[rv9aviator]

I am still fighting a heat problem with the exhaust pipes being too close to the cowl and scorching the fiberglass. The rubber hose exhaust hangers just won't keep the pipes away from the cowl The mufflers are very close to the cowl bottom as well. I am going to change the hangers to attach to the sump and add a cross brace but after looking the situation over I am thinking I also have an exit air problem. The mufflers themselves block a lot of air going to the lower cowl exit area as compared to just exhaust pipes. I am thinking about reshaping the bottom of the cowl to widen the exit area some which will do two things. It will increase the exit air area and give the mufflers and pipes more clearance. I am talking about maybe an inch on each side. I doubt it will increase the exit area much over the original design but will account for the blockage of the mufflers. Any thoughts or advice? I'll post a picture tomorrow looking up into the bottom of the cowl.

 

[apkp777]

Jim, are you getting heat damage to the cowl? I have mufflers and though they sit very close to the cowl, I haven't had any heat related damage (yet?) My tail pipes are practically touching the lower side of the cowl exit and no damage there either. I do have some aluminum tape on the area around the lower cowl, perhaps that helps, I can't say for sure.

 

[DickDe]

Jim...I have an RV6 with an 0-320 with a Vetterman cross over exhaust. My exhaust pipes are close to the cowl with no heat damage but the painted interior of the cowl is covered with sticky backed aluminum foil which Vans sells as a heat deflector. It has worked for about 400 flying hours.

Dick DeCramer
RV6 N500DD
Northfield, MN

 

[rv9aviator]

I have the Vans sticky aluminum sheet with 1/16 fiberfrax between the sheet and the cowl. I guess I'll get the hangers changed and at least that will keep them from moving around. I'm still thinking the exit is a little too small with the mufflers choking the exit.