9.4.2 Fitting Upper Strake

This entry is part 13 of 18 in the series 09 - Fuel System

Because there’s no way to see inside the strakes with the upper skin on, the height of the ribs/baffles is an approximation. To get a perfect fit, duct tape (is there anything it won’t do?) is applied to the inside of the upper skin where it will contact the ribs. A bead of epoxy/Cabosil is run on the tops of all the ribs. The upper skin is then lowered in to position and left overnight. The next morning, the upper skin is carefully removed.

This is the result

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After a little clean up of the spots where oozed too much, it’s time for Jeffco. As you may remember from the sump tank, Jeffco is tricky stuff! First off, it’s not needed with the type of fuel that is presently used for piston engine airplanes (100 octane, Low Lead). But if the fuel is ever changed, it could react or eat through the epoxy. So just about all builders coat their tanks with Jeffco. A very hard, resistant epoxy. The problem is the stuff has a tendency to exotherm (heat up) rapidly. When it does, the mixture will set. So it has to be mixed in small batches and applied. Oh yeah, and you have to keep a wet edge. If the area that you’re working next to sets up, you have to let it harden and then sand it. So this is definitely a good multi-person job.

Shiny fuel tanks!

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The last picture shows the wheel well. Remember how I said that I was going to use the the angled area for additional fuel? That area needs a bit more work. Openings so the fuel can flow in and out have to be cut and then the Jeffco can be applied.

Wheel well jeffco’d:

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Here’s the outside edge of the left strake looking back from the front. On the right, you can see two of the bolts that hold the wing in place. The hole in the bottom provides access to the bolts so the wing can be removed.

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