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Tunnel heat

Ron B.

Well Known Member
On our RV-10 as with many other RV-10s the tunnel heat was a concern. Our RV-10 Andair fuel handle was always warm to the touch and the tunnel panels were close to calling them hot. In the RV-10 tunnel we have the SCAT tubing for cabin heat. I noticed my Andair fuel handle is cold in the RV-14A and so are the tunnel panels (I'm glad) but was wandering why, other than the above mentioned item?
Tim , did you see a difference with yours?
 
Ron, I think it's 3 things:


1) The heater SCAT tube inside the tunnels on the RV-10 is *really * hot. There's a lot of heat generated by that tube. Running it right by the fuel valve doesn't help either. I did line the inside of my tunnel with some reflective insulation and that helps keep the aluminum cool also.
Oh, and, I have that same silver 1/4" insulation wrapped AROUND my SCAT tube from front to rear....that helps keep the heat inside the SCAT.

2) This one's a biggie... On the RV-10 where the heat exits the tunnel it's an aluminum Tee put on the SCAT Tube. Then the aluminum tee attaches to the aluminum tunnel. That Tee gets SUPER hot. I'm sure it's at least 180-200 degrees, maybe even a lot more, but I've not measured it. It will burn you. The aluminum tee conducts the heat to the giant heat sink of the tunnel walls. So up by the firewall, and, under the front seat backs by the front seats, the tunnel gets VERY hot. I can even burn myself on the seat frame when running lots of heat in the winter.

3) On the RV-14, the heater control boxes are further apart, and one on each side of the plane. So there is a lot of localized heating but it doesn't combine to cause a huge issue. In the summer, with my leaky heat valves, my floor got VERY hot. The kids complained that they couldn't wear sandals and the carpet got too hot for them. I really need to get down in there and seal those heater doors better. But, the RV-10 puts those same boxes right on that same already hot tunnel area. They also act like huge heat conductors sinking into the tunnel and firewall. The only real fix for that is to put some silicone hi-temp baffle material between the heater control boxes and the firewall. That will help relieve the conduction slightly. (That's on the RV-10 not RV-14 for those of you following).

So the RV-10 just has too much heat concentrated right into that tunnel, but there isn't really a great way to get the heat to the rear otherwise. Sure, you could probably split into dual front heat just like the RV-14, and run just one SCAT to the rear. That actually could help, but it would make a bigger SCAT mess up front and you have the oil cooler on the firewall that may get in the way. So that design is kind of a compromise.
 
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