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Author Topic: Conversion of Dumas, Comet, Herr and Guillow rubber band kits to R/C - General  (Read 17738 times)
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dosco
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« Reply #75 on: December 03, 2015, 10:07:29 AM »

So are we good?

Don't know what the DLG use.

I do etch the outside of the CA capillary tube prior to glueing it to the balsa structure. I sand the surface of the tube with 400 grit sand paper. Then I glue down the tube with CA and then I follow up with "canopy glue" to encapsulate the tube. I'm sure how well anything bonds to the teflon so I want to make sure the tube is held in place mechanically.

As I'm lucky to still have a Local Hobby Shop I get it form him. I think he uses Smith Industries adhesives as his supplier for the CA capillary tubes. For these small models the length supplied is adequate.

All the best,
Konrad

Konrad:
Some of the DLG guys use teflon tube with either thin carbon rods or stainless wire. Mark Drela (MIT aero guy) stretches the tube first, then etches, and glue in place. He says that it can be stretched 5x its original length.

When you buy the stuff, is it the shorter lengths? I've seen it on the Bob Smith website ... the #305 comes in a 2-foot length.

Regards-
Dave
 
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Konrad
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« Reply #76 on: December 03, 2015, 10:53:02 AM »

For these gummy band to R/C conversions 2 feet has been more than enough.
I've had good luck using "beading wire" (cable) with a diameter of .38mm (0.015") inside the tube. This has even worked well as a push pull set up if you give the set up some thought. But I'd feel more comfortable with a pull pull set on larger models (I've never liked the idea of pushing a rope, but it works on the smaller models ).
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dosco
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« Reply #77 on: December 03, 2015, 12:09:18 PM »

For these gummy band to R/C conversions 2 feet has been more than enough.

Makes sense.

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I've had good luck using "beading wire" (cable) with a diameter of .38mm (0.015") inside the tube.

Beadalon, I assume?

-Dave
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Konrad
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« Reply #78 on: December 03, 2015, 02:39:02 PM »

That sounds like the brand name, stranded cable in a plastic sheath.
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ocminimoto
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« Reply #79 on: March 10, 2016, 07:32:08 PM »

Hey, nice to find this site.

Got back into building the ultra micro conversions. Latest is a Dumas Citabria. 17 1/2" span. Weighs in at 24 grams without a battery and flies surprisingly well.

Had a good read here and have to agree with the experts (Konrad) the pointers given here are invaluable ,will shorten your build time and make flying your model enjoyable as opposed to a sphincter tightening speed demon.

It's all about the weight.

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Re: Conversion of Dumas, Comet, Herr and Guillow rubber band kits to R/C - General
Re: Conversion of Dumas, Comet, Herr and Guillow rubber band kits to R/C - General
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Konrad
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« Reply #80 on: March 10, 2016, 10:52:34 PM »

Thanks,
While I have had some success I'm no expert.

24 grams sounds good. Do you have any engineering specs for us, like the number and type of servos the power system and were you have the center of gravity?

All the best,
Konrad
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ocminimoto
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« Reply #81 on: March 13, 2016, 06:55:39 PM »

Oh silly me,

Radio: I used the brick from my now defunct micro Corsair (which never flew well anyway). Anyone need a fuselage?

Servos: Rudder and elevator only. So the servos are onboard the brick. Also salvaged from the Corsair are the control rods to the tail feathers albeit shortened a bit and the control horn from the rudder and one from an aileron for the elevator.

Wheels: I replaced the wheels with some larger ones from a kids rubber powered kit as the ones that come with the Citabria don't allow enough clearance for ROG launches.

Motor: I was going to use the motor from the Corsair as well but it was too heavy so I installed a motor and drive from the Ultra Micro J3 Cub. Weighs about half as much and has plenty of power provided the drive shaft stays straight. So this aircraft does not like to be beaked in upon landing.

Propeller: I haven't settled on a prop yet and I may end up using a customized one. Currently I'm using some generic props which I think are supposed to be for some kind of multi rotor drone. Three are right handed and 3 are left handed. I'll be using an Ultra Micro J3 Cub prop once I find some. For now I find props with a small hole for the prop shaft, drill it out to 1.75mm and stuff that hole with some 1.75mm 3D printer filament, glue that in place and then drill a proper sized hole for the tiny prop shaft that the J3 drive has. ~1mm.

Centre of Gravity ~20mm from leading edge.

Flying: It's slow!!! That said in calm winds it will fly hands off with no bad habits so far. Note that I only have about 10 minutes on it now.

This plane is for a little contest I've entered. The idea is to convert a rubber powered plane to RC and win a race around pylons in a single basket ball court gym. I tried my other models but they were all to fast for my skills in this little airfield.

With luck I think I might just win. Watch for a video in a week or so. Cool
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Konrad
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« Reply #82 on: March 13, 2016, 09:55:47 PM »

Indoor!
You are doing things way outside the design scope of my Champ build, being about 1/5 the weight it shows! Again good job keeping the weight down.
http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=16387.0
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