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IMS accuracy
Stuart Cresswell wrote in message ...
The message from (Joakim Majander) contains these words: I've been trying to find some information about the accuracy of the time allowances in a IMS certificate. All handicaps are spot on accurate - you accept that when you are rated and when you enter a race under the appropriate conditions. My objective was not to complain about ratings. I just would like to know how close they typically are to real life. If you are going 0,5 knots slower than you "should", you would like to know is that due to poor sailing, poor trim of mast etc or is it just an normal variation in IMS VPP. I know that it may be possible to say that in a particular condition your boat is faster/slower than the rating you have... but I say again you accept the rating when you enter an event under those conditions. Everybody seems to know that, but I would like to see some figures. Remember that unlike other rating systems, IMS is able to take into account different wind directions and speeds. It is your objective to sail round the course more faster than your ratings than the other competitors (or less slower) regardless of the accuracy of the ratings. Of course. Does this mean it is useless to discuss the accuracy of ratings??? What may be of interest is that is a rating results in a TCF corrected/rounded to three decimal places then a change of 1 in the lowest place requires the boat to be 3.6 seconds faster for each corrected hour that she sails. In other words if two boats have corrected times less than 3.6 seconds/corrected hour apart (eg 18 seconds for a five hour race or 259.2 seconds for a 72 hour race) then if the TCF of the slower (on corrected time) boat was incorrect by 1 too low in the last decimal place she should have won. I a agree, that 3 or even 2 decimals on a time-on-time rating is very accurate. In my example we were slower on the last legs by 40 sec/mile. This would transate to ~250 seconds (= half a mile) in an hour in those conditions. On a time-on-time correction (which IMS is not), this would be a disprepancy of 7%. Joakim |
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