Really? PHRF ratings Nauticat et al. - Page 2 - SailNet Community
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post #11 of 16 Old 08-16-2010
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Not to quibble, but I'm not sure that PHRF necessarily measures how a boat sails "to weather." It is more of an all around rating. So a light boat that goes great downwind but doesn't point or go to wind all that well might still get a decent rating, because the rating, in theory, is going to combine those attributes.

Another thing that people forget about PHRF ratings is that they are intended to apply at 15 knots. So if you are racing in the evenings in a 9 knot breeze, it will favor a certain category of boats. Almost everyone complains about PHRF but it is uncanny how accurate the ratings can be. On a 7 knot night, our fleet will be extremely spread out but on a recent night it was blowing 15 throughout and one minute separated the first seven boats in my class. So maybe they do know what they're doing.
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post #12 of 16 Old 08-16-2010
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As noted, the PHRF rating is an average considering upwind, downwind, reaching, light air, heavy air, etc. Every boat will have conditions when it can easily sail to its rating and conditions when it cannot. It is a very useful indicator of overall speed capability in a variety of conditions, but tells you little about specific conditions like upwind or light air. You have to look more deeply at other things like SA/D ratio and D/L ratio etc.
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post #13 of 16 Old 08-16-2010
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IMnsHO PHRF - or another figure based on empirical data - is one of the parameters worth considering for a bluewater boat - Not the primary parameter, but given two boats with the same "score" for all other of your criteria, by all means choose the one with the best (lowest) PHRF. Just make sure you understand how it is derived, and thus can be totally off for a type that is not well-known (or not raced).
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post #14 of 16 Old 08-16-2010
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I think that there are valid uses for a PHRF rating in selecting a blue water cruiser but only if you understand how a PHRf Rating is generated. A PHRF rating is supposed to represent the relative speed of a well prepared boat, sailing a triangular (olympic style) course in the prevailing winds in that region. It is not about upwind or downwind performance across a broad spectrum per-se', but about overall performance on various points of sail across a narrow range of windspeeds.

In a general sense, if you are comparating two boats with relatively close ratings and of a similar type, the PHRF numbers should be helpful. So for example, if you see a Pacific Seacraft 40 with a rating of 174 and a Valiant 40 at 186, (those are not the real numbers) the PS 40 would probably be faster on most points of sail and have faster passage times.

Where this falls apart, is when you talk about boats of vastly different types. So for example there is no fair way to handicap boats as different as say a Beneteau 40.7 at 51, vs my out of date 38 foot performance cruiser at 87, vs a pretty nice and recent coastal cruiser like the Hanse 37 at 121, vs heavy cruising boats like the Tayana 37, or Hans Christian 38 which are all the way up in the 180-190's.

This range in numbers represent a very big difference in speed between these boats, but it does not address the basis of that speed difference. A boat like the Beneteau 40.7 will have and enormous speed advantage upwind in almost all condition, but perhaps not as much of an advantage reaching in winds that might be called hull speed winds where the 40.7 can't surf but there is enough winds for all the boats to approach hull speed.

In a general sense, although these boats are similar in length the big differences in speed across the range of these boats means that they are sailing in different portions of the venue. This can be a significant advantage to the faster boat in a long passage where it may be able to sail through light air where the slower boat might have to sit or motor or sail a little further to get into better conditions. Even in coastal conditions, in confined bodies of water, the faster boat would typically end up taking fewer tacks or covering more of the distance when the wind was at its best.

My point being, that there is no easy fair way for a single number rating to fairly balance those kinds of 'tactical' issues and it makes it hard to compare the real world speed relationship between say a very fast 32 footer (as cited above) or a very slow 35-40 footer as mentioned in the original post.

Jeff


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post #15 of 16 Old 08-16-2010
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Quote:
Originally Posted by SPC View Post
I was surprised to see a 35 Nauticat at 180 which is similar to Hans Christian 38 at 192, Hallberg Rassy 35 at 180, Island Packet 35 at 186, Tayana 37 at 180, and much better than a Westsail 32 at 213 or Island Packet 32 at 198.

Does the Nauticat PHRF of 180 in comparison to the others listed make sense to you?
Despite the ratings listed, I would guess that the Nauticat will be
slower than all these other boats, including the W32, on most points of
sail and in most conditions.
PHRF ratings are initially arrived at by a little educated guesswork,
then generally refined by observed performance. For a type of boat
that is commonly raced, the rating will be a pretty good indicator
of a boats potential. All of the boats listed would have difficultly
sailing anywhere near their ratings on a windward / leeward course.
I doubt that a N35 would ever make it to a windward mark under sail
in light air. Most of these boats will only have a rating, because they
decided to enter a point to point race. Many of these sorts of boats
that are listed in the So Cal PHRF roster have a rating mainly because
they plan to compete in the Newport to Ensenada Race. They are not
raced any other time, so there is no emperical basis to their rating.
If the race happens to be a windy reach, these boats may sail to their
rating and then some. This one reason why So Cal PHRF wisely uses
a three number rating system with ratings for Bouy W/L, Random Leg,
and Off the Wind. Under this scheme, I would give the Nauticat 35
provisional ratings of 264/ 192/198.

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post #16 of 16 Old 08-18-2010
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Thanks for the way better explanation

Jeff,

Thanks for clarifying this. While I did say
Quote:
Just make sure you understand how it is derived, and thus can be totally off for a type that is not well-known (or not raced).
I totally missed the depth you provide in your post.

Quote:
Originally Posted by Jeff_H View Post
I think that there are valid uses for a PHRF rating in selecting a blue water cruiser but only if you understand how a PHRf Rating is generated. A PHRF rating is supposed to represent the relative speed of a well prepared boat, sailing a triangular (olympic style) course in the prevailing winds in that region. It is not about upwind or downwind performance across a broad spectrum per-se', but about overall performance on various points of sail across a narrow range of windspeeds.

In a general sense, if you are comparating two boats with relatively close ratings and of a similar type, the PHRF numbers should be helpful. So for example, if you see a Pacific Seacraft 40 with a rating of 174 and a Valiant 40 at 186, (those are not the real numbers) the PS 40 would probably be faster on most points of sail and have faster passage times.

Where this falls apart, is when you talk about boats of vastly different types. So for example there is no fair way to handicap boats as different as say a Beneteau 40.7 at 51, vs my out of date 38 foot performance cruiser at 87, vs a pretty nice and recent coastal cruiser like the Hanse 37 at 121, vs heavy cruising boats like the Tayana 37, or Hans Christian 38 which are all the way up in the 180-190's.

This range in numbers represent a very big difference in speed between these boats, but it does not address the basis of that speed difference. A boat like the Beneteau 40.7 will have and enormous speed advantage upwind in almost all condition, but perhaps not as much of an advantage reaching in winds that might be called hull speed winds where the 40.7 can't surf but there is enough winds for all the boats to approach hull speed.

In a general sense, although these boats are similar in length the big differences in speed across the range of these boats means that they are sailing in different portions of the venue. This can be a significant advantage to the faster boat in a long passage where it may be able to sail through light air where the slower boat might have to sit or motor or sail a little further to get into better conditions. Even in coastal conditions, in confined bodies of water, the faster boat would typically end up taking fewer tacks or covering more of the distance when the wind was at its best.

My point being, that there is no easy fair way for a single number rating to fairly balance those kinds of 'tactical' issues and it makes it hard to compare the real world speed relationship between say a very fast 32 footer (as cited above) or a very slow 35-40 footer as mentioned in the original post.

Jeff

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