Prone foil wing size ratios based on weight?

Talking to a 50+ yr old prone foiler today he said he “feels like it’s hard to find the truth”. What he meant is he’s been foiling for multiple years on high AR wings that are too small with little success. He was “caught up in marketing hype” and wasn’t on the equipment that he needed to be on. Thousands of dollars later, he has finally found success with linking multiple waves. He’s using larger foils with a AR from 5-6ish and linking waves.

It got me thinking… surfboard manufacturers, like lost…, have volume calculator recommendations based on weight and fitness level (really should be called athleticism & flexibility level imo).

Does a similar ratio exist with front wings?

Advanced Intermediate foiler 145lbs rides 120HA with area of 775sqcm 775/145 = 5.34 ratio

I’m a intermediate: 1210sqcm/200lbs = 6.05

Expert: Adam Bennetts 790sqcm/170lbs = 4.64

Specifically… if I was advising a new/beginner prone foiler, I would tell them to keep their front wing ratio between 6.5-8 (based on waves 1-3ft)



I agree, also feel like Erik was talking about on a podcast the one turn clips on insta are driving this hype around smaller and smaller foils.


Agree this is a genuine issue, I jumped far too early to ~10 AR wings, dropping back down to ~7 was the quickest improvement of foiling enjoyability across varying conditions.

For your ratio, you’d need to factor in aspect ratio? As you go up in AR you need more surface area*. I guess there is some elegant way to factor this in, here is my inelegant attempt

The formula being CM²/AR/Weight, a beginner should aim for 1.5, intermediate 1, expert 0.5. Two questions:
I guess convention would be that the numbers get bigger for harder?
I suppose you’d probably also want the AR to penalise more significantly between 8 and 10 than 5 and 7?

*also more rigidity in the mast etc

As a lightweight rider, I’d be curious to know what other <150lbs foilers are riding. Obviously it makes sense to scale up/down depending on weight, but it seems like surface area is only one variable as noted above, and that the sum of all parts with foil design means that two different sizes of the same model may not end up feeling the same even if scaled exactly with rider weight to end up with the same ratios mentioned above. Seems like all foils are designed for riders of average weight but different needs, as opposed to different sizes being geared towards different sized people?

For example, is a Vyper 130 going to feel the same for a ~60kg rider as a Vyper 150 does for a ~75kg rider if the ratios are equal? (I didn’t do the math on ratios but assume they are equal). Or do those two wings have inherently different feels regardless of weight ratio?


There’s so many factors that influence wing size for prone. The wave/ride speed plays the biggest role in my experience - also according to the lift equation (doubling the speed increases lift by a factor 4).

I’ve tried to use this to come up with a formula that includes speed and wing aspect ratio (and ignores all other contributing factors like wing profiles). It’s based off this nice summary: Hydrofoil. P.S. believe me, these mathematical… | by Ramadhian Ekaputra | Medium

A = 4961.5 x W x (AR + 2) / (V x V x AR)
A is Front wing size for prone surf [cm2]
W is Rider weight [kg]
AR is Front wing Aspect Ratio = Span x Span / Area (Some manufacturers get this wrong)
V is Speed [kph]

This was fudged off the lift equation, an approximation of the AR effect, lots of GPS watch speed data and what works for me - 95kg, 3 years of daily prone foiling mostly on Unifoil gear.

The speed range I’ve used is from 20kph (5.6m/s) which is just above the pump stall speed of most of my gear and around the speed of an average wave - so riding straight to the beach. The maximum speed I took around 28kph (7.8m/s) which is down the line on 5ft+ waves and a small foil. Not doing towing massive waves, this is average fast prone for me. On turns and steep drops I get to around 33kph, but those are spikes on the speed graphs, not the average for bigger wave riding.

Using this formula for my 95kg weight, I get:
Small wave / pump wing (20kph): 1515cm2 (234in2) - Hyper 230
Daily Driver for 3-5ft (24kph): 1089cm2 (169in2) - Vyper 170
Survival in 5ft+ (28kph): 809cm2 (125in2) - Vyper 130

Rider weight [kg] at Average speed (24kph) table:

AR7 wing vs Rider weight:

Here’s the spreadsheet with my ramblings: HydrofoilRatio.xlsx - Google Sheets