what is a good (realistic) alpha/ 5x10 ratio?
a good one for me is -10 kts though I'm still chasing a 20/30 kt combo
should it be a percentage or a fixed number?

depends on the conditions, what's good for a 5X10 isn't always good for an alpha and vice versa, the 10sec needs downwind conditions the alpha cross wind. Some speed banks don't have enough room for a square alpha.
My best alpha of 26kts, in great cross wind conditions had a corresponding 5x10 of 33kts.
my best 5x10 of 37kts, in great downwind conditions, had a corresponding alpha of 22kts.

Hey Speed sailors, where do i find out about what all your lingo means? Eg Alpha? 5x10? Etc. Can someone explain? Or are there rules i can read somewhere? Cheers.

gpsteamchallenge.com.au/
www.seabreeze.com.au/forums/Windsurfing/Gps

2sec = Highest average speed over 2 second period
5x10 = highest average speed averaged over 5 separate 10 sec periods
Alpha 500 = Highest average speed over 500m with a gybe (250m Legs). Must finish within 50m of starting point.
1hr = Highest average speed over a 1 hour period
Nm = Highest average speed over distance of 1 Nautical Mile
Km's = Distance Covered in a day (calendar date)

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olskool said..
Hey Speed sailors, where do i find out about what all your lingo means? Eg Alpha? 5x10? Etc. Can someone explain? Or are there rules i can read somewhere? Cheers.

Olskool, you need to join a team now.

Not always to compete but to participate and track your journey.

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Stuthepirate said. Alpha 500 = Highest average speed over 500m with a gybe (250m Legs). Must finish within 50m of starting point.
1hr = Highest average speed over a 1 hour period
Nm = Highest average speed over distance of 1 Nautical Mile
Km's = Distance Covered in a day (calendar date)

Hate to nit pic Stu, but this is a common misconception, It's over NO more than 500m, most software will give you a valid alpha around 100m but the GW60 watch display, can only calculate alphas over 300m. That's one of the reasons other software will give alphas that the watch doesn't

Nit pic away decrepit.
I was wondering why some of my alpha tracks seemed really short compared to others.

Why was decided to measure distance in km instead of nautical miles? Its always puzzled me.

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Shifu said..
Why was decided to measure distance in km instead of nautical miles? Its always puzzled me.

Well, it sort of puzzles me too but it seemed logical to measure speed in Knots as it is the traditional Nautical speed measurement. (The Euros mostly talk among themselves in KM/hr and some US sailors - are there any left?- talk in Miles)

But we are all much more familiar with KM for distance in Australia and everywhere else but the US.... I guess....

Besides, it sounds grander to use a bigger number!

Also strange to me is the fact that nautical miles are actually metric, not imperial.

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Dylan72 said..
Also strange to me is the fact that nautical miles are actually metric, not imperial.

you mean like 1852m?
I'm guessing here, but I think that may just be the metric equivalent. I bet it wasn't originally defined in meters, must have been something to do with the distance between the knots in the rope.

OK wrong again, got this from Mr Google


A nautical mile is based on the circumference of the earth, and is equal to one minute of latitude. It is slightly more than a statute (land measured) mile (1 nautical mile = 1.1508 statute miles). Nautical miles are used for charting and navigating. A knot is one nautical mile per hour (1 knot = 1.15 miles per hour). The term knot dates from the 17th century, when sailors measured the speed of their ship by using a device called a "common log." This device was a coil of rope with uniformly spaced knots, attached to a piece of wood shaped like a slice of pie. The piece of wood was lowered from the back of the ship and allowed to float behind it. The line was allowed to pay out freely from the coil as the piece of wood fell behind the ship for a specific amount of time. When the specified time had passed, the line was pulled in and the number of knots on the rope between the ship and the wood were counted. The speed of the ship was said to be the number of knots counted (Bowditch, 1984).



Doesn't say what the specified time was though.

So don't tell Pete, he doesn't believe the earth has a circumference

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decrepit said..
a device called a "common log." This device was a coil of rope with uniformly spaced knots, attached to a piece of wood s

is that why the device now says " save/stop log" at the end of the session ???

Don't want to nit pic again Decrepit, your nautical mile definition is pretty correct, however it is one minute of latitude measured at 45 degrees North or South, as the Earth's shape is defined as an oblate spheroid, as it squashed at the poles and bulges at the equator. By the way, Bowditch (The Americian Practical Navigator) is great book if you ever suffer insomnia.

"Longitude" by Dava Sorbel is a good read.

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decrepit said..

Dylan72 said..
Also strange to me is the fact that nautical miles are actually metric, not imperial.

you mean like 1852m?
I'm guessing here, but I think that may just be the metric equivalent. I bet it wasn't originally defined in meters, must have been something to do with the distance between the knots in the rope.

OK wrong again, got this from Mr Google


A nautical mile is based on the circumference of the earth, and is equal to one minute of latitude. It is slightly more than a statute (land measured) mile (1 nautical mile = 1.1508 statute miles). Nautical miles are used for charting and navigating. A knot is one nautical mile per hour (1 knot = 1.15 miles per hour). The term knot dates from the 17th century, when sailors measured the speed of their ship by using a device called a "common log." This device was a coil of rope with uniformly spaced knots, attached to a piece of wood shaped like a slice of pie. The piece of wood was lowered from the back of the ship and allowed to float behind it. The line was allowed to pay out freely from the coil as the piece of wood fell behind the ship for a specific amount of time. When the specified time had passed, the line was pulled in and the number of knots on the rope between the ship and the wood were counted. The speed of the ship was said to be the number of knots counted (Bowditch, 1984).



Doesn't say what the specified time was though.

I guess his comment is based on the fact that both a metre and nautical mile are based on the shape of our planet, which doesn't vary much. Unlike the length of some random Roman bloke's random appendage measured at a random occasion.