12.3.4 Cooling Plenum Intakes

This entry is part 26 of 50 in the series 12 - Engine / Propeller

Now that the plenum is (mostly) complete, I need to get the cooling air into the plenum. In the normal installation, this is accomplished with NACA duct extensions.

I could use these extensions, but they would restrict access to the area between the engine and the firewall. So I decided (big surprise) to go a more traditional route. I created a pair of extensions that would permanently attach to the inside of the cowling. To build these I started with some foam that use formed to the desired dimensions. Then I covered them with a release agent (duct tape). Placed the forms on the inside of the cowling and covered them with a few layers of BID and a layer of Triax.

When they had cured, I trimmed them and created a lap joint where they would meet the rear of the NACA duct. Then I trimmed the forward wall of the plenum.

When it’s time, they will be bonded to the inside of the cowling.


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