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Old 28-04-2011, 20:23   #1
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PHRF as Estimate of Passage-Making Speed

When shopping for a boat that will be used for a two-year cruise, is it valid to use the listed PHRF as an estimate of passage-making speed. I understand that PHRF is based on time around the buoys with an unladen boat. For example, would one expect a loaded down Alden 46, with a PHRF of 84, to be a faster passage-maker than a similarly loaded Mason 44, Passport 40 or Valliant 40, all which have a PHRF's around 140.
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Old 28-04-2011, 20:36   #2
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pirate Re: PHRF as estimate of passage making speed

The thing about cruising is... it aint around the bouys...
Statistics tend to go outa the window... unless your daysail harbour hopping... but theoretically the boat with the best LWL should be the fastest... or so I've been told...
I aint gotta clue... don't pay much attention to that stuff...
Sorry... ignorant know nothing seaman...
But I'm sure thers a 'Techie' here somewhere...
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Old 28-04-2011, 21:34   #3
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Re: PHRF as estimate of passage making speed

PHRF is a rating that combines predictions for all points of sail. Since a long cruise is typically downwind, this won't be particularly appropriate. You might instead look at the PHRF "Downwind" ratings which are used in some regions, or perhaps a downwind-adjusted rating such as the Pacific Cup Rating.

Still, for a displacement boat the basic PHRF rating should get you in the right ballpark. For that matter, LWL (waterline length) is probably an equally good predictor. Depending on how hard you want to sail, and the conditions, on a displacement boat you might multiply the LWL hull-speed by 0.75 or so.
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Old 28-04-2011, 22:28   #4
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PHRF assumes that you never reef and, despite the claims to the contrary, never reach.

And the formula really doesn't understand waterline.
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Old 28-04-2011, 22:52   #5
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Re: PHRF as estimate of passage making speed

It will not be any use for calculating how fast you will sail when making a passage, but it might be a reasonable way to compare different boats for passage making.

However, bear in mind that the lighter the boat, the more its performance will suffer with added weight. Add 1 ton to a 15 ton boat and its performance will not change appreciably, Add 1 ton to a 3 ton boat and its performance will change dramatically. PHRF will assume minimum gear, whereas you will typically passage with lots of additonal weight on board.
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Old 28-04-2011, 23:13   #6
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Re: PHRF as estimate of passage making speed

No. The dimensionalities that go into a PHRF rating do not take into account the sort of comfort, seakindliness and "push" you want in a cruiser. That is not to say that a club racer-cruiser can't be made a good ocean cruiser, but that a PHRF rating isn't going to matter much.

Some light boats are fast to weather but can be slowed greatly by decent sized waves. Others have small rudders and underbodies and flat aft sections and will be squirrelly to steer downwind and pounding in a seaway. The idea of an inshore/coastal low-PHRF boat is usually to trade comfort for speed and not to carry a lot of gear.

Frankly, the average cruiser laden for extended travel is probably happy to make a steady 5 knots. The difference is that the cruiser can do that five knots, more or less, in most conditions: it keeps chugging along whereas the low-PHRF boat may be strong enough for the ocean, but draining on the crew. Also, as has been pointed out, if you load a performance boat, the "performance" decreases noticeably. I have a 30,000 lb. steel cutter and a 33 footer that weighs 9,000 lbs. On the 33er, simply moving about 200 lbs. of extra gear off the boat, swapping in a smaller fuel tank, losing the galley water tank and shifting the batteries made a noticeable improvement in sailing ability, but that would be lost if we started bringing crates of canned provisions aboard. By contrast, drop half a tonne of batteries low in the hull of a full keeler, and she finally get close to her lines and sails better.

That said, there are "performance cruisers", like the bigger Js, Sagas, Swans and so on, that are fast and (mostly) comfortable, but they cost a lot.
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Old 29-04-2011, 00:03   #7
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Re: PHRF as estimate of passage making speed

Quote:
Originally Posted by S/V Alchemy View Post
No. The dimensionalities that go into a PHRF rating do not take into account the sort of comfort, seakindliness and "push" you want in a cruiser. That is not to say that a club racer-cruiser can't be made a good ocean cruiser, but that a PHRF rating isn't going to matter much.

