Black Brant fin thickness

[Charles_McG]

Does anyone know (@PeterAlway ) how thick the 'standard' Black Brant (v 5+) are. I found a 1967 paper that suggests they are 9.6mm thick - but that strikes me as really quite thin.

Especially when I scale it down.

If i try to measure it from the various Rockets of the Word supplements, I get a much higher number.

 

[Bruiser]

Charles,

https://www.rocketryforum.com/threads/black-brant-vc-documentation.154618/ post 23 should help

-Bob

 

[Charles_McG]

Charles, https://www.rocketryforum.com/threads/black-brant-vc-documentation.154618/ post 23 should help

Thanks. The 'search' feature failed me.

I make it out to be ~1.5" at the root and ~1" at the tip. Quite a bit thinner than the BBII fin that is documented later in the thread. But the AIAA paper says they did a bunch of revisions on it.

Close enough for me.

 

[PeterAlway]

Scrounged up my Black Brant V drawing from my flash drive. I get 1.13" thick at the root, and 0.630" thick at the tip. The numbers came from Bristol Aerospace sources that I don't have handy (I'm at work right now).

 

[Charles_McG]

Scrounged up my Black Brant V drawing from my flash drive. I get 1.13" thick at the root, and 0.630" thick at the tip. The numbers came from Bristol Aerospace sources that I don't have handy (I'm at work right now).

Thanks Peter!

I’m looking at 1/5.3 scale to match other builds I have. I’m printing fins and fincan. I run a 2x10mm carbon fiber slat through the fin parallel to the leading edge to improve stiffness. Running straight 1/5 would leave 1 layer over the slat on each side. Which I’ve done before. But having done it before, I’ll go off scale a little to get 2 layers cover.

 

[Bruiser]

Peter's measurements are the same as in the drawing I referenced you to. The thickness drawing is in the top, right corner. Gotta love it when two sources say the same thing

-Bob

 

[Charles_McG]

Peter's measurements are the same as in the drawing I referenced you to. The thickness drawing is in the top, right corner. Gotta love it when two sources say the same thing

-Bob

Ah, I missed that. Or thought it was something else. I was trying to measure it from the A and B profiles at the bottom.

 

[David Schwantz]

Hey Charles, how do you run the carbon stiffener in a 3D print?

 

[Charles_McG]

I print the fins with a slightly oversized channel, then push some epoxy in and ahead of the carbon fiber slat.

I do it all dry first, in case I need to do some filing. And to mark and trim the slats to the angle they meet the motor mount tube. I also print a little receiver piece to help anchor the slats to the motor mount.





This one had a hard, drogue only, landing (nosecone too tight) and I had to repair it. The 2x10mm carbon fiber slat was fine, but it looks like it bent on landing and popped out the single layer sidewalls of the channel. I’m going to 2 layer in the future.

 

[David Schwantz]

Very, very nice!

 

[GlenP]

Another option, it may make more finishing work, it to have two thinner carbon fiber slats in shallow grooves on each side of the fin. Use them like a skin over the plastic in that little strip. Then instead of having two thin layers of plastic sandwiching the carbon, you would have two thin strips of carbon sandwiching the thicker plastic. Not sure if that would work for you or not, it would add some finishing work to fill and smooth the channels. This is more like how a honeycomb panel works and would be much stronger. Just an idea. Nice 3D print job!

 

[Ez2cDave]