Sig Chipmunk Engine Size?

I just got a Sig Chipmunk that a guy in the club gave me after a fox35 did some damage to it. After looking at it, its a kind of big airplane. I am thinking of using a stock OS 35FP-S motor. Will that pull it well to do the pattern on a 11x5 prop? I also got a spare OSLA40 but probably going to use that in an ARF nobler when I get mine when tower gets them again in stock.

The FP-35 will power a Chipmunk just fine. I used a FP-35 in several Superchipmunks, a CL-3 Chipmunk and Sig Akrobat. However, I used a modified FP with the timing changed to avoid the FP-runaway. If you use the LA-40 and a tongue muffler, you will have a package that runs good without modification and weighs about the same as an FP with the stock OS lightweight stunt muffler that came with the FPs.

A good 11x5 should work fine. I usually used a BY&O 11x6 or old top flite 11x6 power prop on mine.

Which Chipmunk and what is the total weight? The original used a Fox which would do an adequate job of light enough. Of course, power is addictive and if you are a bit overweight and don't become too nose heavy, the size of the Chip will certainly support the 35 FP. You could add longer gear legs if needed. I would put on a tongue muffler, though. More power, less weight (all sounds like a beer commercial, doesn't it?)

LAST EDITED ON Jul-29-03 AT 12:29 PM (CDT)
 
>Which Chipmunk and what is the total weight? The original
>used a Fox which would do an adequate job of light enough.

Van Loo used a G21-40, baffle version. So did Mike Stott, who Jim mentored. I do not think any Chipmunk (kit) version is small enough that the Fox 35 would be adequate. The one in the magazine was scaled down to match the original SIG kit, and had a built up wing like the kit. Most of those that were flown by Van Loo & Stott were foam winged planes.

I built two from the second or third series (1970, CL-3) of kits, 53" span, not Van Loo's own 57", and both of mine weighed around 49-50 Ounces with minimal finish. That's way too heavy for a Fox 35. Add a muffler? Totally too much.

>Of course, power is addictive and if you are a bit overweight
>and don't become too nose heavy, the size of the Chip will
>certainly support the 35 FP. You could add longer gear legs if
>needed. I would put on a tongue muffler, though. More power,
>less weight (all sounds like a beer commercial, doesn't it?)

The SIG CL-3 kits' wood selection varied greatly over the years, from heavy to extra heavy, but the LG block was never maple, it was always either basswood or white pine; that part of the kit requires modification, and what to do to improve this has been covered recently here at SSW.

I would use a 46 to 51 engine in a Chipmunk built today (either size).

.
Kiwi

LAST EDITED ON Jul-29-03 AT 12:45 PM (CDT)
 
I dont know what chip munk it is, its the one from Sig and it has a built up wing instead of a foam wing. Its a real nice plane. It weighs around 42oz. my scale isnt the best but does the job. Just got done putting the FP35 in it, it almost dropped right into the fox 35 mounting holes and has a 11x5 revup prop. Cant wait to fly it, but that will have to wait till next week. Leaving to South Carolina later on today!

Hi Ryan, That FP willdo your job just fine. Frank's problem was that his Fox did not hve near enough time on it to put it in any plane let alone one as nice as the one he gave you!

Years ago I built a profile Challenger (the Sarpoulos design) which used the Sig Super Chipmunk wing kit. I don't have the weight of it but used a stock FP 40 and an 11-5 prop. It flew well but I'm sure it would be too much for a Fox 35 to haul around.

Of the ones I had/have, I always used a .40 in them. One had a Fox .40 stunt engine, too heavy. The one I now have has an OS .40 FP and it is just right. I'm the problem:-)

Jim Van Loo
To set the record straight the first Chipmunk had a Veco 35 Stunt and it was a heavy airplane 52oz and the protype had a 57" wingspan. The second Chipmunk had a ST 40 and a foam wing by Mike Stott. This is the one Mike won the Nats with. It is also the one that he used to redo the Chipmunk and is pictured on the box. That is when the gear was put into the wing with gear blocks.

When Al Novotnik drew the plans for MAN he used a Fox 35 drawing and the landing gear on a plywood rib. I never flew a Chipmunk with a Fox 35.

My third Chipmunk was the one that I flew at the Olthe Nats with the blue and white checkerboards on the top and red and white on the bottom. It had a McCoy 40 in it. The McCoy 40 was a good combination, the only thing was that the front bushing would wear to the point it had to be replaced every 40 or so flights. I also flew it at the 69 Nats but the wing had warped during the trip there and I couldn't get it straighened out.

This was the last Chipmunk that I had until Walter Umland kitted it last year. It has a Brodak 40, weighs 47 ounces, covered with Ultra Cote (can't use dope anymore because of allergies.) I have not flown it yet because of health reasons. The kit has been modified to incorporate the availability of today's standards. Walter has done a great job doing the kit.

I have built two Sig Chipmunks and plan to eventually build a third. My first Chipmunk was the best of the two and it was powered by a reworked Como 40. The second model was powered by a Merco 40 (old style) not the new metamorph. The best Chipmunk I have ever seen is Josh Condons (NATS senior 3Rd place 2003, NATS 1St place 2002). It flies great with a Super Tigre 46. I will probably go with an OS LA 46 next time around.

>I just got a Sig Chipmunk that a guy in the club gave me
>after a fox35 did some damage to it. After looking at it,
>its a kind of big airplane. I am thinking of using a stock
>OS 35FP-S motor. Will that pull it well to do the pattern on
>a 11x5 prop? I also got a spare OSLA40 but probably going to
>use that in an ARF nobler when I get mine when tower gets
>them again in stock.

Inquiring minds want to know. How did a Fox .35 damage the airplane? I had one damage a plane once. A Ruffy. The Fox threw a rod and stopped quickly enough to nearly twist the nose clear off the plane!
Bare

It was nice to see Jim Van Loo's reply!

I bought one of the Walter Umland kits Jim mentions and can attest to it being fantastic. I will be running a Stalker-Modusa 46 Rear Exhaust with their green CF muffler and the S-M 3-Blade 10x6 CF prop.

One of Jim's statements to Walter was that he wish he had more power; so, you might try the Brodak 40 that was used on the first kit.

Sure is nice to have inputs from Jim. Can't beat the words of the designer!

Thanks Jim

In addition a good .40 brings almost all the Classics to life. We were really behind the power curve with the larger Classic airplanes. It was only 25 + years later that we all realized it.

Bob, were you ever stationed in Japan-like the late 1950s? just curious, thanks,

The Fox "burped" when he was doing a wingover with it and lost slack on the lines. I had foxes do that to me plenty of times already thats why I dont use them anymore. I flew it a few times with the OS 35. Flew great, did the pattern nice, but changed to a 10x6 instead of a 11x5 because it was flying to slow for my taste.

To Dale Gleason,

I was in Japan 1957 through 1961. Graduated from Yamato HS. I'm just a USAF brat still having some fun with planes.

Did you know my Dad, Robert R Cooke Jr? I think he was a wing commander flying a C-124 and always gone.

Bob