Spar Joiner

This site was last updated on February 15, 2008.

The spar joiner is basically a simple cylinder of CF-epoxy, used to hold the two half spars together. Looking more closely, you'll notice that it's doubly tapered to precisely match the inside of each half spar.

This is the tooling used to mold the joiner. The cloth for the joiner is wetted out with epoxy and layed up inside the mold (the grey cylinder). The mold is supported on either end by the nylon syringe holsters and the bladder is inflated inside, achieving a sort of reverse vacuum bag.

The mold is made in two parts, so it can be split apart to retrieve the part. The interior is cast from plaster. Notice the "extra" nuts set into the right-hand part. These support threaded rods used to force the halves apart after the glue has set.

The joiner is made from a piece of CF cloth, reinforced with strips of CF tow layed spanwise. We lay it up on a sheet of polyethelene, wetting it out with a measured amount of epoxy (we measure it to avoid having to wick away huge amounts of excess epoxy when the bladder is inflated).

The wetted CF is rolled up and put in the mold, and a sheet of mylar is rolled inside that, and finally the bladder is stabbed into the whole mess.

Here you can almost see the bladder inflated in the mold. And while the glue dries, we start working on something else.