Hot Tunnel Solution

From VAF http://www.vansairforce.com/community/showthread.php?t=104558

I have about 10 hours on my RV-10, and like a number of other builders, had an extremely hot tunnel. It was so hot that on my last flight a week ago, I couldn't even touch the side near my right leg after only about 10 minutes in the air. Since I have the fuel lines running through the tunnel, and my transponder's black box is located in it, I grounded the plane until I found a solution.

I came home and searched this website, and found that I wasn't alone. Two suggested solutions caught my eye: 1) replace the aluminum heater bypass valves that Vans provides with the stainless-steel valves made by Plane Innovations; and 2) add firewall insulation (or other thermal barrier) to keep engine heat and exhaust heat out of the tunnel area.

There seemed to be a lot of variations on the threads suggesting solution #2, and nothing seemed clear-cut or used by the majority. So I tried two heat barriers offered by a racing car supply company called "Heatshield Products" which is located here in San Diego. (I've used one of their products -- the "Lava Shield" -- to protect the fiberglass engine cowling from the exhaust pipes in my RV-6A, and that worked very well.) Their website is www.heatshieldproducts.com.

I ended ordering 12 square feet of "Lava Shield", and 12 square feet of "HP Sticky Shield", which are rated at 1200 F and 1100 F, continuous, respectively, and 2000 F intermittent for both products. (I probably only needed about 8 square feet.) The Lava Shield is cardboard-thin, easily cut with a scissors, and has a stick-on backing. The HP Sticky Shield is a little thicker (1/8 inch thick), but also is easily cut with scissors and has a stick-on backing. The stick-on backing makes installation easy.

I put the Lava Shield on the firewall side of the tunnel, and between the firewall and the new stainless-steel heater bypass valves. I also placed it on the floor of the tunnel. I placed the HP Sticky Shield on the cabin-side of the firewall, covering the bottom half inside the cabin. While I was at it, I put Lava Shield on the inside of the fiberglass engine cowling, where the exhaust pipes came close. It took me about a day to do all of this, since the plane is built, and it's a bit tough fitting my hands through all that engine stuff to replace valves and insert heat shield.

Well, I just flew her about two hours ago. It was a sunny, warm (80 F) day, and I climbed to 6000 ft to see what would happen. Eureka! The tunnel stayed cool to the touch, even when engine cylinder temps briefly touched 400 F.

 Another post in this thread

We have used, and have sold, Heatshield Products for several years with good results. They make good stuff at a very reasonable price. I particularly like their HeatShield Mat.It works well on the engine side of the firewall and also works well to reflect exhaust heat away from the cowling. Easy to cut and install too. A bead of high temp silicone or ProSeal will make a very tidy installation on the cowling too.

For Mike Starkey, no, this stuff will not hold up to Dan Horton's fire breathing dragon set up. It isn't intended to be fireproof. It's intended to insulate and reflect heat.

I use this on the engine side of my firewall(s) but would have no qualms about putting it in the tunnel of an RV-10, although there are undoubtedly many ways to insulate that area.

I am building an RV-6 currently and the firewall will get the usual layer of HeatShield mat to help keep the heat out of the cockpit. The floorboards will also get some insulation, but i haven't made up my mind which product will go there yet.

Heat, sound, paint, and trim products

__________________
Vince Frazier
www.flyboyaccessories.com
RV and Rocket Accessories, Tailwheels, Tools, & More
1-888-8FLYBOY (1-888-835-9269)RV-6 under construction
F1-H Rocket "Crazy Horse"
RV-4 "Chief Pontiac"

From Bill Peyton

---

I used fibre frax on the cabin side of the firewall and the floors, including the tunnel, two layers of 1/8". I also installed the stainless heat valves. Everything else is stock. My tunnel is cool to the touch. I believe that the newer exhaust system with the outlet extension pointed downward, is probably one of the reasons the tunnel issue has gone away.

__________________
Bill Peyton
RV-10 - 190 hrs
First Flight Oct 2012
WA0SYV
Aviation Partners, LLC