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segler said..
Hey aeroegnr, I wonder about the weeds you mentioned. Are they worse this time of year? When I foil there in November and March I don't notice much in the way of weeds. Yeah, when the wind has too much west component, this spot is not good and I go down to 75 cent beach.

In general the weeds are worse in the summer. For example, I had a session in mid-june during a cold front where I could use a 6.3 and a fin. That fin is usually no problem in fall/winter weeds, but I got a 2ft ball of weeds on that weed fin that day, and kept catching big clumps.

Sometime when it usually cools off and people starting putting on wetsuits it starts to be less of a problem. But I've had some erratic flights on foil due to collecting stowaways.

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aeroegnr said..

segler said..
Hey aeroegnr, I wonder about the weeds you mentioned. Are they worse this time of year? When I foil there in November and March I don't notice much in the way of weeds. Yeah, when the wind has too much west component, this spot is not good and I go down to 75 cent beach.

In general the weeds are worse in the summer. For example, I had a session in mid-june during a cold front where I could use a 6.3 and a fin. That fin is usually no problem in fall/winter weeds, but I got a 2ft ball of weeds on that weed fin that day, and kept catching big clumps.

Sometime when it usually cools off and people starting putting on wetsuits it starts to be less of a problem. But I've had some erratic flights on foil due to collecting stowaways.

Consider yourself lucky. Here in the Berkshire Hills of Massachusetts (my home outside the academic year) I have to flip the board upside down and swim it out 100m before I can even move it through the invasive milfoil which is concentrated near shore. Once in a while a clump breaks loose and floats into the middle of the lake, where if you hit it at speed you're doing the "scorpion" launch - basically the equivalent of hitting a sandbar. It's pretty interesting how little it takes to affect performance, even well short of the catapult. One spaghetti-strand-sized weed on the stab and it takes far more speed to get up. Two or more and you're not getting up at all.

I'll be back down in your neck of the woods in a few weeks though...

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Awalkspoiled said..

aeroegnr said..

segler said..
Hey aeroegnr, I wonder about the weeds you mentioned. Are they worse this time of year? When I foil there in November and March I don't notice much in the way of weeds. Yeah, when the wind has too much west component, this spot is not good and I go down to 75 cent beach.

In general the weeds are worse in the summer. For example, I had a session in mid-june during a cold front where I could use a 6.3 and a fin. That fin is usually no problem in fall/winter weeds, but I got a 2ft ball of weeds on that weed fin that day, and kept catching big clumps.

Sometime when it usually cools off and people starting putting on wetsuits it starts to be less of a problem. But I've had some erratic flights on foil due to collecting stowaways.

Consider yourself lucky. Here in the Berkshire Hills of Massachusetts (my home outside the academic year) I have to flip the board upside down and swim it out 100m before I can even move it through the invasive milfoil which is concentrated near shore. Once in a while a clump breaks loose and floats into the middle of the lake, where if you hit it at speed you're doing the "scorpion" launch - basically the equivalent of hitting a sandbar. It's pretty interesting how little it takes to affect performance, even well short of the catapult. One spaghetti-strand-sized weed on the stab and it takes far more speed to get up. Two or more and you're not getting up at all.

I'll be back down in your neck of the woods in a few weeks though...

I dealt with something similar in the Seattle area when I launched on Lake Washington...Luckily I never got launched because I was never going fast there.

Although, when there aren't weeds, there are still other obstacles that can launch you. Like a fever of stingrays that you can't see until it's already too late.

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2keen said..
I have a theory, goes like this..
When I get on foil it's not about planning speed or displacement speed but more about "sail pressure" ie once I can generate sufficient power from wind in the sail the board "pops" onto the foil


5.2 km/h or 3 knots waiting for a gust, then the board pops onto the foil. At 3 knots I think it's a combination of surface area of the foil (1100cmsq for my SAB 799) and angle of attack created by weight shift that lifts the board out of the water. Obviously both these things are only possible with power in the sail

Wow, I'm impressed! Especially by the fact that you can start foiling so early, with what's essentially ~2.8 kt board speed (about 1 kt less than I can on racing light wind gear). Presumably, this is on Tabou Magic Carpet, and a small light sail?

I agree with your theory about the sail pressure: with X amount of sail pressure, one has Y amount of board (non-planing/non-foiling) speed. And the "Y" is easy to measure, share, and compare, as opposed to "I can foil in Z knots", because this is much harder to back up with reliable data (wind station or anemometer reading).

