How Much Insulation On Lower Cowl?

[Finley Atherton]

I need some advice on how much of my 9A lower cowl should be insulated from exhaust pipe radiated heat to prevent damage to the paint and the cowl. Obviously the area where the lower left pipe is near the cowl. What about further forward and where the pipes cross over forward of the sump? I assume insulation would NOT be needed where the cabin heat muff comes close to the bottom cowl?? Any photos would be great!

Thanks
Fin 9A

[robertahegy]

Some of the Van's self stick reflective heat shield under the muffler and pipe is all I used. Keep things at least an inch away and you should be fine.

Roberta

[Jerry Cochran]

Fin,

Here's what I did, and fine so far. First off, I painted clear epoxy inside of cowlings to seal same, which prevents oil or fuel soaking in. Then installed lower cowl, took a sharpie and marked area around pipes with a generous outline.
Took cowling off, cut Van's heatshield and firmed it down. I used a chunk of 1" foam I had laying around to press it down.

HTH,
Jerry

[rscott5559A]

Some pictures here on my site at http://www.myrv9a.com/FW4-7-07.htm

Robert Scott
RV9A Wiring!

[kentb]

I looked at your web site. Did you use standard alu. foil while the resin was still tacky or did you use the stickback stuff that Vans sales?

Kent

[Rick6a]

Originally Posted by Finley Atherton

....Any photos would be great! Thanks
Fin 9A

As a data point, initial flight testing on my 6A revealed the need for additional heat shielding. The arrangement has worked well.

[rscott5559A]

I used the stuff that Vans sells.


Cowl Heat Protector
Heat Reflective Material


Description


A self adhesive heat reflective material designed to place on the interior of the cowl in locations where the proximity of the exhaust pipes might damage the resins.
30 inches wide. Sold by the foot.

Robert Scott

[Bob Axsom]

Van's created a new cowl for the RV-6A when I ordered mine and the clearance between the cowl and the Vetterman exhaust system was reduced dramatically according to Mr. Vetterman without his knowledge. I had more like 1/4" clearance. I ran the engine on the ground without any insulation. It burned the cowl along the track of the pipe from the left front all the way back to the cowl outlet. The faceplates and the honeycomb core were turned to charcoal but the shape was retained. I rebuilt the damaged area. I cut off the pipes at the vertical slip joints and made shorter steel links to allow me to raise the pipes as far away from the cowl as possible. I bought the expensive aluminum foil backed woven silica thermal barrier material and glued it to the inside of the lower cowl with 3M weatherstrip adhesive. That did the trick and the outer surface of the cowl in that area remained cool to the touch. I run the engine at red line at times and I found that the left side of the cowl was taking on a toasty shade of brown so I covered the left side of the lower cowl as well and that problem was corrected. Larry Vetterman after learning of my experience contacted me on his own and told me that the change in cowl almost caused his company to fail and he had to work with around 50 builders to resolve the problem before he was able to change the exhaust pipe configuration. If you have an inch or more of clearance and you never run over 2450 RPM the aluminum foil from Van's is probably adequate but I do not believe it would have been adequate for my airplane.

Bob Axsom

[Finley Atherton]

Thanks for the replies. I have the Vans reflective foil on backorder. I also have some spare 1/8? fiberfrax. I am thinking I might use it under the foil where the pipes come close to the cowl. The foil would cover and extend past the fiberfrax so the foil should protect and hold the fiberfrax in place ???

Fin 9A