12.3.4 NACA duct extensions

This entry is part 38 of 50 in the series 12 - Engine / Propeller

Prior to mounting the NACA duct extensions to the inside of the cowling, I placed the extensions in position between the NACA’s and the plenum. Then I installed the upper cowling and marked where the flanges of the extensions would be. I also drilled three holes through the cowling into the extension flanges. Then I removed the cowling and painted the inside of the cowl where the extensions would be along with the extensions.

Once the paint (actually, primer) was dry, I sanded the mating surface of the cowl and the flanges of the extensions. Then I applied structural adhesive to the flanges and mounted taped them to the NACA’s. The upper cowling was then mounted and cleco’s were used to hold the extensions to the cowling.

Once the adhesive had cured, I cleaned the inside of the extended duct and applied a radius of epoxy.

Finally, I used flush head pop-rivets and 1″ square titanium tabs as a mechanical fastener.

Looking back down the right NACA.


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