Starfire Coupler Tubes

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This page will describe the process used to reinforce the coupler tubing by applying a fiberglass cloth to the inside of the tube. This was done exactly the same way for both couplers in Starfire.

To fiberglass the coupler tubes I used 6 oz plain weave glass. This is a roll of G7628 that I purchased from CST. I used two layers of it on the inside of each coupler.

I use 3M Super 77 spray-on adhesive to seal one end of the fiberglass cloth. This is certainly not required but it makes for a nice clean seam without having to fiddle with any frayed strands of fiberglass. This stuff dries in about 10-15 minutes. It can be found at most any hardware store or paint store.

I only seal one end of the fiberglass. The end that is put onto the tube last. The end that goes down first does not usually suffer much stress that causes fraying. The end that goes down last is typically handled a lot more and can tend to fray a lot.

The fiberglass needs to be cut to the appropriate length. I then sealed one end of it with the Super 77 spray adhesive. This photo shows a small 1/4" section of the fiberglass exposed between two layers of newspaper. A very light coat of spray adhesive keeps the ends from fraying.

I use the West System "Slow" mixture for all my fiberglass work. (#206 Hardener.) It gives a reasonably long working time, somewhere around 45 minutes to an hour. I find that by the one hour mark, the epoxy has started to cure enough that it gets a little too sticky and is much harder to spread and apply cleanly. However, it will take all night for it to completely cure.

The pumps that are available for West System cans are well worth the minor cost. This epoxy needs to be mixed in a 5:1 ratio, so the pumps make that easy. One stroke of each and you're good to go.

Gloves are a necessity. I use these vinyl gloves available at Home Depot.

I use the West System pumps to dispense the epoxy into a 12 ounce plastic cup for mixing with a small wood stick. Once it is thoroughly mixed, I pour it into a plastic picnic plate. This increases the surface area of the epoxy so that it will not self heat and greatly extends the working time. The plate also makes it very convenient to roll the epoxy onto a small foam roller. This roller has had the handle trimmed short to make it fit better inside the coupler tube. A small foam brush is also often very handy.

The coupler tubing is simply sitting on the table and held in place with two wood boards. A piece of plastic pipe runs through the middle of the coupler tube. The fiberglass cloth is wrapped around the plastic pipe. The glass can be slowly unwound and carefully applied to the inside surface of the coupler tubing.

The inside surface of the coupler tube has already been coated with a generous amount of epoxy. Do so much that it is dripping or running, but enough to saturate the cloth.

The first small section of cloth has been applied and rolled smooth with the foam roller.

The fiberglass cloth turns transparent when it is wetted by the epoxy.

One full wrap is done. One more to go.

The fiberglass cloth application has been completed and the plastic pipe is removed. The tube can now sit overnight to let the epoxy fully cure.

The fiberglass cloth was cut to a width about two inches wider than the tube. This allows about one inch to overhang each end. Once the epoxy has cured, the overhang can be trimmed away.

The coupler tube is now ready for assembly.

The top bulkhead has a U-bolt in it for attachment of the recovery system harness. The bottom bulkhead has a single hole in it that allows a threaded rod to be mounted. The threaded rod runs the length of the coupler and is used to hold the top bulkhead in place. The bottom bulkhead is epoxied into place and the joint is reinforced with a 1-inch wide strip of fiberglass.

Here is a look down inside the coupler after the bottom bulkhead has been put in place.

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