PHRF Race Time Calculation question

[R. Young]

With PHRF ratings, the PHRF is multiplied by the total course distance and then subtracted from the time to complete the race. Here what I don’t understand. If the distance actually travelled, because of the prevailing conditions is different from the straight line distance, doesn’t the lower PHRF rated boat have an advantage, because the subtracted time is based on the straight line distance rather then the distanced actually travelled? By way of example consider:Course is A to B and back to A. A to B is 1 mile for a total distance of 2 miles. If the wind is such that it is possible to sail in a straight line back and forth then both boats will have (PHRF*2) seconds subtracted. But if the wind is such that one has to tack upwind and jibe downwind, then the actually distance travelled would be closer to about 3.6 miles. However both boats will still have the same (2*PHRF) seconds subtracted (and not 3.6*PHRF). If everything else is equal – doesn’t this give (for this scenario) an advantage to the lower PHRF boat?RogerHunter 37 "Destiny"

 

[Don Alexander]

The Rest of the World Does it Differently

In the UK we do not use "time on distance" but "time on time" instead. This allows for all course and wind strength variations. But it does introduce a whole new bag of other issues. The UK and the USA have agreed to differ over these handicapping systems for years but you might just start a war!!Regards,

 

[Mike DiMario]

Good Point but.....

Roger,You raise an interesting question. I think the answer lies in the facts though. If Boat A is a lower perf say 100 and Boat B is a 120. Really you are not being rated on the actual miles but the difference in ratings.Boat "A" had to travel theoretically the same distance as "B". Boat "A" gets 100 seconds x 2 miles for her 3.6 miles Boat "B" gets 120 x 2 miles for her 3.6 miles. Mathematically I am saying that 100 2 is to 120 / 2 as 100 3.6 is to 120 3.6. It is the same ratio 0.83 no matter how you slice it.I think if one looks at it from this perspective, it may make more sense. It is merely a rating system. in my humble opinion,Mike D

 

[Tony Re]

"All Things being equal??

Numerous variables ..so thing can not be equal. That is why the PHRFs are different.Up wind if heavy ..water line is key (if sails, prop,and skill of crew are equal) ..so a 24 MELGES with a 60 phrf has NO CHANCE against my 40 Hunter ..PHRF 108. At the mark ..going down wind ..let say with 18 knts of wind I can say go 9.6 to 10.5 knts which is fast for 18,000 lbs but the melges can surf big time and go 15 plus. This is why a course ..(bouy race) should not be point to point in PHRF for it should be trangular alowing all to use differen wind angles ..Check this out ..a minus 93 ..THAT'S -93.. 43 foot trimarannever "Spirit of Emu" wich just completed "Cape Flattery" 100 nautical mile did poorly ..for light winds going up wind for 50 miles and down winds for 50 ..I beat this boat for they can not go up wind or down wind....They must tack back and forth and do about 175 miles. So your example would be correct if MATCH RACING ..But then the PHRF is the same..so you would not use PHRF ..and you are saying no one is covering ..which does not happen if your PHRF's are similar. Tony Re Skipper "Re-Treat"

 

[Guest]

Closing remark

Thanks for the replies, I have 2 comments:Re The math and the 0.83 ratio being the same: I don't think the Math holds up, the concept that the ratios are the same just cancels out the affect of the milage - its the milage thats the variable i.e., effectively, if a 120 PHRF boat has 120 seconds subtracted, and a 100 PHRF boat has 100 seconds subtracted then over a one mile course there is a 20 seconds difference calculated. If the course goes to 2 miles then there SHOULD be a 40 second difference For my previous example only 20 seconds would be calculated thus the slower boat has a 20 second disadvantage imposed - everything else being equal.Re the other comment about "Everything else being equal" - Yes you are correct. Talking to racers at my club (Raritan Yacht Club in New Jersey) they are all amused about my concept of "Everything else being equal" - It never happens - except in Physics textbooks!Enjoy the seasonRoger