, 2013, 06:22:41 PM
Don,

Thanks again for your generosity of sharing hard won experience. It will give me plenty more to digest. I am using NoCal models as a tool to learn more about rubber, propellers, building and trimming so am trying to absorb as much information as I can.

I just got back from a local school sports hall where some R/C fliers invited a friend and I to attend. I was expecting it to not be suitable, but had some nice short flights.  We had 5 minutes between the R/C slots and it was a real discipline to have the model ready in time. The removable undercarrage was problematic and a better solution should be found. The R/C flyers were very impressed and at least one may build a NoCal over Christmas!

Using 0.110" rubber with a 60% stint had the model up in the 30' ceiling very nicely. Strangely, I had no trim problems even though I was rushed. The model hit a roof beam with my original aft centre of gravity position (15mm or so aft of the plan position) and recovered fine. It seemed that the more aft position is more sensitive to tail setting but was ok in flight. With 1.2g of nose weight to bring the CG to the position on the plan it recovered within a planes length upon hitting a beam. So, it seemed that the CG position is very conservative on the plan. But, perhaps it really helps when at high torque. My other NoCal model tended to be sensitive to any motor bunching near the back of the motor caused trim problems. So, the more forward CG is the way to go.

Now, my friend has just made a Do335 with a single front propeller. The rear one is modeled as feathered. Do you have any pictures of your example? I would love to show him. But, it might upset him a little to see that it has been done before.

Oh, by the way - Happy Thanksgiving for yesterday.


Title: Re: Cassutt NoCal
Post by: dslusarc on November 29, 2013, 07:47:41 PM
If it is bumping and recovering then your CG is pretty. Too aft CG nocals when bumping the ceiling will get into a mush and and possibly tailslide or start to torque roll. When the CG is good it will bump, drop the nose and keep on going. If you have a ceiling with lots of stuff to hit then running the CG forward to get the quick recovery from bumping is beneficial. The motor bunching at the rear issue is helped somewhat on this model as the the rubber is pretty much balanced over the CG, so equal rubber in front and in rear of the CG and actually the slightly aft cg as it unwinds can help the model cruise a little better on the descent. Just watch for stalling as the model gets lower to the ground to see if it is bunching too much. Sounds like the model is going pretty good for you and good luck at your upcoming contest. I am interested to know how you do and so is my dad. At Thanksgiving yesterday I showed my dad your photos and he said the model looked good and the first thing he asked was how long did it fly so he wants me to keep him informed.

I know we have a photo of the Do-335 somewhere, if I find one I will post it. I know we tried all kinds of combinations and with both props running it wanted to fly in a straight line. I do not think his model went over 5 minutes with both props powered. It was built to the 6.2 gram weight rule and we spent a good amount of time trying to get it to work well and trying big props, small props, high pitch, low pitch and I think it flew best with one prop on the nose. It seemed the rear prop efficiency was greatly affected by the front props wake.


Title: Re: Cassutt NoCal
Post by: lincoln on November 29, 2013, 09:10:12 PM
I don't know what's different, but Richard Ramney seems to have no problems trimming his nocal biplane:
http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=15207.0
Of course, he isn't getting as much time, either. Maybe with his smaller amount of rubber there is less c.g. shift? Or maybe he's flying faster?

--------
My nocal is a Wildcat. It sometimes has a strange habit of falling sideways for, say, 10 feet, after hitting the ceiling. This can sometimes allow backing off fewer turns. I've had flights where it fell the ten feet, then climbed back up, touched, and fell again. Of course I've also had flights where it fell too far.


Title: Re: Cassutt NoCal
Post by: dslusarc on November 29, 2013, 10:26:17 PM
That bipe is a nice looking nocal. I do see the flights are short so hard to say how it will behave on longer flights and the required rubber and torque.  The key is I found on no cal bipes was they had to fly rather flat to not blanket the stab and duration suffered due to that. It would be interesting to see how it bumps around a ceiling and how it acts on longer flights say at least 3-4 minutes. As I said I am going by my own person experience from the past. I am not saying it wont work or fly at all, my Farman Sport Nocal bipe flew about 4 minutes but that was less than the 6 minute Cassut in the same ceiling so was abandoned. When flying wing A-6 was flown years ago they had the stab area allowed in the wing area so 45 sq inches instead of 30 sq inches but the A-6 wings flew about 2 minutes less than the regular looking A-6 so it worked but was not an ideal configuration. I personally do not think a bipe nocal for indoor with max duration as the ultimate goal is the optimal configuration (based on my past experience) unless a very unique aircraft is found. The only other biplane nocal I recall seeing over the years was a racer called the Chuparosa but the Cassut would beat it. It may be that we threw the towel in too early on the bipes we tried but the lack of success and poor performance combined with difficulty to trim compared to the Cassut and then combined with how they were hard to hook up as most bipes have struts so hooking up the rubber was a pain so we abandoned them. Maybe there is some crazy looking ultralight biplane that may be a Hosler killer out there but so far have not found one. There may be more info now that the internet is around, back then my resources were limited to my dads personal book collection and the aviation section at the local library. I do know there were lots of unique one of a kind ultralights in the early 80s. I personally would love a Hosler beater as I am not really a Hosler Fury fan but it does fly well and in Nocal the clock wins not beauty. 


Title: Re: Cassutt NoCal
Post by: dslusarc on November 30, 2013, 12:04:52 AM
To elaborate a little further in regards to my Farman Sport biplane nocal. It was possible to trim the model but say I get it trimmed for a good cruise, then when turns and torque were added the model would stall and mush as I previously described. So the model would not climb out. Then if you retrimmed to get it to climb ok, then the model flew too flat in the cruise and the duration would suffer. It was always a constant battle with the plane you either got good climb and poor descent, good cruise but no climb, you never got good climb, good cruise and good descent which what you need. So I guess I should have defined what I mean by the model being successful or not. Yes it flew but not to expectation. The best trim on the Farman as far as flight time was when the cruise and descent was good, then I ran into the blanketing issue on climbout or when bumping the ceiling, the nose would come up then you could see it happen, it would go into a mush/deep stall and come down to the ground as if it was a leaf. That behavior was identical to the experimental biplane penny plane I had made. That pennyplane had the upper wing 4" above the stick and the lower wing about 4" below and the stab in the middle of the two of them. As long as the nose was down it was OK, but as soon as it came up the same thing, deep stall/mush as if extremely tail heavy. I had the CG about 40% of the wing chord which is crazy forward for a pennyplane biplane so we knew something funny was going on aerodynamically.   


