Quintessential Zero Boat for PHRF - SailNet Community

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  #1  
Old 10-12-2009
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Quintessential Zero Boat for PHRF

I was just looking at PHRF ratings for various boats and noticed that the listed boat closest to zero was a J-125 at -6. There were none with zero.
Is there a sailboat you have in mind that sets the reference point (zero) for the PHRF rating system? Local conditions are different, but, just wondering what a zero rated boat might look like.
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Old 10-13-2009
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The J you refer to is pretty close, there are some Farr 39's that race locally with an 18 rating. I do not recall what the farr 40 1d races at. But a zero boat if designed to such a thing, seems to be about 40-42' or about 12M or there abouts. Guilletta seems to be close IIRC from an IRC conversion of equal boats.

Not sure I would want to go much farther in what would be a zero boat, because if I said 1000# of SA, 8' draft, 12' beam and some other odds and ends, any one of those may make the boat be way less than zero or more than zero. The J's in the 12x and 40-42' older models all seem to be -10 to 20 or so. As are the Farrs in the 39-42' range, Bene first 44.7 is in this range IIRC too.

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Old 10-13-2009
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I understand the rating system, but wondered what the creators had in mind when they set the standard. Interesting stuff.
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Old 10-13-2009
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edited below

Last edited by Sanduskysailor; 10-13-2009 at 10:36 PM.
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Old 10-13-2009
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Whoa, Snort I am going to be nice and assume that you don't get it when it comes to PHRF. No one created a standard of O. PHRF numbers are relative not finite. A rough translation of the O number is 550 sec/mi. That is the time it theoretically takes a boat rated 0 to travel a mile in 10 knots of wind. Most PHRF areas use a J-35 as standard base boat which roughly translates to 622 sec/mi. rating Thus the 0 boat should sail 72 sec/mi or roughly 24 boatlengths a mile faster than a72 rated boat. Each PHRF area uses its own terms of reference in handicapping which allows for local prevailing conditions and course configurations to factor into the rating.

Since PHRF is not a measurement rule with a VPP, handicappers express difference in rating in relative terms based on observed performance, results, handicap ratings of like designed boats and comparisons of performance ratios.

Again this does not hold true for all PHRF areas. Some areas handicap on the basis of results only, some use an average in the National PHRF book. If you look in the National PHRF book the ratings for some boats are all over the map. How does this happen?? A good example might be the Melges 24. If your PHRF area is an inland area with predominantly light air and windward/leeward courses the rating will be a lot higher than an area with offshore races and winds strong enough to plane in. I.E. Austin PHRF-105, So Cal PHRF- 84 for buoy races and 66 offshore.

Bottom line is PHRF is a catch-all name for a locally or regionally administered empirical handicap system with different rules and methods of handicapping depending on where you are in the country. BTW, a Far 40 non masthead spinnaker (old OD config) rates around 0 in a lot of PHRF areas.
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Old 10-14-2009
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Behind all the PHRF numbers is the following formula for production type boats. Custom boats go through a more rigorous measuring process. If you modify your production type boat your local PHRF will use the more rigorous techniques to determine their ratings adjustment. Regional committees tweak the formula itself to fit their local conditions. NORCAL PHRF sticks pretty close to this formula. Because this is a formula similar to the IOR, BOX, etc. rules there is no single base boat. In San Francisco Bay, a custom Schumacher 52 has a zero rating and the Farr 40 is a 6 (they started out as a two years ago). The range out here for mono hulls goes from something like a -149 up to a +274. Next, does anybody want to tackle the Trans Pac rule and why is the Catalina 34 the cut-off boat?

R' = 610-8.36*(SA/Disp^.333)+0.0000511*(SA^2)-55*(P/(J+E)) -30.8*(LWL^.5)-602*(DR^2/SA)

where SA= .5*(I*J)+.5*(P*E)

Last edited by GeorgeB; 10-14-2009 at 11:16 AM.
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Old 10-14-2009
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A J/125 and a NYYC Swan 42 rate a -3 here. There's a Corby 41 - Nasty Medicine (ex Wahoo, won Newport a few years ago) that rates a 0. Did a crossing from Bermuda to Annapolis on a boat that rated -78 one time, that was quick

Last edited by ste27; 10-14-2009 at 08:14 AM.
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Old 10-14-2009
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There is no standard mathematical formula for PHRF. It is an empirical rule. That being said, some committees use a tool (Schell regression analysis) to get a rough idea for the starting point in rating a new boat. If you use that tool to analyze all boats in a PHRF fleet you will find that the results don't neatly correspond to the the actual ratings.
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Old 10-14-2009
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You’re right, there are several ways of calculating PHRF numbers. The regression analysis works for 90% of the boats most of us own who frequent this website. NORCAL base PHRF numbers for production boats are pretty spot on. I agree, the regression formula does not account for individual boat modifications. Where I see the most movement is for the one of a kind boat or a first in class. The Aerodyne I used to sail on started out as a 39 but got bumped down to a 36 the next year when others in the fleet thought we were faster than the regression formula. The following year a Synergy 1000 ran into the same situation. I personally had a similar experience on my 28. The owner of the first boat of its class in the Bay successfully argued that the builder’s published displacement did not jive with the drayage or sling weights so he got them to use the higher number in their calculation. When I got my certificate, I used his numbers, but had to go in front of the committee for a review anyways.
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Old 10-14-2009
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It's a good question -- you'd anticipate a baseline "Zero" boat all other boats are handicapped against. But a zero boat would be so darn fast! It's hard to imagine too many Farr 40ish boats existed when the PHRF lists were first drawn up. Maybe they chose a baseline boat around 175 and projected down from there to a hypothetical zero boat. Maybe they set the zero point where they thought no boat would ever go below that, to prevent negative numbers.

They never expected the Andrews 70 (-90). Mwahhaahaa. NOBODY expects the Andrews 70!



BTW, both the Swan 77 and the Corby 41.5 rate all zeros in the national PHRF ratings. But there's what, two of each in the US? So probably not the pace car you seek.
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