Rail Button spacing on 4" rocket

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TeenRocketNerd

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Hello All:

It's been a while since I've posted, and I suppose that's due in large part to the day-long build sessions I've been undertaking lately. Anyway, onto my question.

I'm starting a new scratch build, and it will be my first time using rail buttons. I'm planning on mounting the rail buttons via wood screws into the upper and lower centering rings, which I will cut out of 1/4" ACG ply The piece of phenolic motor mount tube I'm planning on using is 12" long. The rear CR will be recessed in about 3/16 - 1/4", and the front CR mounted flush with the end of the tube.

My question is simple: Is spacing my rail buttons 11 3/4 inches (if you want to be exact about it) apart far enough? The rocket is only going to be about 36" long and fly on G's (4" dia as noted in the title), so I would certainly be led to beileve that it would be.

Input and/or insight would be greatly appreciated.

Thanks!

~Travis
 
Sounds like you're going to be fine.

No to sidetrack your question, but have you thought about retention? If you're going to use something like an Aeropack, HAMR or the like, you'll need just a little more exposed MMT on the aft end.

Depending on where you get your rail buttons, they'll probably come with machine screws (the kind meant to go into nuts) rather than wood screws. There's nothing wrong with this; you'll just wind up drilling a pilot hole into the CR to accommodate the screws. Take careful measurements so you'll have a good idea where the CRs are, and if you're not sure, use a needle or thumbtack pushed through the BT to find the front and back of the CR, so you can drill a good hole and center the rail button in just the right place.
 
Sounds like you're going to be fine.

No to sidetrack your question, but have you thought about retention? If you're going to use something like an Aeropack, HAMR or the like, you'll need just a little more exposed MMT on the aft end.

Depending on where you get your rail buttons, they'll probably come with machine screws (the kind meant to go into nuts) rather than wood screws. There's nothing wrong with this; you'll just wind up drilling a pilot hole into the CR to accommodate the screws. Take careful measurements so you'll have a good idea where the CRs are, and if you're not sure, use a needle or thumbtack pushed through the BT to find the front and back of the CR, so you can drill a good hole and center the rail button in just the right place.

Way ahead of you Dave, and thanks!

I'm going to use 2 #8 tee nuts, bolts, and aluminum storm door clips (all of which I already have "in stock" ;) ) for motor retention; I'm recessing the rear CR so that the bolt head or screen door clip won't stick out past the aft end of the tube (important with the fin design I'm using, as when built, the rocket will sit on the tube, not on fin tips)

As for the rail buttons, you're right. The LOC 1 inch-ers I have came with machine screws, but I picked up some equivalently sized, yet slightly longer (1") wood screws for secure anchoring... :D

As for careful measurements, I'm methodical, and a measure thrice, cut once kind of guy, so I think I should be okay... :)

Thanks!

Now- OFF TO BUILDING!!!
 
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