I bought a new Starboard 95 cm IQfoil to be used on 150 lt Starboard Foil freeride board and 115+ fuselage, 1000 front wing, back wing 255/-2 with 0 or 0.5+ shim for 10-12 mph wind condition. I am making transition from my free ride foil to race set-up. So far the ride has not very comfortable and I feel like it is too slippery. While searching some guidance for on YouTube, I just noticed following video by Nico Prien and he suggests sanding the new mast by 1000-2000 grit to prevent cavitation. Is this recommended for every race carbon masts? What are the other features that you suggest to make the transition easier?

Reading the different comments beneath this video it seems the debate is still open wether ventilation really caused the catapults.

Also, I highly doubt that sanding should be your first concern when you make the transition from a freeride to a race setup : could it be the "slippery" feeling you'r describing is just the diff in speed between the two setups ?
( sorry I have never ridden a free ride foil)

First and foremost I would concentrate on experimenting with the foil setup (backwing angle) and the position of the rig on the board. This of course with loads of TOW.

But if you really feel like sanding the foil :

Did he try again after sanding? In the same conditions? I think he did not.
It is not clear if the sanding helps against his catapult issue.
Maybe Nico should check his with his team in stable conditions.

Related ventilation video showing the quick flash pulling air from the surface:

Also for the speeds you are going I'm a bit doubtful this will be an issue. He's going like 30knots. You'll be closer to 20. If you do start getting weird crashes like that I'd consider it. But I'd also consider using to heel the board more windward as well because that seems to eliminate spinouts for me at my speeds on the 900.

The slippery feel is just the difference from a freeride to high aspect, likely. It should feel really solid when your board speed is above 15knots or so. You'll get used to the feeling and come to like it I think. Stepping back from the 900 front to freeride gear, the freeride gear feels quite a bit slower and draggy.

It took me a few sessions to really feel comfortable on the race set, and to learn to deal with gusts by pushing higher upwind or going deeper downwind. You'll get there.

I seem to be spamming the thread but I couldn't help but find this:
etheses.whiterose.ac.uk/11335/1/646388.pdf

First excerpt, conclusion from lower speeds (20ft/s or 13.5mph):




Second excerpt, testing up to 62ft/s (42mph, closer to the speed that Nico was going at):






Basically, they noticed a significant difference in ventilation behavior that was dependent on roughness, and had to control for it in scaled experiments of hydrofoils.

Whether or not this was the cause of the crash, it was interesting to me.

Don't think it matters that much unless you're really pushing the limits of the equipment though, but I could be wrong.

What about everyone else who was racing in the same conditions?, they were not foiling out like Nico, the problem is his foil was not strong enough to handle the loads applied to it, and Nico looks like a lighter weight guy. So how do the bigger riders manage to foil fine in the same conditions?, they have stronger foils!

Select to expand quote

Bellerophon said..
Reading the different comments beneath this video it seems the debate is still open wether ventilation really caused the catapults.

Nico is a very good foil and slalom racer, with access to plenty of other top foilers in the PWA and in Europe. His crashes happened in very flat water, and he usually does not crash like this, even in choppier conditions. Not everyone will agree with his assessment, but there are still flat earthers out there, too.

The screen shot Nico used as the title picture actually shows that (a) the foil was still in the water, so it was not overfoiling, and (b) a big air bubble on the leeward side of the mast, a clear sign of cavitation. He is pushing sideways on the board quite a bit with his back foot, and when there's air instead of water on the other side of the mast, it just gives. That's quite easy to see in slow-motion:


But that's Nico's problem, going 30 knots plus, and has nothing to do with the "slippery" feeling. That's just the difference between a race and a freeride foil.

He did say he had sanded his other mast, but not this new one. Guess his thinking is the water doesnt stick to an unsanded mast so air can get sucked down the mast to the foil. Sand the mast, the water sticks to the foil, so air cant travel down the mast. Lets see what happens next time he uses it.

Now seen at checkouts

It does not sound reasonable to me that just because the mast was not sanded it sucks air down. I think there is something off with the design of the mast that allows it to flex under load. If the mast flexes under load, and the load is coming from the windward side, then cavitation would occur on the leeward side, which it does.

Select to expand quote

Sandman1221 said..
It does not sound reasonable to me that just because the mast was not sanded it sucks air down. I think there is something off with the design of the mast that allows it to flex under load. If the mast flexes under load, and the load is coming from the windward side, then cavitation would occur on the leeward side, which it does.

