Contego Fire Barrier Paint
The Sonex cowling is a tight fit, and in a couple of places sits close to the engine or the exhaust pipes. I wanted to ensure the heat radiating out wouldn't blister or burn my cowl. As I was researching possibilities, I found a product made by Contego called a fire barrier "Intumescent" latex paint. The idea is that the paint chars up and provides a heat/fire barrier, greatly reducing the heat transferred into the material underlying it. This sounded like something that I could use.
It took a fair bit of searching, but I eventually located a distributor and had them send me a 1-quart sample pack. They say they are repackaging it in smaller gallon and quart quantities for aircraft use, and are working deals with Aircraft Spruce and Wicks to stock and sell it.
When I got the package, I was impressed with the literature included. There was a glossy brochure of information, a CD of technical and burn test data, and a wood paddle already coated with the paint. The paddle is to burn to prove to yourself how well the paint works!
I followed the directions and brushed 2 coats of the paint on a section of 0.025" 6061 aluminum sheet. The back side of the sheet had a light coat of Randolph white epoxy primer on it. After drying for a few days, I took my propane torch to the bare side of the sheet. The torch was set with a medium flame, and directed at both an uncoated area of the sheet, and at the coated area. The results were dramatic. The temperatures on the back side of the aluminum were approximately 650 degrees on the uncoated area. The epoxy primer took only seconds to blister up and start to smoke. By comparison, the coated area registered about 350 degrees, and the primer only turned light brown after more than a minute of the torch. The Contego paint didn't stop all the heat, but did make a huge improvement. In the event of an engine fire, this stuff would add valuable time to get the plane on the ground safely as well.
I complied a short video of the burn tests. (BurnTest2.mpg, 5 Meg)
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Updated: 21 Feb 06