SonexBuilders.net

While working on the baffles today, I happened to look inside my the engine cowling and was surprised at how close the #1 cylinder exhaust pipe is to the cowling. Check it out:



I'm not sure what to make of it right now. At least it's not touching I suppose. Seems like it would burn the cowling. Maybe exhaust wrap will prevent that from happening?

Hi Paul, with the original exhaust on my 3300 the exhaust interfered with the cowling. I had to cut a hole and mold a blister to clear it. The blister was about as close as your photo shows and it did get a bit hot. It discoloured but never actually burned. A heat shield might be good enough. If you need to do a blister later, a bend from plastic plumbing drain pipe makes a nice mold.

Peter

My first cowl was also much too tight. That one was destroyed in accident in shop, for its replacement, installed a 5/8" prop spacer to move cowl forward by like amount. Improved clearances everywhere. Old cowls had about 2" to trim off back edge, so this was not a problem. Understand newer cowls are pre-trimmed to size and this is no longer an option.

David A.

Thanks guys. I knew the cowl was going to be tight, but hadn't expected this. I think the heat shield is a good idea.

Looks like the cooling air will have a hard time squeezing in there too!

DCASonex wrote:My first cowl was also much too tight. That one was destroyed in accident in shop, for its replacement, installed a 5/8" prop spacer to move cowl forward by like amount. Improved clearances everywhere. Old cowls had about 2" to trim off back edge, so this was not a problem. Understand newer cowls are pre-trimmed to size and this is no longer an option.

David A.

Don't mean to hijack the thread but where did you get a prop spacer?

The photo didn't show up when I looked at the post. My exhaust for #2 on my AeroVee is quite close. I have header wrap on my exhausts and have not had any problems with the cowl.

Don't mean to hijack the thread but where did you get a prop spacer?[/quote]

Machined it from 3/4" aluminum plate. That was the easy part. Machining the required longer SS bushings was the time consuming bit.

Later had conversation with the owner of Lonnie Prince of of Prince propellers where he mentioned they sell as similar spacer that has the bushing made integral to the spacer. Might be worth contacting them if looking for something like this.

David A. Sonex TD with CAMit 3300.