Thread: Discussion Plank 101
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Old Sep 28, 2012, 06:39 PM
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Joined Jun 2007
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Originally Posted by Knoll53 View Post
Thanks Herk. So you're thinking that due to the sweep, that the winglets would be more effective than the central fin??

The Fin is fixed, no rudder. I'll start with the central fin and see if I have any complaints. I'm planning on a wing loading from 9 to 15 oz/s.f. so it should really move least compared to the Manatee. I'm more concerned about pitch control than yaw.

Attached is my guess at the CG range.

Hi Kent - no the fin you have drawn will be effective - though such a tall fin does introduce a rather undesirable rolling moment when it encounters yaw - particularly on a fairly low AR wing.

I like the fins at the tips because they increase the effectiveness of the elevons, have a favorable effect on induced drag, and by splitting the fin area into two surfaces reduce the roll effect mentioned above. All quite subjective on my part.

With that CG range the SM would be ~3% aft and 8 % forward. Looks right to me. I'd probably start a model like that at about 5%.

The model shown was an experiment to see how a flying wing could handle DLG launching. It did quite well - responded very well in that high yaw environment. I included it in the discussion because the layout was similar to your plan.
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