Title: Re: Cassutt NoCal
Post by: lincoln on November 30, 2013, 12:49:08 AM
Seems like a really long biplane would be needed so that the downwash is weaker before it gets to the tail. Or maybe just one with a long nose so the downthrust was more effective? Assuming you don't get any ceiling hits after the torque goes down, I guess. A tandem with a lot of stagger might work and some decalage between the two wings might work, I suppose, although perhaps it wouldn't be efficient enough.

I have seen a V-173 nocal fly quite well. I don't think it was especially light, though. Maybe if the props, nearly at the wing tips, don't count as part of the span, that might be the way to go. Apparently the real thing flew as well as a plane with much more span, because those big props, rotating outwards, weakened the tip vortex. I imagine one could use a long prop shaft with a semicircular curve and a prop at each end to keep things synchronized.  The one I saw didn't seem to need it, however.

A flying wing might be ok if the thrustline was quite high and the c.g. was pushed back as far as practical.  That's what I did with my A6 flying wing. Can't think of a full scale airplane like that at the moment, though.


Title: Re: Cassutt NoCal
Post by: dslusarc on November 30, 2013, 07:53:51 AM
I have seen a V173 as well in nocal form but not one that would come close to breaking 5 minutes. Farman "post card"s have been made but they have very short noses and have CG issues due to that. Lacey, Fike, Bonzo, Chambermaid, various Farmans over the years, Demoiselles, The only one I think I have never seen which may be interesting is the Farman F1020.   


Title: Re: Cassutt NoCal
Post by: piecost on December 13, 2013, 06:23:28 PM
A progress update...

I added the racing number to the fuselage. It is inkjet printed onto white Esaki tissue set in the panel of red tissue. It really looks pretty!

I improved the undercarrage retention, but it is not perfect yet. I kept jettisoning the gear in flight!  I plan to build a lighter gear and may end up gluing them on perminantly. Frustratingly I broke the rear fuselage with my chair.  I repaired the fin but did not notice a crack in the boom until I was at the flying session. In desperation I added a square of aluminium tape! that must weigh about 0.05g and will prove impossible to remove. But, I got to fly.

I completed a 12" propeller with 20" pitch as recommended by Don. The blade is a minimum induced loss shape with a chord of 1" at 75% radius. It was formed round a 3" diameter thermos flask at 15º. It is rather twisted and cambered and I should try to find a 4" cylinder.

I flew the model tonight and found that it barely climbed - even with 0.145" rubber. But, it was nice and stable and needed no down/side thrust changes from the 9" propeller. So I was encouraged.

Weight schedule:

Airframe + Propeller + Nose weight = 7.15
40% Rubber: 0.145" x 200% prop to Stint x 40% Prop to rear peg = 1.86g
60% Stint to represent 0.140" 200% rubber to rear hook = 2.69g

So, does the requirement for 0.150 or more rubber sound reasonable? Or could I reduce the propeller chord? Could the overtwist and camber be requiring more torque? As usual; any ideas are welcome!


Title: Re: Cassutt NoCal
Post by: piecost on December 13, 2013, 06:24:19 PM
The 12" propeller compared to the 9" propeller shown on the plan


Title: Re: Cassutt NoCal
Post by: dslusarc on December 13, 2013, 08:36:38 PM
We form our props on a 5" diameter can at about 15 degree angle. I think the can you used is too small diameter. We then set the 20" pitch at the 75% radius location. We have never gone over about .130" rubber.


Title: Re: Cassutt NoCal
Post by: piecost on December 13, 2013, 09:21:31 PM
Thanks Don


Title: Re: Cassutt NoCal
Post by: dslusarc on December 14, 2013, 08:51:51 PM
Also the bigger props tend to run shorter heavier loops. How long is the loop of rubber you are using and how many turns are you putting into it?


Title: Re: Cassutt NoCal
Post by: piecost on December 14, 2013, 09:27:08 PM
Don,

I was running with a stint which measures 60% from the prop to rear hook. So, a 40% motor - but with twice the length of the available distance between stint and prop. If that makes sense. I was going up to about 700 turns - as much as I dared. This stint is scaled to the 50ft ceiling at Boulby where the nats are held.

In a mad panic this evening I finally located a suitable cylinder; a decorative galvanised bucket containing a candle. This was removed and the blades reformed.  They look much more sensibly twisted, but a little scorched form the oven. Now for a few hours sleep before the event. I will, hopefully, report back that the model needs less rubber.


Title: Re: Cassutt NoCal
Post by: piecost on December 14, 2013, 09:49:44 PM
To be clearer; I have a stint 7.3" long and a motor about 9.7" long


Title: Re: Cassutt NoCal
Post by: dslusarc on December 14, 2013, 10:41:53 PM
9.7"/.4= 24" full motor length. That may be a bit long for a 12" prop. You may want to try for a loop in the 18-20" range. I just went and looked at my Nocal motors motors and they are in the 18-21" length range. So I would shorten up the loop. The bigger prop will spin a lower RPM as well so the long loop is not needed as you do for a small prop spinning faster. Good Luck!


Title: Re: Cassutt NoCal
Post by: piecost on December 15, 2013, 02:49:25 PM
Find attached a picture from today. Notice the scorched propeller blades! I tissue covered the root to prevent splitting and the paper browned in the oven.

The model, again, failed to climb and didn't get halfway up the 24' high ceiling, even with 0.160" rubber (a 8.25" loop)!. It took about a minute to climb to 10-12' and descend again. There was not much of a difference in flight between 0.120" and 0.160" rubber. The obvious culprit I can think of is the side/down thrust. It has large amounts of side thrust and little down. But, the flight pattern did not show obvious signs of too much down. I plan to add the recommended rudder deflection and see if I can reduce the thrustline angle. I have had a bright idea to measure the down and side thrust - so may be able to more accurately set it.

I plan to give the model an overhaul; a lighter undercarrage and perhaps the original wood tail. It just seemed very odd; the propeller simple soaked up the increased rubber torque without any large increase in height. I was winding up to max turns and broke at least one motor in doing so!

