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bel29 said..
it's not just the foot; besides which, I think the deep foot is a bit of a thing of the past, or at least is a feature of foil course racing as opposed to foil slalom racing sails.
regardless, my foil slalom sails don't have a noticeably deeper foot than my fin slalom sails (duotone warp). that said, there are clear differences:
-draft position: higher, further forward on foil sails
-entry: much more camber on fin sails
-profile: much flatter profile on foil sails
-loose leach: more looseness on fin sails
-outline: higher aspect on foil sails
-cam pressure (although this is adjustable): less on foil sails (for smoother exit from the foil gybe)
-weight: foil sails noticeably lighter
on the water, I'd say the main difference is that the fin sails generate more low end power, provide more lift to rail the board on the fin (which is way further back on the board than the front foil wing) and probably have slightly better high end range (more tension in the sail, more cam pressure, so a much more blocked profile)
all that said, I'm sure you can use a foil race sail on a fin slalom board (and vice versa). it would just be less efficient.
This is a good list, but there's maybe some more.
Note that we sail foils and fin boards in a different way, and that means the sailor's stance is different on each board.
1) On a slalom fin board we accelerate the board up onto the plane and fin lift eventually allows the board to 'fly' off the fin and tail of the board. That acceleration process means we rake the rig back more as we get going fast, and so less sail foot is needed.
The fin sailor also pushes sideways on the fin and holds the rail of the board down, and that is easier when the drive of the sail is set low down.
2) On a foil board, the foils give vertical lift and the sailor stance over the board is more upright - as that allows sailor weight to be applied downwards. The foil board is either up on the foils or not, and so there is less rig rake change as we get going, meaning the sail can be cut with a much lower foot to 'close the gap' . The upward pressure from the foil can also benefit from the drive being set higher in the sail. And this, in theory, means a different cut to the sail, in terms of draft position and tightness of the leach.
3) The third issue is highly complicated, and that's about sheeting angles for the rig. In all sailing and windsurfing we sheet to apparent wind, which is a combination of the 'true wind' of the day and the' created' wind which is a function of board speed. Created wind is like the wind you feel when you stick your hand out of the window of a moving car, and on a board that created wind always runs nose to tail , whereas the true wind of the day flows at an angle across the board, with that angle depending on our course direction. Foil boards tend to get going in much lighter winds, and that means the created wind is often a higher proportion in the apparent wind that we sheet to. So in other words you can stay sheeted in hard, even when heading well off the wind. It's that difference in the typical sheeting angles that means the optimum cut for a foil sail is very different from a typical racing slalom sail. The typical foil sail used in lighter winds is higher aspect, with a longer luff length.
4) There are however plenty of standard cut sails that will fit foil gear as well as slalom gear, and you just rig them a bit differently for each use. For foiling you might rig the sail with less downhaul to create a tighter leech, and you might also set the extension longer, just to get the sail set higher off the deck of the board. Having the 'wrong' type of sail won't stop the fun, and it's only at the top/professional level of racing, or where going for GPS speed records, that you absolutely need a dedicated sail.
cris21
> 9 months ago, 21 Nov 2023
