Upscaling the Scissor-wing Transport

[jkn]

This is the project I've always wanted to do. R/C... dual aileron servos and elevator. It seems to me there has to be some folks who have done it and Im hoping someone can point me to more information. I'm want to upscale it 2.5x so I can use 2.6" dia kraft tubes for the airframe. Also it would seem that I could keep weight down by using coroplast for the wing, though it wont so nice. Im hoping I can draw off of someone else experience but any info/suggestions will appreciated.

Thanks
ps My understanding is that boost-gliders , legally, can only use mid power motors. Is this true ?

 

[jflis]

awesome project! I **trust** that you will keep TRF abreast with pix...

As for the wing, I would suggest that you consider a built-up wing like that used in a conventional R/C airplane. Strong, lightweight, easy to build...

keep us posted!

jim

 

[SwingWing]

Keeping the weight down is going to be a concern, for sure. I built a 3" version that is in this thread.
https://www.rocketryforum.com/showthread.php?s=&threadid=7167
This 3" bird starts to push the 3.3 pound limit on notification vs. waiver/HPR. It weighs right at 3# with motor. This is a free flight model, adding R/C gear would push it over the top
I don't think the coroplast will have the rigidity/strength to survive boost. Jim's idea of a built up wing would be stronger, or if your wallets fat, some honeycomb carbon fiber would be perfect!

 

[jkn]

Yeah the weight. I wanted to go with 3" tube but decided 2.6" would save more. Is 2" tube a better choice ? I have thought about building up the wing but actually it seems that a monokote covered balsa frame may be weaker ultimately. Using 2mm coro done in normal SPAD fashion should work OK. I'll probably flatten two sides of a hardwood dowel as the spar as I dont want a very thick airfoil.(I could use two?) Even though it may be heavier I dont think the 2mm coro will make a huge difference. Obviously the coro wont look as good but it's soooo much easier to put together. (SPAD's are as fun to build as they are to fly!) and easier to rebuild . The coro wing makes servo placement alot easier too. I was planning on using two HS-81MG's in the wing but they are fairly heavy at 19gm's each. The new HS-56's look kinda interesting and only weigh 11 gm's though Im skeptical of their torque. Im not sure what I'll use on the elevator though Im thinking a 225MG. I'll more than likely use a HS55 to trigger the wing deployment. A GWS rx looks like a good choice and only weighs about 9gm. A 4 cell NiMH batt pack should be right around 1oz. The entire flight pack should weigh 3 to 4oz , thats not too bad. Now if I can get the wing to come in under 8 oz I think I'll be doing good. Can anyone give me an estimate of what 20ft of 1/4" tub kevlar , 36" chute , hardware, and wadding weighs ? I guess thats the weight I'll be saving eh ?

SwingWing,

You did a fantastic job ! I have a feelin mine wont be looking quite like that !
What are the dimensions of yours , length & WS ? I could probably bombard you with questions but I'll just ask a couple more...

How do you suggest I make the wing's pivot mechanism , taking in account that I plan to use a servo to trigger it ? I definitely dont want the servo to bolster the load. I know Im at a disadvantage here as I havent built the original Estes kit.

The booster. I've seen a couple pics and somewhat see it's 2 fin design but dont quite understand how I should go about constructing it at this scale ? Any suggestions ?

Thanks all !

JKN

 

[SwingWing]

Originally posted by jkn
SwingWing,

How do you suggest I make the wing's pivot mechanism , taking in account that I plan to use a servo to trigger it ? I definitely dont want the servo to bolster the load. I know Im at a disadvantage here as I havent built the original Estes kit.

The booster. I've seen a couple pics and somewhat see it's 2 fin design but dont quite understand how I should go about constructing it at this scale ? Any suggestions ?

Thanks all !

JKN

I made my wing pivot just like the Estes version, just scaled up 3x. I didn't scale the material thicknesses, or it would be made of 3/8" plywood. ( I used 3/16) It is actuated by the pop-pod pulling a dowel out of the end of the wing, and then an elastic thread (rubber band)pulls the wing around.
Take a look at the Estes plans at jimZ's sight if you have not already.

https://www.dars.org/jimz/est1265.htm

I have a copy of the originals from around 1976.
I also drew the patterns in 2D cad, so I could easily scale them to any size I want. Let me know if you want them and what form works best (.dxf, .pdf, .tif, etc.)

The booster is actually a pop-pod, that ejects out the rear and floats down on it's own chute. I offset the motor slightly to try to conteract the tendency of the wing to produce lift during boost, angling the boost to the wing side. You can overcome this with a little down elevator via the R/C gear.

The 3x SWT is 3 1/16" in diameter, 48" wing span and about 68" Overall length. It has a single 29mm mount

The attached is the motor mount end with the pod installed

 

[SwingWing]

One more quick pix of the pod out beside the glider.

 

[jkn]

SwingWing,

Hey thanks for everything. I've decided to go ahead with the 2.6" scale as planned. Parts are on the way. Will answer back once it get underway. Thanks for your help. The pics are invaluable btw !

 

[shrox]

Too late now I guess, but the BT-70 tubes and nosecones are lightweight and 2 1/8" wide.