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Old 12-07-2006, 03:50 PM
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CPMcGraw CPMcGraw is offline
Join Date: Mar 2005
Location: Mobile, Alabama
Posts: 5,357
Exclamation Revised Plan -- Andromeda

Last night I tried to construct a fin unit for this model, but found that my original layout was too fragile to hold itself together. If I used the SEMROC 0.05" fiberboard, it might work, but I don't know how fins that size and with so little actual structure might hold out in terms of warpage. So, I'm making a few changes in the fin design.

First, I'm beefing the thickness up to a 1/8" sheet instead of 3/32". Second, I've eliminated the fancy trims attaching the hardwood dowels to the front and rear edges. Third, I've lengthened the two dowels to fit into notches. Fourth, I've moved the outer dowel inward, and returned to a solid tip area. Fifth, I've reduced the actual balsa count to four pieces. Sixth, I've located and drawn into the patterns the slots for the two ST-13 shrouds.

Once these parts are assembled together, the paper-skin-laminated balsa should have all of the requisite strength for handling the stresses of launch and landing.

One note of caution -- the A8-3 requires a 48" rod to become stable, so I am removing it from the recommended motor list. The altitude on the A was only 120' anyway...

Length: 24"
Diameter: 1.34" (ST-13 shrouds)
Fin Span: 5.82"
Weight: 2.08 oz

B4-4......337'......Dv 9 FPS
B6-4......347'......Dv 4 FPS
C6-5......850'......Dv 12 FPS

All of these motors reach flight velocity on a standard 36" launch rod.

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Name:  Fin Patterns Full Sheet [v3].jpg
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Attached Files
File Type: rkt Andromeda.rkt (66.4 KB, 81 views)
Craig McGraw

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