Alice’s Rainbow Bobby, a very alternative take on Launch Lab Rocketry’s Bullet Bobby:
PARA’s Jim H gave Alice this kit at January’s launch. It’s labeled as a Level 2 build but I think it’s a good kit for beginners. There’s almost no knife work (the fins come completely cut out) and you can produce a good result without sanding, sealing, or papering. Alice built the whole thing herself with minimal guidance.
I did wind up doing most of the spray painting as the cans are too big for Alice’s hands to make the rainbow she wanted in such a small length. Even I had to talk her into dropping a couple colors. But I did follow strict specifications and supervision to achieve her intensely deliberated paint scheme. There was even a household vote on candidate designs. I admit I was skeptical at first of the stickers layout she came up with, but the rocket turned out very characterful and wonderful.
The debut launch was… dramatic. The launch lug somehow bound on the rod and took it for a ride as the rocket looped hard into the ground right in front of us. After some field repairs to re-attach fins, launch lug, new parachute, etc., the second flight went up well but again lost a fin on landing, ending flights for the day. At this point Rainbow Bobby’s had fins ripped off on 3 out of 4 flights. Part of it is that the official motor recommendations are a bit underpowered and the delay too long for how much nose ballast is mandated by the instructions—it comes down hard. Compounding that, many launches this year have featured rock hard frozen ground, wrecking numerous rockets on landings that might be fine in summer.
To some extent I think the kit should have been designed with through-the-wall fins given how little attachment they have to the body and how far below it they hang. One tweak to the kit as-is that I’ve applied in our repairs is to drill holes in the body tube where the fins attach, to allow glue plugs to form inside. However, it’s a tradeoff; reinforcing inside the tube makes it harder to replace fins if/when they break rather than tear off. Another thought is that the ballast might be too much. It makes sense, but intuitively seems like a lot when you actually hold the rocket. Perhaps the design doesn’t account for the effect of base drag from the low fineness ratio (its stubbyness)?
But, this past weekend the ground was soft and it just happened that both of the cars next to us had their own Bullet Bobbies! So of course we had a Bullet Bobby Blast-Off, from which all rockets were recovered undamaged.