How to cut and drill Cowl?
 

Hey Guys,

Please suggest best method or cutout size and shape to get air to the carb for a Richmodels Yak 54 with an OS 46 FX sidemounted.

See the pic where inner cowl lip meets at the carb mouth, rather obstructing the induced airstream. Without an air intake cut in cowl, I suspect low pressure area inside lip of cowl will starve carb for air.

This is the motor I WILL use, underpowered or not, with Slimline Pitts style muffler to exhaust at bottom of cowl. Any tips for marking, cutting and protecting edges of cowl are appreciated. It appears this cowl is fiberglass reinforced plastic.

Cutouts or holes for glow plug, needle valve, and exhaust pipes will be made with a Dremel tool. Also plan to mount hardwood blocks on front edge of fuse former for cowl screws. Do you use grommets to prevent cracks from screw holes?

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RE: How to cut and drill Cowl?
 

This may be a dumb idea, but how about putting a volicty stack on the carb, extending through the outside of the cowl? That would keep the leading edge clean.

I'm fighting a cowl now myself. I have built a Great Planes Super Aeromaster. The stock cowl was built up balsa with a plastic nose on it. I did an awful fiberglass job on it so I now have a Fiberglass specialities cowl on the way. I know I'll have to cut a hole in the side large enough to drive a truck through. I'm using a Magnum 91 four stroke with a pitts muffler. About half the engine is going to be outside the cowl and a big chunk of the end of the muffler. I've butchered the wood cowl for a pattern to cut the fiberglass one. I sure hate to screw it up. I'm looking forward to some real answers to your question. I'm sure I can use them also.

Don

RE: How to cut and drill Cowl?
 

You don't need to do a thing.

See that space behind the cowl? That's full of AIR.

There's no low-pressure area there. The carb will suck that air just as well as any.

RE: How to cut and drill Cowl?
 

If you have to cut the cowl,the cleanest thing Ive found is a dremel with a sanding drum.The 1/4" size works well for smaller areas and the 5/8" or 1/2" works for roughing in area such as a muffler exit.