Surf Foil specific performance dimensions

After listening to a few podcasts I started to think of a few key performance dimensions, especially regarding Erik’s developments.

Obviously this is nearly entirely subjective and possibly inflammatory, but I wondered from those of you who have used all of them have mental recordings of their relative performance? (i mean I know everyone does)

(Reedin is entirely speculative based on what KDMaui seems to like from a foil, and it being a mid aspect - and the fact that I’m frothing to try one…!!)

Here is a first attempt

  1. what of these would you agree with on the dimension front? ie is there a better dimension for “pump ease”
  2. Are there 5 better dimensions to measure a surf foil?
  3. Are there better “combination” features than the ones listed in the second image?

*disclaimer I have only used Axis and am a noob


I love this Matt! It’s exactly how I think about foils. Something I would add is glide which isn’t exactly speed or pump. It’s kind of like Umami. Hard to describe but you know it when you feel it. Glide was one of the objectives for the Uni we’re doing. Absolutely frothing to share it! First 2 sizes are done :slight_smile:


Cheers thanks @Erik, yeah glide makes a lot of sense… I wonder if I should replace “pump ease” with glide, but stoked to hear it resonated, and that you are doing well on the uni project.

I was thinking, what is the simplest trade-off dimension with a surf foil, and I guess it boils down to glide and turn (manoeuvrability)?

ie an example (relative positions again made up):

               899  1095    150     980
glide <---------------------------------------> turn

Comparing to surfboards:
Glide is like board length - where a longer board is more likely to let you get past flat sections on a wave, glide is similar
Turn is like board outline - rounder outline allows for a more dynamic turn, straighter is faster

Maybe the other dimension to add is speed (slow is like a rockered shortboard, great for in the pocket powerful waves, fast is like a flatter board, better for flatter waves).

Fun stuff

This is great! I’m still trying to wrap my head around the different feels of the foils, which I like better and why. Having a good mental model of the tradeoffs helps. Here’s a rough sketch of the kind of mapping I’m trying to understand, but I don’t know nearly enough to actually fill it out. But it still helps to give me a sense whether I should be tuning, changing parts, or changing systems to get the feels I’m looking for.


Whenever anyone talks about how well a foil turns, I’m not sure how to interpret it. I feel like there are different aspects to turning. How easy it is to initiate a turn is one factor, and how hard it is to adjust or exit a turn once it’s started (how locked into the turn you are) is another. With some foils the roll resistance remains fairly constant, whether the resistance is high or low, but some really resist any changes to roll axis once a turn is initiated. I think I’ve heard it referred to as a pivot turn vs a carving turn and I guess it’s personal preference which people prefer.

1 Like

Epic. Nice list!

I suspect it may end up like spaghetti as I can see quite a few that should be linked (both thickness & foil sections to speed)

Perhaps worth trying to do the primary drivers or something?

  1. foil section is primarily “Lift related”,
  2. results in either more or less left,
  3. more lift = less Top speed, more Stall speed

And grouping the Lift related feels
Top/Stall Speed, Lift (Glide)

I think it’s a great start, and if I can find the file I may end up revewing my post above!

Another note (still pondering this concept, after @Erik’s umami comment!) - I think Glide is also worth comparing to Minimum Sink Rate

  1. Min Sink is altitude conserving, which I think approximates to "how long can I stay off the water to pick up another bump.
  2. Glide ratio is “how far can I get without pumping”

Any gliders care to comment?