Steve Hansen wrote: Why haven't we seen this with a surfski?
Three main reasons:
1. In those sports where hydrofoiling has been going on for years (sailing, kitesurfing, windsurfing) it is still limited to fairly flat water. Though the 'model aeroplane' style foils on the SUP (pretty much the same as those used on kite and windsurf boards for quite a while) are probably more suited to foiling in waves, when you are standing on a board and can transfer weight almost instantly to control the angle of the foils.
2. Have a look round any of the top surf-skiers (or K1 paddlers) blogs and you'll see lots about types of training but very little about the technical side of the sport. Kayaking seems to have this belief that technical development is something handed down from 'The Manufacturers' to 'The Great Unwashed'
![:) :)](/media/kunena/emoticons/smile.png)
in terms of new products. The idea that you could get on and do it yourself is quite rare. Question racing kayakers on aspects of boat design and mostly they'll stare at their feet and mumble "that's just the way it is"...
3. That the rules for sprint K1s (which being an Olympic discipline will have the biggest focus on finding a competitive advantage) pretty much preclude foils by limiting rudder width and number.
It's unlikely that the 'model aeroplane' foils would work on a ski as you can't move your weight around quick enough from a sitting position. That leaves a few other options. However first you're going to need the following - a lot of patience, quite a lot of money, an expert composite builder and an elite surfskier who is open-minded enough to accept that they might have to completely relearn all the skills they take for granted!
- Simplest option would be two sets of surface piercing foils (or maybe 1 and a t-foil rudder - see 2000 in the link above). The angled foils control flying height without the need for moving parts. If you reinforced the deck of a ski you could just bolt them straight on without too much complexity.
- The present International Moth system with two t-foils with ride height controlled by a wand. This still proves a challenge to the moths in waves though (but they are moving at up to 60kmh in lots of different directions which makes it particularly challenging). For a ski you'd want to bring the foils as close together as practical (so they are in similar bits of the wave you're on). Maybe one at either end of the cockpit?! You'd probably want a hull just long enough, and with enough freeboard, to achieve takeoff speed - once it's up and flying the hull is just aero drag and weight. And how far forward (and with what gearing) you'd mount the control foil would be a definite puzzle... You's probably want the foils to be somewhat dihedral (sloping upwards to the tips as this would aid stability).
- The more subtle option - a single rudder mounted foil. It won't fly the boat, but is proven(?) in several sailing classes (International 14, National 12) to reduce drag by interference with the stern wave. The gain is small but it only has to be 0.1kt to add up over a 1-2 hour race. Whether it would work the same on a kayak is not clear. You'd probably need to mover the rudder further back and also the whole cockpit as the lift from the rudder would make the boat nosedive otherwise.
So there are a few random thoughts to run with. In one sense foiling should be easier in kayaks as the speed range is much narrower that for wind powered craft. On the other hand things like paddle design would also need to be developed to deal with having to paddle from an elevated position. There is also the question of whether it is a good route to go down - foils are expensive, delicate, awkward to store and a bit of a black-art!
They are fun, but only slowly becoming user friendly for the non-elite pilot! Whether they are the future (as every sailing magazine and website seems to claim) is still rather unclear.