Can some animal planforms be models for sail design

The varity of animal planforms indicate needs beyond recreational sailing and most involve muscular input. I have focused on one common and easily observed bird,the gull when airborne with minimal muscular input, hanging motionlessly above the beach in a stiff onshore breeze. There are some nice vector diagrams of flapping flight with lift and drag vectors rotating with extreme AOA of apparent wind in down stroke; L developing a forward component for thrust and D an upward one, breifly possible through hysterisis and following up stroke. Hanging gull's wings appear fairly level, seabreeze may rise upon meeting land creating high AOA to rotate vectors but no stall or
up stroke. LEV on sweptback handwing might allow sustained rotated L and D vectors to oppose headwind without flapping,in essense a forward thrust.

In gusty winds main adjustments seem to be sweepback angle and flicking of anhedral handwing up to, my guess,keep LEV attached. On turning sideways, bird is blown inland indicating large forward vector in this state of equilibrium. Gulls , trailing boats , are in very turbulent air making analysis difficult but seems same principle applies Often gulls' forward glide speed is greater than the boat, requiring them to turn back to the wake zone.

This forward thrust of a fixed wing in natural wind is very tantalizing to a sailor. Another teasing performance,though one with muscular input, is by the Monarch butterfly, which have easily out sailed me upwind in a stiff breeze.

 

Here's an example, the Transition Rig.

 

A batsmosail ?

 

Manfred Curry, a german sailor, experimenter, heavy weight thinker, of the early 20th century, did a lot of this kind of thought. Curry wrote several books with inclusion of observed bird flight. He was evidently influential with the likes of Junkers and Messerschmitt and had access to their wind tunnels. Try googling him.

 

Bat flight is amazingly dynamic with high muscular input, maybe a diet of flying insects would add insight, but looking for lift without flap. I have stumbled on a potential non muscular input feedback system for sail trim. I , assume, with CP at mast pivot, aerodynamic center moves enough to trim sail, have sailed rig D without sheet. As with self steering out performing helmsmen, at least chasing the wind if not the course, better overall trim might result.
The Transition Rig's lower concave LE is also in the gull's arm wing which I have ignored in my narrow LEV focus. The website and prototypes are beautifully finished products but I have no idea how his rigs sail or if Fleche rig is for vortex lift. Removing all spanwise camber in similar planforms brought the rig to life for me. Sunfish hull has limitations, thought of A frame on Hobie 16, nice to see its use. Thanks again for the breadth of your sources

 

http://www.whalepower.com/drupal/

 

http://www.boatdesign.net/forums/showthread.php?t=16276
www.tolweb.org/Coleoptera
i've looked at a beetle for inspiration, more in the pdf in my gallery and came to this sail http://www.boatdesign.net/forums/attachment.php?attachmentid=18802&d=1202825025

 

A Proposal by Tara Chklovski

This paper could affect the way you think about wings and propellers, it goes back to nature for a closer look.

Click on "PROPOSAL"
http://www-scf.usc.edu/~tchklovs/

.............................................................................................

This is another interesting site about "lift" with many sections, see "next" button:
http://www.aeronautics.ws/optimization.html

 

Tara's proposal is interesting, but it has a hidden, fatal, assumption. Everything she presents is based on comparing wings on the basis of the same span. But there's nothing that limits span, per se, in the evolution of a bird's wing. If you allow the span to vary and optimize the performance with some kind of strength constraint, such as wing root bending moment, you invariably end up with a pointed planform.

The reason is simple. Induced drag for a given amount of lift is inversely proportional to span squared. A pointed planform has more induced drag than an elliptical planform of the same span, but it can have a much greater span within the same strength constraints. The increased span more than makes up for the loss of efficiency of the planform shape itself.

The rooftop sections of Ormsbee and Liebeck have their drawbacks, but his basis for designing airfoils is pure hooey. This paper by A.M.O Smith is a much more reliable discussion of high lift airfoils. Even if it was written by an aeronautical engineer.

 

That last post of mine was a re-copy of something I posted before. The last paper was highly criticized in a Physic Forum, they tore it up. I forgot about that, it was pretty funny to watch.

I have to get more paper before printing the AMO Smith 30 page pdf, looks like a great paper - thanks.

 

A.M.O. smith's paper shows how effective the head and main sail combination could be if gotten right. Tough to apply sailing conventional boats, would be nice to have springy telltails giving both direction and speed of flow, another drag problem, but back to nature.
If the lift and drag vectors are rotated forward in flapping flight, reducing drag could be a negative, especially in hovering, [http://etd.caltech.edu/etd/available/etd-05292004-183807/unrestricted/thesis.pdf.] yet the Dragonfly has 2 element high aspect wings.For soaring and gliding higher aspect dominates, even the Humpback's "agility" due to its high aspect fin rather than unique surface deformation. So most of nature's examples do not encourage my design direction, but sailing these rigs and the hanging gull egg me on.
Arrow planform, armwing thrust forward, hand wing swept back, illustrating high speed flex gliding position in Tara Chklovski's proposal is in the hanging gull and my sailing rig F with raised apex. For diving hawk (http://jeb.biologists.org/cgi/reprint/201/3/403.pdf) wing loading and anatomical stress limit may indicate position but in condor study, (http://jeb.biologist.org/cgi/reprint/58//1/225.pdf) its also for fliding up wind.
In blanacing higher apparent wind, less area, lower aspect or is geometry only dictated by folding anatomy or does arrow planform allow high AOA of vortex flow to tilt lift, drag vectors forward with less drag. Answer still in the wind.
Time for sailing, its a primitive design method but from AMO Smith's final 10 points "when the vortex develps, conventional calculations are about 100% in error". I can't be far behind that number, assume inverse true now, despite Java Foil's "quite inaccurate...with span wise flow and strong vortices".
No idea of proportion of pressure due to surface flow and/or vortex but with CP so far forward assume span wise flow over feeds vortex causing premature expansion, and drag pulls enlarged vortex off surface into ambien flow. Raised apex could allow shared flow between two vortices. A LE with less supporting area might have same effect but hard to structure without tip deflecting to leeward. This reverse spanwise cambor results in high initial AOA diminishing aft with less frontal area and possibly less vortec expansion and delayed separation as curved surface follows vortex's trajectory. Trailing edge flow is not off of but up along edge into vortex, is there any downwash or is all flow ejected aft in vortex? And what are drag consequences? I seem to have no cordwise flow as in mid aft area of tyical triangular delta wing which could limit growth and pull vortex aft faster. LE geometry working at lower AOA would reduce drag, nature favors sharp, small lip to leeward looks promising in models, and after handling problems I could favor a rounded apex. All this leads to the obvious; reduce the vortex to a streamline but can't let go of my attachment to the LEV yet. Thanks for the feedback.