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LongPac preliminary results
- Thread starter Sparky
- Start date
brianb
Olson 34 Driver
Fun with Numbers - PHRF effective ?
This spread sheet and plot does a crude statistical analysis of long pac results. Note except for a couple exceptions finish position is highly correlated with PHRF rating. Meaning, assuming PHRF is a true measure of boat speed, that for this race and conditions a lower PHRF rating meant a better finish position. The really notable exception being Green Buffalo. She and Jim should get some prize for really beating the odds, obviously the Green machine picked a superior course.
Brian
This spread sheet and plot does a crude statistical analysis of long pac results. Note except for a couple exceptions finish position is highly correlated with PHRF rating. Meaning, assuming PHRF is a true measure of boat speed, that for this race and conditions a lower PHRF rating meant a better finish position. The really notable exception being Green Buffalo. She and Jim should get some prize for really beating the odds, obviously the Green machine picked a superior course.
Brian
tiger beetle
N/M 45 Tiger Beetle
What happens if the analysis is performed using results based on time on time instead of time on distance?
- rob
brianb
Olson 34 Driver
Hi Rob,
This doesn't try to acct. for any rating system. It simply compares the PHRF rating, which is a huge factor in T on T and T on D, with the results. For this race & condx. it shows one can reasonably predict position by simply knowing the PHRF rating. Hence, no rating system is fair. In some other conditions maybe we would have seen much less correlation with PHRF, which would have been what I would have expected in a perfect rating scheme.
This doesn't try to acct. for any rating system. It simply compares the PHRF rating, which is a huge factor in T on T and T on D, with the results. For this race & condx. it shows one can reasonably predict position by simply knowing the PHRF rating. Hence, no rating system is fair. In some other conditions maybe we would have seen much less correlation with PHRF, which would have been what I would have expected in a perfect rating scheme.
Since this race involved deteriorating conditions - wind dying out to nothing over the course of the race timeframe, the results are not surprising. The fast boats escaped, the slow ones didn't. Conversely, if the conditions had started poor and improved, the slow boats would have been favored. I don't see how one would ever come up with a rating system that accounts for changing conditions over the timeframe of the course.
- Mark
Rating Systems
I agree with Mark, especially in ocean races over a considerable distance. But just the opposite can be true, too -- with faster boats encountering lighter winds as the slower boats catch up.
Not only did the slower boats encounter diminishing wind, there is also the current effects at the Gate to take into account. "Nancy" arrived at Max Ebb Sunday morning. From somewhere off Stinson until we got under the S. Tower, the speedo was saying 6/7 knots and the GPS was saying 3/3.5 If we'd arrived at Max Flood I think the GPS would have shown speeds exceeding the knot meter.
We stayed north, expecting the wind to be Northwesterly, but on Saturday and into Sunday morning we were almost running in light wind, making 3/4 knots. Not the Wyliecat's strongest point of sail.
Had we stayed further south and been able to reach more (a Wyliecat's strong point of sail) we probably would have nearly doubled our speed for 24+ hours.
After the N. Farallon it was more of a reach and our boat speed picked up - but due to the ebb, not over the ground.
We had no weather info (Gribs, etc.), so were sailing according to a 96 hour forecast that was out- of-date.
I need to learn how to use Gribs before next year's PacCup, and would appreciate any tutoring/help anyone would be willing to give. We'll have SSB and a sat phone for that race so can download things.
We were pleased with the 7th Place overall.
Pat - "NANCY"
I agree with Mark, especially in ocean races over a considerable distance. But just the opposite can be true, too -- with faster boats encountering lighter winds as the slower boats catch up.
Not only did the slower boats encounter diminishing wind, there is also the current effects at the Gate to take into account. "Nancy" arrived at Max Ebb Sunday morning. From somewhere off Stinson until we got under the S. Tower, the speedo was saying 6/7 knots and the GPS was saying 3/3.5 If we'd arrived at Max Flood I think the GPS would have shown speeds exceeding the knot meter.
We stayed north, expecting the wind to be Northwesterly, but on Saturday and into Sunday morning we were almost running in light wind, making 3/4 knots. Not the Wyliecat's strongest point of sail.
Had we stayed further south and been able to reach more (a Wyliecat's strong point of sail) we probably would have nearly doubled our speed for 24+ hours.
After the N. Farallon it was more of a reach and our boat speed picked up - but due to the ebb, not over the ground.
We had no weather info (Gribs, etc.), so were sailing according to a 96 hour forecast that was out- of-date.
I need to learn how to use Gribs before next year's PacCup, and would appreciate any tutoring/help anyone would be willing to give. We'll have SSB and a sat phone for that race so can download things.
We were pleased with the 7th Place overall.
Pat - "NANCY"