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Old 09-24-2018, 09:00 AM
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tbzep tbzep is offline
Dazed and Confused
 
Join Date: Mar 2005
Location: TN
Posts: 11,604
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Quote:
Originally Posted by Andy63
Hi all.

I'm piecing a build together of FSI's Black Brant II. I downloaded the instructions from oldrocketplans.com/fsi/fsiMRK-14/FSI_Black_Brant_II.pdf. I printed the fin page and began to take some measurements. Compared with the scale drawing from G. Flynn (11/1/1971) the FSI fin seems to come up being on the small side. The tail cone also seems to want to be fatter at the nozzle end, too (1.75" vs 1.4" @ 1/8 scale). Has anyone else noticed this? I'm finding it rather difficut to find more than just a few sources of scale data on this bird.

Thanks all.

IIRC, that was needed to fit in the motor tube and not be so thin that it ripped itself apart on the lathe. I did a lot of sanding due to a fairly rough finish on the boat tail, but I didn't try to make it perfectly scale. It's been a lot of years and I don't have mine in front of me or I'd measure it for you.

Don't forget that it took an FSI 27mm motor and you will need to go 29mm. You can go 24mm if you really want to scale the boat tail, since we have composite E's that are plenty strong for a safe flight and some low end 24mm F's.
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