N5.7 Hydrodynamics

Is that a word?
If a asymetrical hull pulls a hobie 16 uphill while going upwind, does a symmetrical skegged hull pull my 5.7 downhill when going upwind? or is it neutral in that respect?

neutral . The skegs act as daggerboards, centerboards or as the flat side of an asymetric hull. an asymetric hull doesn't pull it gives a bite to stop slipping side ways. so the skegs are always in bite mode like an asymetric hull where as a dagger or centerboard boat you can take the bite out to allow slippage.

disclaimer - I am not a naval architect, although I did drss up as one at Halloween.
As poster said, the effect of symmetrical hull shape is neutral in that its shape does not produce lift the same way as an asymmetrical hull shape does.
But you can use your leeward hull in a boardless boat to produce a kind of lift effect, almost an angle of attack effect, even if only temporary or rhytmically while going upwind.
Consider this - just as your sail has a center of effort (approximately the geometrical center of your sail area), your hulls also have a resistance to being pushed sideways in the water. Think about the projected shape/area of the underwater portion of your hulls, and how that shape changes if your weight is forward, vs weight near the back.
On a boat like the 5.7, with very long, straight hulls, compared to boats with a large daggerboard, you can more easily change the location of this "center of hydrodynamic resistance", relative to the center of effort of the sails, by moving crew weight forward or aft (the same hull shape with a centerboard will always have centerboard area at the same location, reducing the effect changing crew weight location on the change in hydronamic resistance location). More of the bow in the water, means sideways slip of the boat in the water is resisted more by the front part of the hulls than by the back part of the hulls. I think this change in the relative location of the two forces (sail force vs hydro force) is what allows a 5.7 with weight forward to point much higher than a 5.7 with weight back.

Although I suppose the above force analogy holds true for boats with asymmetrical hulls, most of them (H16, P16) have topside hull shapes that are prone to diggin in & pitchpole. NACRA hull shapes,especially 5.0 & 5/7, are great for burying the bow, since it's almost impossible to pitchpole. So you really get a lot of benefit from driving the bow in, without danger of pitchpole.

Note it's a lot easier to tack when the bows are not buried so deep in the water, you want the weight back, the skeg & rudder are close, and turning radius seems better when you only have 16ft of its total 19ft waterline in the water.

jim in austin
5.7 boardless & 5.5 boarded