Fin options - Northern Colorado Rocketry

This topic has 18 replies, 7 voices, and was last updated 16 years ago by MikeS.

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October 5, 2009 at 11:42 pm #40793
Mitch Smith
ok, would it be better to use 1/4″ plywood and then glass them or use 1/8″ G10 for the fins. Getting ready to start ordering stuff for another rocket and will be glassing the airframe.
October 6, 2009 at 12:26 am #51221
edward
Moderator
What are you wanting to do? 1/8 G10 is *very* thick. I used it once and then haven’t since. I generally use 1/16″ or 3/32″ thick. Both I’ve had success in beveling. I’ve used 1/4″ plywood but didn’t like that I couldn’t get the finish as nice and was filling it and the pores in the wood.

Edward
October 6, 2009 at 12:37 am #51222
Mitch Smith
Higher speeds. Mach 1+. I already have the oversized extended loc magnum. I was looking at possibly getting the big nuke 3e which has the options of either 1/4″ plywood or 1/8″ G10 fins. More of a kit to learn dual deploy with but having the option of the higher speeds.
October 6, 2009 at 1:27 am #51223
edward
Moderator
It is going to take a lot to push a Big Nuke (5.5″ diameter) to mach plus. I’m thinking very high thrust 54mm motors or 75mm motors. I’d get the rocksim file and see what motors it takes to make it go mach before you make your purchase.

Edward
October 6, 2009 at 1:55 am #51224
Mitch Smith
This one will be with the 75mm mount. CTI has some big L’s in the 6xl case that will do it. I am leaning more toward the wood fins and just glassing them.
October 6, 2009 at 2:29 am #51225
edward
Moderator
Shrink it to 4″ and you’ll be sure to break mach 🙂

Edward
October 6, 2009 at 3:40 am #51226
Bruce R. Schaefer
Plywood at Mach? Splinters. Use G10 on everything with light (& different) layers of composite material. Did you see JW’s record altitude rocket? See the Mach burn on the fins? Plywood will not take it. If you’re serious, use serious materials. Seriously.
October 6, 2009 at 3:50 am #51227
edward
Moderator
Another consideration is do you have the parachute space for the 75mm motors weight.

Edward
October 6, 2009 at 4:36 am #51228
Mitch Smith
It should have the space. It comes with the 75mm mount along with a 18″ drogue and 60″ main. I am starting to think at this point to just build it with the plywood and just not worry about speed at this point and do a scratch build later for speed and altitude.
October 6, 2009 at 7:27 am #51229
Chris LaPanse
Plywood at Mach? Splinters. Use G10 on everything with light (& different) layers of composite material. Did you see JW’s record altitude rocket? See the Mach burn on the fins? Plywood will not take it. If you’re serious, use serious materials. Seriously.

That entirely depends on the fin shape and exactly how high you take it. Mach 1.3 with fairly thick, well designed plywood fins is completely doable. Even mach 2 should be doable without any composites. Of course, you have to be quite careful about it, but there’s nothing about mach that requires composites. It certainly is easier to use them though. One good method that would work fine would be to use plywood with a layer of tip to tip glass. This would avoid much of the expense sometimes associated with composites, while adding significant strength to the rocket.

Sometime, I should make a high speed rocket with no composites at all, just to see how fast I can get it to go. It could be fun 🙂
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