Fin strength

[Rick Lindsey]

I've got a Canadian Arrow that I'm planning to kit-bash into a scifi moon-rocket. The fins that I'm planning are a bit more delicate looking than the ones that come stock (they're bigger, curvy, and come to a pointier point). Since the fin-stock that came with the kit won't work (it gives me a nice template for getting the fin tabs right, but my fins are bigger than the laser-cut ones in the kit), I'm left with choosing a fin material.

I'm also still waffling on whether to use an estes 24mm motor tube (came in the kit), a LOC 24mm motor tube (got some in the basement), or a LOC 29mm motor tube (again, pretty sure I've got some in the basement). The 29mm tube would require new centering rings, but it'll fit out the back of the boat-tail just fine.

The three materials I'm considering are : paper'd balsa, with a laminated LE/TE, basswood, and plywood -- all in the same thickness as the stock balsa (since that's the size slot I'll have in the boat-tail). If I go ply, then I'll definately upsize to a 29mm mount. I'm thinking basswood will be plenty strong, though, and I can't help but wonder whether the basswood is that much stronger than papered balsa, especially if I laminate some narrow strips of balsa along the curved leading and trailing edge.

Any/All input is appreciated!

thanks,
Rick

 

[Balsa Bob]

Any chance we can see a sketch of the fins?

 

[Rick Lindsey]

Originally posted by Balsa Bob
Any chance we can see a sketch of the fins?

This is probably not to scale, but gives you an idea of what I'm shooting for...

It's 2.6" diameter, with basically as little body tube as I can get away with between the tail and nose cones.

-Rick

 

[TeenRocketNerd]

I'd go ply fins and 29mm babay!

for 24mm, I would use basswood.

do I smell a build thread ? *hint* *hint*

 

[Rick Lindsey]

I picked up some of each today (3/32" balsa, bass, and ply) -- I don't know if my hobby knife will be up to the task of cutting ply (or even bass?) though! Might be time to pick up a coping saw at the hardware store... (I've got a razor saw, but alas, these fins aren't straight!)

-Rick (who supposes he might could do a build thread, if his arm were twisted, but he builds slow )

 

[TeenRocketNerd]

Originally posted by Rick Lindsey
I picked up some of each today (3/32" balsa, bass, and ply) -- I don't know if my hobby knife will be up to the task of cutting ply (or even bass?) though! Might be time to pick up a coping saw at the hardware store... (I've got a razor saw, but alas, these fins aren't straight!)

-Rick (who supposes he might could do a build thread, if his arm were twisted, but he builds slow )

*TeenRocketNerd reaches over and twists Rick's arm...

good luck on the build! If you have a dremel, you should be able to get the cuts *close* and then sand down to the lines. Otherwise go with the coping saw if power tools (band or scroll saw) aren't at your disposal.

 

[Rick Lindsey]

Originally posted by TeenRocketNerd
If you have a dremel

Alas!

Oherwise go with the coping saw if power tools (band or scroll saw) aren't at your disposal.

I've got a circular saw!

-Rick (in the market for a coping saw)

 

[TeenRocketNerd]

I wouldn't try a circular saw, I can see that ending messy, and being bery innacurate at cutting any kind of curves... might try the dremel with a cutting wheel though if you still crave power tools to cut your fins!

 

[Balsa Bob]

You'll have little trouble cutting basswood with a sharp Xacto blade.
Also, there's nothing wrong with using a razor saw to cut plywood to the approximate outline, and then sand to shape.