For low wind days I am currently riding a 1280 cm frontwing with an AR of 6. Looking to upgrade to something higher aspect but with more or less the same low end - AR8 at 1100 or 1300cm is currently on the shortlist. The spot I ride often has a lot of water movement, even in low wind: chop, current in various directions, and waves. Basically a lot of water moving around in all directions. The current frontwing picks up on these movement real easily, which sometimes makes manoeuvres such as upwind tacks tricky as everything becomes unstable when an underwater bump hits the foil in the turn.
So during looking at potential new toys this got me wondering: does aspect ratio play a role on this behaviour? Is a significantly higher aspect ratio front wing less sensitive to turbulence/water moving etc? Or is it worse, since a high AR has better glide and thus also when going against the direction of water energy (e.g. upwind tack) will be more prone to being negatively affected? Or is size in square cm the biggest factor (the bigger surface area, the bigger the impact of all water hitting it). Or are there other aspects of the shape of the wing that mitigate being prone to underwater turbulence?
Higher aspect foils are more sensitive to changes in angle of attack so are more sensitive to movement in the water than low aspect foils.
Highly loaded foils (less area for a given rider weight) are less sensitive to movement in the water than lightly loaded foils, because they either operate at a higher angle of attack or at a higher speed.
The amount of area out towards the foil tips matters - the more area out near the tips, the bigger a roll moment movement in the water can induce. The same is true for span, a wider foil has a bigger lever arm.
Svensdon has summed it up well. The only solution is to reduce foil size, but of course that comes with a compromise in bottom end. 1280 down to 1100 is a pretty small step. Maybe down to 1000 might see more improvement.
Of course there is more to foils than AR and surface area. It sounds like maybe you're considering a carving wing like the F-one SK8? That may yield more improvement. I've never tried the SK8, but I know that my 1000cm2 AR 6 foil is way less affected by water movement than my 1305cm? AR 9.9 wing. The 1000cm2 foil is also way looser in roll, generally.
So in your situation I'd go for a foil that is designed for carving. The AR could be 6 to 8 depending on brand.
I started out with low aspect foils that were probably close to AR 5 or 6, often sailing in quite choppy water where the 1700 and 2000 cm2 foils would become unmanageable (at least for my mediocre skills). Going down to a 1300 foil in the same line really helped a lot. I since switched to a higher aspect (near AR 8) foil with 1500 cm2 that's about 25 cm wider than the previous foils, and it behaves more like the larger foils with respect to water bumps (but also with respect to low end). In high wind and chop, it also becomes uncontrollable for me. My speeds on the AR8 1500 and AR6 1300 are quite close, so the two other factors that Svendson mentions which increase sensitivity to bumps in the water seem to be dominant. Based on that, I'd assume that a 1300 higher AR foil would probably react similar to your current 1280, or perhaps even more, to the underwater bumps. Nikita's advice seems spot-on.
Good input by Svendson.
Another factor that I think plays a big role in such conditions are the stiffness of the foil. Both the front wing, fuse and mast.
A flex in the construction changes the angle of attack and it all goes out of control, especially if there is a lot of moving water.
I sail a lot in choppy conditions. And often places where wind swell hits cliffs and rocks, and comes back, so you get cross chop. Or what we like to call waffle chop??
Using a 1000cm2, with 100cm span as my biggest front. And smallest is 580cm2 with about 90cm span.
(90kg).
And I dont feel any big Issues.
Upwind tacks are always easier on flat water, and it is easier on the 1000 than on the smaller ones.
But i dont experience problems as you describe.
Cheers,
Oyvind
A front foil which is stiff in the middle/root but flexible in the tips could be a good thing. Maybe consider going longer in your fuselage, for the pitch stability benefits. This is if you can find a hydroplane which has good roll-carve response. HA can still turn reasonably well. For good roll-carve response look for front foils which have thin tips with some wash-out, and rear foils which generate enough downforce in the outside tip upon roll change.
Thanks for the feedback so far. Was looking at the new Seven Seas 1100 or 1300. Also already have the Sk8 950 but that needs wind and speed to get up, so not suitable in low wind chop as there is not enough wind to generate speed and the chop slows the board down a lot even if there is a little gust...
But if I understand correctly, smaller front wing would be the best solution to counter over-sensibility to chaotic water movements but then I would need to get my low end efficiency from somewhere else. I have a DW/mid length on the way so hopefully that will allow me to increase the planing speed efficiency, and consequently allow for a smaller front wing to be used (theoretically). Will see how that works out with the Sk8 950. Ideally, that set up might get me going on a 5.5m in 10-ish + knots, but that seems optimistic. 1100 SS would be next on the to-try list then I guess, as the 1300 SS would just be as sensitive as my 1280, if not worse.
I had a phantom 1480 and moved to seven seas 1200 and now sk8 950. I wing in SF with high winds chop and swell with strong current. The seven seas cuts through chop and swell much better than the phantom. The SK8 is even better but I think a 1300 seven seas would be a good option for really light wind.
Strekke I find it's about AR, but because of what typically goes along with AR. Foil thickness is the big one for me. Generally foils of low AR tend to be thick (leading edge). Foils of high AR tend to be thin.
If I ride one of the Axis red fuse compatible foils, I find they are difficult to control on waves and in locations where there's disturbed choppy water - lots of feedback. Get on the black fuse compatible foils and I notice the difference - much smoother ride. So look at the foil from front on, as if it's coming directly at you. If it's thick, then it develops lots of lift and I find that they have a greater capability to pump the foil to get them up and flying when you're in marginal conditions. Downside is this lift becomes excessive on waves and in chop giving lots of feedback. Get on a thinner foil and you'll find they can be a little more difficult to get flying, but on a wave or in disturbed water, they give a much smoother ride making manouvers and general control much easier.
This comment is not orientated towards you as it sounds like you're beyond the basics, but the important thing is for learners to master the basics with a learner orientated foil before progressing to a thinner (generally) more advanced foil.