I had great fun and the model attracts a fair amount of attention.


Title: Re: Cassutt NoCal
Post by: dslusarc on December 15, 2013, 03:55:18 PM
One thing to look for if you have lots of side thrust or down thrust is the prop shaft binding in the thrust bearing with a motor hooked up to it. It may spin freely with no motor but bind with a motor when lots of side thrust present. Have you tried different batches of rubber? I have a batch of super sport that is horrible. Also when you went to a short loop (8" ) did you lighter up the partial stick to match the weight of the lighter loop?   


Title: Re: Cassutt NoCal
Post by: dslusarc on December 15, 2013, 04:39:19 PM
It may be at the higher weight with the ballast a 12" prop maybe too much or maybe there is too much blade area. I just went back and looked up my Cassutt prop in my building notes. My prop was actually a 10.5" x 17" pitch. That is the prop I flew over 7 minutes with. I know my dad was running 12", I will have to talk to him to get the exact pitch he was running (I think he still has his notes). I know he first started with a limited Pennyplane prop when he tried 12" but he also did trim off some blade area as well. 


Title: Re: Cassutt NoCal
Post by: piecost on December 16, 2013, 06:37:35 PM
Thanks for your further research, I'll certainly be interested to learn more and am primed to construct more propellers. My money is on the binding issue. I hope to trim using the rudder and reduce the side-thrust (I fly in halls just wider that the length of a badminton court). That must help, even forgetting the binding - the thrust wasted to the side is considerable.

I also need to recheck my rubber testing calcs. I will check my integration against Martyn Pressnall's example (article in a March 2003 Aeromodeller) - at the moment I have a specific energy of 1400ft - Pressnall had 1965ft for Tan II. So, mine could be low - but I do not have enough experience to know if my result is poor for Super Sport rubber.


Title: Re: Cassutt NoCal
Post by: rick121x on December 17, 2013, 01:55:05 AM
The torque required to produce thrust is an exponential function of the propeller diameter, and so diameter changes make large changes in torque required ... of course there are many other variables... you might try reducing the pitch. It is only intuitive, but I believe the large prop diameter is the main problem.

Examples: Locale - a 33 foot ceiling gym. My 5 gram Zero climbs strongly on 1/16 super sport with a 6 3/4 in. prop.  I believe that a slightly larger prop might improve the duration and with a slower climb rate. My penny plane, at 3.2 grams, has a very slow climb rate with a 12 inch prop and 1/16 super sport. (I have been using 1.25  pitch diameter ratio.)

I have found that with no-cals, beginning with 3 degrees decalage is a good start. If the plane flies a bit fast, then the angle is probably too little. My current method is to begin with a 46% CG, then adjusting the decalage for a good glide. I do this without prop and rubber using clay balance weight. Then, knowing that the plane is trimmed for fairly efficient flight dynamics, I replace the prop and rubber and rebalance at that 46% location. Then use the thrust angle and rudder setting to achieve the desired power pattern. Yes I know the longitudinal trim changes with rudder settings, but that's a manageable concern.  :D

Finally, all the adjustments are open for fine changes when searching for that optimum flight. My opinion is that the basic aerodynamics should be near correct at the get-go.

Good luck, Richard



Title: Re: Cassutt NoCal
Post by: piecost on December 17, 2013, 05:16:00 PM
Thanks Richard for the advice. I am primed to make some more propellers, but firstly I measured the side thrust as 17º wow! I have changed it to 3º as per the plan, and am adding the rudder deflection and tail tilt. I am pretty confident that this will do the trick.

By the way; my NoCal Prairie Bird is still flying well


Title: Re: Cassutt NoCal
Post by: rick121x on December 17, 2013, 07:27:01 PM
.......
By the way; my NoCal Prairie Bird is still flying well

That makes me very happy.  :)  I loved seeing the pics of your very nice workmanship on your Prairie Bird.

And I kind of agree about going back to basics on your Cassutt, I have had to do that several times on these tickle-ish little indoor planes.


Title: Re: Cassutt NoCal
Post by: piecost on December 17, 2013, 08:30:06 PM
Richard,

That model reminds me of Cinderella; it is very much neglected as I play with newer, more fancy models. I have come a long way since that first NoCal - I now use thin Ambroid and my glue joints are lighter and stronger, propeller spars are elegant tapered objects rather than crude fence posts and the tissue stays stuck to the wing. If time allows, I would like to make another Praire Bird and do it more justice. It just seemed to work without much trimming and gave the best flying fun to building time.

Don mentioned tail tilt to help the right turn on the Cassutt (Right Hand tip low - I assume) Any suggestions as to a sensible amount? The NoCal Praire-Bird uses 1/4inch = about 2º. I was going to use a similar angle - or eyeball it and use as much as I can before it looks like "too much". Now I have reduced the right thrust to about 3º I figure the model will need all the help it can get.


Title: Re: Cassutt NoCal
Post by: dslusarc on December 17, 2013, 11:14:53 PM
When the model is at rest the stab tilt is about half the dihedral angle of the wing. As far as side thrust, if you go over about 5 degrees than something else needs to be adjusted.


Title: Re: Cassutt NoCal
Post by: Hepcat on December 18, 2013, 07:43:36 AM
In response to reply #28 about right hand turn.

This is another occasion when I wish, for clarity, we used port and starboard!  If sitting in the 'Cassut', facing forward and the nose of the aeroplane was moving in the direction of your right hand (to starboard) then you would be in a right turn.  If you wish the tailplane to assist in this right turn then I think (unless the CG is very far forward) the starboard tip would need to be raised. I'm sure that is right!  Right?  ;)

John


Title: Re: Cassutt NoCal
Post by: piecost on December 18, 2013, 01:11:56 PM
John, yes it is lax of me to not use port and starboard. Thinking about it; I am not sure which way the tail should be tilted - I guess it depends whether it is producing lift or download. I assume that on duration types it is certain that the tailplane is producing lift (aft CG with large area & positive cambered tailplane) then starboard tip up causes a yaw to Starboard. On a model with forward CG, a smaller non-cambered tailplane and the tail is definitely producing a down load (i.e. the Cassutt) the port tip up causes a yaw to starboard. I think that is it...

As an aside; I am still enjoying prop picker - see attached for the Cassutt.