Fluid mechanics is filled with weird things like this. A lot of airplanes have vortex generators on their wing top surface to increase turbulence and thus increase the angle of attack before flow separation. BUT, air is about 1000x less dense than water so different techniques are used. The paper I linked above shows that roughness DOES affect when ventilation occurs on a hydrofoil, so it's within the realm of plausibility.

The difficulty is we are already talking about fluids, which is a hard subject, but two-phase flow as well (liquid water and gaseous air) interacting in 3d. Not easy to model...

Throw in torsion of the mast, which can affect things if it's big enough, and it's a very complicated multiphysics problem. Lots of variables, hard to do. I think other control issues would start to manifest from mast torsion first, or a bad vibration that would look different. Because, if you do start getting appreciable flexure on something in water, it will start changing the flow dynamics and result in something like flutter and rapid disassembly. Not a big air bubble coming off the mast like you see in the video. Fluid/structural coupling (which is what flutter is) is going to have a lot of force in a liquid.

Am I 100% sure this caused the crash? No, but it's worth considering. I personally wouldn't sand my high modulus carbon mast unless I had an issue, and would be sure to check to make sure it wouldn't declass me from the IQFoil rules (light sanding is allowed but I don't know the specifics).

How do you know if Nico actually didn't have a seaweed or a reed on the mast, it happens to me (obviously at other speeds) when I have some straw or garbage in the form of a ribbon on the mast, the board slides as if it were flying sideways. I imagine myself at more than 30 knots and forcing a skid and into the water

Select to expand quote

foilarg said..
How do you know if Nico actually didn't have a seaweed or a reed on the mast, it happens to me (obviously at other speeds) when I have some straw or garbage in the form of a ribbon on the mast, the board slides as if it were flying sideways. I imagine myself at more than 30 knots and forcing a skid and into the water

It's possible

But, I'm thinking about where I normally sail. It's got nasty clumps of weeds. Requires a weed fin if regular windsurfing. If I'm shlogging on a foil, they get wrapped in the foil and keep me from pumping up into flight.

But...when I'm on foil the foil just tends to blast through the weeds. As far as I know, as long as I'm up and going fast, those weeds don't matter much?

aerongr have you contacted SB about it? Once you sand it whatever warranty claim you had is gone. My AFS mast is similar in shape to the iQ foil mast, water does not stick to it, and it has large glossy stickers on the top, and it does not cavitate.

Select to expand quote

Sandman1221 said..
aerongr have you contacted SB about it? Once you sand it whatever warranty claim you had is gone. My AFS mast is similar in shape to the iQ foil mast, water does not stick to it, and it has large glossy stickers on the top, and it does not cavitate.

No it's more of a class qualification thing. I don't think I'm going to need to sand it for IQFoil. I only spin out and crash like this if I'm riding the board very flat, which I rarely do now. If I was racing PWA I would consider it because it seems like it matters when you're pushing 30+ knots. I've yet to break 25mph or so on the 900, hoping for better wind to get up to 30mph with the 650 front.

Select to expand quote

Sandman1221 said..
It does not sound reasonable to me that just because the mast was not sanded it sucks air down. I think there is something off with the design of the mast that allows it to flex under load. If the mast flexes under load, and the load is coming from the windward side, then cavitation would occur on the leeward side, which it does.

Let the Boardlady explain it to you

boardlady.com/fast.htm

Slick, hydrophobic surfaces have more turbulent boundary layers which makes it easier for the water flow to separate. It's been known for 40+ years. A friend of mine spent some of his teen years wet sanding the bottom of their sailing boat to make it as fast as possible (and it was).

btw, we are talking about ventilation, not cavitation. None of us here are going so fast that the water is turning into water vapor.

Select to expand quote

Paducah said..

Sandman1221 said..
It does not sound reasonable to me that just because the mast was not sanded it sucks air down. I think there is something off with the design of the mast that allows it to flex under load. If the mast flexes under load, and the load is coming from the windward side, then cavitation would occur on the leeward side, which it does.

Let the Boardlady explain it to you

boardlady.com/fast.htm

Slick, hydrophobic surfaces have more turbulent boundary layers which makes it easier for the water flow to separate. It's been known for 40+ years. A friend of mine spent some of his teen years wet sanding the bottom of their sailing boat to make it as fast as possible (and it was).

btw, we are talking about ventilation, not cavitation. None of us here are going so fast that the water is turning into water vapor.

Paducah did you not read my most recent post?, seriously! Explain why it does not happen to my foil when it has everything you are saying is required for it to happen.

