Genuine Lee-Bow Question for GRF (not a p*ss-take)

Before you start off the exponent of perpetual motion you'd do well to start of by defining your terms.

Originally posted by GarethT A quick question on behalf of a young windsurfer: Assuming ‘your’ lee-bow effect is the same as mine (tide pushes you towards the wind thus increasing the apparent wind and moving it round giving you a ‘lift’), does it have the same impact when you’re planing upwind on the fin as it does in more of a ‘displacement’ mode, or is it reduced as there is much less of the board in contact with the water?

In answer to your question yes. There are often times here at Hythe when the wind is a light sea breeze from the East, if the tide turns it becomes possible to plane on a shortboard because of the additional input of a couple of knots on not just the fin, but everything which enables you to get enough momentum to get on the plane generate more created wind the combination of which gives you full planing apparent wind.

Here in Dinghy world there have been a couple of would be big boat book sellers saying there's no such thing as lee bow effect, which is total bollox. The key particularly for us windsurfers is the added element that the tide brings to the true wind enabling us to albeit often dynamically, but just the same get ourselves up and on the plane.
Up wind off the Fin? yes it still works but at our venue not quite as well because often the angle is too shallow, but I can assure you, you'll go faster, cover more ground on the tack with the tide on your lee bow than you will on the other downside tack, particularly if the planing threshold is part of the equation.

Now finally, where it doesn't make any difference and the big boat boys have their point, offshore, open water, it does make no odds, given what you gain on one tack you lose on the other, however the point I used to make on tactical lectures was always go faster earlier, why? The same reason you don't screw up the start. At the start of a race with sixty odd boats make a couple of seconds mistake at the start you lose sixty places, make the same couple of seconds error at the top mark you might only lose one or two places if that, so following that logic, better to go faster earlier..

The thing about foil size is just relevant to the speed, if you're just using the fin then chances are you're planing or trying to, and centreboards are only efficient in sub planing mode anyway, so it's horses for courses and more energy is more energy wherever it comes form, the more you have the faster you go.. So Tide either powers you up or depowers you, it's that simple.

Edited by iGRF - 30 Apr 14 at 11:54am

Tide moves everything in it, which is often enough to sail from even if there is absolutely no wind. We did a race on the Thames once, it was dead still, yet we raced on both tacks all the way from Putney Bridge to Barnes or wherever 120+ boards all purely using just the river flow. Lee bow both tacks, lovely jubbly and loads of pumping protests..

Edited by iGRF - 30 Apr 14 at 11:59am

Doesn't necessarily move it more slowly, certainly exerts less force, which is what we're concerned with...

Originally posted by L123456 Originally posted by GarethT I thought I did define what I was talking about. I fear what you describe is a misunderstanding of physics ...  I start with a simple question ... Imagine you are out at sea beyond the site of land ... You are sailing in 5 knots of breeze ... How do you know if that is 5 knots of gradient wind or 0 knots of gradient wind and 5 knots of current?