Sukhoi 39 Frogfoot - RC Groups
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Dec 18, 2004, 12:28 PM
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Sukhoi 39 Frogfoot

This is my latest depron 'jet' project. After the Swallow and the Vampire, I decided to make something a bit more 'scale'. I designed it at 40" span, but when I got my enlarged drawings back it looked enormous! After a bit of umming and ahhing, I decided to go with it. Here are some of the components:

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Dec 18, 2004, 12:30 PM
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I used white depron for the load bearing formers as it seems to have less 'flex' than the black:

Dec 18, 2004, 12:34 PM
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I used some of the techniques I've seen on this forum... The turtle deck has 6mm sq strips added each side. They fit into notches in the formers. I'll have some 'meat' to sand a decent shape...

Dec 18, 2004, 12:37 PM
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The engine pods are laminated from 3 layers. The inner 2 are hollowed out. They act as an anchor for the wing, which has an undercambered section...

Dec 18, 2004, 12:38 PM
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Whoops, should have said, I'm aiming for a semi-scale model of this:

Dec 18, 2004, 12:48 PM
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Power will be supplied by a MEGA 16/15/4 'combat'. The motor will be mounted 'inboard' and will use a 5mm cf rod as an extension, running through 2 ballraces. A mate made me a lovely motor to shaft adaptor...

Dec 18, 2004, 01:21 PM
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Ralph A. D'Amelio's Avatar
Looks real good. Nice to have someone make up the s/m bearing. What do you plasn to use for races.


PS, I also have found that the black depron is a lighter density than the white.
Dec 18, 2004, 01:35 PM
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I got the turtle deck on, also the canopy template, only need to make another eight of 'em! lol

I'm using 5mm internal 11mm external ball races. Another mate found 'em in a heli spares bin at our local shop
Dec 18, 2004, 02:06 PM
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Here is the real thing

Dec 18, 2004, 02:11 PM
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Yep, that's the one
Dec 18, 2004, 04:11 PM
smug in granny panties
monkamarm2000's Avatar
You always pick my favorite planes Neil! lol

Dec 19, 2004, 10:12 AM
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Lol, great minds...

I thought I'd put the bits I've done so far together to see what it looks like.

It might look OK after a bit of sanding? OK, a lot of sanding then

I've decided to change the shape of the wings a little. Less sweep, wider tips. The 'scale' wing I cut looked a bit 'tip stally' to me

I'm not convinced about the motor either, but we'll see...
Dec 19, 2004, 10:33 AM
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RNAF's Avatar
Hey Neil,
looks like a great jet! Good luck with the build!

Dec 19, 2004, 12:31 PM
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Thanks Dave

I cut the 'sport' wing. It has a little more area and the chord at the tips is greater. I threw it together to see what it looked like

Dec 19, 2004, 12:43 PM
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RNAF's Avatar
Looks like a potential,
have you got any idea about wingloading?
Perhaps if this wing works good, you could try the scale one!


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