Flow pattern video of experimental sail needs analysis.

[lunatic]

The flow pattern in drawing 1 and at 20* -30* angle of attack (AOA) in videos http://www.youtube.com/watch?v=z91al4uBm9g consistently appears during best performance in sailing telltaled prototypes (drawing 2). These flat sails have no forward facing surface except 1 1/2" leading edge (LE) round spar, yet seem unexpectantly handy to windward despite drag of backside lift. Sharp LE rigid wings were poor performers on all points of sail. I have no velocity or pressure measurements for these flows but a 27 sq ft sail would surf a Sunfish in 15 -20 mph wind. Seems to have some potential, but what is going on here?
Much of lee surface flow is spanwise (accelerating? attached?) up into leading edge vortex (LEV) and some chordwise on aft expanding area above foot with tip vortex below. Upper flow exiting trailing edge (TE) is pulled up into trailing LEV (drawing 1). Would there be any advantage to pulling all disturbed air into a single trailing vortex, with all surface flow and all TE flow up into LEV? What happens to downwash, induced drag, circulation, closed vortex system? What would be going on here?
These sweptback rigs have a pronounced delay in response to wind gusts, I assume this is time for LEV and subsequent surface flow to take effect, and may be related to some unique handling characteristics. Model 2 of video has LE sweepback similar to sailing prototype B in drawing 2 which had exceptional tacking ability. Initial intense vortex lift, starting at apex, has large turning moment resulting in tacking speeds that could catapult an inattentive sailor from the boat. Other prototypes were self-trimming, some sailed without a sheet. The aerodynamic center seems quite lively in these rigs and might be exploited for some smart handling.
All models in video have a triangular section LE spar, base facing forward, for upwash on more forward facing surface and a vortex inducing sharp edge (drawing 3). Model 1 and 2 are rigid flat plates, model 1 has tear drop section stiffening foot. LE spar of model 3 is straight for ease of construction and extends above output of grated fans producing ambient flow but shows LEV forming over cambered sail for additional forward facing surface. I assume spanwise flow is accelerated into LEV without the constraint of pressure recovery and attachment might be maintained by rotating LEV (drawing 3). Looks to have potential for high lift, but for what drag? All this forward facing surface depends on minimum initial sweepback yet enough for good LEV formation.
Unfortunately, this seems to conflict with single trailing vortex idea as sailing prototypes E and F (drawing 2) with greater sweepback had more flow up into vortex, though heeling in actual sailing may be a factor. No prototypes had adjustable sweepback while sailing since a graduated sweepback would be fairly constant for good initiation and maintenance of LEV? and a rising apex would eventually create a foot LEV, competition for surface flow and another trailing vortex in the wake.
Reducing lower aft area by shortening foot and increasing TE rake produced more upward flow in model 2 with hollow leech and model 1 with fence, less so with only straight leech. Same aft cut on model 3 with quickly improvised very baggy sail resulted in only thin line of chordwise flow on aft half of foot. Cupped leech looked very draggy but, with telltales streaming parallel to TE, is this really a TE? seems more of a tip in need of a fence. Last video images show fence on cut away model 3 with all flow up into LEV and only a weak tip vortex, almost a single vortex system.
These flow patterns look somewhat structured but, turned so far from ambient flow, is any advantage gained. Future direction hard to determine with so many assumptions and questions, and as I barely have a grip on classical theory, I could use some feedback before building another prototype.

[gonzo]

The video seems to show a rigid sail. That would make its behaviour very different from a soft sail. Also, you only show one side of it. In which ways do you claim it is different from a lateen or crabclaw sail? Have you tried putting telltales on any other sail for comparison?

[yipster]

i went kiting delta wings, try'd telltales without getting much insight
havent taken the fan out yet, but find this interesting stuf, busy with other things tho but keep me posted!
have you seen the testrig Marchaj used and illustrated in his book seaworthines the forgotten factor?

[lunatic]

Originally Posted by gonzo

The video seems to show a rigid sail. That would make its behaviour very different from a soft sail. Also, you only show one side of it. In which ways do you claim it is different from a lateen or crabclaw sail? Have you tried putting telltales on any other sail for comparison?

Model 1 and 2 are rigid, model 3 has a soft sail though, in last part,it has a rigid TE fence. Windward flow was chordwise parallel to ambient. No claims here, flow is unique to these various planforms and likelly exist elsewhere.

[lunatic]

Originally Posted by yipster

i went kiting delta wings, try'd telltales without getting much insight
havent taken the fan out yet, but find this interesting stuf, busy with other things tho but keep me posted!
have you seen the testrig Marchaj used and illustrated in his book seaworthines the forgotten factor?

In Marchaj's "Sail Performance", chapter 11, The Sail Power of Various Rigs, he warns that "commonly used tell-tales are of no help in tuning the crab claw sail..." but gives little warning of the backside drag of LEV rigs, and favors axisymmetrical flow.Chapter ends with "Such research, although interesting, was beyond the scope of our investigations". Seems still work to do.