Mast Pulling Up Water

Foils and Boards - Gear Talk
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Ever since it got cold and I changed to the 80 cm mast (from a 75 cm) I have the problem of water getting pulled up to the board, then sticking there and pulling up even more water. On bigger foils it’s not so bad, but on smaller foils below 900 cm^2 I fall each time this happens because it is pulling my board down from hard. Sometimes happens every 2 minutes. I had at least 30 downwind sessions with those foils, same board, shorter mast and never had that problem to make it noticeable.
Did anybody ever have something like that happen?
The new mast looks completely normal…

Here’s an image to show what I think is happening (board never touched the water).

Bildschirmfoto 2026-01-01 um 15.25.30
Bildschirmfoto 2026-01-01 um 15.25.301142×1210 168 KB

here another one where I feel like that is too much water coming of the board :smiley:

Turn Nils Mango
Turn Nils Mango1920×1920 407 KB

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did you have the same problem and sanding like in the video helped?

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Your getting ventilation of your mast, air is traveling down the mast onto the wing, then it feels like one side of your front wing is ripped off and you crash.

First, clean your mast just prior to entering the water, window cleaner works well. Get rid of any greasy fingerprints and once clean DON’T touch it.

If this helps the problem you may need a mast sand, see video but always clean your mast before use. Some masts are just prone to ventilation, much more of a problem when kitefoil due to higher speeds.

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Cleaning any grease from skin or sunscreen is fundamental to perfo.

Sanding helps a lot too, intutively we want a shiny surface but it is wrong.

Try cleaning/degreasing and if you like it try the sanding.

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Could water near freezing is about 2x more viscous than 80 deg water. I imagine this could cause the change. Water molecules are more “sticky”

I notice more drag (harder to pump) in could water.

Bit of a monologue about it here:

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Hells bells! I won’t complain about winter again!

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What “i think” happens to cause the water spout is this:

If the mast surface is very hydrophobic (shiny new,sticker,greasy…) the water flow detaches more easily.

At high speeds or when side loaded this can cause a fatal ventilation with air sucking down all the way to front wing.

But even when going slower the water is detaching at the water/air boundary,it gets pushed sideaways from the mast to a depth of few cm.Sou you are digging a bit of a hole in the water as you travel, at the trailing edge the hole gets quickly filled in and shoots up the mast.

All this sucks energy and is drag you do not want.

Not a hydrodynamics expert,just interested in the nerdy stuff :slight_smile:

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Probably this

Try the other mast and see if it stops? Likely the mast is greasy if so. Interesting theory about the cold

there was a cool thread about it here, didn’t converge, but I wouldn’t be surprised if there is something in the cold water idea, but nothing conclusive so far

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Thanks guys. I even hear a kinda slurping sound when it happens sometimes (I think). Most of the time it’s just a little pull to one side for fraction of a second and then it’s gone again. This seems like it would fit the ventilation theory I guess?

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Sounds like ventilation. I get the same thing kitefoiling. For me it normally occurs during a hard turn in flat water.

You can hear air getting sucked down the mast (gulping sound), you lose lift on one side of the wing, and then after that I typically crash.

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yes, the slurping sound is common. pour water on your mast and see if it beads up or sheets off. You want it to sheet as long as possible, if it beads you need to clean and maybe sand it. 1000 grit is good for a surface refresh since you can sand fairly aggressively without changing the shape of the foil