Pitchy,


>>gps instantanious speed readings are not as accurate as you would think.

I didn't use instantanious GPS speed readings.


>>And I don't think that a 500m average distance has anything to do with the instantanious speeds that the boats can achieve.

-1- you think or do you know ?
-2- If I say that may cat attained 50 knots speed on a reach, what do you read into that ? Instantanious speed or sustained speed ?
-3- A series of instantanious speed will lead to higher 500 mtr. speeds. It is also the official speed measuring way.
-4- Bacaradi run used a stretch of 500 feet, taking a Tornado 12.53 seconds to cover. When does a measurement become instantanious speed ?


>>So the truth is probably somewhere between 33knots and 25 knots.


What is truth ? Please define truth in this respect.

What ever your answer to the above question, the claims made suggest something that ISN'T true, namely sustained speeds above 23 knots for more than 13 seconds.


>>If you _really_ want to measure instantanious speed then you need a radar gun.

I don't agree GPS units can be dependable. Set the unit to poll every sec or so and read out the track. Plot the travelled distance per read-out look for a segment that shows only very small swings in travelled distance over a few samples and calculated the average speed from that. Errors in GPS read-out show themselfs as large swings in travelled distance from sample to sample. Engineers and educated persons will recognize this as the statistical defined DEVIATION. Look for a data series with a small deviation component.

Besides who said that a radar gun is accurate ? I know how that works and it you point that thing at the mast and it swings forward you get the same offsets as GPS unit can have.


>>We bought one for our regatta and anyone wishing to test their speed is welcome.

Sounds like a good test. I'll be glad to hear the results.



Wouter