Wednesday, May 16, 2012

Zipper damage on Formula 75 flight


During my level 2 flight, recovery appears to have been a second or two early, and perhaps also more horizontal than ideal as the rocket did veer a few hundred feet into the wind while coasting. Sadly because of clouds, it was hard to track the rocket through apogee. If I had added a camera, it could have provided a good record and served the function of a telemetry-type data recorder. In any event, I was able to certify (just barely, as this zipper was small) but this is my first ever zipper on a rocket. That includes many paper rockets. And who would have expected it to happen on a fiberglass airframe? The force involved must have bee pretty significant. The recovery shock cord is 3/8ths inch kevlar! The skyangle 'chute was a good idea because it survived what must have been a seriously violent ejection, and safely recovered the rocket.

I plan to repair this zipper by waxing the nosecone, then putting a thin sheet of wax paper on the shoulder. After applying a tiny bead of epoxy to the inner zipper, I will insert the nosecone to hold the epoxy flat. Hopefully some of it will soak into the airframe fibers. More generous amounts of epoxy will be applied to the outside, where I plan to also use wax paper to compress and flatten the area. After cure time, I will obviously have to sand this part down. But I expect that the rocket will be able to fly again with no further problems. I may want to get the cherry bomb/fireball or consider electronics so that I no longer have to rely on simulations to set the delay time. Any advice?

The next option would be to cut off the end of this airframe or get a hefty coupler in there and stretch the rocket with a 36 inch section of airframe. I think that would better reinforce the airframe and would also result in a huge rocket! But at a cost.

2 comments:

Unknown said...

For your level 2, what motor and how high did it go?

High Power Rocketry said...

This was a J285 and it went to about 6,000 feet.