I posted this on the engine forum but got no reponse. How about some help on the problem from the conversion guys.

I'm routing the exhaust tubes from custom mufflers on my MVVS 26 gasser powered 1/5 scale OV10 Bronco through the nacelles to exit at the scale location on the outside of the nacelles. Part of the outer 7/8" SS tube is exposed inside the nacelle with all the engine ignition and throttle servo electronics. I'm running a 3/4" exhaust tube inside the 7/8" tube for isolation of the heat. I was hoping that the airspace between the 7/8" tube and the 3/4" exhuast tube would be enough to reduce the heat inside the nacelle.

Can anyone tell me the approximate temp. of the exhaust and is there anything you guys would recommend to insulated the exposed tube inside the nacelle. The outer tube is a tight fit through the balsa and ply construction but I could increase the hole to allow for some form of insulation. I have some woven fiberglass sleeves that are good for up to 1000 F but they don't insulate much.

The exhaust gas temperature can be as high as 1300 degrees shortly after it exits the engine, depending on the carb mixture settings. It cools fairly rapidly, though at full throttle a muffler can still glow red from the heat. They sell a heat wrap for tubular exhaust headers for cars in the speed shops that might help you.

Good luck,
AV8TOR

Dead air space is a great insulator.

I was thinking about 2 insulator/spacers between the 3/4 and 7/8 tubes.
If you could bring outside air into this space and have the heated air exit near the tail of the exhaust
Basicly make a heat exchanger

If you simply insulate it it will stay hot for a very long time