6.7.3 Main Spar Triax Layups

This entry is part 21 of 42 in the series 06 - Fuselage

The main spar is an incredibly over-engineered C-beam that protrudes out each side of the fuselage about 5 feet. The main wings will bolt to this spar so it’s very important that it be securely attached to the fuselage. The initial installation is done with structural adhesive. But that’s only a start.

The first step is to make a foam bridge from the top of the spar to the top of the main gear bulkhead. Here’s the left side with a piece of divinycell foam bridging the space between the top of the spar and the top of the gear bulkhead.

 2008-01-30 IMG_5896

Here’s the right side after I’ve coated the foam with a slurry of epoxy and microballoons. I’ve also created fillet in the corners to make an easier radius for the layups.

 2008-01-30 IMG_5897

The same location with all the layups in place.

2008-01-30 IMG_5898

At the location above the spar, there are 10 layers of triax. Some of the layups run down the foam bridge and go almost to the floor. Others go towards the windows. In all, there are 12 separate pieces of triax. And that’s just on one side. The light colored patches are peel-ply. Thin dacron that’s placed over the layups and makes the surface of the fiberglass smooth. Very important at the edges since without it a lot of sanding is required.

The following day, did the left side spar reinforcing layups. No pictures since it’s the same thing I did yesterday. But, I was done by lunch

There are some really sharp edges so it’s a good idea to hit the edges with some sandpaper otherwise lots of blood will be left behind. 



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