Title: Re: Cassutt NoCal
Post by: OZPAF on December 18, 2013, 05:14:56 PM
The detailed trimming advice in this thread is very interesting - thanks fellows.
Re your tail tilt query - I would be surprised if your CG was far enough forward for your Tail to be carrying a significant degree of down load while trimmed for endurance.
I agree with John - Starboard tail tip high for a turn to starboard- er right.
Good luck with it.
John


Title: Re: Cassutt NoCal
Post by: dslusarc on December 18, 2013, 06:39:14 PM
The model will turn the direction of the high stab side. Another easy way to remember is to make the stab level then see how the wing is banking. The model will turn to the low wing as if it was in a banked turn. 


Title: Re: Cassutt NoCal
Post by: Hepcat on December 19, 2013, 05:20:08 PM
Response to reply #31

Piecost,
The phrase “picking up the ball and running with it” comes to mind and I am delighted to see that is what you are doing.  In the relatively short time since I sent ‘Prop Picker’ to you, you have obviously taken it apart and put it together again with a lot of new features.

I should be very interested to hear the sort of things you have been doing and, just as important, any ‘no,nos’ and downright errors in my original work.

John


Title: Re: Cassutt NoCal
Post by: piecost on December 23, 2013, 01:44:00 PM
Hello John,

I have attempted to PM you. Please let me know if you haven't received it and I'll try again

Thanks


Title: Re: Cassutt NoCal
Post by: dslusarc on December 29, 2013, 08:40:13 PM
Here is a prop that should work well for you. This is a copy of the prop blade I used on my 6.2 gr Hosler Fury for 116 foot ceiling height. The prop is 10" diameter and 15" pitch and was formed on a 5" diameter can.  When I print the image I select "print actual size" and it comes out correct size. I drew a 5" line so you can make sure the blade is printed to the correct scale just to be sure. 

Don


Title: Re: Cassutt NoCal
Post by: Indoorflyer on December 29, 2013, 11:28:16 PM
Wow, that's very cool Don; thanks for sharing your prop template.  I've been messing around with a Wittman Tailwind nocal, and since I couldn't make up my mind to model a W-8 or a W-10, I'm doing both!  Your prop layout may just be the ticket for a good starting point, propulsion-wise...


Title: Re: Cassutt NoCal
Post by: dslusarc on December 30, 2013, 12:21:23 AM
Yes it is a good general prop template for nocals. For light nocal, (like my Cardinal at 2 grams) I use a similar shape but with a narrower chord.

Don


Title: Re: Cassutt NoCal
Post by: piecost on January 03, 2014, 11:08:55 PM
Don,

Thanks for supplying details of the Hossler propeller. I may or may-not build it; but either way I find the information very useful. I am starting to compile a database of propeller geometry to assist me in my own future propeller designs. I keep record of diameter, pitch and will calculate the solidity and camber. If you can recall a typical rubber motor dimensions then I will be most grateful as I can enter the details into Hepcats prop-picker spreadsheet. This aids matching the propeller and rubber characteristics and I am always on the lookout for details of successful models. Such theoretic tools are great providing that the assumptions are sensible and details of well designed models featured on this forum help to refine those inputs.

My first own design NoCal prop blades looked like Pringles - they were even the right shape and colour

I had a little time over the holidays to look into the magic behind the forming propeller blades round a cylinder at 15º. I created a spreadsheet calculation for my 12" propeller blades with my original 4" diameter and later 5" forms. The effect on camber is more marked than that of twist. The 4" cylinder gave a camber of 10%, the 5" gave 6.5%. Can you tell me what a reasonable value might be?

I received a Pennyplane kit from Father Christmas which has nice pre-built propeller with around 10% camber also. This seems rather high to me. It was very similar to my 12" Cassutt propeller, but perhaps more paddly than my Minimum Induced Loss shape. I understand that these are rather out of fashion.

I recently aquired a copy of Making Scale Model Airplanes Fly by W.F. McCombs. This contains a graph of Blade tilt angle versus can diameter/prop diameter. For P/D>1.3 this suggests a 4" diameter form. Perhaps scale models tend to have smaller, more highly loaded propellers requiring more camber.

Finally, I had a terrible flying session tonight, combined with a revelation! So it was a most useful evening.

I flew the Cassutt with side and down thrust as per plan, combined with tail tilt. I installed a 0.120" motor but  I hadn't properly matched the stint mass and so the pitch trim was way out. The model turned left rather than right and often steeply hit the floor and broke off a propeller blade - luckily not splitting the wood. In desperation I added trim tabs on the wing and rudder.

Then I noticed...

I had given the model 1/8" left rudder rather than right! No wonder it needed 17º side thrust to turn right! Whilst anoyed at making a stupid error I am pleased that an explanation has been found for the models behaviour. I should be able to squeeze in another short evening session, to test the fix, before the next all-day event. I must make that lighter undercarrage...


Title: Re: Cassutt NoCal
Post by: dslusarc on January 03, 2014, 11:51:22 PM
That prop on a .110" x 20" loop with 2100 turns I had a 5:34 flight in a 50 foot ceiling building. By the way what is that software/spreadsheet are using to plot Larrabee blade shapes? I have been looking all around the net and can not find anything like that.

Don


Title: Re: Cassutt NoCal
Post by: frash on January 04, 2014, 10:34:41 AM
Piecost,

There are a couple of "Bucket Prop" spreadsheets posted in the Builders' Plan Gallery, Airfoils & Propellers. They might help you avoid extreme camber by using larger diameter or more highly tapered conical forms. Alternatively, maybe you will improve the spreadsheets.

Fred Rash


Title: Re: Cassutt NoCal
Post by: piecost on January 05, 2014, 06:01:57 PM
Fred,

Thanks, I'll have a look at these. It will be interesting to see if I am on the right track.


Title: Re: Cassutt NoCal
Post by: OZPAF on January 06, 2014, 02:13:23 AM
Piecost,
Here is a copy of Fred's read me file with an earlier and later version of the spreadsheet in the next post.
I had saved these some time back.
John


Title: Re: Cassutt NoCal
Post by: OZPAF on January 06, 2014, 02:20:59 AM
Spreadsheets renamed with png file name. Remove file name and add dot before xls to use.
John


Title: Re: Cassutt NoCal
Post by: frash on January 06, 2014, 10:22:33 AM
OZPAF,

Thanks. Your scheme is a cool way to bypass some of our downloading "protections". Sometimes when others have had problems, I have emailed .fhr files to them. Nonsense to most computers, but my initials. Sent with note to rename to .xls or .exe as needed. I was unaware of your scheme.

