Wednesday, April 07, 2010

Fixit tips

I haven't tried to keep a list of the rocketry tips that I use. Maybe I should go the Wayback Machine and see if I can find my old web site's tips pages?

Anyway, here are a couple of repair tips. Two old and one new.
  1.  To replace a broken shock cord, you can install a Kevlar leader along the side of a launch lug as follows:
    1. Punch two small holes, one on either end of the lug in the fillet area.
    2. Feed the Kevlar twine into the back hole and fish the end out.
    3. Tie a double knot and pull the knot against the hole.
    4. Feed the loose end through the upper hole and fish it back out.
    5. Keeping the line taut, apply a fillet with 5-minute epoxy, and work a bit into the rear hole where the knot is.
    6. If not exclusively using the Kevlar as a shock tether, you can attach some of your favorite sproingy material.
  2. Add a couple of folds of tape (I prefer duct tape) at the point where the Kevlar line touches the body tube.  This will reduce Kevlar-induced zippers.
  3. Now for the new one.  I found several of my Nomex 'chute protectors were tearing in the middle.  Holes will allow gas to pass so this is not good.  I found duct tape works as a decent patch material.  It adhered well and was still in place after the flight.  I don't know low long it will last, but it's cheap and easy to replace if it falls off.