Random aeration/ventilation of the rear stab.

[plummet]

Hey gents. I'm getting random aeration of the rear stab leading to instant smack downs.

Usually when there a bit of mast height out of the half mast or more.
It occurs when I pitch the foil down, Or when I am carving to usually powered up heading back into the beach cross wind to broad reach (cross on wind. Chop, swell around 1m to 1.5m.

I initially thought is was my hack skill. But my pitching of the foil is now reasonable.
I then thought the rear stab was physically breaching the surface due to the chop/swell combo. I've been watching the stab a couple if times and its still firmly in the water.

Any ideas?

I'm at a point of progression where i can ride around reasonably without crashing (excluding gybes which i still suck out) except i'm getting this random aeration. Causing quite painful smack downs thats decreasing my stoke. I want to push further and faster but am weary of this.

Ideas i have.

Maybe my mast is too short for my swell/chop combo? 90cm.
Mast maybe too flexible causing a wobble and subsequent ventilation of the mast.
Mast trailing edge may need better tappering for less ventilation.

Perhaps a combo of all of the above.

Or maybe i'm operating the hf outside its mild conditions goldilocks zone and using it in very challenging enviroment that its not ideal for?

[Kamikuza]

Get some video, especially line mount...

[plummet]

don't have a line mount. But maybe I can screw a gopro to one of my fin bolt holes.

[bigcane]

Most likely it is ventilation coming down the side of the mast. Had this experience when i built a mast that was too thick compared to the chord length. My current mast is 13mm ish x 110mm and no ventilation problem. But originally when it came out of the mold a section of it was closer to 14mm thick and this ventilated alot. Fixed it with a sanding block

[Peter_Frank]

Most likely it is ventilation coming down the side of the mast. Had this experience when i built a mast that was too thick compared to the chord length. My current mast is 13mm ish x 110mm and no ventilation problem. But originally when it came out of the mold a section of it was closer to 14mm thick and this ventilated alot. Fixed it with a sanding block

Very likely yes - I have heard from several (also Gunnar as I recall), that the mast profile itself can be essential regarding "eddies" and ventilation

Another issue could be too thin/less lifting rear wing, combined with too much negative aoa so when you push (fast) with your front foot to compensate for the foil going up, the even more negative aoa to the waterflow exceed the stall limit so it actually stalls - which will feel the same as when ventilating.
I have tried this myself experimenting with smaller stabs, and doing tight carves.

If it is the latter, it might disappear with time, as you will get a much more relaxed and fluid ride when half a year or a year has passed and you get better muscle memory for hydrofoiling
Time works wonders regarding your ability to ride both slower and faster and without stalling nor ventilating

PF

[Kamikuza]

If it is the latter, it might disappear with time, as you will get a much more relaxed and fluid ride when half a year or a year has passed and you get better muscle memory for hydrofoiling
Time works wonders regarding your ability to ride both slower and faster and without stalling nor ventilating

PF

This too. Looking back at my video, I wonder how I let those wiggles drop me in the drink. Even venting the wing doesn't bother me anymore....

...gen I got the new kit and it's back to square one. Or maybe two...

[plummet]

Most likely it is ventilation coming down the side of the mast. Had this experience when i built a mast that was too thick compared to the chord length. My current mast is 13mm ish x 110mm and no ventilation problem. But originally when it came out of the mold a section of it was closer to 14mm thick and this ventilated alot. Fixed it with a sanding block

Maybe this is the issue? I'm 15mm x 123m. Too fat perhaps?
Also my mast shape is not perfect. Its the first wing shape I have ever shaped. maybe I need to reshape it better, loose some thickness. What width do you recommend for a 123mm mast big cane.

[plummet]

I've mounted the gopro. Lets see what it looks like.

[bigcane]

Hi plummet, proportionally based on my mast it seems that somewhere around max 11.5% to 11.8% of the chord would be a good thickness. Maybe some others can measure their masts if they have some decent calipers and provide more data as well. As mentioned by Peter above, the profile is also important. If it is just happening on one tack then it is probably the profile. Perhaps the wide point is too far forward. Hopefully the video will shed some light on the issue.

[tkettlepoint]

mine mast is 120mmx10.8mm out of mould finished 11.1 with clearcoat on it. square TE ( was sharp enough to cut) toned it down. My r&D rider didn't feel that much change. on thing you could do on your next mast rake the fuse ahead 1-2 degrees will help any bubbles to go up and not down

if the AOA is to great on the rear it will also make a bubble faster as you gain speed .
Production wings are from .5 to 6 degrees from what I have seen. We have lowered the AOA for higher wing and raised it for low wind.

terrie
www.jellyfishboards.com