Your way worked fine for me for the newer version 78, but I had difficulty on the older version 72. Is it still working for other people? My newer Excel does not handle it well? Does it need revision?

Solver is great when you want to optimize several variables at one time.

Fred Rash


Title: Re: Cassutt NoCal
Post by: OZPAF on January 06, 2014, 04:30:16 PM
Fred - well thank you for your info and efforts in the first place. I have run both spreadsheets on my computer but I am still running Windows XP and office 2003!
The optimiser is a neat addition.
John


Title: Re: Cassutt NoCal
Post by: piecost on January 10, 2014, 10:39:14 PM
John & Fred,

Thanks for the information about the bucket propeller spreadsheet. It looks very useful. I will have to compare the results with mine.

I had some success tonight; with the corrected rudder deflection: 3mm right rudder, tail tilt, 4º right thrust and 2.4º down thrust. I used Dons recommended motor of 19.5" loop (full motor length) scaled to a 40% motor (60% stint) of 0.130". The model was still underpowered but turned tightly enough to be safe within a badminton court and the top of the dome where the nationals are flown. The flight pattern was lovely, but a little lacking in stability with the CG at 45% (50mm aft of the wing leading edge). A lighter tail would help. I am confident that I can now worry less about trim, really start getting the motor sorted and get into the rafters.



Title: Re: Cassutt NoCal
Post by: piecost on January 26, 2014, 04:12:58 PM
I finally constructed a lighter undercarrage and a new canopy. The new undercarrage is removable, as before (but hardly nessesary) but weighs 0.26g relative to 0.46g. The new canopy 0.08g compared to 0.23g for the original. It is from lighter, thinner wood and the edge where it meets the wing is unsupported. I am very pleased and do not expect to make such an improvement again for a ling time. I attach a picture of the new and old canopies.

I had a mixed session tonight. I made a 12" diameter (20" pitch) propeller with 20% less chord than my previous example. The model still needed 3/16 rubber to climb! So, that didn't really help. I had some nice flights and started to use my torque meter to judge how close to get to the ceiling. Unfortunately, the model hit a basketball hoop, vertical dived into the ground and broke off the nose of the motor tube. I will take advantage of the repair to remove the tube and to move the rear hook forward, as recommended. This should remove the need for noseweight.

Don, When you mention flight times; is that for 2 flights combined?

I am continuing to test my rubber in comparison with randomly bought stuff to see if I have a duff batch. I still cannot understand why I am needing much thicker rubber than recommended.



Title: Re: Cassutt NoCal
Post by: dslusarc on January 26, 2014, 08:53:14 PM
Flight times are for single flights. I am thinking you have poor rubber. Once at a flying session years ago a student had a model that would not do over 1 minute. I put a loop of my rubber on it and with the same turns it did over 2 minutes.


Title: Re: Cassutt NoCal
Post by: piecost on January 27, 2014, 12:37:39 PM
Thanks Don, I'll look into the rubber further.


Title: Re: Cassutt NoCal
Post by: piecost on April 28, 2014, 07:03:33 PM

It has been a while since I last posted since the model hit a stowed basketball hoop and vertically dived into the ground in January, breaking off the propeller bracket. I took the opportunity to overhaul the model and lighten it to the 6.0g BMFA rules.

A new motor tube and boom were constructed and wing and tailplane mounting tubes fixed to perfectly align with the wing and tailplane posts. The rear motor hook was moved forward 2 inches to the wing trailing edge, giving a 10.4" propeller bracket to peg length. This enabled me to remove the nosweight. The wing was lighted by removing one of the centre ribs and fettling the leading and trailing edges. I glued the tissue back onto the wing ribs with thinned PVA where the Spraymount had failed, this lead to slight wrinkles at the trailing edge. This doesn't seem to affect the flight performance so I will not recover the wing.

The weights for the overhauled model are:

Rebuilt & Overhauled Cassutt 21 April 2014 to 6.0g BMFA rules:

Nose Weight                                        0.00g
Fuselage                                              2.47g 
Undercarrage  (new)                           0.26g
Tailplane     (new)                               0.40g
Wing (lightened)                                 1.93g
Canopy  (new)                                    0.08g
Propeller 10" x 15"                             0.86g
Stint 50% for 0.110" x 10" Loop        1.50g
Rubber:  0.110" x 10" Loop               1.50g
AUW                                                     9.06g
CG      48mm aft of LE, 1mm aft of plan  41%  chord               
Airframe                                              6.01g   Perfect!                 

All Up Weight                                      9.01g

Right Thrust              4.0º
Down Thrust            2.5º

Before the crash I was experimenting with 12" propellers and found that I needed 3/16" motors to get a climb. I built new propellers with less chord and with less pitch but didn't have time to try them all.

Don speculated that my rubbber may be at fault and also gave details of a propeller design that he had success with (reply #36). The blade planform was given for a 10" x 15" propeller. I constructed this and was kindly given some Oct 97 Tan II rubber to try. Since I fly under a 25' ceiling I used a 50% motor and stint to simulate the 50' ceiling of the Nationals venue. The motor was 0.110" wide and simulated length of 20" as Don recommended (reply #40).

I only managed a few flights with the model under a 25' ceiling but the best was:

Wind to 990 turns and 0.82 oz.in torque
back-off to 910 turns and 0.51 oz.in torque
Landing turns 240 turns  and 0.24oz.in torque

The model performed a stally initial climb and took about 50 seconds to reach the ceiling before landing at 2m15s. This smashes my previous best of 1m30 by a country mile. I notice that the model landed with rather a lot of turns left, but I was not winding the motor to anywhere near the maximum and should be able to get more out of it. I might try winding to higher turns and backing off to the same torque.

I quickly tried an identical motor made from my Super-Sport, but the trim was off and I didn't manage a comparison flight. So, I cannot really tell if the rubber is the culprit or the propeller. I believe that my 12" propellers required such thick motors that the total model weights were 11g to 12g. My model is now around 9g total and flys more slowly for it.

So, now I am happy that the model is in the same ball park as Don's.

