This graph shows the performance predictions for a foil in fresh and salt water at 5, 15 & 25C.Not an insignificant difference, but still just in the 5-6% range between 5-25C.
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However it looks like the fresh was colder than the salt based on the wetsuit
interesting… Temperature difference does make more sense although the board will also be a bit lower in the water adding to the initial drag
Curious if Tom Earl has anything to comment on the subject going from cold ish UK to Australia
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Another reason why staying high on the mast helps, especially calm water dock starting where the warm water is in the top layer. And boy this makes me feel better, I’ve not been around much in the summers, so I progress every fall, and then wetsuits and honey.
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This is a massive take. So true. I paddle up in the ocean but have recently had a few sessions on lakes where this would def be similar to your conditions. Def during the Spring months the gradients are more pronounced… Im floored at the difference while on FOIL when having a high mast & FOIL just beneath the surface. I think the lowered drag of my 85cm mast does contribute as well. Plus more room to lower the AoA and gain speed. Def preferable up there! Since starting this post the local water temp is up to 13C from 7C. She’s still a challenge but its a different animal. Once again, I can see that the lowered sea temps (towards fall & winter) will be a great training tool. A grinding stone to sharpen the skills and conditioning on.
foiling in the surf zone, there will be no temperature stratification effect at all, especially if there is even a little wind.
Staying high on the mast has a pronounced effect in these conditions. While it may be true that warmer water at the surface could theoretically reduce drag, I really doubt that is what you are actually feeling. Perhaps so, but just keep in mind that staying high on the mast has been proven to work super well in all known conditions
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Where Im foiling there is no surf. Theres a sandbar that at a higher tide allows for a meter and a half of water which is perfect for the temp variance that would help things… I think. Feels that way anyways. I do take your point though… most likely water is moving and mixing fast enough to create an even mix. The sandbar should heat up the shallow water no?
This is the condition locally:
when I lived right on a deep water lake for a summer, I quickly learned that if the wind was dead for a day or so, the stratification comes and the surface water can be much warmer. As soon as even a little wind comes up, the water chills down fast at the surface. I assume that to be mixing. Generally any water movement seems to dissipate stratification.
Your example is a bit different - a large sandbar that has sun might heat up all the water in that area - which isn’t stratification really. If its super calm you might get stratification, but I doubt it in the ocean.
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Roger that buds. I think youre bang on the water has to be super still for the stratification to layer properly.
I love how deep down the rabbit hole we are going here, thanks for a great discussion everyone!
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Once you are dealing with shallow water then I think you may need to consider additional variables such as ground effect and what occurs locally for me for shallow water is silt.
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I’ve been SUP down winding not far from you, in the San Juan Islands, WA state. Never foiled in any warmer water than this (typically mid-high 40F winter, low 50’s summer). It’s quite doable, of course, as we see from foilers all over the world. I’m about to head to Baja, where the water will be warmer and possibly more saline. Curious to see/feel how things differ there. Thank you all for the interesting topic!\
Ah nice. I think what you’ll find, as I’ve thought on this one long and hard (that’s what she said) is that its not necessarily easier to get on foil but when you’re up it easier to carry the speed necessary to STAY on foil. You will have a front row seat for this rolling thesis. If you think of it please report back as Id love to have this confirmed, if not just anecdotally. Enjoy the Baja!
Here is another consideration: Water Depth
I was tow foiling with Jimmy Jams, Spoiled by the Foil, in San Diego. The boat driver quizzed me on how deep that water has to be for the Supra (Tow Boat) to throw an effective wake that can be ridden by a foil. Answer = 11+ feet
In the San Francisco Bay the bumps get terrible from Coyote Point, at low tide, as we approach 3rd Avenue. When you hop off at the end of the run it is often 5 feet deep. Aka too shallow.
More than just the bumps getting bad coming into 3rd during low tide, it also gets all silty and you have to deal with kiteboard wakes which are surprisingly annoying when the other conditions are poor.
In my experience: Surfing (non foil) the European atlantic felt very different from the Pacific (for ex. Nicaragua).
Foamies that you would easily duckdive clean in Nica will tumble and spin you for sure in europe.
Water feels a lot heavier.Cannot find the links now but it is denser at the same temp (salinity i think was the reason).
So density, viscosity (due to temp as shown in.previous posts) , sediment differences and 4mm of rubber wetsuit … that explains why i suck at connecting waves on foil 
I had a back to back session moving from one spot to another with 10C difference in temp, described here:
After a few more sessions, I have the following theory about colder water
- It dramatically reduces the lift of the foil
- It does not decrease the drag of the foil, and more importantly, does not decrease the mast drag
The outcome is that the same setup in colder water is more sensitive to riding low on the mast.
This is most noticeable on a high aspect foil where 30cm of additional mast drag could possibly double the total drag.
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I just watched a Duotone Tech Talk vid about shims and they agree with you.
Colder water,less lift.
Min. 05:15 in vid
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