Recently I realized that I haven't built a new rocket start to finish in well over a year, partly due to this funk I've been in. It's been a hard couple of years. I put the finishing touches on my Estes Mercury Redstone, yes, and slapped together a quick model from spare parts of other rockets, but I haven't started and finished a new model in way too long.
It's time to remedy that. I grabbed the Estes Super Big Bertha off the build pile and started it during my week's vacation from work.
I like the built up fins. I've done multi-ply fins on some scratch builds I've made, and they can make for very strong fins. I don't plan on beefing up anything with plywood on this one. I want to keep it light and be able to fly it on F15 black powder motors. I bet I could even get away with a D12 in this and keep the altitude really low on small fields if I watch the weight. If I want to use something thrustier, maybe I'll make a second one with plywood centering rings.
Surprisingly, this will also be my first BT-80 rocket! I have built other 2.6 inch rockets before, but they all used heavier tubing.
The fins on the Super Big Bertha are really great. 1/8 inch balsa cores and 1/16 inch balsa skins make fins which are about 1/4 inch thick when assembled. Take your time - this part can be tricky.
Instructions suggest CA (cyanoacrylate glue - Super Glue, basically) for this step. I use CA sometimes, but avoid it when I can. And in this case, I think laminating them with wood glue might make for a stronger fin. Not that it's critical - they're not likely to brake. But the wood glue, if properly applied, should soak in and make the fins one solid piece.
I spread the glue on the spars of the core, evenly and thin, then press the skins on. After holding them tight for a minute or so, I press them between waxed paper and heavy, flat books. Only one skin at a time - you want to make sure they don't slide around when you're placing them under the press! After 20-30 minutes of dry time, I flip them over and do the other skin. Then I leave them under the books for AT LEAST a day for them to dry thoroughly. Any residual moisture can still cause the fins to warp after you take them out from under the heavy weight.
The edges may not all line up perfectly when you do this - ideally, the outer skin will be slightly larger. You'll then sand everything even. Just make sure the root edges are even - that would be the hard part to fix.
Don't throw out the sheets the fins are cut from - lots of good scrap balsa there for other projects!
I really like these fins - they're solid!
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Daniel - great choice for getting back in the groove! I’m not even all that big a fan of the BB design but my Super BB is one of my best flying rockets. I tend to build fairly light but I’d never use an Estes D12 - the flights I’ve done over an E12 have been ok (light winds and a rail are your friend!) but the D12 just doesn’t have enough of a kick for a SBB. What I’m really looking forward to is trying out one of the 24x70mm QJets - the QJ D22 in an adapter should be the great small field motor for the SBB - approximately 400 ft apogee fits my field size at the nearby park perfectly. The QJ E26 will probably push it higher but I like the safety margin off the rod with the faster burning D motor.
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