Optimizing flying wing design

Raptortech

Foam Addict
My question is fairly simple: how does one decide on the ideal dimensions and ratios for a flying wing given the target cruising speed and payload or other relevant flight characteristics.

For a more conventional aircraft, I feel like I have a fairly good intuition as far as changing the wing design to get the desired characteristics. Wing area is roughly proportional to payload for a given flight speed. An undercambered airfoil will be slower and lift more, but not perform well inverted. A more symmetric airfoil will be faster and more acrobatic. A relatively thin airfoil will be faster, but may have a high stall speed. A higher aspect ratio wing will be more efficient. etc.

Those are not ultimatum, but rather rules of thumb and variables I consider when I am designing a new aircraft.

In the case of flying wings, I feel like I have much less intuition about how my design choices will affect the final aircraft.

Specifically, what are the (general) effects of increase sweep, more taper, a larger center section, and higher aspect ratio on flying wing flight characteristics?

The designs of many of the most popular flying wings follow a relatively similar ratio: the versa is pretty similar to the Ritewing Zephyr II is pretty similar to the TBS Caphirana.
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Is this some optimal shape? If so, how come the Ritewing Zephyr III and Ritewing Drak, which are entirely different, perform so spectacularly?
 

Raptortech

Foam Addict
Anybody have any ideas? It seems like the new FT arrow has more sweep than the versa. Is that for increased roll rate?
 

earthsciteach

Moderator
Moderator
Flying wings are pretty interesting. They are far less forgiving in terms of cg location than conventional aircraft. The more sweep a wing has, typically the easier it is to get cg right, assuming you have a pusher motor. Center section, taper are probably more a product of utility and aesthetics, respectfully. Aspect ratio is related to the desired performance/efficiency of the wing, same as in any other plane, as you mentioned.