Chipmunk engine?

[Clint Ormosen]

Some of you know that I started a JVL Chipmunk kit for VSC 20. My intention was to use a Brodak 40 in it, as the plans show. But I also have a new OS 46LA that I could use. I like the Brodak engine run and am not familiar with the OS 46. Is there really enough of a power difference to justify going to the 46? Also, the 46 is taller and will be harder to hide in the cowl.
Opinions?

[Dan McEntee]

  The .46 will also require you to use .018 lines. If the plane finished out anywhere under 50 ounces, I would go with the .40. I have flown a Super Chipmunk quite a bit with .40's and .46's, and i like the smaller lines better. If I felt I had to have a .46 in it, it would be a classic ST .46. Properly trimmed, that combo can handle the extra drag of the .018 lines, I think.
   What kind of kit is it?
   Good luck and have fun,
    Dan McEntee

[Clint Ormosen]

Oh yeah, I forgot about the 018 line requirement for the .46. I don't want to do that. The Brodak will be fine.

   What kind of kit is it?
   Good luck and have fun,
    Dan McEntee

The kit is one of Walter Umland's kits. The classic legal VanLoo Chipmunk.

[steven yampolsky]

I fly my JVL Chipmunk with B40. It has PLENTY of power plus like Dan wrote: .015 lines are not allowed with LA46.the model also balances properly with B40. With LA46 you will need to add tail weight.

[john e. holliday]

As stated, go with the B-40.  I remember back in the 70's a young man building and flying the Sig Chipmunk as designed by Jim Van Loo kit.  It was powered with a Fox Stunt 35 that was box stock with no muffler.  it was flying so slow I kept waiting for it to fall out of the air.  He would do the whole pattern, but, would not fly competition.  Keep us posted.  DOC Holliday

[Clint Ormosen]

The Brodak it is. Thanks for the imput guys.

[Randy Powell]

Pete Peterson's awesome Van Loo Chipmunk (also an Umland kit) uses a Brodak 40. Pete's dinked around with it a bit and it runs very well. Plenty of power.

Does Brodak still sell this engine with the giant venturi? A friend had one that kept running away on him unless he overloaded it with a big prop. We finally got him to change out the enormous stock venturi for a smaller one and it solved the problem and the engine runs great and very consistent. Just wondering.

[Clint Ormosen]

Randy, as far as I know, they still come with the tall venturi. So does the .25.