Hey guys, I messed around with rockets as a kid and now my nephew is in to them. Last week we were working on some together and I quickly remembered how much I hated gluing the fins on so I made up this little jig. I have a small metal working shop at home with a lathe and milling machine so it was pretty easy to do. It took about two evenings to build and it's made out of aluminum so it should last a live time.

The jig has several different settings for the fin guides so you can have different numbers of fins. The fin guides bolt into place and the bottom plate is slotted so they can be adjusted closer or further away from the center. I made up five different sized mandrels that bolt into the center to hold the body tube in place so I can work with most sized rockets.

We made up two Comanche 3, three stage rockets with a total of 18 fins and glued them up in 15 to 20 min. I'm using CA glue to glue them in place and then remove them from the jig and add fillets with 5 min epoxy.


Dale P.

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That's beautiful machining work! One question though, since the aluminum guide blocks register to the sides of the fins, don't you need different thickness blocks for different thicknesses of balsa fins?

Jeff

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Yes you would, but I only use the same size wood for my rockets. I'm not a fan of balsa and use 3/32 light plywood from the Hobby shop. It only weighs a bit more than balsa and is much stronger. I off set the fin guides for the 3/32" ply wood, but can use shims if I need to use something different.

Dale P.

3/32" balsa is liekly the most common size anyways, so this sounds fair.

one comment though - hate to mention it - but your fins are on wrong , the trailing edge was used as the root edge, and the grain is parallel to the tube ( easily broken off ) .

Always loved the COmmanche, need to add one to the que, especially with E9-8 upper stage

I have five different rocket kits here and most of the fins measured 3/32" so I figured that would be good enough. Even if they are off by a few thousands they will still be on square, straight and spaced perfectly from each other.


As for the Comanche fins... Your right! I just looked at the picture on the box and I did glue them on wrong. Bummer . The rocket in the picture is balsa, but the second one I built is micro plywood so there isn't any issues with strength on that one. The big questions is will it fly with the fins in this position??? If so I will just leave them. We built to fly them, not for show so as long as it will fly safely I don't mind.

Thanks for the heads up. Guess we got a little ahead of our selves.

Dale P.

As far as the fins go, it should be good since they appear to be in the same relative position. They may have a bit more drag than the standard configuration, but being this is a 3-stage then that is a positive development (at least in my mind, you won't have to walk as far). They are on straight so it should fly well, and since you are using epoxy fillets and a wood that doesn't flex much, you shouldn't have any problem with fin flutter in the flight envelope.

I like the craftsmanship of your fin jig. Very nice and for what you are doing is a good solution to get fins on with precision.

Keep us posted with the rest of the build and give us a launch report.

Greg

Thanks for the good news!!!

They are going to get painted tomorrow, but won't be flying until the summer. It's just too cold here to do much outside. Shooting them off in the middle of a frozen lake would be a great spot to launch, but the cold takes some of the fun out of it. We have a few more rockets to finish up, and then we will pack them all up for a few months until it's nice out again.

Thanks again for your help,

Dale P.

If you haven't filletted the fins with epoxy yet you can still remove them with CA debonder.

__________________
Never trust an atom. They make up everything.

4 out of 3 people struggle with math.

Chemically, alcohol IS a solution.

NAR# 94042
SAM# 0078