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How to correct time for PHRF?

Sep 15, 2016
615
Catalina 22 Minnesota
Ok so I know what your thinking “another PHRF question?” but hear me out. I know my boats PHRF and understand how the ratings are initially derived and adjusted locally for conditions etc… But my question is how does this apply to the actual corrected time in scoring the race?

Here’s a scenario. I race a small C22 against much larger cruising boats. My C22 rates at 289 locally with a fixed wing keel (heavier boat design and much shallower draft than the swing). I typically race boats in the 96-150 rating range so everyone gives me time (and a lot of it I know). But how do you calculate how much time?

It is PHRF * number of miles in the total race / 60 sec/min? or is there more to the calculation?
 
May 17, 2004
3,434
Beneteau Oceanis 37 LE Havre de Grace
Each boat will have their “corrected time” computed. Corrected time is (elapsed time in seconds) - (PHRF * distance in miles). The boat with the lowest corrected time wins.

The way to think about it when you’re actually on the race course is more relative to the boats around you. Know the course length ahead of time, and multiply that length by the difference between your PHRF and that of the boat in front of you. That will give you some number of seconds. If you stay within that many seconds at the finish you correct out ahead of him.

Having said that, the difference between a PHRF in the high 200’s and ones around 100 is really dramatic, and I don’t think PHRF does a very good job of handling differences that large in most conditions. But that’s a whole other PHRF discussion. :stir:
 
Sep 15, 2016
615
Catalina 22 Minnesota
Each boat will have their “corrected time” computed. Corrected time is (elapsed time in seconds) - (PHRF * distance in miles). The boat with the lowest corrected time wins.
So then how do you figure for a staggered start where everyone's start time is adjusted based on pHRF so that in theory they finish at the same time? According to the calculation above you would still need to adjust for the total elapsed time. Also is the elapsed time the 1st finishing boat (fastest) or your boat using your rating?

Having said that, the difference between a PHRF in the high 200’s and ones around 100 is really dramatic, and I don’t think PHRF does a very good job of handling differences that large in most conditions. But that’s a whole other PHRF discussion. :stir:
Having raced a few years and progressing up quite a bit I seem stuck in the middle of the pack so I am inclined to agree with you. There is always a fast pack of 2 or 3 and then a large gap followed by the rest of us. The fast group often finished 30 min to an hour in front of the rest of us. Not real encouraging to get new people started.
 
May 17, 2004
3,434
Beneteau Oceanis 37 LE Havre de Grace
So then how do you figure for a staggered start where everyone's start time is adjusted based on pHRF so that in theory they finish at the same time? According to the calculation above you would still need to adjust for the total elapsed time. Also is the elapsed time the 1st finishing boat (fastest) or your boat using your rating?
With a normal start, each boat’s corrected time uses their own elapsed time in the formula.

To give an example (with simple numbers for easy math) - if you have a 2 mile course, you finish in 30 minutes, and your competitor with a 100 PHRF finishes in 25 minutes:

Your elapsed time is (30 minutes * 60 seconds per minute) = 1800 seconds.

Your corrected time is 1800 seconds - (289 * 2) = 1222 seconds.

His elapsed time is (25 minutes * 60 seconds per minute) = 1500 seconds

His corrected time is 1500 - (100 * 2) = 1300 seconds.

Your corrected time is less than his, so you win.

For staggered starts (pursuit style) you kind of need to work backwards to pre-calculate start times based on handicaps and course length.

Basically you have the highest PHRF boat start first, then each next slower boat starts later by the difference between their PHRF and the next faster boat, times the course length. Then whoever finishes first wins outright.

So for an example of that, say you have a 2 mile course, and 3 boats rating 289, 100, and 90. The 289 will start at the first start time, say 10:00:00. The 100 PHRF boat owes him (289-100)*2 seconds, which is 378 seconds, so they’ll start 378 seconds after 10:00:00. The 90 PHRF will start (289-90)*2 seconds after the 289 boat, which is 398 seconds after 10:00:00. All of the handicap is therefore pre-calculated, so whoever crosses the finish line first wins.
 
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Likes: LakeShark
May 25, 2012
3,809
john alden caravelle 42 sturgeon bay, wis
the straight line length of the course is not the miles you will actually sail. beating to weather, tacking down wind, chasing the strongest wind, ......
so the math does not really work now does it. so many things to consider ......:banghead:
 
May 17, 2004
3,434
Beneteau Oceanis 37 LE Havre de Grace
the straight line length of the course is not the miles you will actually sail. beating to weather, tacking down wind, chasing the strongest wind, ......
so the math does not really work now does it. so many things to consider ......:banghead:
In theory the handicaps are set knowing that the actual distance sailed is greater than the course length. But beyond that yeah there’s no really good way to model the differences encountered by boats that sail different speeds.
 
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Likes: jon hansen
Sep 15, 2016
615
Catalina 22 Minnesota
With a normal start, each boat’s corrected time uses their own elapsed time in the formula.