Find attached a picture showing the new rear motor hook position




Title: Re: Cassutt NoCal
Post by: piecost on April 28, 2014, 07:06:03 PM
Attempt to attach picture


Title: Re: Cassutt NoCal
Post by: piecost on June 30, 2014, 08:13:33 PM
I entered the Cassutt in the UK nationals held at Boubly Potash mine on 20 June 2014. The usual NoCal rules applied with a minimum weight of 6.0g

I am pleased to say that the model won the completion!

This is my first win at such an event and I am very pleased with my progress since the debacle of my MB5 last year.

The site is a wooden structure that measures 150ft at the base, by approximately 65ft high with bracing wires attaching to a central boss 50ft from the floor. A roofed single storey partition contains a gym and forms one side of a 5 a-side football pitch and a 4ft high partition along the other side of the pitch divides the floor into a pit area for the model flyers. The roof of the gym is protected by a sloping net that forms a hazard to model planes.

I had regularly practiced under a 25ft ceiling with 50% motors, of similar size as recommended by Don (10.25” loop of 0.111” wide, 1.5g) and had recorded a best time of 2m15s. So, I was hoping for double that time in the dome.

My flight used the same partial motor as in practice and found the familiar pitch trim problems as I had in practice. The adjustment of the down-thrust and elevator was very sensitive and it proved difficult to get the model to climb without stalling or being totally under elevated. I ended up putting a 0.3mm shim on the aluminium propeller bracket as I could not make fine enough adjustments when using pliers to bend the propeller bracket.

The elevator was adjusted in 0.15mm increments (about 0.1º) since the impact on the flight path was so great! While this may indicate that the CG is rather aft;  I had confirmed that the CG was with 1mm of the plan and the model recovered from hitting obstacles quickly. Perhaps the tailplane was flexing and causing trim problems.

I changed to a full motor; a 20.5” loop of Tan Jan 2014 Super-Sport weighing 3.0g. I managed a 4m23s flight after hitting the wires a couple of times and stalling at the start of the descent. The propeller locked at 5ft altitude due to bunching round the propeller Z-hook.

I next put in my first competition flight using a fresh motor and achieve 4m33s despite a mid-air with a LPP and flying through someone’s legs! A memorable flight! I had split the delicate tail boom in attaching the motor to the fiddly rear hook – up till now I had only attached a wire stint since I had used partial motors. The flight time was near double that obtained using the 50% motor in practice sessions at a 25ft high site and so I was very happy.

The second competition flight was not as good; the model performed low, tight circuits without climbing for the first 30 seconds and only reached halfway up to the wires. This flight had a fresh motor with more turns and less torque so I don’t know what caused this. The top of climb was stally, as was the descent. The flight time for this disappointing flight was 3m48s.

But, this was enough to put me in the lead, the nearest model achieving two flights of 3m09s.

Although I had a comfortable lead I decided to try and beat my best time. A fresh motor with slightly less turns and torque gave the perfect climb, without a hint of stalling. But, the model brushed the wires and performed a perfect landing on the boss in the middle of the dome. It stayed there until the end of the competition, until dislodged by a balloon when it performed the perfect descent. That flight would have been cracking…

This was very frustrating, but my model kept its comfortable lead throughout the rest of the day.

So, I was very happy with the result but was not impressed with my hang-up and that I didn’t achieve many competition flights. I was hoping to achieve a progressively improving time on each flight. Large differences in flight times indicate a poorly sorted model/flyer.  I believe that a 5 minute flight was certainly possible in the site and that will be my aim for next year. I noticed that the model was landing with 20% to 30% of winding turns, so I may next try a thicker motor (0.120” ish) and back-off turns more.

The air conditions in the afternoon for my third flight became difficult due to turbulence and unpredictable drift. This was attributed to the dome being covered in dark felt tiles and the effect of the sunlight, in combination with air conditioning units for the gym. The LPPs and lighter models really suffered.

Although I used different motors on the three competition flights, they were close enough to be identical and I used less turns and torque on the last flight. However, the air in the dome had heated up during the afternoon, and reached about 27º if I remember correctly. It is more likely that my model is not performing consistently, perhaps due to tail flexing than the air conditions or rubber power increasing with temperature causing the extra height on the third flight.

I unpacked my recently completed spare Cassutt model and had it performing nice low-powered circuits after 3 adjustments of the tail angle. I was delighted with this model and look forward to more flying in the next indoor season. I intend to explore different motor lengths and thicknesses to get the most out of the model.


Title: Re: Cassutt NoCal
Post by: piecost on June 30, 2014, 08:14:23 PM
The dome!


Title: Re: Cassutt NoCal
Post by: piecost on June 30, 2014, 08:15:36 PM
Cassutt and spare Cassutt (I should have given the new model a different number)



Title: Re: Cassutt NoCal
Post by: OZPAF on June 30, 2014, 08:54:58 PM
Congratulations PC - what a good report too.
That was a fitting reward for your careful analytical approach. What were you using to achive such small tail incidence changes?
Good luck with the new one.
John


Title: Re: Cassutt NoCal
Post by: Prosper on July 01, 2014, 04:36:50 AM
Very interesting piecost and a great story, thanks for sharing.

Stephen.


Title: Re: Cassutt NoCal
Post by: piecost on July 01, 2014, 05:08:22 PM
Thanks John & Stephen,

I measure the tail setting angle by measuring from the top of the tailplane, near the tail plane adjustment post, to the top of the fuselage. I used to use a 7inch rule, but now use a digital caliper that I bring along for rubber stripping etc. The model is somewhat flexible so my claimed fidelity of setting/measurement may be imagined rather than real.


Title: Re: Cassutt NoCal
Post by: piecost on July 01, 2014, 05:21:42 PM
The thrust line measurement may be of interest. I use a spare nylon nose bearing with a length of wire threaded through, held in place with adjustable collets. I mount the device on the model and adjust the length of the wire so it just touches the tube. From measuring the length and knowing the gap between the wire and the tube at the nose bearing I can calculate the right thrust. Similarly I use the wire to determine downthrust by eyeballing the length of wire needed to intersect the top edge of the tube when viewed side on. Hopefully the picture will explain better than the text.


Title: Re: Cassutt NoCal
Post by: piecost on July 01, 2014, 05:22:51 PM
I made a graph to aid adjustment.


