Mast ventilation - all the rage. But what the hell is it?

Am I crazy, I’ve done a heck of a lot of foiling SUP/prone/winging. I can’t say I’ve ever noticed mast ventilation. Everyone seems to be talking about solving it, but I’m not sure I have this problem.

Same as when a wingtip ventilates. When a mast leans over it is a lifting surface. It can ventilate and you immediately fall. It’s very very annoying. I’m one of the people that can make certain masts do it and then I get mad at the mast and sell entire setups.

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I’ve found it happens more riding fast with higher upwind angles, against the wave direction, generally some leaning too. Not sure which of those factors was cause and which was just correlation.

Used to happen to me with the original Cedrus. Almost never happened with the Katana mast. Comes out of nowhere fast and can’t be corrected and you lose lift for no discernible reason. Ive seen it on video and you can see a big air pocket propagate from the mast down to the foil.

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It appears that some people are more subject to ventilation than others.
I heard that if you’re lightweight it may happens more.

My experience says it mainly depend on the conditions / spot.
For me it is when it’s offshore : with 5-10cm super thigh chops, going slightly upwind and especially on my starboard. In such conditions I can easely ventilate.
But almost never with onshore conditions where I go upwind slower and with bigger bumps and freefly the other way.

People I know that struggle with ventilation often sail in such conditions.
On the other and, people I know that only goes for onshore conditions don’t even know what is ventilation.

Never had this problem with surf and SUP downwind.

From a gear perspective, mast profile and thickness have a huge influence.
Never happened with a FOne HM for instance.

So my guess it that it depends on speed + angle of the mast / chops + mast itself.

I never had mast ventilation riding my Gofoil V1.5 masts while friends were having issues with the Axis alu 19mm, Cedrus V1 19mm, and some others.
Then I got a Gong 86HM thick stiff mast designed for the bigger Sirus foil and ventilated it going upwind in apparent wind in 10 knots leaning right over on fairly flat water, then used it again with a much faster Ypra-S 900 team edition in onshore small waves, that time could ventilate every single tack on demand if I leaned the mast over, going above 18 knots and crossing a small swell with white water.
This never happens with the thinner faster Gong 92HM mast even above 20 knots with the same foil.
I’m 150lbs.
It feels like going through white water, bubbly shaky sensation and you start losing lift, it’s fairly gradual with the Gong mast and I could correct it at times if catch it early by slowing down and having the mast more vertical.

Here is a blog entry that discusses ventilation extensively and also shows videos of it occurring as well as fences preventing it:

In short it can happen on nearly any mast for a variety of reasons, the #1 being riding style. Yes thickness and profile have an impact, but you can also have structurally-induced ventilation (mast twisting). Wetted area has a bigger impact than profile/thickness, because it provides more area for the surface tension of the water to help keep it attached. This is why Evolution Wind is shaped the way it is.


Must be a combination of my weight (#205+wetsuit), conditions, and riding style.

I have a feeling that folks riding upwind more like a windsurfer treating the mast as a fin are much more subject to this phenomenon as I understand the discussion above and at Kyle’s link. I’ve always made a point of pushing straight down through the board and getting my upwind performance from the board angle rather than pushing sideways on the board through the mast as a fin.

Thanks everyone!
I had no cluewhat it was…and was too afraid to ask…now i still don’t know :laughing:

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Ventilation is sucking air down below the free surface to places it wouldn’t normally be. When foiling and the mast draws air down below the free surface, a sudden crash is the usual result. The exact mechanisms I am unsure of, suspect loss of lift on the stab in mild cases (due to the air) and possibly aeration of the main foil in more severe cases.

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