Discussion in 'Low Power Rocketry (LPR)' started by qquake2k, Mar 7, 2010.
Fantastic work by all, very inspiring. I sense a new purpose to some scrap wood in my garage.
And it's so simple, now that I've actually read the whole thread.
Until I did, I couldn't wrap my head around the issue of how to make sure the fin was actually centered on the body tube, but now it's amazingly obvious!
Thanks to everyone who designed and worked on these jigs!
It's so simple and yet brilliant. Bravo52 actually gave the idea to use shims of varying thickness to center the fins.
The realization that the shim can simply be a piece of the same material I'm using for the fin is what *finally* got me to understand how the jig works.
I typically use 1/8" balsa for my fins, and I've got literally dozens of 1/8" x 3" x 36" sheets of balsa lying around.
If it matters, I think I just thought of a modification that would let you be absolutely sure the fins on opposite sides of a 4-fin rocket are perfectly aligned with each other.
Make 2 of the jigs, with the second one being a mirror image of the first one.
Mark the body tube as usual.
Attach the first fin using the normal jig as described earlier in this thread.
Place both jigs on a base made of MDF or similar that you know is flat.
Rotate the body tube so that the first fin is lying on the mirror-image jig and then attach the second fin using the normal jig.
Tada! Perfect alignment!
You would need to cut a slot in the base for the first and second fins to fit through,and there would need to be an open space underneath the base, while you're attaching the third and fourth fins.
Yep, I use pieces of fin material, which in my case, is usually 1/8" or 1/4" plywood.
I finally built one of these. I used a 1x6 MDF board that I found in the Home Depot Clearance pile. MDF is a engineered wood fiber product that is pretty dense, heavy and stable. I glued two pieces together to make it twice as thick, and then cut it to shape. It is held together with glue and staples from a pneumatic stapler, don't even try to use nails and a hammer, and for screws, a clearance hole is necessary or else it splits. I glued three dowels into the lower section and they hold the top piece in alignment with the lower piece. For shims, I use the leftover fin material that is in the kit, that way I always will have the right thickness. I used rubber bands to hold the body tube on for now, I may go to elastic later, but the rubber bands that I have worked pretty well. I have only one kit built on this but I will never go back to any other way to attach fins.
That turned out really nice!
I'm wondering if making one of these out of plywood would be better. Ply shouldn't warp like dimensional lumber could, and is less likely to crumble if there's something that accidentally hits it with any force (e.g. floor). Then again, it can have some pretty nasty edges if left untreated.
MDF or Melamine are much more dimensionally stable than plywood.
I used MDF on my small one, and kiln dried redwood on my large one. Haven't had any issues with either, and I store them in my garage.
I wouldn't use regular B-C plywood, I would try and find some nicer stuff, Baltic Birch Plywood, Apple Plywood, Or any plywood that has an outer layer of Melamine, or high quality veneer. For that matter, a sink cutout from a counter top would work nice with that Formica on it, as long as it was a smooth Formica. The key is to have wood that will not warp on you, that means it has to be completely dry, or it needs to be an engineered wood.
Whoa... Leave it to us to make a simple design into an overly complicated one, consider ten thousand ideas then end up with a very simple design. I <3 rocketry
This thread quickly inspired me to build a jig, coat about 30 bucks using 2x8 redwood.
Works great thanks!
Many choices! I am going to have to build my own. I like the idea of Formica or countertop.
Wow, it's been a few years since I started this thread. I'm glad it's still inspiring. I have built literally dozens of rockets with this jig. Never had a problem.
And once again, you have inspired more.
I'm not very active anymore, although I attend launches when the weather cooperates.
I rarely launch high power so I understand. As prefect, I tend push the buttons and fly less.
The VP of one of our clubs is almost always LCO. The only one he ever launches is his pinata rocket, filled with candy for the kids. When I do launch, it's mid or high power. I haven't launched low power in years.
We just have to get back out there and fly.
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