a70eliminator

Scratch building and want to ask you guys running gas engines if it's ok to build my cowl around the muffler like in the pics or should I leave it hang out in the open?

a70eliminator

Truckracer

My Feedback: (19)

It isn't unusual at all to have the muffler inside the cowl. The issue you will run into though is that a fairly large opening will be necessary just so you can get the cowl on and off over the engine and muffler. Where possible, I try to use a wrap around Pitts style muffler in this kind of airplane to aid in cowl installation, among other reasons. The Pitts will also be quieter than the stock muffler. The same would apply to a fiberglass or built up wood cowl. Some modifications may be needed to the lower firewall area to clear the Pitts muffler.

av8tor1977

My Feedback: (6)

Here's how I did my 50cc Extra, and I have a 30cc Giles that is done the same way. 110 degrees here sometimes and no troubles with the engines overheating. You can see how I made some "elephant ears" off the side of the engine mounting box. These seal the engine compartment itself to the cowl so that air can only pass over the engine. Then below the engine, I took some very lightweight aluminum roofing flashing and made a circular scoop type exit. Notice that I left a lip on the bottom of that exit. That is very important to help extract hot air from the cowl. No problems encountered with the mufflers mounted as you see in the pics. You don't have to have a giant air exit if you put a lip or lips on the exit to cause a low pressure area which helps evacuate the hot air from the cowl. In the case of this Extra, the cooling exit had to be large to get the cowl on. But with rear mount, (Pitts type) mufflers, such a large exit would be unnecessary.



AV8TOR

a70eliminator

Thanks for all the pics.

av8tor1977

My Feedback: (6)

You're welcome. My setup is probably overkill, but I like to forestall problems, not deal with them. Most guys with single cylinder engines just let the head and part of the cylinder hang down in the breeze, cut an exit hole in the cowl two to three times the entry size, and go fly. A twin cylinder engine installation is where you get into baffling, etc. being truly necessary.

AV8TOR

Lifer

My Feedback: (1)

You always have the option to rotate the cylinder. Can save a little by not having to purchase an after-market muffler:

earlwb

Yes, many folks have had the muffler cowled in completely. It is not a problem. You do want to leave at least a small air gap around the muffler as it could burn the cowl, or something. Depending on the cowl shape, size, engine and muffler, some people angle the engine so that the muffler is more enclosed with a larger air gap round it too.

a70eliminator

making progress'

av8tor1977

My Feedback: (6)

Nice work. That should cool just fine. A purist might say to open the bottom inlet a touch, and close off 75% of the upper two, but I say go with it as is....

AV8TOR