I have had some experience with making carbon tubes but nothing using a square mandrel. Has anyone had experience they can pass along.
I am looking to make a 3.5" x 3.5" by 48" square tube using extruded aluminum as a mandrel. Will the sharp corners cause issue with releasing?
Thanks for the help.
http://www.compositeforum.werksberg.com/showthread.php?t=1163
Use this thread for an outline and somewhere in it I talk about using half round dole to compress the sides in with the film tape.
Check out www.shrinktape.com for they have some hints as well, like Werk said, using half dowels as the pressure point for the sides.
You WILL need at least 1/8" radius on the corners. For 3.5" sq, I would go at least 1/4" if you can?
Great, thanks. I’ll try some samples first.
Other thing I though of was to have 2 “c” channels made that fit tightly over a center beam. You could slide the center beam out after it cures and work each half of the C channel loose independently. I guess I have a few methods to try.
I used to get free sample of the heat shrink tapes from Dunstone (great people) and after my class was closed I was giving them away with composite purchases.
I might still have some left around here but I also may want to keep some here…
That is a good idea actually. You would need a gap in the channels to really get any benefits with that method. Else, you are pulling the center out, and STILL have to pull the C channels out 
To avoid issues with the gap, might need to wrap the mandrel in plastic release before lay up.
Now that I thnk about it, I think my old company experimented with box tubes, by some sort of expandable angle pieces, and wrapped it all in mylar tape or something. When cured, just loosen the bolts(think turnbuckle style), the 4 pieces collapes, and pull out. Getting it all square was an issue I think though.