Custom Scratchbuilt Couplers

Did you ever get your hands on a couple of nice lengths of kraft paper tubing and say to yourself,"If I could put these 2 pieces of tubing together, I could build a really cool rocket!" Then you discover that you have an oddball size tube of which "no" couplers are made for. That actually happened to me once..."ONCE!" After that it was custom coupler fabrication all the way, and the only tools needed to accomplish this is: pencil,ruler,sandpaper and a jigsaw. I draw a straight line lengthwise on the tubing(keeping the line square to the tubing as possible) then make my cut. I draw another line 1/8" from either edge and make another cut, repeating this process until the coupler "snugly" fits inside my BT. Once that is accomplished, I sand all my edges inside and out. From this point I use hoseclamps to hold it closed until I epoxy the seam on the"INSIDE" diameter, very important! I aint gonna kid ya, the most difficult part of this project is holding the coupler down while cutting, so I have a solution. Wedge the coupler tubing in between 2 pieces of 2x4's, then clamp down the 2x4,s. Give them a little tap with a hammer on the outside of the boards to help "compress" the tubing a little more. I also clamp a 1/4" piece of wood on the end so as to prevent pushing the tube out of its jig. This works well.
Unless you have an adaquate supply of whatever tubing it is you have acquired, you usually have to cut a piece off of the tubing itself to build the coupler...but I think its worth it! Considering that now you can build a rocket out of "ANY" tubing you like. I have even gone as far as to glass the inside for additional strength. Have I gone too scratch?????

Thanks for the tip, I've been looking all over for a tube that I could use as a coupler for my 63mm rocket. I'm gonna give it a bash right away

To make the cut, a Dremel with a cutting wheel works great and reduces the amount of pressure you need to use to clamp the tube as you can let the rotation do he work.

Also, if the tubes are thin and you're nervous about a straight edge to edge connection, you can lay a strip of fiberglass along the inside of the coupler along the seam as well. I save all my scraps from glassing tubes for just such an occasion. Since it's on the inside, it doesn't have to look purty.

There is a section on Infocentral at:
https://www.info-central.org/index_search.html
under the "construction" menu about making couplers. It gives the formula that tells you how much to cut out of the wall of the tube when fabricating a coupler in this manner.

Bruce S. Levison, NAR #69055

Cool link...there's a math formula I can really use for quick coupler fabrication.Thanks Bruce......................