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For some 4 years now, I have been flying mostly Nostalgia Gas designs, covered with either tissue or UltraCote, and relatively easy to add washin to the inboard wing panel to keep the inboard wing up in the glide, and to induce an opposite direction roll in the climb.
Along came the Bounty Hunter. Due to the triangulation of the back 3/4 of the wing, all warps, not built in, came out within a couple days. I could either shim up the appropriate leading edge during the building phase, or add a length of trailing edge stock reversed on the left side. This was what was shown in the Model Aviation article. I like to jig things up tight and build flat on the table so the reversed TE stock is what I did.
The airplane flew pretty nearly right off the board. I could not help but observe that this reversed TE idea would be much easier to “tune” in the field as opposed to warped-in washin. Too little and add more TE stock. Too much, and cut some off. It worked so well, I built my ZEEK (7 maxes @ KOI) flat on the board and even though the structure would have allowed it, used reversed TE stock on the right wing instead of warps. It worked equally well on this pylon ship as well as the previous hi-thrust model. Both models exhibited the excellent trait of the glide circle tightening appreciably in lift, although this latter might be due to the use of stab tilt for glide turn.
Now I am anticipating building some geodetic models, specifically Pilfered Pearls. The plans call for the leading edge on the right side, half-way out to the first joint, to be cracked and shimmed all the way out to the tip! Geez Louise! About half of the right wing will be built up in the air, off the surface of the workbench. This begs the additional question: what if I put in too much washin, or not enough. With that structure, what you build is what you get. No changing in the field or anywhere else for that matter.
I would REALLY like to build the whole thing flat and add the reversed TE, due to ease of initial construction and flight trimming.
What are the pros and cons of the two approaches? Are they equal or is there a clear aerodynamic advantage of warps, built in or otherwise over the reversed TE?
I like the built-in warps.
On the P Pearl , use what it says. You can build all the staight ribs and bottom spars with it flat. Then jack it around and add the diagonals. Once they’re in you’re not gonna move it much. I have wash-in warps on all my Marvals and JaysBirds. Some also have TE stock as trim tabs.
I’m not a fan of wings that can be warped. They tend to move around. That’s usually not good.Wow, I agree with Dan… The structure should be built the way it is intended to stay not have the covering force the wing to where it should be. This is especially true with plastic coverings. Yes, you can heat shrink them and warp them where they should be, but it will stretch and change with heat.
It is more effective to move the entire structure instead of just adding the “flap”. But, does it really make a difference? Hard to say…
It really isn’t that hard to shim the structure and then match the ribs. If you miss, just sand the structure to make things fit.
The other method is to make up some quickie tapered shims. 3M Spray mount them to the edge of the board and sand them to shape- This only needs to be at the LE or TE…
If I can do it, then you can easily do it!
Howdy Boys,
Hey I messed up and built my electric Astrostar wing flat. Now I’m ready to test and would like to know how long a strip of trailing edge stock is used to create 3/32 or so of washin.
Thnaks in advance,
Mike
If I remember correctly, it took about 2″ of 1/2 x 1/8 T E stock to trim the one I built. If you scroll through the electric notes there are some other notes on how much thrust offset and rudder shims I used.
The Astrostar 404 was a great flying model and very easy to trim.
What power system are you using on it?Just in passing, I built my wing flat and covered with Polyspan. I steamed in just the right amount of warp in it for the initial test flights.
It was gone in a week. so steaming it didn’t work, which is why I ended up using the wedge as suggested by Luddite Dan Berry.Cheers!
I put a 2 1/2 ” piece on and will test it in the morning and advise. Set up is an AXI 2212/12 spinning an APC 8/4 non folder Thunder Tiger 30C 830 battery. Little porky at 17oz.
Thanks for all your input.
Mike,
I got a better climb using a set of 7.5 x 4.0 blades on a Jennings hub, after trying the 8″ blades. Used the same motor.
Check the specs under “Pete’s new model” in the electric section.
Also, your weight is OK at 475 grams Mine was heavier due to heavy spars, etc, etc.
Not saying my set up was the only answer but not a bad place to start.Cheers!
Pete yes your thread was the inpiration for this model. Becoming a real need after my Satellite did its best ice pick imitation. I have on of Jims hubs and have used the the 7.5 4 folder I was out of blades so I tried the 8 x 4.
Flight report
Climbs very steeply and showed a very little turn to the right in 5 seconds.
so I took some incidence out and added a little right rudder shim, seemed ok. Extednded the motor rum to 7 seconds still climbs steeply but now it starting to chase it tail. Take more incidence out remove the rudder shim, Better but still doing it. Take even more incidence out and add some more washin strip. Thinks it better but still chasing it tail. Wind is up so time to go home.At home check incidence only to find out I’ve gone from a degree and a half to 0-0. 😯 washin strip is 3 3/4long 1?2 by 1?8 TE stock. I put the incidence back to one degree and may try some left tab next time. FYI CG is 2″ in front of trailing edge approx 75% I’m open to suggestions
Basicaly it climbs steeply straight away for 4 to five seconds the does a chandale to the right and starts to chase its tail. I do have left thrust in it.
Thanks Dan we will give it a shot.
Well had a day off from work and went and tested. Put my 7.5 x 4 folder and added left tab. Now fly’s great. Thanks for all the advice
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