Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Sig Kobra(25size) w/32sx

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Old 01-22-2010, 12:52 AM
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evanspa
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Default Sig Kobra(25size) w/32sx

I am finishing up a Sig Kobra with a 32sx. Can someone tell me the best prop for this combo?
Also, any one who has built this kit, how did you set up the ailerons? Mine seem to have a bit of slop. should I go with dual Ail servos?
Thanks all
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Old 01-22-2010, 02:04 AM
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Default RE: Sig Kobra(25size) w/32sx

I'd break it in with a 8x6...then fly with a 8x7 for awhile. I'm not sure what the ideal combo is with this plane, but the 8x8 might be the fastest prop you put on it. If the airframe drag is too much, you might have to settle for the 8x7.
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Old 01-22-2010, 12:55 PM
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Default RE: Sig Kobra(25size) w/32sx

thanks, motor is about 8 yrs old and runs like a raped ape.!
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Old 01-23-2010, 11:43 AM
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Default RE: Sig Kobra(25size) w/32sx

Ditto on the 8x7. Absolutely no comparison in speed for that motor. Several of my buddies and I have been experimenting with 32sx, 35AX, and TT.36, and we have been able to get 135mph in a dive. We are flying the GP Combat Series (P51, P40 and Mustang). If you want even more speed, and you will, buy a Jett muffler for that bad boy and watch it scream.
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Old 01-23-2010, 12:04 PM
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Default RE: Sig Kobra(25size) w/32sx

8X7 should be about the best if you have the stock trike gear.

Mine was built as a taildragger and has a Jett .30 quick and agile.
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Old 01-24-2010, 02:42 PM
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Default RE: Sig Kobra(25size) w/32sx

I made a few changes, Retracts, tail dragger, Sheeted and glassed(minwax) wings/tail. Painted with auto paint. My AUW is 4 lbs 2 oz. About 3/4 lbs over the stock weight. I was thinking I needed a little more torque. I'll try an 8x7 and 9x6 for kicks.
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Old 01-24-2010, 02:57 PM
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Default RE: Sig Kobra(25size) w/32sx

I bet you mean thrust, not torque. Don't drop the rpm of the motor with respect to the flight prop of choice, keep it singing so you have all the potential power available, but trade pitch for disc area (gear down) for earlier flights - this is what you are already plannng to do by swapping the 8-7 for a 9-6 or 9-5. Thrust comes from power applied to the appropriate prop choice. The drag is increased a little bit with the increased weight so the same prop choices should work, but you won't be able to yank it off the runway as quickly.

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Old 01-24-2010, 03:35 PM
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Default RE: Sig Kobra(25size) w/32sx

Yes Thrust is what I'm thinking. The nice thing about this 32 is it has as much power as a 40.
I'm trying the props listed because that's what I have. I am getting ready to build an AK models F-16 Prop-Jet and just wanted to try the Minwax Glassing technique. I mostly fly Slabs (MoAss60) So the speed thing is an experiement
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Old 01-24-2010, 04:29 PM
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Default RE: Sig Kobra(25size) w/32sx

Yeah, those are good choices. I only put down 9-5 because if I had all three on hand I'd check them all just to observe the differences and what they had to offer in terms of performance. I bet the 9-6 is perfect for test flights and decent sport performance; the 9-5 is probably thin on pitch to be of use in that aircraft.

I never did get my own OS .32 when they were on the shelf, but I've messed with them. Nice engine indeed. I want one for a Screamin Demon.

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Old 01-24-2010, 06:11 PM
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Default RE: Sig Kobra(25size) w/32sx

Thanks I'll update my findings, once I get her airborn. I also have a 9x7 I'll try.
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