Chapter 18: Constructing the Turtleback

Step 2: Constructing the Turtleback

It took me all day to fit the foam strips into the jig.  The first two forward strips go in easy and the seam matched up nicely. But as you add more and more strips, the compound curvatures get worse and worse.  So you end up doing alot of custom cutting and sanding to get the seams to match up.  I drilled holes into the lattices and used drywall screws to hold the foam into the jig. Using drywall screws is actually easier, faster, and cleaner than gluing the foam down with 5-minute glue. And when the time comes, you’ll be able to remove the T-back from the jig without gouging out the foam. 

You definitely should use the aluminum strips to help support the seams and to keep them matched together without joggles.  It’s kind of hard to envision this from the plans, but the aluminum strips are shown very clearly in pictures on Norm Muzzy's and Brian DeFord’s websites.  I got away without using any aluminum strips because the seams were matching up nicely.  To be sure, I used nails in some places at the seams to pin/hold the strips together edge to edge.

Two other tricks I’d like to pass along. As the plans indicate, the foam strips start out as 48 inches long, so you’ll be gluing pieces onto each other to get the length required to fit the jig. I used the hinge method to do this. Furthermore, I made sure that all glue joins were where the windows would go, or were located on the starboard side of the T-back. Believe me, everyone approaches the pilot’s side of the plane. Very rarely do they “inspect” the starboard side of the plane. That’s why no one will notice John Slade’s mistakes because he tends to make mistakes on Charrie’s side of the plane! (Just kidding, John.)

Masking tape? I didn't use any! Its only purpose is to cover the foam seams so that micro and epoxy won't drip through to the outside of the T-back.  You'll find out later that it's hard to contour and shape the outside surface of the turtleback if the epoxy and micro have leaked through the seams.  Many builders complain that the masking tape won't stick to the foam anyway. I had no gaps in the seams and I don't "pour" on the epoxy when I do glass work, so my seams stayed clean with no leakage.