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SCRATCH BUILD CHALLENGE!!!

earthsciteach

Moderator
Moderator
#1
Anybody interested in a little contest? You will win absolutely nothing, except for the pride of successfully accomplishing a cool task!

CHALLENGE: Build a RC airplane that is tube launched!
Requirements:
Tube must not exceed 6" in diameter (imaginary bonus points for smaller tube diameter)
Length of tube may not exceed 6'. (imaginary bonus points for shorter tube length)
Mechanism of launch is up to you.
Entire plane must fit within tube when in launching position.
Plane must be stable in flight, capable of sustained flight through the charge of a 1300 mah, 11.1V battery. (imaginary bonus points for larger battery capacities)
The launch and flight of the plane must be on video to prove success

Everyone successfully completing the challenge will be a winner! I'll see if Fred can give us silly little badges for our user names or something. Anyone interested???
 

Ak Flyer

Fly the wings off
Mentor
#4
Teach you have got a crazy imagination. I love it :applause: I already have an idea, we'll see if I get any build time soon.
 

earthsciteach

Moderator
Moderator
#5
The idea was inspired by the US Army's tube launched recon UAV named, Switchblade. It weighs two pounds, is tube launched and carries ordinance of some sort.

I also have an idea of how to launch it and build the plane. Its pretty simple, actually (if it works). But, I am determined to get this fpv wing done before I get into something else. Stupid ADD strikes again!
 

Ak Flyer

Fly the wings off
Mentor
#6
I know what you mean. I have to stay focused on one thing at a time which is nearly impossible with 3 kids lol. Right now it's heli's but that's going well so a scratch build may be near but I also have to finish a balsa rebuild.
 
#7
I wish I saw this a few days ago. I have the perfect idea of how to do this using something that I have always wanted to build. Could probably shoot the plane out at least 100m (if not more) before even thinking about deploying the wings :D
Unfortunately I have just brought everything to build a tricopter.
Think I'll get designing the plane now and when my next pay day comes... :D
 
#9
Couple sections of pipe, a little psssst, a click and then a little pop :D
The more I think about it, the more I want to do it. Just need to figure out how I'm gonna reliably deploy the wings.
 

CrashRecovery

I'm a care bear...Really?
Mentor
#13
If your talking a spud gun you have some homework to do. You can use normal PVC pipe but don't go cheep either. I forgot what the type is called but the wall is a little over 1/8 inch thick. Now before you buy your pipe you need to read this.

How big should my chamber be??????
For combustion based spudguns.

Everyone wants to know what size to make their chamber. Or "How big is too big"? Or "How big can I make my chamber before it blows up on me"? Or "How can I get more distance out of my spudgun? I have a chamber that is 6" PVC pipe 48" inches long and it just doesn't seem to shoot very far".

For optimum performance the chamber should be 1 1/2 times the volume of the barrel. This is what is referred to as a 1.5:1 ratio. The reason for this is as follows. You want the spud to exit the barrel when combustion is almost complete, thus making use of all of the power created by the thermal expansion of the combustion gases. During the combustion, the chamber pressure will continue to increase until combustion is complete. Having a barrel that is sized to the correct ratio with the barrel allows the spud to keep gaining speed throughout the entire length of the barrel. Having a barrel that is too long or a chamber that is too small will cause the spud to slow down due to drag. If the potato has not exited the barrel by the time combustion has finished, the amount of pressure behind the spud begins to drop off very rapidly and in turn the spud is greatly affected by friction as it slides down the barrel without full pressure behind it. However, if the barrel is too short or the chamber is too large, the spud will be long gone before it has a chance to achieve maximum velocity. It would, in this case , only be making use of a small amount of the power from the thermal expansion gasses.

So in this respect, it's not the size that matters!!! And to answer the the question from the guy with the 6 x 48" chamber -- You would need a 2" barrel, 24 feet long to make it work the way it should. (not that I recommend building a chamber that size in the first place)

The volume of a piece of pipe can be found using the following formula.

Volume = Pi x radius sq. x length--(in inches)
Example: 12" piece of 4" ID pipe.
3.14 x 2 x 2 x 12 = 150.72 cubic inches of volume.
so there you go. Figure out how you want to make your flight surfaces fold or whatever and are you going to build a plug (salvo) around the plane or just make a stopper to push the the plane out.
And if your wondering if I'm talking like a Internet know-it-all.... Nope I've been an avid tater cannon builder for some time. Here is my latest build
 

Attachments

earthsciteach

Moderator
Moderator
#16
I shot a sub (sandwich) from a previous one of mine from about 10 feet away from a concrete block wall. It was nothing but deli confetti. Ah - good times!
 

MrGravey

Senior Member
#17
This sounds like a great challenge and one I would like to play with some time in the future. I, however, need to spend more time working on the tube idea as the "spud gun" is considered a home made firearm in the state of Georgia and is therefor illegal or make, own, or fire. Other states are this way too so be sure you know your laws before firing your plane from you spud gun, you might end up losing both...
 

MrGravey

Senior Member
#20
How about a compressed air model?
I think that would be fine but to be honest I worry as much if not more about the safety of the air model. It is also a bit harder to deal with. You have to have an air compressor to power the thing. I'll watch this video and see if this guy has a better idea than the way I have thought to make an air powered spud gun in the past however. Maybe its easier than I expected.