Easy Chopper (hopefully) build 2

BABAR

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Well, figure I need to actually build something to renew my credibility on this forum, rather than just gabbing on other people’s excellent builds.

this is try number 2 on a helicopter idea that has been hovering in my brain for a while.

with the exception of monocopters, the FlutterBye, and maybe the Maple Seed (maybe also called the cyclone) helicopter recovery rockets tend to be complicated things. This will be an attempt to make something “relatively” simple and hopefully reliable and very very easy to prep.

it will also be a voyage into using some alternate materials, as this will use Mat Board from Hobby Lobby instead of balsa (I know, heresy!)


for 12 bucks a sheet 32”x40” should at least give me a lot of paper fins (we’ll see how well they compare with balsa), and not having to sand or do too much finishing doesn’t hurt either.

going to use ribbon for the rotor stops, and nothing but gravity, wind and hopefully some simple but clever engineering (fingers crossed vs foot in mouth) to get the fins to open. I am stealing some ideas from @neil_w and Estes Flip Flyer as well.

I am at the partially cut out stage of the Mat Board combine Rotor Fins. The opening mechanism is sort of based on observations with some failures of my standard rubber band actuated helicopters, namely that with blades attached to the FRONT of the rocket, if the rocket has significant forward velocity at deployment (either too early or too late, as an L-0 watching videos of rockets with electronics “magically” deploy at perfect 0 velocity apogee is still cool) anyhoo, if rocket is moving too fast the airflow over the rocket sometimes keeps the rotors from opening if your pull mechanism is not strong enough. So thought, on the other hand, if the hinges are in the BACK, the airflow of the falling rocket SHOULD pull them open, and if they are dihedralled (okay @Rktman i made that word up), they SHOULD stay open.image.jpg
 

Lee

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I had been contemplating something similar – a square BT, chopper blades hinged at the aft end, tilted slightly outward at the forward end to “catch the air”, held in place during lift with an over sized nose cone, released when the ejection charge blows the nose cone off. The fins would support the outward deployed chopper blades. Since the rocket is square, perhaps 2 fins per panel to support the deployed chopper blades.
 

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BABAR

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Something useful for many. Cheap lightweight engine block for low power.

1/16” piece of BT-20 (or corresponding motor mount, works BT-5 and BT-50 just as well)
image.jpg
Snip out a section
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Make sure it rolls up in tube

image.jpg
Mark casing I like 1/2” sticking out

image.jpg

Put glue in tube (white school glue is fine, you want slow tack so pusher doesn’t catch

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Put block in end of tube

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Mark casing

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Push in to depth

Be prompt, gently insert and immediately remove.

image.jpg
 

BABAR

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nose pyramid (aka cone). 32 mm wide (width of folded rotors), 25 mm angles.






image.jpg

folded up



image.jpg



add some color, should have put the tape on before I cut it out

image.jpg
 
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BABAR

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Piston will push off nose cone.
image.jpg

Rear end is a tape rolled centering ring , with cut outs to vent gas when partiallyimage.jpg ejectedimage.jpg
 

Lee

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So, is the chopper finished?
Has it flown yet?
Did the rotors "catch the wind" and deploy?
 
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