Aerodynamics of the slot

[sailor2]

Slots , apart from breaking up sail plan into small enough to be manageable areas, serve the function of increasing the angle of stall and hence the Cl max, at the expensee of max L/D ratio.

Hence the predomination of una rigged ultra high performance sail vehicles, which are always sailing at high V/W ratios ie small angles of attack and at vector angles where the most important faactor is L/D.

In other boats obtaining high Cl max can be more pertinent.

If area is reduced going for higher Cl without changing Lift_force, it doesn't necessarily chance L/D much. As a result C-cats don't have less L/D downwind as they would have if they were allowed to have more area with same mast height & less Cl. That means high Cl max can work in high performance boats as well just fine. Would be much harder to have the same situation on iceboats as that would require so short chords that low Re-number would prevent it from working.

Originally Posted by Steam Flyer

The only thing I can add is that in light air, -all- boats are sailing at high ratio of boatspeed to windspeed, but low-aspect ratio sails seem to generate more power.
FB- Doug

Yes, because going for max L/D with high mast also means less force for same heeling moment. So even for upwind, max L/D isn't optimum for best performance. Even more so in practise as mast height can't be increased just as one wants it to be meaning one must sail with less heeling moment if trying to get better L/D and drop in lift force is even more dramatic.

[sailor2]

Originally Posted by Tcubed

Therefore telescoping spars are very advantageous.

Did you meant to say would be ?
If not, could you provide examples of such boats with telescoping spars.

[Tcubed]

<<<<<<If area is reduced going for higher Cl without changing Lift_force, it doesn't necessarily chance L/D much. As a result C-cats don't have less L/D downwind as they would have if they were allowed to have more area with same mast height & less Cl. That means high Cl max can work in high performance boats as well just fine. Would be much harder to have the same situation on iceboats as that would require so short chords that low Re-number would prevent it from working.>>>>>>

I'm not quite sure what you mean here but the first point is not very clear as the induced drag penalty must be weighed against the wetted area penalty.

Also c cats work within the restricted area rule which always favors high AR.
***
No, it is are. Just read the references (post #14) for well established examples.

And Chabrenas, time has not changed anything, reducing weight and windage aloft (hollow spars or not) remains just as relevant as always.

Bottom line for light wind ; Lots of sail area , as in lots.

[Tcubed]

And lots !