I was wondering if anyone could have any use of some basic wing experience and theory.
I am really experienced in aerodynamics.
Hydrodynamics are different in some parts though, as the water is more dense (reynolds numbers), and regarding cavitation which is an important issue at high speeds.
The cavitation and the profiles to avoid this (to avoid rapid pressure changes) is a science of its own, and I wont get into that.The basics regarding the wing, as I see it, when comparing wings with the SAME surface area :
A low AR wing has more drag, because of induced drag (tip vortices from the pressure differences top/bottom = turbulence = drag)
A high AR wing has more lift than a low AR (some think the opposite, I know), because the low AR wing will lose lift at the tips, because of the vortices.
The high AR wing also has less drag of course.
So why use low AR wings ???
Because, the very same feature, the tip vortices (which is generally the pressure difference top to bottom that will try to equalize around the wing tip, thus lose a lot of lift and add drag), will make such a wing MUCH easier to ride, because it wont stall abrubtly, like a high AR wing.
A high AR wing will typically be able to lose its lift at the same time over most part (or all), when pressed over the limit, or when sucking air down from the surface from a rider error (or big chop), and it will stall (stall = too high AOA for the given speed = separation on the top of the wing = lose its lift thus you crash).
Whereas a low AR wing will be much more foregiving, and make a very soft stall, actually more often recover from the stall again. The reattachment hysteresis is also "better", meaning easier to recover.
It will also be less prone to a stall from air from the surface, as the AOA is different over the wing, because the tip vortice changes AOA.
Apart from that, one can also diminish AOA at the tips, if having a swept wing - and this way obtain a much more stable wing, easier to ride without "bopping" up and down, and with very gentle stall characteristics (and/or use a smaller tail wing as not as needed).
Gentle stall is really important for beginners, and when riding on the lower speed limit.
The physical strength and stability is also much better with low AR wings.
A fast wing is a high AR wing, right ?
No, not directly connected this way.
A fast wing is a wing with a low drag profile and lower max lift, which means a more flat profile maybe not even concave at the bottom.
A wing like that rides with less lift and less drag, so faster (higher top speed).
If you increase AR, you will get even less drag indeed, but that is only part of it.
Increased AR has much more influence at high lifting profiles, so for going max upwind a cambered high AR wing is the best actually - whereas for pure speed, a low cambered but only medium AR wing will work fine
Above is not what we typically see from the brands, but this is, IMO, merely because most have chosen to carry two types:
One lower AR lots of camber for beginners and easy to do tricks/waveride.
One higher AR fast(er) camber for race.
And not a foil for pure speed...
If you go solely for speed (not race), the trick would IMO be to go with a low drag (low camber) profile, quite high AR, and a smaller wing (less area = less drag).
But everything is connected - as if the wing gets too small, it needs more lift, and will maybe operate at too high AOA for having the lowest drag, both because of the profile polar and more induced drag.
So all these parameters, polar curves and induced drag (which is higher with stable swept wings) and size drag has to be calculated across, to find the optimum size and type.
I might be wrong if something does NOT match in hydrodynamics, like it goes for aerodynamics.
Please correct me if wrong...
But I think it is the very same (apart from cavitation issues).
Hope above can be useful as knowledge for those interested ?