Trimming down fins? - Northern Colorado Rocketry

This topic has 15 replies, 8 voices, and was last updated 19 years, 2 months ago by Conway Stevens.

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July 26, 2006 at 5:35 pm #42974
Dale Netherton
Participant
John, I would seriously suggest chucking up your fin can in a metal lathe. I think we both know someone (EK) that can help. Then you can tell how things are with the fins, maybe they are not as perfect after all. Then you can trim them all down evenly with sandpaper on a block while it is spinning. You can form the fins anyway you like then just re-adjust the taper. Maybe use a mill for that.
Just a thought.
I will volunteer to provide adult supervision (EK) and maybe some beer to clear the throat of dust. Maybe we should call (EK) first….I shouldn’t speak for him.

Dale.
July 26, 2006 at 10:24 pm #42975
Bruce R. Schaefer
Go with the 4:1 rather than the 5:1 ogive. The sim should show you the difference it makes. Nose cone shape makes a big difference, perhaps even your 200′.

Uh, nevermind. I did an ad hoc sim, and it only made a two foot difference. 🙄 Trim the fins, but don’t give up too much stability. Ed’s right keep the tower as short as possible. Then again, my SSS is 4″ too long, and the fin span 1″ too long. Don’t listen to me. 😕
July 27, 2006 at 11:56 am #42976
Anonymous
The cone length is interesting to me. This may be the place to try it.

Dale — yep, EK is who I’m talking to about the milling project. I’ll let you know when I head over there. I’ve been on the road a L-O-N-G time, this has been a bad stretch ‘o biz travel. Ugh.
July 27, 2006 at 1:48 pm #42977
Warren B. Musselman
Moderator
My sims consistently show better altitude with shallower cone angles – meaning a 6:1 cone performs better than a 5:1 cone performs better than a 4:1 cone. At least on trans-mach flights.

Warren
July 27, 2006 at 2:50 pm #42978
Bruce R. Schaefer
Warren’s right. Speed is the key. If you’re going mach 1 and faster, then pointy is good. If you’re going slower, then a more blunt or rounded cone is better.
July 28, 2006 at 4:32 am #42979
Conway Stevens
Participant
John you mentioned that you dont paint them and they are primer? How about doing something so that way the body of the rocket is as sleek slick and slipery. Like a polish job with a great wax job after it. followed with a highly modified friction reducer rubbed all over the shortened tower so that way the amout of area touching the tower wil slip and slide very easily.
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