A tribute to fallen rockets
Before getting into the details of Effed Up, I would like to post a tribute to two rockets that perished. You may learn a little from my losses.
The rocket on the right is Eyelash, which is described in another post.
The center rocket was called Gee Willikers. It launched but had a tracking failure. My GPS wouldn't fit so I used a 216 MHz RF beacon. At apogee the signal turned from a beep to a click, which in my experience can happen if the transmitter antenna is damaged. I tracked the click for a while until it went over the hill at our site. Despite searching I never regained signal. Gee Willikers is the only rocket I have left in the sage.
The rocket on the left is the original version of Effed Up. It shattered during a pre-flight charge test. This rocket was designed for rear motor eject with a piston. It had GPS tracking and deployment in the nose cone. The electronics sled was screwed in using a long screwdriver. Here are the parts before and while gluing the body to the nose cone:
The rocket had a wrap of aluminum foil in the upper end of the body tube that I put there to minimize damage from deployment charges. I included it as a first layer over the mylar/mandrel when I made the tube. The body was made out of just 3 layers of 1.43 oz cloth to save weight. Ultimately this was not strong enough.
Inside the body tube there was a unique piston. The charge went in the top, then an internal bulkhead, and the parachute in the bottom. No nomex required. The piston was designed to transfer the motor thrust to the bottom of the electronics bay rather than the body tube.
The entire airframe with piston was just 26.4 grams and I added 16.1 grams of nose weight (tungsten + glue).
It all looked good until I did a pre-flight charge test and 0.5 grams of powder turned out to be way too much. I should have started with 0.1 gram. The airframe shattered and the F10 motor shot out the back rapidly. It shot so rapidly that 200 lb kevlar retaining the motor broke at a knot.
I decided to rebuild the rocket with a more traditional separating nose cone and no motor eject. I also decided that I could reuse the name since the rocket never launched.
Even if the airframe hadn't broken, I think that the rocket would likely have lawn darted during its maiden flight. During the first flight of the rebuilt Effed Up the F10 motor, which was friction fit using blue tape, got really stuck in the body tube. I haven't experienced that before. I think the case of these long burn motors gets really hot. It isn't clear to me if the epoxy reached the glass transition temperature or if the blue tape melted. Either way the motor was really stuck. I sprayed in high temperature silicone lubricant and I squeezed the tube and prodded with tools for a long time, trying to get the lube up into the bonded region. Eventually I got it free. This would have been bad when relying on motor eject.
Before subsequent flights I used automotive wax on both the motor and inside of the airframe. It was strange to wax a friction fit motor. The friction fit did successfully retain the motors and they slid out post flight without sticking.