Lee-Bow..... Windsurfers...etc (Dons tin hat)

'Lee Bow effect' wasn't my term, it was yours, in a dinghy sailing collective sense, so I use it to describe the positive convergence of both fluid energy flows on your craft. I'd be perfectly happy to call it something else, we never hear the opposite, 'weather bow effect' or windward bow effect, neither are a 'thing'. But I do feel the sport and it's proponents are denied a serious discussion on the positive and negative effects of joint fluid energy combination in the act of sailing.

Originally posted by Oatsandbeans The 2 fluids air and water affect the motion of a boat that is at the interface. But that interaction is dependent on the relative velocities and direction of the 2fluids. Whether one is stationary wrt to the sea floor or not is inconsequential.

The sea floor is irrelevant. What is relevant is the speed derived from the two combined energy sources and the craft helm's skill and ability to combine them or mitigate the negative effect of one acting against the principle of sailing.

Edited by iGRF - 18 Sep 19 at 7:07pm

I'm going to have one last go at this.

You have to accept that you exist at the confluence of two fluids.

You are 'tethered' to one fluid with the rig, and you are equally tethered to the other fluid by the hull and foils, without either the basic principle of sailing fails to work. So mozzys raft suggestion fails because it removes one factor..

Usually on still water there is only one energy source, which acts on one set of foils whereas the other set beneath the water act purely as an equal and opposite resistance until the craft begins to move, then it can be argued that the Bernoulli principle also applies and the sub surface foils also produce lift.

So far nothing controversial.

The controversy surrounds the introduction of an energy factor into the 2nd fluid. My argument and the argument that supports the 'myth' is that according to the attitude of the hull and foils on the 2nd fluid, that the energy from the direction of that fluids flow can be either added to the energy produced by the primary source, or subtracted from it.

Everything else appears to be a confusion of terms.

The fact that the RYA don't teach it is because it is convenient that the 'myth' has been debunked by the Perry article, that whilst true to a degree in vast open waters where there is little to be gained or lost simply because what may be gained on one tack will simply be lost on the other.

RYA tuition of tactics at windsurfing level is woeful, and in truth there have been heated discussions on the subject.

The only way I can see to prove the theory would be tank tests with moving water that can be angled perhaps on a turntable in an airflow and the use of models to prove the point.

But it is fact that both fluids, the wind above and the water below, do contain energy that can be tapped if both fluids are moving and I challenge anyone to deny that.

Ergo Sailing motion is derived from the sum total of BOTH energy sources.

Edited by iGRF - 18 Sep 19 at 6:55pm

Tethered river ferry is driven by rivers current, but only because it is tethered by cable from bank to bank, wouldn't have same effect if trying to tether using sails.

Edited by 423zero - 18 Sep 19 at 7:17pm

But are you sure rich96?