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Old Nov 11, 2008, 06:28 AM
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What could possibly go wrong?
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Market Harborough
Joined Apr 2006
4,166 Posts
Originally Posted by Don Stackhouse
Incidences and thrust line are things that apply to each individual design. There is no "magic" one-size-fits-all combination that works on all designs. If you have something that is very similar in moment arms, volume coefficients, C/G location (both longitudinal and vertical), wing and canard airfoils and aspect ratios, pitching moments, etc., then their incidence requirements may be reasonably similar. However, if you have significant differences in your design compared to the ones your "rule of thumb" is based on, then the setup will need to be different. Simply changing the desired flight condition at neutral elevator, or changing the C/G and associated static margin will alter the required incidences.

Changing the vertical location of the C/G will change the required thrust line angle.

Each design needs to be evaluated on its own merits.
Well I got lucky apparantly, so in progressing to a Beechcraft Starship, I'll stick to the incidence and thrust lines I have now!

Don, you mentioned the Starship and its variable sweep canard. I have a plan to introduce this, linked to flaps by a system of rods and cranks.

Step one in development now will be to replace the existing swept canard on my crash dummy with a narrower, straight one, closer to scale, and re-enter the details in the CoG calculator. Then see if my luck holds.

for setting up the flap / canard system, I'll run some different sizes and sweep angles through the CoG calculator till I get roughly the same CoG for both configurations.

Step two will be to build the actual model and fly the plane, flaps down and canard forward. Once I get some height, I'll try pulling in the flaps and sweeping the canard.

What could go wrong?

My experience of communicating with Don is that it may be a mistake to ask that question. But I will try to keep up


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Last edited by nickchud; Nov 11, 2008 at 06:34 AM.
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