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Old 06-03-2009, 11:33 AM
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CPMcGraw CPMcGraw is offline
BARCLONE Rocketry
 
Join Date: Mar 2005
Location: Mobile, Alabama
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Quote:
Originally Posted by blindeye2
The rocket never left the launch pad. Try using additional thrust.
Have not been able to figure it out. I am running a trial ver 9
I have attached the ROCKSIM file.
thanks
bob


Found it...

Check the MATERIAL drop-down box for your fins. Change it from "CUSTOM" to something else (BALSA works well ). I've corresponded with Tim and Paul about this, and they indicated they had tried to purge this 'custom' material out of the database. They did, but the entry you see in that box is not coming from the database. It's hard-wired into the program code.

In other words, it's a bug that got past them...

I ran the simulation on your design after changing that one entry, and tried a D15-6. I got just under 1300', needing only 16" of the launch rod, and deploying the parachute at a soft 3 FPS. Change the "Sweep Angle" on the fins to 18.50 degrees and you won't need any ballast in the nose to offset the extra mass of the engine -- the D15-6 had a margin of 0.98 with the fins like you had them. You want the margin to be at least 1.00, or better, for the model to be flight stable. With the sweep angle change mentioned, the flight-ready margin is now 1.04.

Not bad for a first attempt! Have you been using an earlier version for a while?
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