04-03-2006, 10:55 PM
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BARCLONE Rocketry
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Join Date: Mar 2005
Location: Mobile, Alabama
Posts: 5,357
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New Plan -- Scrappy
James noticed an interesting way to work with inside tubes with his Thunder Strike design, and it may be better than the cut-and-paste method for simulating tubes that are partially hidden and partially exposed.
I had to try his method out, and here's what I came up with.
Another "Schoolyard Sounder"...
Length: 18.3"
Diameter: 0.759" (ST-7)
Fin Span: 4"
Weight: 0.6 oz
1/2A3-4T.....235'.....19 FPS
A3-4T........565'.....20 FPS
Although the Dv is high for both motors, they're within limits. Just reef the chute and you should be safe.
As with some previous designs, the fin shape makes a big difference in the stability numbers. Adding that step in the leading edge can raise the margin while reducing the fin area as a bonus. Also, pulling the fin tip back at an angle is having a positive effect on the margin, while also reducing the total fin area.
Enjoy!
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