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  #41  
Old 07-05-2006, 07:15 AM
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Solomoriah Solomoriah is offline
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Quote:
Originally Posted by CPMcGraw
A8-3.......232'.......9 FPS
B4-4.......584'......33 FPS
B6-6.......610'......26 FPS
C6-7......1350'......11 FPS

All motors reach flight V in the length of a standard rod.

As you can see, this bird has a wicked mid-power deployment issue. At the low and high ends, however, the deployment velocities are within acceptable limits, and are actually quite low. Using plastic components instead of balsa, the stability margin with the C6-7 is 1.10, safely above the 1.00 minimum limit. With balsa, it was down to 0.87...

The recommended B engine for the Screaming Eagle was a B4-6, which ought to resolve the deployment issue. Mine worked fine for several flights, until the motor mount separated; I eventually threw the entire model away (hey, I was a kid!)

When I bought the "outfit," Centuri offered a free rocket with purchases over $10.00 (if I remember rightly) and the Bandito was one of the options. So, I ordered the outfit and a pack of B4-6 engines, the lowest-power engine shared between the two rockets, and requested the Bandito as my gift. I was self-taught... I had no experienced adult to help me. When I launched the Eagle, it flew more or less exactly like they told me it would, and I was quite pleased. But then I shoved a B4-6 into the Bandito and launched it... I didn't think I'd ever find it! They billed the Bandito as a high-performance rocket, and to novice me it sure was.

BTW... the Eagle seemed prone to weathercocking.
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  #42  
Old 07-05-2006, 10:21 AM
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CPMcGraw CPMcGraw is offline
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Quote:
Originally Posted by Solomoriah
The recommended B engine for the Screaming Eagle was a B4-6, which ought to resolve the deployment issue...

BTW... the Eagle seemed prone to weathercocking.


Solo,

I just modified the RockSim motor file to allow for a 6-second delay in that B4. The results do not change all that much, except that the additional time allows the model to reach another 10' in total altitude, and the Dv drops only to 31 FPS.

Screaming Eagle was stable, and had sufficient fin area. Weathercocking is a good sign you have greater a than 1 calibre margin; with the B4-6, the margin is 1.28...
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  #43  
Old 07-05-2006, 10:57 AM
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tbzep tbzep is offline
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How about running a sim of it with an A3-4T? Maybe an A10-3T while your at it...
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  #44  
Old 07-05-2006, 12:07 PM
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CPMcGraw CPMcGraw is offline
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Quote:
Originally Posted by tbzep
How about running a sim of it with an A3-4T? Maybe an A10-3T while your at it...


The A10-3T is the optimal 13mm motor. Reaches 260' with a Dv of 10 FPS, and can reach safe flight V in the length of a standard rod. The A3-4T requires a 50" rod to reach that V, has a 22 FPS Dv, and only gains an additional 3' altitude.
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