There is a defect in that foil, wether in the design or construction, and people here is trying to cover that fact up!

Select to expand quote

aeroegnr said..
Also for the speeds you are going I'm a bit doubtful this will be an issue. He's going like 30knots. You'll be closer to 20. If you do start getting weird crashes like that I'd consider it. But I'd also consider using to heel the board more windward as well because that seems to eliminate spinouts for me at my speeds on the 900.

The slippery feel is just the difference from a freeride to high aspect, likely. It should feel really solid when your board speed is above 15knots or so. You'll get used to the feeling and come to like it I think. Stepping back from the 900 front to freeride gear, the freeride gear feels quite a bit slower and draggy.

It took me a few sessions to really feel comfortable on the race set, and to learn to deal with gusts by pushing higher upwind or going deeper downwind. You'll get there.

After looking at some of the foiling videos, it seems the rider positions are different for a race set-up vs free ride foiling. As you indicated, usually the board is tilted in race foiling as opposed to freeride foil set up. My foot on the free ride usually toward the center like in the picture. Are you also putting more pressure by the harness as well as heel pressure on the side of the board?

Select to expand quote

SA_AL said..


After looking at some of the foiling videos, it seems the rider positions are different for a race set-up vs free ride foiling. As you indicated, usually the board is tilted in race foiling as opposed to freeride foil set up. My foot on the free ride usually toward the center like in the picture. Are you also putting more pressure by the harness as well as heel pressure on the side of the board?

Yeah, on my IQFoil setup, definitely. I will hike out some on freeride kit if powered up good but I'm hardly ever riding the race foil with the board flat unless I'm going downwind. Tilting it helps gusts push the nose down and gives you more stability it feels.

Will be interesting to hear from Nico if after sanding the issue disappears. If not?????? Defective foil set up?

Have MFC fin that I cannot stop the ventilation problem. Only MFC fin I've had issues with. Started with polishing it. 3M makes these ultra fine sanding sponges used to finish off surfaces to a smooth finish. Didn't work. Then started sanding to add texture. Eventually up to I think 200 grit wet dry. Gave up on that fin. Sometimes you get a dud that's beyond help.

Select to expand quote

aeroegnr said..
I seem to be spamming the thread but I couldn't help but find this:
etheses.whiterose.ac.uk/11335/1/646388.pdf

In all the noise, missed this link. Started on it tonight and only part way through but excellent reading. Thanks!

I'll read further but does remind me of Zeeko's AVS (Anti Ventilation Skin)

zeeko-kites.com/gb/windfoil-series/440-windfoil-xlw-front-wing-.html

Select to expand quote

SA_AL said..
I bought a new Starboard 95 cm IQfoil to be used on 150 lt Starboard Foil freeride board and 115+ fuselage, 1000 front wing, back wing 255/-2 with 0 or 0.5+ shim for 10-12 mph wind condition. I am making transition from my free ride foil to race set-up. So far the ride has not very comfortable and I feel like it is too slippery. While searching some guidance for on YouTube, I just noticed following video by Nico Prien and he suggests sanding the new mast by 1000-2000 grit to prevent cavitation. Is this recommended for every race carbon masts? What are the other features that you suggest to make the transition easier?

New update is from Nico on the issue of sanding mast

Select to expand quote

SA_AL said..

SA_AL said..
I bought a new Starboard 95 cm IQfoil to be used on 150 lt Starboard Foil freeride board and 115+ fuselage, 1000 front wing, back wing 255/-2 with 0 or 0.5+ shim for 10-12 mph wind condition. I am making transition from my free ride foil to race set-up. So far the ride has not very comfortable and I feel like it is too slippery. While searching some guidance for on YouTube, I just noticed following video by Nico Prien and he suggests sanding the new mast by 1000-2000 grit to prevent cavitation. Is this recommended for every race carbon masts? What are the other features that you suggest to make the transition easier?

New update is from Nico on the issue of sanding mast

That sounded a lot like a brand manager attempting to fix a video wherein he told the truth about a product he represents.

Select to expand quote

lwalker said..
That sounded a lot like a brand manager attempting to fix a video wherein he told the truth about a product he represents.

Agree!
Very probably his boss(es) "suggested" him to make another video!
No offence, Nico! I like you and your videos!

...but I am wondering why SB still have not officially released their new Foil range (Evolution)!
You can find pictures and videos all over - except on the SB page!

Come on SB; winter starts today on the northern hemisphere!
There is not much to do for us, but to surf the internet!