Title: Re: Cassutt NoCal
Post by: piecost on July 03, 2014, 05:00:19 PM
Finally, I have had problems with the tailplane warping so I have gone to elaborate lengths to prevent this by clamping both tailplanes between foam board. THe over-complex box holds the wings in jigs with the correct dihedral and washout.


Title: Re: Cassutt NoCal
Post by: OZPAF on July 04, 2014, 08:46:16 PM
Thanks for that PC. Its a different world of flying - small accurate adjustments while dealing with a liavery light and flexible airframe. Another fascinating area of aeromodelling.
John


Title: Re: Cassutt NoCal
Post by: piecost on August 19, 2015, 01:55:51 PM
A tip for anyone building a Cassutt with a removable wing; avoid putting the rear hook exactly inline with the wing trailing edge. If the rubber knot is at the back then it pushes the wing trailing edge up a couple of mm and causes the model to dive-in. When I moved the position of the knot forward it touched the motor tube so I ended up unbending the rear hook to move the motor down and away from the tube. This caused the tube to bend more with high turns and needed a change in side thrust.



Title: Re: Cassutt NoCal
Post by: piecost on October 05, 2016, 06:52:44 PM
I haven't posted for a year, but I am pleased to say that I won the NoCal class at the 2016 UK Nationals. Thanks to Don and others for the freely given advice. I had built two identical models for the competition 2 years ago, won with the first model and have now won with the second.

I was confident in this class because in previous years I had only seen one other Cassutt (with a small propeller) and no Hosler Furys. My plan was to record two times quickly on the first day of the competition, starting competition flights once I had achieved over 4 minutes in practice. This achieved; my first competition flight recorded an attempt at 5m11s since, gallingly, the removable undercarrage had fallen off! I then set a first competition time of a mediocre 3m33s. I wonder if I had hit bad air as it was, only the 2nd wind on a fresh motor. The second and last competition flight that day was at 4m17s. I was not entirely satisified with my times being below 4m30s but noted that I was in the lead and packed the model away. I thought that I had done enough. I mantained the lead on the second day of the competition.

I was enjoying the last afternoon of the competition flying Legal Eagle and noticed a nice looking yellow Cassutt at high altitude. I had not seen this model before and was startled from my complacency to see times of 4m29s and 4m31s posted. The tight grouping of the scores almost rattled me as much as their value. I quickly flew both competition flights on my Legal Eagle and re-assembled my cassutt. The removable tailplane was set with a digital caliper and I flew a competion flight without bothering to check the trim. My hands were trembling so much that I had trouble attaching the motor to the rear S-Hook (why did I have to make it so difficult to attach a motor?). This rushed flight managed to reach 4m30s. My 2nd best time of 4m17s left me in 2nd place. It was going to be close.  There was no time to rest the motor so I selected a similar, fresh, motor and wound harder and backed off less. The model only climbed to 45' (10' under the girders) but acheived 4m58s. Fantastic! That put me into the lead again.

Since I was so near to 5 minutes and the other Cassutt had one competition flight left I decided to go for broke and try to beat the 5 minute mark. I reasoned that there is never a better time to hang-up a model in the ceiling than at a national competition. I selected anoher fresh motor, wound and backed-off to a higher launch torque than before. I was careful to launch between the girders. The the model climbed at 30º until level with the girders. It edged closer on each circuit to a Warren Girder and went out of sight for a couple of seconds in every circuit until finally touching, diving a few feet and recoving. My heart was in my mouth. Luckily it didn't have too much climb left and circled just below the structure and descended safely for a 5m08s, out of turns. The competition only had 20 minutes left to run, so I had done it!

It proved to be a thrilling afternoon!

Data for the 2 best flights:

Prop: 12" P/D = 1.2
Temperature: 19.5ºC
Rubber: Tan II May 97, 3.26g/m, 18" Loop, 3.04g
Wind to 1670 turns & 1.47 oz.in
Back of 68 turns to 0.71 oz.in
Landing turns  110, torque 0.17 oz.in
no touch, max height 45'
4m58s

Prop: 12" P/D = 1.2
Temperature: 19.5ºC
Rubber: Tan SS 17 Jan 2014, 3.21g/m 18" Loop, 2.93g
Wind to 1600 turns & 1.45 oz.in
Back of 70 turns to 0.73 oz.in
Landing turns 0
Touched girder at 2m56s
5m08s

I wonder if I can push the duration a little further in the next session, since the 4m58s flight did not reach the girders.

Finally, at the Nats someone mentioned building a Holser Fury. This has upped the ante, so I bought a plan from Volare. The structure seems quite chunky (presumably for ourdoor use) and I was thinking of applying the Cassutt structure to the plan outlines. In another thread/forum Don recommended using up to a 14" stick (a 40% increase over the Cassutt). Now, if I keep the mass/length of the rubber constant then the model mass will increase by 33% whilst I the wing area is 16% higher. So, the wing loading will increase by 15%. Even though the wingloading has gone up I wonder if I can get away with the same propeller as the Cassutt (12" dia, P/D =1.2)? Or do I need to reduce the pitch to get more power? (higher rpm offset by the longer motor).

I only want to build a Hosler if I can expect a significant duration increase. Would it be reasonable to expect a 6 minute flight under a 56' ceiling?


Title: Re: Cassutt NoCal
Post by: OZPAF on October 06, 2016, 02:36:22 AM
Congratulations and thanks for such a detailed report. What a way to win!
John


Title: Re: Cassutt NoCal
Post by: dslusarc on October 06, 2016, 09:17:49 PM
Congrats on the Cassutt win. I will let my dad know it will make him happy :-)

