Brief Description: Accessory Cooling Blast Tubes - Part 1
Since some of the accessories on the engine can get pretty hot under normal operation, it is suggested that small cooling blast tubes be installed to minimally the left and right magnetos and optionally the alternator. The preferred method is to use some 5/8" nylon ducting coming off the engine baffling chamber and directing the air directly onto the various components.
The 5/8" duct available from Van's (DUCT CBT-5/8) doesn't have the slit down the side that you normally see with similar tubing from the hardware store or a local "Shack". Also, according to the documentation included with the tube kit, it is a high-temp variety. The corrugations on the tube allow you to drill a 11/16" hole in the sheet metal baffle which corresponds perfectly to the smaller diameter of the duct. With a little poking and prodding you can get the tube to stick in the hole very securely.
Over the mags, I left the end of the tube about 1" from the surface of the mag, pointed right at the center. Seems like it should cool them down.
I opted to run a duct to the back of the primary 60a alternator. I opted *not* to run a duct to the 20a secondary alternator figuring that it would be off most of the time and didn't warrant the reduction in baffle chamber pressure by drilling yet another hole.
I did opt to run a duct to the GPS antenna enclosure. This seems like an area that will get very hot on a hot day, and the sensitive electronics will probably prefer to be cooled. There are a couple of small holes in the back of the enclosure to allow the air to escape. Should provide plenty of cooling for the antennas.
