My MAC Performance Hyper54, which has been through hell, had a crack in the forward airframe that was getting too big for fixing and I didn't want to sacrifice what precious space I had in the forward compartment by cutting it off, so I decided to replace it with a slightly longer airframe section. MAC kits are made of canvas phenolic (a wonderful material for rockets), but I couldn't get it in time for the launch a few days away. I could, however, get a piece of PML kraft phenolic in time - with almost identical dimensions - from my friend Bernie.
While drilling a hole for one of the av bay attachment screws, I managed to push the drill bit through one side new airframe and out the other. And not clean holes. So I patched those up with JB Weld and then pretended it didn't happen. During the test fit with full recovery gear, I noticed the nosecone didn't sit flush to the airframe all the way around. It looked like some uneven sanding at that end of the airframe had caused it to be out of square. But it was such a small gap and it only covered about 25% of the circumference. Should be fine.
Oh, and I forgot the vent holes.
Flight Profile: During powered boost from a 6-grain CTI K711 White, the rocket oscillated rapidly while transonic which was immediately followed by a puff in the smoke trail that seemed to contain debris. The rocket then stabilized and continued into a normal trajectory and apogee event. However, I spotted the main parachute fully deployed where the incident occurred, which is not normal at all.
My theory is a combination of that nosecone gap and the lack of venting were enough to get the nosecone off-axis resulting in the disintegration of the already compromised airframe. Remarkably, the force was enough to snap the 1/4" tubular kevlar shock cord, yet the rocket - with the av bay as the nosecone now - somehow continued on to 9K' and was recovered undamaged even though the only parachute available had previously disembarked and was lazily drifting toward Miami.
Lost a Wildman FWFG nosecone, a high-performance thin-mil Rocketman parachute, and one Tracki GPS transponder.
While drilling a hole for one of the av bay attachment screws, I managed to push the drill bit through one side new airframe and out the other. And not clean holes. So I patched those up with JB Weld and then pretended it didn't happen. During the test fit with full recovery gear, I noticed the nosecone didn't sit flush to the airframe all the way around. It looked like some uneven sanding at that end of the airframe had caused it to be out of square. But it was such a small gap and it only covered about 25% of the circumference. Should be fine.
Oh, and I forgot the vent holes.
Flight Profile: During powered boost from a 6-grain CTI K711 White, the rocket oscillated rapidly while transonic which was immediately followed by a puff in the smoke trail that seemed to contain debris. The rocket then stabilized and continued into a normal trajectory and apogee event. However, I spotted the main parachute fully deployed where the incident occurred, which is not normal at all.
My theory is a combination of that nosecone gap and the lack of venting were enough to get the nosecone off-axis resulting in the disintegration of the already compromised airframe. Remarkably, the force was enough to snap the 1/4" tubular kevlar shock cord, yet the rocket - with the av bay as the nosecone now - somehow continued on to 9K' and was recovered undamaged even though the only parachute available had previously disembarked and was lazily drifting toward Miami.
Lost a Wildman FWFG nosecone, a high-performance thin-mil Rocketman parachute, and one Tracki GPS transponder.
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