Body Tube source?
 

I would like to find a source for a body tube diameter of 12 foot at 1/100 scale which would work well for both space shuttle SRB's and the Falcon series . The size would be a 1.44" OD halfway between a bt 58 and a BT 56 . Does anyone know of a good source? Or has anyone had success making their own tube ?

This size is not presently available. It is one of three sizes missing in the old Centuri/Semroc system of Series tubing. There is no Series 14 (the size you want) or Series 17 (1.70 ID/ 1.74 OD) or Series 19 (1.9 ID/1.94 OD). As you note, Series 14 would be great for 1/100 scale, 144 inch rockets like Titan and Atlas. I'd be good for 1/10 Hawk sounding rockets and for 1/64 LRB on Shenzhous as well.

But nobody makes 'em.

Yet.

Look at BMS for a 38mm coupler.

is it special order at BMS i couldn't find it .

C55-34 1.280x1.212x34 inch long T55 coupler stock $5.00
C60-34 1.592x1.524x34 inch long T60 coupler stock $6.00

A 38mm coupler size would be a little too big for what you are looking for:

https://www.discountrocketry.com/mo...ler-p-2299.html

1.515" OD rather than 1.44". If no one makes this size then your best alternative would be to "cut down" the diameter of a slightly larger tube, like the BT-60. Calculate the difference in circumference of the smaller tube and the BT-60 using c = 2 x pi x r ( or d x pi). Mark a vertical strip on the tube equal in width to the difference in circumference and cut it out, trying to cut as straight as possible. An angle tool is very helpful. Use the strip as a glue tab and join the cut ends together. Saw a post on the net a couple of years ago showing this but can't seem to find it now.

Another option is to make your own custom sized spiral or convoluted tubes using kraft paper. However this would entail using a mandrel or tube that is the exact size you need to wrap around, so you would have to construct it or get lucky and find one that's the exact size. Way too complicated.

If the OD is the important measurement, you could blend the two techniques. Start with a slightly undersized body tube, like a Quest 35mm (1.340 id and 1.387 od). Then use that as a core, and wrap your tube-making material around it. Kraft paper for taping off around paint jobs works well. The walls would be a bit thick (1.44 od to 1.34 id = 0.1 difference, or 0.05" wall thickness), but would be comparable to some of the heavy-wall tubes.

David's method has the advantage of being able to use the centering rings and possibly cones for the core diameter. You can built up the cones by "fiberglassing" using a worn out nylon stocking and using either finishing epoxy resin or polyurethane to fill the weave. Because the nylon is stretchy it will conform to the contours of the cone. Pull the stocking over the cone and then "paint" the resin or polyurethane into the weave using a cheapy brush. Repeat the painting until the weave is filled.

Apparently, a stocking in the trash does NOT necessarily mean it's being thrown away; it may be in there for discipline. So always check with SWMBO before using an old stocking for this technique.

Don't ask me how I know.

I have made custom tubes by cutting down larger ones and by inserting strips to make larger ones. Cutting down a larger tube is easier on smaller diameter tubes. If you pick the right size, you can use the strip you cut out as the backing material for the seam and it will already be conformed to the tube shape. You can still use centering rings and cones by cutting a notch to fit the backing strip. This is an easy step. This method should be slightly lighter than building up a tube, assuming gobs of glue aren't applied.

That may be the funniest thing I've read in months :)

Doug

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:chuckle: :chuckle: :chuckle: