Gps speed v wind speed

There is a wide variety of variables that drastically alter the idea of what is respectable. eg: water state, wind speed, equipment, your weight etc.

the only useful intel that I have garnered from a brief amount of time trying to go fast/er is try to go faster than everyone else




bit daunting when you've got Slowboat hammering down the sandbank at 40+knots regularly at your local, but you've got to have something to aim for, right?

It's a sliding scale if you have the right gear for the conditions, you can do double the wind speed. eg at 12 kts you can do 24.
But at 20kts you can't do much more than 30. it takes about 30kts to do 40 and about 50kts to do 50.
As said this varies with conditions and rider.
There is slow water and fast water, the numbers above are what I can do in very good conditions. and I'm somewhere around average.
apart from the 50 in 50. I haven't come across those conditions, and I'm now too old to think about it. also 24 in 12, I don't have suitable light wind gear.

So in 18 to 30kts you should be getting close to 30 at 18 and close to 40 at 30.
23kts is not speed sailing.

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remery said..
In smooth water, I reckon 36 knots in 18 is good going.

Slowy may be able to do that, but nowhere near it for me.

Yep, that's me 25kts to do 35

I was thinking of 2sec speed on those days where the forecast was 12-18.

Thank you John340, that sets out very clearly an approx range of speed goalposts for me plus the outline kit selection. Gunna nail it to my garage door. Ive got a long way to go.

Jason, you say there aren't speed sailors where you sail.
Speed sailors will usually travel to good speed sailing spots, (like wave sailors are attracted to good waves). This could be you don't have good speed sailing conditions. If that's so, you may not have as far to go as you think.

Lake George can have mirror flat water at 15kts, and no whitecaps at 30kts.
So if you don't have good conditions you won't be going as fast.

I got very close to a 32, so it was probably a good 20kts.
The Mandurah anemometer is in wind shadow with a SW, so it under reports windspeed big time.

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John340 said..
The sliding scale is correct. A summary of 4 days results from this year's trip to Lake George follow:
Date, Board, Sail, 2 Sec, Max Wind, Multiplier
3 Feb: Falcon 115, 7.7, 29 kts, 14 kts, 2.1
2 Feb, Falcon 97, 7.0, 34 kts, 20 kts, 1.7
4 Feb, Falcon 97, 6.2, 38 kts, 25 kts, 1.5
5 Feb, JP 80, 5.7, 40 kts, 30 kts, 1.3

Very approximately - take the square root of 55 * wind speed

It's interesting that it's reasonably close over a 2:1 range in wind speed. Wind power force increases with the square of wind speed. Drag is a combination of square terms and semi-linear terms (skin drag, planing hull drag)

Although we all have experienced this, it feels mathematically counter-intuitive that the bigger gear, with more skin drag and lighter winds is more efficient.

I suspect the factor I've always overlooked is that the hydrodynamic drag terms are scaled to the board speed, while the aerodynamic drag terms are scaled to the apparent speed, not measured wind speed! As the wind picks up and overall velocity increases, the aerodynamic drag forces increase significantly more than the hydrodynamic drag forces. This will be especially true for upwind courses vs. downwind courses.

Got it, thanks. In short :

Target 1 : break 30 knots in whatever wind. That will have me singing in the shower

Target 2 : break 30 knots in 20 knots of wind. You will all hear me singing in the shower

I have flat water so no excuses.

big respect to you lot that have it nailed down.

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ozzimark said..

Although we all have experienced this, it feels mathematically counter-intuitive that the bigger gear, with more skin drag and lighter winds is more efficient.

All your points are valid, but I think there's another that you've overlooked. The ratio of sailor area to sail area.
light winds big gear the sail area is high, strong winds smaller gear ratio is lower.
And theoretically power is constant, it's directly related to sailor weight.
Whereas drag increases with speed.

Am in southern Portugal, waiting for the summer breezes to come thru. You are welcome to come join, mostly wingfoilers around me. A couple of slalom lads pop up when conditions are perfect, then I have to pull rank as the strip is narrow.

Thanks all. 25 knts in around 20 knts gusts. 7m, 100L Futura for my 78 kg. Standard 32 cm fin. Comfortable to hold once going, slingshot part a bit bumpy in 20-30cm tight knit ripples with 4knt tide into wind. Couldn't get the railing going to hop over them.

I thought the 2 local speed lads were just lazy as they were out only 30 mins either side of high tide. Turns out, that unlike me the rookie, they have an affection for their fins, board nose, ribs and battens. I now know where the sandbanks are hiding. Gunna keep the local repair man busy.

21/12/24 Albany

You've started a Liptons longing here.