Bird wing recovery

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.


Jan 27, 2010
Reaction score
I'm new to the forum and still a rookie in the rocket building world though I understand the physics... ...mostly.
I'm thinking of building a rocket that launches as a normal rocket on an Estes C class motor. At ejection charge, a burn string releases a pair of wings out slits in the body sides. The wings unfold in nearly the same way as a bird wing works using kabob skewers or something for bone's and some yet to be determined joints. I'll skin it with trash bag or something.
Kind of an elaborate system I know and probably won't launch very high because of the weight of the wing bones. But the dramatic effect of seeing a rocket transform into a bird will be worth it. Anyone attempt such a thing before?
Something sort of like that, but I was thinking on also having an elbow and wrist joint in addition to that rocket's shoulder joint.
If it ain't over complicated it ain't worth doing at all...

If you are going to do a joint at the middle, I would highly recommend looking at Robart hinges. I'm using them in all of my new competition helis and it makes radial space a non-issue. You'll want either the 3/32" or 1/8" depending on the size of your rocket.

Also, for the 'bones' I would use either birch dowel or CF rod. If you get CF rod with 3/32" or 1/8" ID, then you can fit the Robart hinge right into it without any fuss. With the dowel, I'd just fit a launch lug on the end and glue the hinge into that. Just make sure not to get glue in the hinge pins.

Finally, for your first attempt what we in competition call a 'flex-wing boost-glider,' or 'flexie' for short, I recommend you go with something of a similar style to what Sandman pointed out. They are a lot easier to get flying properly. Also, weight is your enemy. Keep it down where ever possible.

Have fun!
Yeah, it's been done before, but that doesn't mean you can't have fun playing with it and designing your own.

I remember seeing a "parasite"-type flex-wing glider that folded up and stowed inside a body tube, came out with the parachute at ejection and glided down seperately. Sorry, I don't have a link, maybe someone else here will remember the same thing and jump in with more info.

You might enjoy reading up on some background research at:

You can also do a search on TRF 2 (this website) and on TRF 1 (click on the "archive" tag in the blue bar above) using words like flexie, para-wing, rogallo, boost glide, etcetera.

And welcome to TRF! come on back and keep us posted on how your design turns out (you will be the "expert" on this stuff!)
Welcome to the forum!

Sounds like your discribing flex-wing or swing-wing gliders as several have already posted. Most of the flex wings I build are done with 1/8" square spurce spars and 1/4mil mylar or just about any very Light weight plastic shopping bag. Springs are made from .020" music wire tied and CA'ed to the spars.

Flexie's are really fun, Estes has over the years produced a few different combinations that you might like to try, currently the Scissorwing Transport is easily available. most of the others can be cloned using JimZ or ninfinger sites from the plans.
Good luck, remember flying rockets is for fun...Flexies are super fun but mostly fly away :D

132-sm_5A-A Flex-Wing BG_09-08-92.jpg

214a1-sm_MM 8thA-Flex-Wing-Glider_09-08-99.jpg
Last edited:
a couple more tips about Flexie construction;
It is important that the rear of the fabric between the spars has a bit of slack. We've found that a couple (one each side) 35mm film canister placed under the fabric as it's taped to the pattern provides enough "fluff" for proper glide. It's also been my experience the a 2 or 3 degree up tilt in the center spar helps stabilize the glide.
Good luck and have some fun.

Flex-Wing-b-sm_3- 12in & 1-14in Flex-wings_99-05.JPG

Flex-Wing-c1-sm_Close-Up Spar&Spring thread wrapping_07-99.JPG

Flex-Wing-d-sm_2in 3° center spar elevator break_06-01.JPG

Flex-Wing-e-sm_Completed Flexie Storage Hanging_07-14-07.JPG
I appreciate all the help. I'll definitely update with pictures as work progresses. With the spring only joints, was there any trouble with off-axis rotation? Did the join flex as if on a hinge or was there any significant flex away from the rotation angle?
I appreciate all the help. I'll definitely update with pictures as work progresses. With the spring only joints, was there any trouble with off-axis rotation? Did the join flex as if on a hinge or was there any significant flex away from the rotation angle?

In a word No!
Even if deployed Upside down a quick loop, or more like flop puts the glider in correct glide angle with no visible flex or rotation once hand trimmed to a set path....I try for 300-400 foot circles. If the breeze is too strong they seem to ignor the trim and fly more or less with the wind.
Perhaps there was a misunderstanding. I was referring to the hinge behaving as a ball joint and not a hinge.
The next problem to solve is the wing release method. I am thinking a burn string to release a rubber band pulled pin out of a "belt" holding the wings inside the slots in the body tube. I can see the me mechanism in my head better than I can describe in words. Hopefully I was clear enough that you can see my thought too. Any better ideas are greatly welcomed.
I think I found the solution. I was way thinking the problem. If I wrap a rubber band around the dowel ends, I can easily close up the wing and then it springs out with the right amount of force.
I had tried using bits of spring steel that I liberated from a ID tag cord winding mechanism. Not springy enough and tends to kink too easily.
I used Breathe Right strips (the clear type). Again not strong enough.
The rubber bands is just right and adjustable depending on how many wraps I give it.