How long should the rail be for mini-buttons?

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T-Rex

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As I mentioned in the "What did you do today" thread, I now have 4M/13ft of 20mmx20mm rail to use for mini buttons. Obviously that is a tad long, and I noted that in that length, it bows.
The question becomes how long should I make my rails?

The way I see it, I have 2 real choices, both of which are good.

A. Make 3 equal sections 4ft 4in long. The Rail-Buttons web page advertises a 4ft piece of rail to go with their buttons....
B. Cut it in half giving me 2 sections about 6' 6". A little extra rail never hurts.

I guess there is a 3rd option, 2 pieces 4ft, and one 5ft....

Any experience out there with the mini buttons and 20 series rail? Has 4ft been long enough, or have you been in position to need more?

Thank you!
 
1'10", 3'8", 7'4"

You can now make multiples of length from 1'10" to 12'10".

More practical might be 2ft, 4ft, 6ft and stick them all in a PVC carrier. Use the surplus to manufacture section joiners.
 
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The best length, other than logistics, is based on what you want to fly on it, not the rail size. Speed off the rod and all that stuff. Other than high power, everything I fly can go off a 4' rod/rail.
 
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4' rail is the one I grab most often for rockets equipped with the mini buttons. Like dhbarr mentioned having a 6' around in the tube is real handy for big and slow or a windy day.
 
Thank you for the suggestions, many things to consider. Originally I was thinking to give a section to the club, but maybe I'll be selfish and keep it all. I'll just transport it to launches that I attend.
Part of my dilemma was that I do have a couple rocket/motor combos that would require a longer rail. After seeing the amount of whip in the full length, I wasn't sure if a longer piece was feasible.
 
I have both 6' & 5' segments on the mini rail pad I built for our club. Some of the rockets I built to fly from them definitely benefit from the longer sections, as I like slow lift offs or occasional 24mm clusters on larger rockets. I wouldn't use anything shorter than 4'; my personal feeling is that mini rail is sort of substitute for 1/4" rod, and would carry the same size rockets roughly speaking.
 
Thanks jawa. Better to have it long and not need it, than need it and not have it.
I tend to prefer low and slow myself, so having the longer rail makes sense. dhbarr said above 2', 4', 6', but I think I will go with 3', 4', 6'. I just have to figure out how to connect the 3' & 4' sections if I need 7' (without buying an excessive number of specialized parts)
 
Use the 6ft section as the backer for that splice.

Excellent plan! But I still need a way to attach them together. I have worked with 80/20 at a past job, I don't want to have to buy a bag of special screws and connector plates. I'll have to go out to the garage and have the pieces in my hand before I will understand how to make it work. Small carriage bolts in the slot run through the backer maybe. I'll fiddle with it next week while I am home alone (family flying out, I'll be taking care of the homestead in peace for 2 weeks! :marshmallow: )
 
The irony here is that I just did this same thing with a couple of pieces of unistrut to make a 20ft antenna mast.
 
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