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.
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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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Hey
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: https://projectcedrus.com/cedrus-development/notes-on-ventilation/
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.
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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 
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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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Hi,
I literally in this situation.
I currently ride a Fone HM 14mm 95cm carbon mast for Kite foiling.
My issue is i am getting loads of ventilation in small side on chop when going hard upwind and in tacks.
Does anyone have the same experience with this mast as its sort of ruining my foiling experience.
Thanks
I have the Gong 92cm HM for kitefoiling it never happens like you said.
With my Fone 95cm HM 14 if the conditions are perfectly then its great but as soon as there is some side chop it ventilates when heading upwind and in tacks.
Any help would be appreciated from kitefoilers thanks
Kitefoil is more susceptible to ventilation due to the higher speeds. It seems the tapered masts are less likely to ventilate, well that’s my experience anyway.
Some masts ventilate more than others, cleaning is really the only option and if that fails a brand change.
based on my understanding of physics of the ventilation phenomenon - we won’t have this problem if the mast has zero angle of attack through the water. It is only if the mast has a non-zero angle of attack - ie. we are getting side-load reaction from the mast.
I could see how this occurs more often with kiters because of the angle of the kite lines force reaction versus the wing. But I still maintain it is something that can be managed by riding style. I challenge anyone with this problem to do an experiment:
Try going out on a day where you are experiencing ventilation, and make a conscious effort to angle the board and foil such that the force of your feet goes directly down through the board, no side loading. If the board/foil doesn’t have enough angle, then you’re going to be open to ventilation.
This really could be habits from kiting with boards that have fins and footstraps, which allow a rider to push sideways against the fin.
All that said, some mast foil profiles are going to do a better job of non-zero angle of attack. But generally, that would be the opposite of low drag.
I only experienced the mast ventilation in the very beginning of my learning process, just after advancing from a bigger stabiliser (with winglets) to a totally flat stabiliser. Especially when winging toe side. I then quickly learned to adjust my technique, to be more subtle and not to force the mast to go too much sideways through the water, and the problem went away. And then came back to some extent, when I started using much smaller area flat stabilisers, and again it was easy to learn to be more sensitive with the input I was giving to the foil.
Now, when I deliberately want to cause the mast to ventilate, I feel it’s easier to do that with a thicker mast. And with the nice 12.5 mm masts (surf and race masts) it’s much more difficult to make it to happen.
Based on my experience with lots and lots of different masts over the time (mostly of the same brand though) I would say the ventilation is largely a problem with the technique. Or maybe I have just been lucky and haven’t had a bad mast.
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How can you tell if it’s your mast or wing that’s ventilating when in a hard carve ?
Mast ventilation isn’t technique.
I have a Gong HM tampered carbon mast NEVER ventilates….I then go on my F-One HM mast and ventilation happens.
Same rider, same board, same technique.
I had ventilation issues with a Gong V2 mast.
But the Takuma Alu masts never,ever ventilate.I have always wondered why designers did not just copy that profile 
My general assumption is that If you don’t breach the wing, then it’s probably mast ventilation. If you breach it’s probably (but not definitely) the wing venting.
I agree mast ventilation is most easy to induce when taking a hard angle with a wing and harder to replicate when on a wave.
I also wonder how much of the ventilation equation is surface treatment. Someone mentioned the Takuma aluminum mast, which has a much different surface treatment than all of the carbon masts. Maybe this impacts skin friction and reattaches the flow better than the smoother carbon masts?
Wing,surf and supfoil.
Just the standard Takuma Alu V1.
Never had ventilation, reasonable stiff and glidey.I am 75kg,ride 850 and 1100 cm2 wings.
Takuma interfaces are bad but i epoxy the mast to fuse,mast to plate and fuse to front wing connections.
These masts are also very affordable.
The only time I’ve felt mast ventilation is pushing very hard upwind in short period chop (wing or kite). It occurs in these circumstances because when the board is leaned over hard the mast acts as a lifting surface (moving with non zero angle of attack). Moving through chop introduces air onto the low pressure surface on the bottom side of the mast (when leaned over) - which can propagate down the entire mast. It feels like the foil suddenly falls out from underneath you.
I dislocated my shoulder kite foiling after a mast ventilation when pushing the foil particularly fast a few years ago - this made me pay a lot closer attention to the phenomena and how to avoid it.
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