8.6 vs 10.1 AR when the swell is big and the foil is small

I’m headed into the summer and while I’m fairly set on foils in the 850ish range for my daily drivers but I am wondering about my big swell and high wind days in the eastern gorge.

My last session out it averaged 30 knots, gusting to 40, my 2.5m wing was maxed out on the upwind reaches, (dreamy downwind), head high to slightly overhead swell and I was riding my Cloud IX fs900 foil with an AR of 10 and a span of 93cm. This was super fun, so much speed and glide in that foil that you can practically straightline down the river and never stop gliding. I had to break off swell rides when I was getting too far from my launch. However, I had a moment or two where I almost felt like I was gathering too much speed, and I was getting a little locked in.

I have an fs700 AR 8.6 with a span of 77cm that I assume will be similar in speed, but will drop in glide while increasing in playfulness. I also have a fs550 that I could pull out of the dark corner of my closet at 8.5 AR and 68.5cm span. Last, Cloud IX is releasing an fs732 soon which will have something around 10 AR and an 87cm span.

I don’t get as many truly big, overhead swell days as I would like, so I’m hoping someone with more experience can give me a bit of guidance as I dive into these next few sessions. Do folks still prefer higher AR when conditions are big with a wing? Should I consider my lower AR foils to be just as good, if not better, at managing the speed and staying playful?

No jumping, just cranking turns on big swell is my goal here.

Thanks in advance for any help!

Personally, I prefer some of the lower AR surfier foils in higher powered conditions. I don’t necessarily need as much glide when conditions get more powerful, and as long as it can keep up with the swell, an 8 AR foil with a fast tail is a lot more fun to carve.

I generally use higher AR / glidier foils when the conditions are lower powered as I need that glide to connect the pockets of power in the water.


This is pretty much exactly what I was expecting to hear. I’m going to give that 700 a crack and see how it performs the next day or two.

1 Like

Same result here as Velociraptor, from a similar but slightly different angle. I relate AR to wave steepness, not necessarily height or speed alone. If waves are 2m high but 12 seconds with a 100m wavelength, they are not very steep so I need the efficiency of a high AR foil to extract the energy out of the wave. If waves are 2m high but at 4s and 40m wavelength, they are much steeper and I don’t need the high AR efficiency so then a can choose a narrower, looser, and more stable low AR foil. Still like to go gliding sometimes if the water state isn’t too hectic but generally foil more relaxed and thus better when water is moving everywhere with something around 8AR. Even take out my trusty old very thin 6AR foil for a good rip sometimes.

In general, for the same area and maximum thickness, the high AR foil will have a lower top end than then a low AR foil due to the increased frontal area and increased volume, but the low AR foil will need more power to keep up with and go faster than the high AR foil.

1 Like

I agree with this. My initial reply was a bit simplistic. Had some very powered conditions this winter where my 8 AR foil wasn’t quite fast enough to keep up with the long period, but fast swell, so there are definitely nuances.

Believe OP is in the Gorge though, so my thoughts around the lower AR seem applicable to a higher powered conditions there. Drooling over that forecast!

1 Like