9.3.0 Internal Strake Structures

You need some fairly stiff cardboard for this templating method to work well. Luckily I already had some that I saved, but double luckily my neighbor just bought a bunch of cabinets for his home office that came with nice, big pieces of stiff cardboard! Yay! Thanks neighbor John!

The sidebar explains the process I’m using. The photo below shows the first few bulkheads. (The bulkheads form the fuel tank itself while the baffles are internal to the tanks and are used to help keep the fuel from sloshing around a lot during flight.) It’s relatively easy to get the bottom pieces to fit but much more difficult to get the top pieces to fit properly. Being able to slightly adjust the edges (using my belt sander), then slide the top piece into place with the top strake half on was invaluable. It still was a pain, though, because I had to climb inside of the fuselage and reach through the baggage opening to make those adjustments! All told, I spent the better part of a week making all eight of the templates. The good news is that I should be able to reuse these for the left side with only slight adjustments. (The photos you see here are for the right side of the airplane.)

If you look carefully, you’ll notice that I’m using popsicle sticks as feet for each template. I’m holding each “foot” down with some duct tape. While adjusting and positioning the top piece, I just use a small spring clamp to hold the bottom and top pieces together inside of the rectangular holes. You can see those clamps on the piece labeled “3 & 4” on the right side of the photo. Once everything fit properly I drilled some 1/4” holes through the top and bottom pieces and using some 1/4-20 bolts, washers and nuts, I bolted the pieces together so that they wouldn’t move. You can see the bolts in the bulkhead labeled “1” in the center of the photo.

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Creating the templates for the bulkheads.

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Closeup view of the method I'm using for creating the templates.

The photo below shows all but one of the templates in place. This photo gives you a good idea for what the actual fuel tank looks like. It extends from the leading edge (except for the far left and far right sections) along the number 1, 3 & 4 bulkheads as well as the #8 bulkhead on the far left. Part of the fuel tank also butts up to the side of the fuselage aft of the baggage compartment where the two temporary wood blocks are glued to the side. (They are there to temporarily support the strake top piece while making the bulkheads and baffles.) The fuel port passes through that section of the fuselage and eventually into the sump tank located in the back of the fuselage. (See Section 9.5.0) Fuel never touches the center (main) spar. The area aft of the #1 bulkhead and left of the #8 bulkhead remain open.

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All of the right-side bulkhead and baffle templates are now complete.

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Inside view through the baggage compartment opening showing some of the bulkheads.

Now that the templates are finished, it’s time to make the actual bulkheads and baffles. That process starts on the next page, Section 9.3.2.

ui© John Trautschold 2018