Alpha Percentage of 10 Sec Average

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?

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.

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%

Thats getting up there

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.