Cowl Plugs
Hey Doug,
Get some low density "closed cell" foam sheet--3+ inches thick. Use closed cell as it will not hold water.
Use your band saw and cut out two circles about 3/4 to 1 inch larger than your openings (James 360 openings on mine are 4 5/8th inch dia). Glue a small piece of aluminum on the back side of the circle--drill a small hole through the center of the foam and aluminum. Run a piece of woven 1/8th inch nylon line through the hole and make a knot on the back side to keep it from coming out. Attach the two plug lines together and, at the center, make a loop a couple of inches larger than the prop root. Install the plugs with the center loop around a prop blade. This will insure if you try to start your engine with them installed, the blade will pull then out and sling the plugs away. I also attached a smaller plug to the line for my inlet opening on my James cowl.
The prop blade loop was added to mine after we had a "very experienced pilot" jump in his RV6 (Kestrel Airpark, Texas) and take off with the plugs installed--CHTs hit 500+ before he got out of the pattern---he landed--then cried!!
Hope this helps.
Cheers,
db