The "sail pressure" description is spot on IME. I think the wing surface area and,type (low aspect)
play into it. In 25 knots, I can launch in a a board length or 2 with a 3.7 sail. I'm usually overpowered in those scenarios, but the "board speed" is really low. I'm leaning way back and pop up quickly. Kind of like a wake board behind a motor boat. I suspect a small board with a 140lb rider makes it easier.

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FormuIa said..

2keen said..
I have a theory, goes like this..
When I get on foil it's not about planning speed or displacement speed but more about "sail pressure" ie once I can generate sufficient power from wind in the sail the board "pops" onto the foil


5.2 km/h or 3 knots waiting for a gust, then the board pops onto the foil. At 3 knots I think it's a combination of surface area of the foil (1100cmsq for my SAB 799) and angle of attack created by weight shift that lifts the board out of the water. Obviously both these things are only possible with power in the sail

Wow, I'm impressed! Especially by the fact that you can start foiling so early, with what's essentially ~2.8 kt board speed (about 1 kt less than I can on racing light wind gear). Presumably, this is on Tabou Magic Carpet, and a small light sail?

I agree with your theory about the sail pressure: with X amount of sail pressure, one has Y amount of board (non-planing/non-foiling) speed. And the "Y" is easy to measure, share, and compare, as opposed to "I can foil in Z knots", because this is much harder to back up with reliable data (wind station or anemometer reading).

This was on my MOZ custom board 170x66. I think having a small surface area and footstraps is what allows the weight transfer to pop onto foil.
Interestingly my Tabou Magic Carpet which is in 195x78 requires more board speed and more gradual lift onto foil.
The sail used in the graph was the North 4.2 wave clear, super light and unbelievably responsive
Next time out I'll try and work out the stall speed of the foil, got a feeling it's around the 3 knot mark

Amazing. Made me rethink my gear choice (large and heavy race equipment) :)

Yesterday's chart, when we had marginal thermal winds, most of the time approx. 6-10 knots (hard to say without a station nearby), with only occasional tiny white caps forming. To my surprise, the track and the real time watch measurement don't fully align. The (s)lowest points of the track before pumping to foil are as low as 2.9 kt, whereas in reality I was observing my watch (FR245) and it needed ~3.7 kt (6.8 km/h) of min. speed to have enough sail pressure to start pumping for my skill. I'm sure a decent racer or a better, more skilled rider would be able to pop up on the foil even sooner.

Once you get up on the foil, it starts to go relatively quick for the given wind speed, thanks to 1000 cm2 race wing and 9 m2 sail. Jibing was tricky in 2nd part of the chart, most of the time it required extra pumping to gain back the speed.

Would love to see other gear comparison, eg. @2keen's small and light setup, and a downwind-displacement wingfoil setup in such conditions.

Hey awalkspoiled,

Having to swim your upside down board out past the weeds is a fact of life this time of year at many spots on the Columbia, too. Swimming 100 meters with a sail (acts like a sea anchor) is slow and tiring. When I don't want to swim I just slog out through it to deep water, stop, flip the board upside down, and clear off 50 pounds of salad, then restart and sail away.

Wingers have this easy since their wings float on top and offer very little drag resistance. They swim out some 10x faster than me.

In early season when the water is still cold (10 C) there are no weeds. However, now at 22 C the weeds are everywhere.

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segler said..
Hey awalkspoiled,

Having to swim your upside down board out past the weeds is a fact of life this time of year at many spots on the Columbia, too. Swimming 100 meters with a sail (acts like a sea anchor) is slow and tiring. When I don't want to swim I just slog out through it to deep water, stop, flip the board upside down, and clear off 50 pounds of salad, then restart and sail away.

Wingers have this easy since their wings float on top and offer very little drag resistance. They swim out some 10x faster than me.

In early season when the water is still cold (10 C) there are no weeds. However, now at 22 C the weeds are everywhere.

Yep - Frustrating. What I can sometimes do is slog out foil-first for a while, then do a quick board-180 which sheds some of the collected weeds, then slog out to clear water and clear the rest of the stuff.
im very interested in the board speed vs power discussion. It seems to me that I can always tell when I'm about to have enough power to blast out of the water, and the sensation often comes when I'm going pretty slowly. In other words, I can be pooching along barely moving, feel a lift coming with my back hand, and pump out onto the foil. I suppose the board is probably going about 7kt when it lifts, but it doesn't spend much time at that speed because it's accelerating so hard.