To give an example (with simple numbers for easy math) - if you have a 2 mile course, you finish in 30 minutes, and your competitor with a 100 PHRF finishes in 25 minutes:

Your elapsed time is (30 minutes * 60 seconds per minute) = 1800 seconds.

Your corrected time is 1800 seconds - (289 * 2) = 1222 seconds.

His elapsed time is (25 minutes * 60 seconds per minute) = 1500 seconds

His corrected time is 1500 - (100 * 2) = 1300 seconds.

Your corrected time is less than his, so you win.

For staggered starts (pursuit style) you kind of need to work backwards to pre-calculate start times based on handicaps and course length.

Basically you have the highest PHRF boat start first, then each next slower boat starts later by the difference between their PHRF and the next faster boat, times the course length. Then whoever finishes first wins outright.

So for an example of that, say you have a 2 mile course, and 3 boats rating 289, 100, and 90. The 289 will start at the first start time, say 10:00:00. The 100 PHRF boat owes him (289-100)*2 seconds, which is 378 seconds, so they’ll start 378 seconds after 10:00:00. The 90 PHRF will start (289-90)*2 seconds after the 289 boat, which is 398 seconds after 10:00:00. All of the handicap is therefore pre-calculated, so whoever crosses the finish line first wins.
I think I have a handle on it now thank you. I always wondered how to do the math as it seemed mysterious whenever it came to calculating times and when I asked how it was done no one could give a clear explanation.
 

JRacer

.
Aug 9, 2011
1,236
Beneteau 310 Cheney KS (Wichita)
Having said that, the difference between a PHRF in the high 200’s and ones around 100 is really dramatic, and I don’t think PHRF does a very good job of handling differences that large in most conditions. But that’s a whole other PHRF discussion. :stir:
That is why in some races you will see several PHRF Classes, Chicago Mac for instance. They will have each class only include a certain range of PHRF numbered boats so you don't have huge differences between the fastest and slowest boat in the group. Perhaps your Club/Group could break up the fleet into multiple PHRF Classes and narrow the spread.
 
Sep 15, 2016
615
Catalina 22 Minnesota
That is why in some races you will see several PHRF Classes, Chicago Mac for instance. They will have each class only include a certain range of PHRF numbered boats so you don't have huge differences between the fastest and slowest boat in the group. Perhaps your Club/Group could break up the fleet into multiple PHRF Classes and narrow the spread.
It makes since the problem is I am the only boat that has such a high PHRF number. It’s also why I haven’t joined either of the 2 clubs on the lake (24 mile long section of the Mississippi called Lake Pepin) since they really don’t seem to attract the smaller trailer sized sailboats. I sure wish they would see the number of sub 30 foot boats at the docks in the marina, or the number out sailing on any given afternoon, and try to attract them. Otherwise there are only 3 to 5 racing boats at either club.

I really enjoy racing and improving. I simply don’t have the budget to go out and purchase a racing only boat. Perhaps in time I’ll convince a few others to come long and then we can have our own start.
 
May 17, 2004
3,434
Beneteau Oceanis 37 LE Havre de Grace
That is why in some races you will see several PHRF Classes, Chicago Mac for instance. They will have each class only include a certain range of PHRF numbered boats so you don't have huge differences between the fastest and slowest boat in the group. Perhaps your Club/Group could break up the fleet into multiple PHRF Classes and narrow the spread.
That’s done around here too, splitting PHRF spinnaker classes into A, B, C, etc, generally with each group covering 40 seconds. It depends on participation though - most participants would rather sail in a single class of 6 boats than 3 classes of 2 boats.
It makes since the problem is I am the only boat that has such a high PHRF number. It’s also why I haven’t joined either of the 2 clubs on the lake (24 mile long section of the Mississippi called Lake Pepin) since they really don’t seem to attract the smaller trailer sized sailboats. I sure wish they would see the number of sub 30 foot boats at the docks in the marina, or the number out sailing on any given afternoon, and try to attract them. Otherwise there are only 3 to 5 racing boats at either club.

I really enjoy racing and improving. I simply don’t have the budget to go out and purchase a racing only boat. Perhaps in time I’ll convince a few others to come long and then we can have our own start.
That’s a pretty common problem unfortunately, and a bit of a negative feedback loop. As less people are racing classes need to be combined across wider splits. The combinations disincentivize participation, which only makes the consolidation worse. I’ve seen a few efforts here to get more boats racing in specific classes so they could be split out again, but none that have been remarkably successful.
 
Sep 15, 2016
615
Catalina 22 Minnesota
That’s a pretty common problem unfortunately, and a bit of a negative feedback loop. As less people are racing classes need to be combined across wider splits. The combinations disincentivize participation, which only makes the consolidation worse. I’ve seen a few efforts here to get more boats racing in specific classes so they could be split out again, but none that have been remarkably successful.
its a sad reality I'm afraid. Thanks for helping me understand how to calculate my time. After playing with the math a bit I think i finally got it.