Select to expand quote

eightbft said..
...but I am wondering why SB still have not officially released their new Foil range (Evolution)!

Do you know how long it takes to open all those boxes, resand the masts and then close the boxes back up? Days, weeks, perhaps. Have seen pics of boxes being unloaded at my closest retailer.

Yeah, agree the above posts. I think he got a call from someone in Thailand sh**ing themselves. Nothing in the video that would dissuade me from buying an SB foil (I still spend my most of my life a good 10 kts slower than where the issues were occurring) but having seen some of the reactions here and the vapor that goes along with it I can see why corporate would be wanting to calm the waters.

Select to expand quote

Paducah said..

eightbft said..
...but I am wondering why SB still have not officially released their new Foil range (Evolution)!

Do you know how long it takes to open all those boxes, resand the masts and then close the boxes back up? Days, weeks, perhaps. Have seen pics of boxes being unloaded at my closest retailer.

Yeah, agree the above posts. I think he got a call from someone in Thailand sh**ing themselves. Nothing in the video that would dissuade me from buying an SB foil (I still spend my most of my life a good 10 kts slower than where the issues were occurring) but having seen some of the reactions here and the vapor that goes along with it I can see why corporate would be wanting to calm the waters.

Massive recall, warranty, defects.... latest is that QAnon are waiting in Dallas for JFK and new sanded foils to arrive. Of course the rest of the ones using the foils at the races were all crashing too. I heard the 2024 IQ foil is being cancelled too.

Evolution is already in some stores.

Select to expand quote

Paducah said..

eightbft said..
...but I am wondering why SB still have not officially released their new Foil range (Evolution)!

Do you know how long it takes to open all those boxes, resand the masts and then close the boxes back up? Days, weeks, perhaps. Have seen pics of boxes being unloaded at my closest retailer.

Yeah, agree the above posts. I think he got a call from someone in Thailand sh**ing themselves. Nothing in the video that would dissuade me from buying an SB foil (I still spend my most of my life a good 10 kts slower than where the issues were occurring) but having seen some of the reactions here and the vapor that goes along with it I can see why corporate would be wanting to calm the waters.

Yep - He actually mentions that Tiesda You spoke with him at Gruissan about it - clearly read him the Riot Act. There is also a LOT more cutting and splicing in this video than is usual for Prien (who's pretty fluent usually), suggesting that they had someone there helping him dot the I-s and cross the T-s.

kinda off topic but I agree with what others are posting about lack of info in the SB website about their products. Some stores are already selling the evolution masts and fuselages but no much info about it.

Yeah I've seen the evo stuff here in the shop but SB is very disappointing with the product info. I really want to see a range of suggested wind ranges for the foils and their expected sails like Phantom has, like 1/3 of the page down: www.phantom-windsurfing.com/foils

Select to expand quote

WillyWind said..
kinda off topic but I agree with what others are posting about lack of info in the SB website about their products. Some stores are already selling the evolution masts and fuselages but no much info about it.

It is a much better strategy then some other foil manufactures. They promote the product non stop, get new riders and don't have the product. It also has to do with distribution. Starboard foils are distributed from a company in France. Complicated structure with Starboard, Tiki Group, Severne International and Foils Sport.

Evolution wings & fuse are newer design. Mast 300 lower end, 400 IQ (similar) and 600, well you pay for it. 1300 & 1700 wing works with the system. There will be videos coming out soon from a vendor.

Select to expand quote

ZeroVix said..

WillyWind said..
kinda off topic but I agree with what others are posting about lack of info in the SB website about their products. Some stores are already selling the evolution masts and fuselages but no much info about it.

It is a much better strategy then some other foil manufactures. They promote the product non stop, get new riders and don't have the product. It also has to do with distribution. Starboard foils are distributed from a company in France. Complicated structure with Starboard, Tiki Group, Severne International and Foils Sport.

Evolution wings & fuse are newer design. Mast 300 lower end, 400 IQ (similar) and 600, well you pay for it. 1300 & 1700 wing works with the system. There will be videos coming out soon from a vendor.

Not necessarily: it's been 6 months or more now since the news about the "evolution" series have been emerging through various "leaks" on fb, yt and forum posts.

I can't understand this strategy where customers are beiing "informed" by racers and employees in an unstructured manner, (whilst most of them are not as fluent in english as Nico)

First and foremost new products should be lauched on the official website, where everyone would be able to find the objective information.

Otherwise, you'll get rumours.