As far as the Hosler Fury. Once you build one you will not go back to the Cassutt. The Hosler does the time easier in my opinion. At the Kent state contests, which is a 50 foot site we could get just over 6 no touch flying at 6.2 grams. I would have to go look at my plan again to see what I would now make the motorstick to. I built mine with an 18" stick thinking it will fly on long thin rubber on a smaller prop and was completely wrong. It likes a big prop and heavy loops of rubber. My dad was flying his on 1/8" wide rubber, mine was using around .115" wide and Larry Loucka uses around .110" wide and is due to prop variations. Larry is running a symmetrical prop, and my dad uses a LPP style prop. As long as you can keep it under 7 grams it will fly good. The tissue is a lot of the weight, using Gampi will save weight but you have to dye the tissue red however you get to have more weight in wood structure. Mine was Esaki covered and was exactly 6.2 grams and was difficult to get there as the tissue is about 3 grams due to all the area. My dad and Loucka used gampi so were under wight around 5.5 grams so could use ballast to trim as needed. The Hosler needs about 1/8" positive in the wing and about 1/8" neg in the stab. Make sure the boom gong back is strong and also tie the outline to the tailboom in a few places to stabilize it in twist. You don't want the tail wobbling. Also it will need right rudder and setup essentially the same as the Cassutt. The Hosler likes to fly nose high so just let it. They also usually need about 3 degrees right and 2-3 degrees down thrust. If I were to make a new one I would also put about a 2% airfoil in the stab instead of flat no airfoil. My dad and I have flat and Loucka has an airfoil and I think his handle high torque better as his tail lifts some to hold the nose down when climbing out. Visually he looks like he has less down thrust than my dad and I do. Also one day when really humid the flat tissue sagged to upside down airfoil and the model flew horrible, so we did a test and if we pushed the tissue up again the model was in trim, if it drooped then the model stalled. So we decided having dedicated ribs and an airfoil would be good in the stab.   

Don    


Title: Re: Cassutt NoCal
Post by: piecost on September 21, 2018, 09:55:35 AM
I entered the Cassutt in the 2018 nationals after taking a break from flying. I wasted much of the previous
day dealing with accuracy problems on my digital torque meter and ended up sharing a wire torque meter
the meter with a friend flying an F1R. This employed a shorter length from meter to winder than needed
for my Cassutt. So, I opted to use the shorter length rather than incurring the complication of both of us
having to adjust the length prior to each flight. Whilst, the actual torque readings could not be trusted
incremental changes could be used. Also, I could not stretch wind hard for fear of breaking the shared
torque meter and of tipping the tripod over!

l started at very low launch torque and increased it progressively each flight. Despite my care; I still
managed to hit the roof beam and so lowered the launch torque on the next flights by 0.5g.cm. This
reduced the maximum climb by over 6 feet! This was surprisingly sensitive, especially compared to the
torque dropping by well over 1g.cm after winding as the motor settled and I massaged the knots away

There were only four entries in the competition and two were Cassutts, including the yellow model that I
encountered two years ago. I saw it flying with well-judged flights skimming the bottom of the roof beams
progressively increase its duration from 2:18 upwards. It employed what looked like an 8" prop so I was
confident that I had the edge with my 12" airscrew
My first competition flight of 2:42 exceeded the best time, so far, of the other models. Subsequenty; the
other Cassutt reached its limit at 3:01, with one flight remaining. My second competition flight reached
3:18 with plenty of allitude to spare. This put me ahead. The yellow Cassutt did not use its last flight
perhaps realising that there was no more time to be gained.

Since I still had four competition flights left and was not skimming the ceiling; I planned to wind harder
and back-off to the same launch torque. A third competition flight was not needed and I moved on to
flying Osprey. I had not reached the full potential of the model in this site, but had won the competition
I was delighted that the model remained in trim after not touching it for 2 years. The care in making a
complex foam-board box to hold the components true had pald otf. I found that I did not even have to
remove the wing to load the wound motor, but did break the removable undercarriage a couple of times

The UK NoCal rules are being changed to reduce the minimum weight to 4.0g in a bid to end the
dominance of the Cassatl's (a case of sour grapes). But I have been told that an infamous Hosler Fury
will soon be under construction. I think that my model will remain competitive even if someone builds a 4g
model next year

Data for Ihe best flight:
June 16 Super Sport 3,12g/m x 18 loop & 2.93g
Wind to 1130 tuns
Back off 6 turns
20' max height no touch
Avarage rpm 284
3m18s

I had a similar axperiance to LPP in this competition. I had employed the same motor optimised for a 56
celing under 28 conditions. I was barely winding the rubber and only employing 80% of cruise turns! A
switch to a lighter mator, wound harder, should yield Improved flight times


Title: Re: Cassutt NoCal
Post by: OZPAF on September 22, 2018, 06:08:10 AM
Thanks for that PC -the trimming info always fascinates me - even though I'm predominantly a RC Glider pilot.

John


Title: Re: Cassutt NoCal
Post by: Mefot on September 29, 2018, 03:21:03 PM
Congratulations on the win Piecost  :)

Looking at the Hosler Fury as a 4 gramme model. Do you think it is possible to build one to that weight. It seems to me,as an outsider to this type of model, that the tissue would be 75% of the weight, leaving very little for the structure ?


Title: Re: Cassutt NoCal
Post by: piecost on September 29, 2018, 05:43:47 PM
No, the Hostler is a 6 to 7g model, it seems. If we were still flying in the Brabazon hanger then I might be inclined to build one. I am not sure what the most competative 4g nocal would be. Since we only has 4 entries this year; I am wondering if anyone will build to the lower weight for 2019


Title: Re: Cassutt NoCal
Post by: piecost on November 07, 2019, 02:46:34 PM
I did not devote enough time to this class at this year's nationals and managed to break the motor stick at the nose. I wonder if the model had sustained previous damage since it did not have a hard landing. The model was very nose heavy and I resorted to tail weight in an
attempt to trim. It was also flying in rather tight circuits.

 I had not flown it since last year's competition and it clearly needed some attention. Not having used the model for some time it becomes possible to make a fairly objective judgment about it; almost as if it were constructed by someone else. I found the propeller S-
hook too tight on the O-ring when installing motors and the rear S-Hook ridiculously difficult to remove the rubber. The location beneath the wing trailing edge did not help.
.I no longer removed the wing to install/remove the motor as this was a pain and risked damage. The removable canopy was very fragile and was damaged, the balsa broken and the tissue peeling off.

 I will modify the broken model. I will remove the stick and boom and move the rear peg 1 inch aft, away from the wing to ease motor loading/unloading and to help with the nose-down trim. I will also open out the propeller S-Hook to aid installing the motor. I will employ a conventional rear hook. It was annoying to break the model and not have time to rig the spare since the winning time from the best  two flights were only 4m15s. Something I should have been easily able to surpass.


Title: Re: Cassutt NoCal
Post by: piecost on November 07, 2019, 02:47:11 PM
Broken motor stick