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BLG - Ballistically Launched Glider: A new project/build thread

earthsciteach

Moderator
Moderator
#1
Several months ago I proposed a challenge to design and build a tube launched RC plane. There really wasn't much response. But, this idea has been ruminating in my brain ever since.

Over the last couple of days, the general concept has begun to solidify. My plan is to encase an rc glider, similar to a DLG in construction, in a sabot. The glider's wings and tail feathers will fold back to fit within the sabot. The sabot will have the appearance of an artillery round with the casing attached.

The sabot/glider will be fired out of a cannon similar to a potato gun. Upon reaching apogee, the sabot, triggered by a TX, will break apart releasing the glider. Most likely, this will be a two tx operation.

I foresee the glider having a wingspan of about 1000 mm. The sabot will have an OD of about 3-1/4". Still have a lot of details to work out, not the least of which is getting the wings to fold and fit within the ID of the sabot.

Oh, and I get to build a really big potato gun!
 

xuzme720

Dedicated foam bender
Mentor
#2
Teach, I like the thinking however a second Tx just for release might not be necessary if you just have the wings unfolding pop the sabot apart. I'm thinking something like velcro dots to hold the sabot tight enough for launch but able to be popped open pretty easily. I'm just not sure if high speed airflow won't just rip the sabot open from the pressure of launch. Mythbusters chicken gun comes to mind...
 

Billchuck

Senior Member
#4
You could have a pin set up to hold the sabot together, and pull the pin with a plane mounted servo much like a tow cable release. Build the sabot so it slots together at the back and has some spring to push it apart at the front, and maybe a parachute inside to recover the sabot.
 
#5
So I was thinking of another mechanism to deploy the wings without having to do the Jim walker/saddle back flip over method.

The wings could be folded back along the fuselage with a hinge at the trailing wing root. You have a bungee in the front with cables that run to the leading edge wing root via a pulley/pivot that is mounted mid fuselage and mid wing. There would be a release pin mechanism by the tail to hold the wings back. When this is released the tension from the bungee pulls the wings forward via the cables. Small notch clips will then click the wings in place and prevent them from re folding until they are manually released.

Here's a sketch
image.jpg

I remember seeing this a long time ago but it only folds for transport. Beauty though.
 
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rcspaceflight

creator of virtual planes
#6
I'm newish to the forum so I didn't see your original thread until more recently, but your challenge got me interested in trying this. I experimented, but only a little bit, and I took two bamboo skewers and tied them together with a rubber band. I can bend them back and the rubber band pushes them back straight. The skewers are actually too weak for it to work, but carbon fiber or arrow shafts and surgical tubing should spring load the wings and it'll be simple and cheap.

I also think that a flying wing might be best. Wings that pop out and have elevon controls. Just a simple pop up rudder as a stabilizer, but no rudder control. Simpler will be better for this project.
 

earthsciteach

Moderator
Moderator
#7
Billchuck - that is very much along the lines I was thinking.

Jason - cool idea. I like it! I think I'd have to get the wings to rotate 90 degrees along the length of the fuse, as well using this design. Hmmmm.....

rcspaceflight - I don't think that I could fit a flying wing into the space of a 3-1/4" tube.
 

rcspaceflight

creator of virtual planes
#9
rcspaceflight - I don't think that I could fit a flying wing into the space of a 3-1/4" tube.
Sure you can. You're just not trying hard enough.

But seriously I just meant that you probably don't need a fuselage and that the fuselage would just be added unnecessary weight. Your wings won't be that big if your shoving an entire plane into a hole that small. The smaller the wings, the lighter the plane needs to be.

To make the wings big enough I think you'll need two or three wings stacked on top of each other. But not like a bi-wing, more like a KF Step. That way you can use three separate 2" wings to basically make one 6" wing. And if you stack it correctly, then you could use flat wings that form an airfoil. But I think you'll need spars in each wing segment to keep them straight. Foamboard can get sloppy.
 
#12
to make a wing fit think vapor/mini vapor/ kite/hang glider.. you spring load the wings, rubber bands, surgical tubes.etc the carbon tubes/arrow then spring out and lock into place... when they spring out they pull tight the material on the wings... maybe nylon from a kite.. that package could be very, very small with a center boom the same size arrow. You then add a nose cone, think rocket.. now you buy some Styrofoam, or pool noodle split it, fit glider/wing but let the noise cone of the glider stick out of the noodle, think bullet in the shell..

Launcher pvc pipe, a few fittings and compressed air.

Dump the valve, noodle bullet shoots out tube, foam halves split, wings pop out, lock into place and pull material tight.. you then have control of your glider or wing.. all this could be accomplished with 5ch easily.. many DLJ don't have rudder control.. so they're 2ch, 3 with rudder control, 4th ch could remote activate the dump valve on the tube.. ch 5 and 6 could be used to raise/lower and rotate the tube.
 

xuzme720

Dedicated foam bender
Mentor
#13
That's kind of what the link above shows. I couldn't find the video for it but it just pulls out of the tube, pops open ready to fly...
 

rcspaceflight

creator of virtual planes
#16
earthsciteach, I am seriously trying to do this also and I hope to start a build log thread on my progress. Although, I'm wondering if a glider is good enough or if I should put a folding prop on it. I also don't have a potato gun or compressed air cannon. So would building a glider with a 2 foot (not even) wing span that folds small enough to fit into a tube with pop out wings and rudder be enough proof of concept?
 

Tritium

Amateur Extra Class K5TWM
#20
I usually ship by Swiss Post. For that plane it's $6.99 for a total of $11.98 to the United States.
Last time I used Swiss Post the company that sent to me was out of business long before the merchandise arrived some 3 months later! :(

Thurmond