BT-56 body tubes

[TNmike]

Are these used currently used in any Estes or other brand kit? I know a few vendors still sale the tubes, but are BT-56's becoming a relic of the past?

 

[ozwald]

I'm actually building an Estes Black Brant II and it is BT 56 tubing. (2000 vintage kit) I wanted to add an AV bay cause I've set it up to run 24/40 F24's and I got a BT 55 bay from Apogee and was curious if it would be a sloppy fit. It actually fits the tube perfectly?

 

[T-Rex]

BT-56 was always a one-off kind of thing. Estes held on to it after they bought Centuri, to continue a couple of the Centuri designs but now, yes, it has finally been discontinued. A couple of vendors still have some, but they all say that when it is gone, it's gone. Nose cones are few and far between, pretty much just the 4 packs that Estes used to sell that are collecting dust on the shelves.
I am in process of a couple BT-56 down sizes just to use the nose cones I got in a parts lot.

 

[BEC]

BT-56 is Centuri ST-13. See the Semroc section of eRockets......

 

[TopRamen]

I mentioned BT-56 in my Eggspress thread, and it got interesting.

 

[caveduck]

Since BT-56 == ST-13, the world isn't totally ending for that size. The Estes plastic NCs and fin cans are going to go away, but I'm pretty sure you'll still be able to get balsa ones from eRockets/Semroc, at least under the #13 designation, though probably not in the exact same shapes.

 

[T-Rex]

removed

 

[T-Rex]

BT-56 is Centuri ST-13. See the Semroc section of eRockets......

Actually not quite...
ST-13 is listed as 1.340 OD, 1.300 ID.
BT56 is listed as 1.367 OD and 1.346 ID.

Effectively the same but not interchangeable if you wanted to make a repair. eRockets does list several balsa nose cones for ST-13, none for BT-56

 

[TNmike]

Shouldn't the BT-56 be 1.346 OD and 1.304 ID, just to clarify?

 

[BEC]

Actually not quite...
ST-13 is listed as 1.340 OD, 1.300 ID.
BT56 is listed as 1.367 OD and 1.346 ID.

Effectively the same but not interchangeable if you wanted to make a repair. eRockets does list several balsa nose cones for ST-13, none for BT-56

Some time ago I was told BT-56 was the same as ST-13....so I've never looked for BT-56 dimensions. I sit corrected.

 

[T-Rex]

Shouldn't the BT-56 be 1.346 OD and 1.304 ID, just to clarify?

SON OF A ........ Yes, you are correct. I must have fat fingered the eRockets page. My apologies to all. ST13 and BT56 are the same, only 0.006" different.

<hangs head in shame>

 

[T-Rex]

Some time ago I was told BT-56 was the same as ST-13....so I've never looked for BT-56 dimensions. I sit corrected.

Nope you are correct, I got the dimensions wrong.

Now that I have confused half of the rocketry world, I'll just go to my corner and shut up again...

 

[BEC]

Oh how I know that feeling.

OK....I'll stick to my earlier story then.

 

[TNmike]

T-Rex, I'm not for sure you fat fingered it. I believe I have seen those numbers (a typo) somewhere myself, perhaps at erockets. And yeah, I would think a lot of things could be made to work out with only 0.004" difference in the ID. A sheet of copy paper measures 0.003".

 

[lcorinth]

Some of their RTF and E2X rockets are BT-56. The Amazon and Patriarch are two that I have somewhere on the shelf.

I like the shape of the BT-56 plastic nose cones, and since Sunward seems to like that size, I got lots of tubing for them as well.

 

[caveduck]

The confusion on the size of BT-56 is very understandable. The current eRockets/Semroc site lists seriously incorrect dimensions for BT-56 of ID 1.346, OD 1.367 for their BT-56 items, but on one of them says "same as Estes BT-56". The legacy Semroc site doesn't even list BT-56, so we don't have Carl's fiendishly meticulous research to go on. I'm not sure where the few mils of offset between the Centuri tube spec and the Estes spec came from. Estes listed ID 1.304, OD 1.346 in the 1995 catalog and later, but didn't list BT-56 sizes anywhere I know of until the 1990s, 20 years after the absorption of Centuri. (Yeah I've been researching this a little for my OpenRocket parts files)

 

[LithosphereRocketry]

now, yes, it has finally been discontinued.

Estes' website still lists the Metalizer, which is BT-56... They also have nose cones, but no tubes. Extra stock maybe?