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FormuIa said..

2keen said..
I have a theory, goes like this..
When I get on foil it's not about planning speed or displacement speed but more about "sail pressure" ie once I can generate sufficient power from wind in the sail the board "pops" onto the foil


5.2 km/h or 3 knots waiting for a gust, then the board pops onto the foil. At 3 knots I think it's a combination of surface area of the foil (1100cmsq for my SAB 799) and angle of attack created by weight shift that lifts the board out of the water. Obviously both these things are only possible with power in the sail

Wow, I'm impressed! Especially by the fact that you can start foiling so early, with what's essentially ~2.8 kt board speed (about 1 kt less than I can on racing light wind gear). Presumably, this is on Tabou Magic Carpet, and a small light sail?

I agree with your theory about the sail pressure: with X amount of sail pressure, one has Y amount of board (non-planing/non-foiling) speed. And the "Y" is easy to measure, share, and compare, as opposed to "I can foil in Z knots", because this is much harder to back up with reliable data (wind station or anemometer reading).

I agree the low board speed is surprising BUT it needs sail pressure which means wind. For the 4.2 I'm guessing 15knots plus.
I have no doubt that while light wind racing gear may require a higher take off speed it can be done in lighter winds
I like Wsurfaustin's analogy of wake boarding behind a motor boat - you need power
Today I tried to measure stall speed. Once again using the SAB Foil 799. My guess was close to take off speed, 5 km/h or 3 knots the results surprised me


I was on foil the whole time in this snapshot. It felt like I was almost stopping during my gybes and at time's pointing high and foiling at what felt like a slow walking pace. I am confident I could not have gone slower without stalling. What surprised me was the speed never dropped below 12 km/h or 7 knots nearly double the take off speed
Does this support the theory that (powered) take off is not lift from foil but angle of attack and weight shift?

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2keen said..
Does this support the theory that (powered) take off is not lift from foil but angle of attack and weight shift?

The powered take off happens because the weight shift increases the angle of attack of the foils, which increases the lift from the foil. That makes the board climb out of the water. But the increased angle of attack also increases drag, and quite a lot (imagine the project area of the foil when viewed from the front). So you need power in the sail to drag you "up the hill". Once the board is out of the water, the foil can be leveled again, reducing drag. But you still need some power in the sail to accelerate you from the initial climbing speed (3 knots) to the stable foiling speed (7 knots in your example). Usually, you have more than the absolute minimum sail power for this, so you keep accelerating to a higher speed.

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boardsurfr said..

2keen said..
Does this support the theory that (powered) take off is not lift from foil but angle of attack and weight shift?

The powered take off happens because the weight shift increases the angle of attack of the foils, which increases the lift from the foil. That makes the board climb out of the water. But the increased angle of attack also increases drag, and quite a lot (imagine the project area of the foil when viewed from the front). So you need power in the sail to drag you "up the hill". Once the board is out of the water, the foil can be leveled again, reducing drag. But you still need some power in the sail to accelerate you from the initial climbing speed (3 knots) to the stable foiling speed (7 knots in your example). Usually, you have more than the absolute minimum sail power for this, so you keep accelerating to a higher speed.

Great explanation.

I found out thru experience that too much lift (either by 330 rear stab on SB 115+, or too much shim), won't necessarily help with early foiling. The foil will rise the board out, yes, but then it will stall due to not enough speed. Maybe a better skilled rider would be able to pump it though and gain extra speed. Wind speed is below 8 knots in this case.

@2keen: okay, 15 knots make sense, I was thinking that this is happening in low single digit numbers and was wondering how are you able to foil in marginal winds :)

Re: feel vs board speed

I'm finding that in similar wind, a cm less downhaul is very noticeable in enough "pull" on the 9.0 hgo. I really want to do adjustable downhaul one of these days.

Totally agree with the sail pressure theory and for me I need a gust that lasts a bit not those short ones that bait you into using a lot of energy.As far as stall speed some times I have to tighten up a jibe because of other riders as log as you don't delay the sail flip it sometimes surprising how slow a foil will go without dropping 3knt? maybe slower.