I just bought some new foil gear. I've used two of the three wing sets i bought, and one of them whistles when foiling. Does anyone know why this happens ? It's more of an intermittent / on and off whistle. I hope it doesn't happen with the wing set i haven't tried yet as well. It's kind of annoying. The wing set is also brand new. And by wing set i mean front and rear wing / stabilizer.

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Sambo # said..
I just bought some new foil gear. I've used two of the three wing sets i bought, and one of them whistles when foiling. Does anyone know why this happens ? It's more of an intermittent / on and off whistle. I hope it doesn't happen with the wing set i haven't tried yet as well. It's kind of annoying. The wing set is also brand new. And by wing set i mean front and rear wing / stabilizer.

. some times the finish on the trailing edges is not ideal and need to be sanded . try mixing up stabilizer and front wing to identify which one is whistling. typically its the stab

Will do. Thanks mate.

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thedoor said..

Sambo # said..
I just bought some new foil gear. I've used two of the three wing sets i bought, and one of them whistles when foiling. Does anyone know why this happens ? It's more of an intermittent / on and off whistle. I hope it doesn't happen with the wing set i haven't tried yet as well. It's kind of annoying. The wing set is also brand new. And by wing set i mean front and rear wing / stabilizer.

. some times the finish on the trailing edges is not ideal and need to be sanded . try mixing up stabilizer and front wing to identify which one is whistling. typically its the stab

I'm assuming the same thing can happen with front wings as well ? Based on what you just told me I've got a whistley front wing. I just remembered mixing up stabs and front wings recently.

sabfoil.com/en/blog/whistling-hydrofoil-sand-foil

I have got only one frontwing that whistles, it took very few sanding to fix it. Don't sand the trailing edge to a sharp knife, this is f....g dangerous.

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PatK said..
sabfoil.com/en/blog/whistling-hydrofoil-sand-foil

I have got only one frontwing that whistles, it took very few sanding to fix it. Don't sand the trailing edge to a sharp knife, this is f....g dangerous.

Thanks

My AFS F770 wing will lightly whistle sometimes, definitely at high speeds, but like the guy said I think temperature too, cooler water temperature maybe below 80 degrees F. It tells me I am going fast, but adds to the stress and is a bit of a distraction, which is not what I want going fast. Will try sanding it.

Looked at the trailing edge of the F770 wing under 15x magnification with good lighting, could see a few tiny white specs, ran my thumb nail along the edge and then could feel what are best described as tiny nicks in the trailing edge, only on the bottom side. Could not feel anything running my finger along the fairly sharp edge, which is what I normally do, occasionally. Checked the F1080 and S670 wings they only had 1 or 2 tiny nicks. Used 1200 sandpaper to clean up the edges on all three wings, did not take much for the F1080 and S670, took a little more work on the F770 because there were more of the tiny nicks. But not much over all using 1200 sandpaper, 400 seems a bit too much for what I had, which was a well finished edge with some tiny nicks.

On the F770 wing the topside of the trailing edge had a radius, while the bottom edge that I sanded was pretty flat, so in the end I made the trailing edge a touch sharper!, oh well, my shins have protection and are pretty good at avoiding the edges by now.

And I like to use the wet/dry sandpaper "dry", yes it creates dust, but not much, and I will run my finger over the edge after a few runs and can see how much I removed by the dust on my finger, also can see how much dust is accumulating on the sandpaper. Not the case if sandpaper was wet.

Thanks for the video thedoor!

The AFS-2 was famous for noise, but it was more of a howl than a whistle. In 2017 Sailworks worked the trailing edges of the stabs for their customers to mitigate it. On my stab you could reduce it, but not remove it entirely. Mine still sings.

The consensus at the time was that it was trailing edge vortex shedding. You could mitigate it by changing the shape of the trailing edge. This was a well known phenomenon in hydro power plant turbine blades. There are technical papers about it out there.

I think there is more to it than that in our foiling equipment. I believe there is also a natural resonance frequency (with additional harmonics) in the structure. Mine has three specific pitches depending on speed. The pitch frequency does not vary continuously. Instead, it has a quantum-like set of specific frequencies (harmonics). This is consistent with structural resonance.

So, bottom line. If it is an airy whistle, sanding the trailing edge might take care of it. (NP talked about sanding the trailing edge of their pink mast to eliminate an airy whistle.)

If it is a howl or a singing, not much you can do except get different wings or stabs that have different structures/stiffnesses, etc., to get a quiet ride.

In the gorge, many of the original AFS-2s are sitting in garages since riders have gone to such gear as Moses/SABfoil. I took my AFS-2 to Florida to use as a higher speed alternative to my i76 (which is quiet). Even in Florida's hypersaline warm water, compared to the Columbia River's fresh cold water, mine still sings with the same three harmonics regardless of which front wing I use (F700 or F800--old names). I just live with it.

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segler said..
The AFS-2 was famous for noise, but it was more of a howl than a whistle. In 2017 Sailworks worked the trailing edges of the stabs for their customers to mitigate it. On my stab you could reduce it, but not remove it entirely. Mine still sings.

