Repairing broken fins on L1 rocket

[pmscientist]

All in all, I’d have to agree with Ken. For L1, straight plywood should be just fine (unless you’re going for something in Adrian’s style 🙂 ). I would have to say that 1/8 seems a bit thin though, 3/16 or 1/4 would be alot better. G10 and fiberglassing are both good options as well.

One thing to consider is where damage is likely to occur. On a cardboard rocket with just the fins reinforced, if the fin hits hard, G10 and fiberglass are strong enough that it may be the fin can assembly that takes the damage. A fin repair is likely much less work than a fin can rebuild.

Just for some reference, I flew a modified Binder Excel+ at Ofest on an I566 and an I285. It has un-reinforced 3/16 plywood fins (beveled @5 deg. to a 1/16 wide edge). According to the RRC2-mini, it reached 600fps on the 566, and 640fps on the 285. Probably some error there, but even if it’s 10% off, that’s still pretty close to 600fps on the 285. In addition to that, on the landing from the 566 launch, it landed fin first with no damage at around 20fps. One thing I like about the fins for this particular kit is that there are no hard edges, which from an engineering perspective is a very good thing in this application.

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