Canters tacking

[Andy P]

In dinghies, gybing boards are used by some classes. ( ie foils that rotate in vertical plane, so not aligned to hull fore and aft line )
These are most popular in hulls that are rounded bow section eg 5o5, and are not used very often in the classes with more pointed bows - like most development classes / skiffs with straight stems

As gggg says, the pointy bow hulls obtain much more side force from the hull shape. So it may be more efficient for the roundy hull designs to align the hull with the leeway angle ( by 'gybing' the board a few degrees ), and reduce hull drag.

[Paul B]

Originally Posted by Andy P

In dinghies, gybing boards are used by some classes. ( ie foils that rotate in vertical plane, so not aligned to hull fore and aft line )
These are most popular in hulls that are rounded bow section eg 5o5, and are not used very often in the classes with more pointed bows - like most development classes / skiffs with straight stems

As gggg says, the pointy bow hulls obtain much more side force from the hull shape. So it may be more efficient for the roundy hull designs to align the hull with the leeway angle ( by 'gybing' the board a few degrees ), and reduce hull drag.

Yep, people have been using gybing boards for a long time, like the 5-Ohs. I had one on my old I14. I agree that you can try to align the hull with the direction of travel to eliminate some drag. But it does not make sense to try to over-rotate so as to have the bow pointing below the line of travel.

[Paul B]

Originally Posted by gggGuest

[FX sigh]
Look there's nothing magic about leeway, and its only the *hull* going sideways by coincidence - well almost. Its all about the underwater foils. They have to create lift in order to provide a sideways force for the rig to work against. They also have to be symmettrical so that you can change tack. The way you get lift out of a symmettrical foil is by having it at a slight angle - angle of attack its often called -to the medium flowing past it..

Like wow.

Originally Posted by gggGuest

Its the same for sails as for keels/daggerboards. .

Are sails symmetrical foils?

Originally Posted by gggGuest

[FX sigh] Upwind you need a lot of sideforce at low speed so the keel has to be at a greater angle to the water. Downwind you need less sideforce and are going faster so you need the keel at a considerably smaller angle..

Hmmm...you have a strange way of stating things...

I would think that downhill you wouldn't want ANY lift (aka Drag) from the keel.

Originally Posted by gggGuest

[FX sigh] If your keel or daggerboard is fixed rigidly on the centreline then the only way you can sail is to set up the angle of attack/angle to the water with the whole boat. So it seems as if the boat is going sideways, and you call it leeway. Its just a refelction of what the keel is doing, nothing more..

Like wow.

Originally Posted by gggGuest

[FX sigh] Now if you can rotate the keel relative to the hull then with angle of attack of the keel the track stays the same - it has to stay the same to get the required sideforce. The keel is always at the same angle to the track. However the direction the hull is pointing relative to the track varies according the amount of angle you put on the hull. .

Like wow. Ever hear of the One Tonner Terrorist from 1974?

Originally Posted by gggGuest

[FX sigh] Now I have little idea and care less about whether having the hull pointing above the track, right on the track or below the track is better. I can think of pros and cons for all of them and it would take serious research to find out, and the results would probably be individual to particular hull configurations..

Let's have Lord "research" it. I'm sure he can read a couple of magazine articles and report back "facts".

Originally Posted by gggGuest

[FX sigh]OK this is a slight over simplification because water flow round the hull does contribute to the sideforce, but with a high performance keel and a flat modern type boat it doesn't contribute very much.

Thanks for keeping it simple for us.

[ned]

wintch cainters are slow to tack but hudrulic cainters arnt

[ancient kayaker]

On the gybing board issue, it's all about whether the boat will do better with no leeway on the hull. There has to be leeway at the board to generate lift. So a gybing board would seem to be most worth while for a hull that generates significantly more drag with leeway. I would expect this to be more apparent on hard chine hulls and less apparent on rounded hulls. A rounded hull that has so much leeway that it needs a gybing board would probably benefit more from a bigger board or one with a better profile.