The consensus at the time was that it was trailing edge vortex shedding. You could mitigate it by changing the shape of the trailing edge. This was a well known phenomenon in hydro power plant turbine blades. There are technical papers about it out there.

I think there is more to it than that in our foiling equipment. I believe there is also a natural resonance frequency (with additional harmonics) in the structure. Mine has three specific pitches depending on speed. The pitch frequency does not vary continuously. Instead, it has a quantum-like set of specific frequencies (harmonics). This is consistent with structural resonance.

So, bottom line. If it is an airy whistle, sanding the trailing edge might take care of it. (NP talked about sanding the trailing edge of their pink mast to eliminate an airy whistle.)

If it is a howl or a singing, not much you can do except get different wings or stabs that have different structures/stiffnesses, etc., to get a quiet ride.

In the gorge, many of the original AFS-2s are sitting in garages since riders have gone to such gear as Moses/SABfoil. I took my AFS-2 to Florida to use as a higher speed alternative to my i76 (which is quiet). Even in Florida's hypersaline warm water, compared to the Columbia River's fresh cold water, mine still sings with the same three harmonics regardless of which front wing I use (F700 or F800--old names). I just live with it.

Segler, did you ever try sanding the trailing edge of the mast, like what was recommended for the NP pinkie? Will get back after I have some higher winds to test out the F770 wing to see if the sanding helped. F770 definitely have a bunch of tiny nicks on both sides. Just checked the stab, it had a couple of nicks on one side, so I cleaned them up with 1200 paper, but only heard whistling with F770 recently. Have heard it in the past with F1080, but it had some major scratches and dings early on, fixed them and it is quiet, and have been good about not damaging it more

And did you ever check to see if the wings were precisely aligned with the stab?, and stab a 90 degrees with mast? That was certainly an issue with all my wings and stab.

All the foils I've ridden start whistling at a certain speed. The one that whistled the least was the infinity 99. But the infinity 76, phantasm 926, and starboard 900/725/650 have all whistled. I'd mess with it if I felt a vibration through my feet, and I might be losing some top end speed but haven't felt the need.

Sorry...didn't see that the video had been posted. It definitely works.....

Hey Sand, yes, we tried sanding the mast (like the NP pinkie), and even the front wings.

When foiling was first starting out, and Sailworks started getting into it in 2016, Bruce Peterson rode the AFS-2. He had several of them. He did all the sanding stuff on all the various trailing edges. He could reduce the singing, but even that varied with the foil. Some he was able to make almost quiet. Then, when he was selling these to the Gorge Cup racers and other customers (like me), he supported them with advice and actual sanding labor in his loft. He developed a set of sanding sticks, and you would see him over his sink in the back of the room, wet sanding. He worked mine several times.

Some of the racers actually liked the noise since they could hear each other out on the course. If someone was bearing down on you from behind, you knew they were there.

He/we never had the noise problem with the LP that he also sold, and then later with the Moses/SAB, which he now sells to the exclusion of everything else.

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Sambo # said..

thedoor said..

Sambo # said..
I just bought some new foil gear. I've used two of the three wing sets i bought, and one of them whistles when foiling. Does anyone know why this happens ? It's more of an intermittent / on and off whistle. I hope it doesn't happen with the wing set i haven't tried yet as well. It's kind of annoying. The wing set is also brand new. And by wing set i mean front and rear wing / stabilizer.

. some times the finish on the trailing edges is not ideal and need to be sanded . try mixing up stabilizer and front wing to identify which one is whistling. typically its the stab

I'm assuming the same thing can happen with front wings as well ? Based on what you just told me I've got a whistley front wing. I just remembered mixing up stabs and front wings recently.

Can happen to front wings too. I just heard whistling stabs is more common but no data to support

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segler said..
Hey Sand, yes, we tried sanding the mast (like the NP pinkie), and even the front wings.

When foiling was first starting out, and Sailworks started getting into it in 2016, Bruce Peterson rode the AFS-2. He had several of them. He did all the sanding stuff on all the various trailing edges. He could reduce the singing, but even that varied with the foil. Some he was able to make almost quiet. Then, when he was selling these to the Gorge Cup racers and other customers (like me), he supported them with advice and actual sanding labor in his loft. He developed a set of sanding sticks, and you would see him over his sink in the back of the room, wet sanding. He worked mine several times.

Some of the racers actually liked the noise since they could hear each other out on the course. If someone was bearing down on you from behind, you knew they were there.

He/we never had the noise problem with the LP that he also sold, and then later with the Moses/SAB, which he now sells to the exclusion of everything else.

Thanks segler!
And I was out on my AFS W95 with F770 wing today and heard the familiar whine, it actually sounded like it was coming from the boom or sail, and then I realized the bottom batton on the sail had punched through the batten sleeve end so that the batton went into the luff sleeve, releasing tension on that batton, I usually use the F770 with that sail, 7.2 Freespeed. So maybe it was the sail?, will find out after I fix it. Have had problems getting that batton to rotate for a while, now I know why