FOILS ON OFFSHORE RACING MONOHULLS

Let's start first with the ones that are used on the IMOCA that use foils, the last ones designed by Verdier and used on the Vendee Globe. These movies explain it better than any words:

But this design obviously has a problem: it substituted daggerboards that offered a very good grip upwind for foils that add practically nothing to the performance upwind and the little they offer is probably more than annulled by the extra drag.

We can see on this image (left) that when an Imoca goes upwind with the keel canted, the only thing that is on the right place as an upwind foil is that big rudder. That's why the new boats have a lousy performance upwind and the reason why on the last Fastnet, a race with upwind and downwind sailing, all the new boats were clearly beaten by older boats, even if the crews on the newer boats were probably better.

Hugh Welbourn, the father of the DSS system was the first one to show some designs regarding what could be the new foils on IMOCA boats. I made a post about that two years ago but what he proposed, even if with some similitude with the system they use had a basic difference: It would also contribute to upwind sailing.

Looking at the drawing we can see that in what regards lift it would work basically the same way but that the angle of the foil, in his more vertical part is completely different. This one is practically parallel to the rudders, meaning that it would contribute effectively for the upwind sailing performance.

Why nobody went for it? I don't know. But there is probably a good reason, or maybe not, maybe they just trusted more the one that has been designing the more successful IMOCA racers (Verdier), that has the support of VPLP in what regards very expensive programs for hydrodynamic studies and even tank testing.

Curiously the foils of the new Figaro III, designed by VPLP and probably also by Verdier, have nothing in common with the foils of the IMOCA boats, probably because the boat will be raced in many races where the upwind performance is as important as the downwind one and also to offer less drag while going upwind on light winds, also much more frequent on the racing program of the Figaro. The Figaro has also a fixed keel and that change many things in what regards foils and upwind performance.

There are also other type of foils being developed on the mini of Simon Koster, designed by by Mer Fort, even if on this one I don't understand why the foils are turned to the inside of the boat and not to the outside. These foils will also provide upwind grip. Till now the results have been not great, being the better a 3rd on the Mini en Mai race, but I am sure that the mini class, as usual, is going to contribute with a lot of experimentation and different solutions, in what regards foil development and different solutions, I hope already on some of the boats for the next mini Transat.

Anyway they are only at the beginning of the development of these foils and I am sure that very interesting and more efficient evolution will follow, just look at this baby: