Looking for BT-21 or BT-20+ and odd items
 

Hi folks, So in my attempt to scratchbuild a Fake Wulf I have been gathering parts. What I cannot find is a BT-20+ or also called BT-21 tube I guess, and also a pretty thick 21-55 balsa centering ring. Everything else was easy enough to find, but these, well not so much. Anyone have any idea where I might buy these items?

Try BMS or Semroc

Not having the tube dimensions, I'm going to guess that the BT-20+ tubing is a slip fit over
BT-20.
This vintage Totallu Tubular product?
http://www.erockets.biz/totally-tub...t-20-34-1-pk-1/
Or maybe the ASP variation?
https://www.asp-rocketry.com/ecomme...nt=13&navPanel=
ST-7 is larger than BT-20 and not a slip fit over BT-20:
http://www.erockets.biz/st-7/

Thanks everyone, so far.........
 

I have found everything except the 21-55 thick balsa centering ring.............but I have some leads.....

BT-30 is an old Estes size.
OD: 0.767
ID: 0.725

Not sure where BT-20+ originated.
OD 0.770"
ID 0.744"

eRockets (Semroc) has both.

You can take a regular 20-55 centering ring and sand it until it fits. Otherwise, print out a template and cut your own. I seldom buy centering rings anymore. I usually make them from cardboard or balsa.



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Are you doing a build thread on the scratch Fake Wulf?

Why not just sand or “Dremel-out” a fiber 2055 centering ring? BMS has those. The fiber is really tough, and lightweight.

I realize you found the other parts, but for for the benefit of others, BMS, stocks several “+” style tubes that slide over a regular tube.

BT-20+ may be what CMR called RB-77. Their regular tube was RB-74, and RB-77 was a slip-fit over it. Apogee (Ed LaCroix version) had similar sizes of their BlackShaft tube (and maybe their regular tube too)

This tubing is on erockets.biz It is also available on the ASP website. Just a slight bit smaller in diameter than the Quest size T-20 available from BMS. It should be a simple matter to enlarge the rings. A sheet of sandpaper wrapped around an engine casing works well. BTW,, the t-20+ tubes will probably be discontinued due to the change in the NAR payload requirements. Apparently it was too challenging. LOL.

I believe that the "+" usage came from Totally Tubular.