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-   -   Looking for BT-21 or BT-20+ and odd items (http://www.oldrocketforum.com/showthread.php?t=17187)

stevefaxon 03-31-2018 10:58 AM

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?

ghrocketman 03-31-2018 11:52 AM

Try BMS or Semroc

astronwolf 03-31-2018 12:21 PM

Quote:
Originally Posted by stevefaxon
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?

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/

stevefaxon 03-31-2018 07:29 PM

Thanks everyone, so far.........
 
I have found everything except the 21-55 thick balsa centering ring.............but I have some leads.....

tbzep 03-31-2018 08:19 PM

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.



.

jeffyjeep 03-31-2018 09:50 PM

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

LeeR 04-01-2018 12:07 AM

Quote:
Originally Posted by stevefaxon
I have found everything except the 21-55 thick balsa centering ring.............but I have some leads.....


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.

Royatl 04-01-2018 11:45 AM

Quote:
Originally Posted by tbzep
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.



.


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)

jdbectec 04-01-2018 06:42 PM

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.

stefanj 04-02-2018 09:20 AM

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


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