Just curious to see what others are getting for this percentage?

Today was:

Alpha: 21.08
10 Sec: 25.55

Percentage: 82.5%

Today:
Alpha 23.48
5x10 28.95
perectage = 81.1%

I think the stronger the wind the lower the percentage, & not sure about the lower end of wind either, might be a bell curve statistically?

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hardie said...

Today:
Alpha 23.48
5x10 28.95
perectage = 81.1%

I think the stronger the wind the lower the percentage, & not sure about the lower end of wind either, might be a bell curve statistically?

I agree, most likely between 20-30 for the 5x10, would be ideal

Perhaps a more interesting measure is Alpha speed versus the top speed recorded during that alpha.

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Te Hau said...

Perhaps a more interesting measure is Alpha speed versus the top speed recorded during that alpha.

That takes too much thinking

Anyway my best is this:

Alpha: 19.7
5x10 Sec: 23.6

Percentage: 83.5%

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Te Hau said...

Perhaps a more interesting measure is Alpha speed versus the top speed recorded during that alpha.

This makes much more sense than alpha to 5x10 ratio although an equation that includes the fastest and slowest speeds would give a more accurate outcome. I'm not a mathematician but I'm positive someone could come up with a suitable equation i.e. fastest + slowest divided by the square root of the width of your board times alpha speed less fin length to chord ratio

I did a quick check and found an alpha to 5x10 ratio of 94.5% (from a really crap session with one okay alpha but 5 really bad 10sec runs) . It's an arbitrary value that doesn't tell much.

PS - Magnus - that's a pretty good alpha considering your 5x10 though.

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PS - Magnus - that's a pretty good alpha considering your 5x10 though.

Gees thanks sausage man, see ya at Burrum

This makes much more sense than alpha to 5x10 ratio although an equation that includes the fastest and slowest speeds would give a more accurate outcome. I'm not a mathematician but I'm positive someone could come up with a suitable equation i.e. fastest + slowest divided by the square root of the width of your board times alpha speed less fin length to chord ratio


Not quite at that level, but GPSAR comes close. Has a gybes analysis section which gives all sorts of data.
Analysis is based on the centre of the turn and referenced to wnd angle so a quite different evaluation from Alpha 500.

Last month's alpha day
28.8 max / 24.23 alpha 500 ..... 84.1%

And even better, Nov 13 ......22.44 Alpha / 25.7 max ...... 87.3%

Best alpha not necessarily best ratio

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Te Hau said...

And even better, Nov 13 ......22.44 Alpha / 25.7 max ...... 87.3%

Best alpha not necessarily best ratio

Thats getting up there

Are we looking for one hundred percent? Clearly the high percentage will be achieved on equipment not very fast but gybes very nicely.

My Tabou Rocket 140 is a very nice board to gybe and seems to peak out at around 25 knots for me.

Yep, looks like light wind alphas give the best peak/alpha ratio.

Pays to make sure the GPS unit settings are correct also.
It seems that if the minimum speed setting is set high (in Data logger or Memory card), you get a faulty, high alpha reading.
You can see this on the speed graph analysis which shows a loss of low speed data in mid gybe.
This gives a jump from one data point to the next instead of a nice, smooth speed trace through the middle of the gybe.
This gives an abnormally high gybe speed.
These min speeds should be set at a maximium of 3kt.

This is my best percentage so far that i can find.

Max speed during alpha 500:29.35
Alpha 500:25.52
percentage: 86.9%