E80 Spring 2016

Fiberglassing a Body Tube

Before You Begin

A properly fiberglassed tube will have a much higher strength than an unreinforced tube. Fiberglassing isn't hard but requires attention to details. In addition, there are several safety items you must pay attention to:

  1. Inhalation hazard: Fiberglass dust and short glass fibers can cause serious respiratory problems. The main danger from inhalation comes from sanding. You must either wet sand or have full respiratory protection when sanding fiberglass. Since full respiratory protection is expensive (the little paper dust masks aren't adequate) and requires training, wet sanding is recommended. For wet sanding, you don't need to immerse the part in water or have water running over it. Simply dip or wet the sandpaper with water, sand, and then dip or wet the sandpaper again before it dries off. The fiberglass dust will adhere to the wet sandpaper. Dispose of the wet sandpaper in a sealed bag before it fully dries. John Coker doesn't wet sand the ends of his tubes, but you will, right?
  2. Epoxy vapors: Epoxy must be used with adequate ventilation, either under a fume hood, in the paint booth in the RDL, or outside away from any building that might pull the fumes into its ventilation system. While epoxy doesn't generate nearly the fumes that CA does, you still need to follow good safety protocols.
  3. Skin protection: Epoxy carries a strong risk of causing skin sensitization and allergic reaction. Don't increase your risk. Always use nitrile gloves when there is the slightest chance that you might come into contact with uncured epoxy. John Coker uses his gloves when contacting epoxy. You should as well. In addition, when you are wet sanding the cured epoxy, be sure to wear nitrile gloves so that you don't come into contact with fiberglass dust or short glass fibers. Both can cause serious itching and potentially more serious complications. John Coker didn't wear gloves while sanding, but you will, right?

Section 1 – Cutting the Fiberglass

John Coker, a legend among hobby rocket enthusiasts, has many helpful techniques and hints on his website. Here is his video on how to cut fiberglass. He should really be wearing nitrile gloves, but otherwise, his instructions are excellent. We have cutting mats and rotary cutters for you to use.

Section 2 – Rolling the Tube

Here is John Coker's video on how to glass a tube. We know of no better instructions (if you disregard his few minor safety violations). We recommend using dust-free cloths (like a Swiffer) rather than isopropanol for cleaning the tube, because the paper tubes will absorb isopropanol and distort.

Section 3 – Slots and finishing

The slots in the body tube for the fins and the launch lugs should be cut out before fiberglassing the tube. It's easiest to cut the fiberglass away from the slots when the epoxy has reached the leathery semi-cured stage, after about two-to-five hours. You can cut through the mylar if you can see where the slots are. Use a sharp razor knife. Cutting after the epoxy has fully cured will be much more difficult, but can still be done. Be sure to dry fit the fins into the fin clips on the motor holder before trying to glue them in place.

If you use either mylar or mold release, you can probably simply spray primer on the finished tubes without initial sanding. Remember when sanding the fiberglassed tubes that you must either wet sand or have full respiratory protection if you sand through the primer into the fiberglass..

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