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 doubler

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Old 01-02-2010, 12:03 AM
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G-Man
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Default sig doubler



What do you guys think of a sig doubler with a os 32 sx ? any input would be nice....

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Old 01-02-2010, 12:20 AM
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combatpigg
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Default RE: sig doubler

One of our local clubs races Doublers with OS.15s. They're nice planes, a little bit of work for a club .15 racer.
For the .32 you would end up with a pretty fast plane.
Have you done conversions like this before?
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Old 01-02-2010, 12:23 AM
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Default RE: sig doubler

Nobut i have the help of a friend, im looking for anyone that might have tried this combo, i think this should be fun for my first fast
model !


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Old 01-02-2010, 12:08 PM
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Default RE: sig doubler

You will need to move the firewall back enough to keep the prop in the same location as the .15 prop would have been. The firewall needs to be anchored in there good..I make my own tri-stock out of bass, spruce, etc. to add beef to these glue joints along the perimeter. Packing the nooks and crannies with balsa sawdust then drizzling in thin CA helps. I don't recall what the stock wing hold down design is, but you want to have four 1/4x20 nylon screws that pass through vertical grain balsa block [or wood dowel] inbedded in the wing. I would look at some of the build threads at the pylon forum for more details.
A pair of hard balsa spars [1/4x1/4] will be enough for the wing. Glue 3/32" balsa sheet vertically along the backside of the spars for more shear strength.
Make sure you do a good job of anchoring the servos, this plane will be capable of tearing out any part of the control system that is weak.
Set the throws mechanically for no more than 1/4" from center of elevator and about 1/8" for ailerons.
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Old 01-02-2010, 05:20 PM
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Default RE: sig doubler

I was not able to move the fire wall due to tank size and fit, I glassed the center section of the wing and i hope the stock 1/4 20
wing bolts will do the job.I think my biggest problem will be flutter so i pulled the alerons off and im going to add some more hinges...
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Old 01-02-2010, 10:15 PM
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Default RE: sig doubler

You probably could have used a skinny bladder (tetra style) tank in there. You just need to get the balance right. As flutter can be a concern, It should not be too much of an issue. Generally you will get it with the ailerons and then only if you have the strip style that carry out all the way to the tip. If you have fixed trailing edge at the tip you should be fine. Remember everything in the control system otherwise needs to be tight.
I recommend fiberglassing everything that needs to be strong. Firewall, (use toothpicks or dowels here also) wing hold downs and servo mounts. It seems like I have had more wings blow off of my fast airplanes than anything else.
This is a very popular design for one design racing. I had a kit but never built it and stole all of the wood for something else. Then, I was smart enough to lose the plans! Oh, well. Good luck
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Old 01-03-2010, 05:42 AM
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Default RE: sig doubler

Thanks vert ,I will do my best to make it tight, i hope to give some positive feed back after the first flight is done, I'll
post some pics when i get a chance !!
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Old 01-07-2010, 09:35 PM
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Default RE: sig doubler

here's a picture of the plane that i plan to put the 32os sx with a red pipe
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Old 01-31-2010, 05:31 AM
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Default RE: sig doubler

well we have the doubler ready to fly, Any guesses as to how fast it will be?......ill post a flight report after all is done along with some pics....
by the way go DAGO RED IN 2010......
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Old 01-31-2010, 09:38 AM
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Default RE: sig doubler

I'd guess you might make 110 or so..? It ought to be fun at any rate. The Doubler was designed in a time when "racing" often involved buzzing around at 75mph. I bought an old Doubler kit a while back and was very surprised at the amount of airplane for a .15. But of course radio equipment was classified as cargo back then due to the size and weight. My original Doubler kit has a "racing wing" option - trimmed down wing ribs - does this have that too?

I wouldn't worry about the 1/4-20 wing bolts.

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Old 02-01-2010, 12:43 PM
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Default RE: sig doubler

Does anybody know the C.G. range indicated by the Sig Doubler 2 plans?, got an old one ready to remaiden. Its set a little ahead of the spar and gonna fly regardless, but it would be great if someone could post Sig's recomendation please!
Thanks in advance hopefully!!!
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Old 02-10-2010, 07:04 AM
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Default RE: sig doubler


ORIGINAL: C_Roundy

Does anybody know the C.G. range indicated by the Sig Doubler 2 plans?, got an old one ready to remaiden. Its set a little ahead of the spar and gonna fly regardless, but it would be great if someone could post Sig's recomendation please!
Thanks in advance hopefully!!!
Re-maiden flights went quite well, thanx anyway whole speed community.
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Old 02-10-2010, 08:45 AM
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Default RE: sig doubler

Good show. I didn't bother posting the Doubler CG because I had no idea if the Doubler and Doubler II had identical planforms, moments etc.. so I figured it could cause trouble as easily as help.

What engine are you using? I'm wondering if I should scrounge a .32-.36 when it comes time to finish mine. From the looks of the aircraft anything in a .25 block seems about right.

In keeping with nostalgia, maybe I should not be a powerfreak and simply fit it with the new old Max .25 I scored last fall on the marketplace. That would call for a dope finish I think, and would likely be a nice sport flier.

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