Some light boats are fast to weather but can be slowed greatly by decent sized waves. Others have small rudders and underbodies and flat aft sections and will be squirrelly to steer downwind and pounding in a seaway. The idea of an inshore/coastal low-PHRF boat is usually to trade comfort for speed and not to carry a lot of gear.

Frankly, the average cruiser laden for extended travel is probably happy to make a steady 5 knots. The difference is that the cruiser can do that five knots, more or less, in most conditions: it keeps chugging along whereas the low-PHRF boat may be strong enough for the ocean, but draining on the crew. Also, as has been pointed out, if you load a performance boat, the "performance" decreases noticeably. I have a 30,000 lb. steel cutter and a 33 footer that weighs 9,000 lbs. On the 33er, simply moving about 200 lbs. of extra gear off the boat, swapping in a smaller fuel tank, losing the galley water tank and shifting the batteries made a noticeable improvement in sailing ability, but that would be lost if we started bringing crates of canned provisions aboard. By contrast, drop half a tonne of batteries low in the hull of a full keeler, and she finally get close to her lines and sails better.

That said, there are "performance cruisers", like the bigger Js, Sagas, Swans and so on, that are fast and (mostly) comfortable, but they cost a lot.
PHRF is not a measurement rule. Boats are not designed to it. Anybody that sends in their $25 (or whatever it is now) for any boat will get a rating. I was once on a race where a 45' wood obviously cruising boat had the same handicap as the 26' Islander Excalibur I was on.

I agree that PHRF would not be a predominate factor in determining cruising speed for the reasons given above, but for similar boats with similar displacement to length ratios it would give some idea of relative speed, heavily weighted for upwind work.


From:
What is PHRF?
HOW DOES PHRF ASSIGN A HANDICAP?
Performance Handicap Racing Fleet (PHRF) handicaps are based on the speed potential of the boat, determined as far as possible on observations of previous racing experiences. For new boats, handicappers typically compare the new boat to others that they are familiar with and references, if available, to designer's predictions, IMS or MORC handicaps. They look for boats of the same type, based on sail area to displacement ratios and then make adjustments based on the differences. In addition handicappers generally look to see if the boat has raced in another PHRF group. If using measurement rules such as MORC or IMS, care must be taken as measurement rules are type forming. If the boat wasn't designed to the rule, then the handicap likely will not be representative of the boat's potential. Since measurement rules evolve over the years, the age in the rule must also be considered.
The handicap can then be adjusted, based on race performance. This is the difficult part as the quality of the racing program has to be taken into consideration. Just because a boat finishes last all the time or, on the other hand, wins many races, does not necessarily mean that the handicap is wrong. In most areas, the overall philosophy is that, for new boats, any error in the handicap is on the side of being a bit harsh, since it is always easier to raise a handicap than to lower one.
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Old 29-04-2011, 00:19   #8
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Re: PHRF as estimate of passage making speed

I did not mean to imply it was a measurement rule in your sense, but perhaps a "measuring rule" in which weight is given to certain parameters conducive to upwind work, etc.

I sail on Lake Ontario, and the fact that an Alberg 30 can beat on time a J-29, say, suggests that PHRFs an attempt to combine apples, oranges and cuckoo clocks into a Venn diagram of some sort. I do agree that PHRF ratings are suggestive of a certain kind of performance, but I feel that in an effort to include and somehow rank vastly different vessels as if they were in a hypothetical single class is more inclusive than accurate. It's probably the best way to keep club racing vital, but it's more interesting to see a level fleet of, say, CS 30s or J-105s slugging it out than to wait for the results as the slowest boat in the pack...but to whom everyone gives time...finally crosses the line in the twilight.

Actually, that boat is commonly a decent cruiser!
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Old 29-04-2011, 00:54   #9
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Re: PHRF as estimate of passage making speed

Only way to actually know this is to go cruising the boat you're gonna use... and just for the record... if you wanna go someplace..... then probably it will be upwind!
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Old 29-04-2011, 03:52   #10
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Re: PHRF as estimate of passage making speed

Pretty useless as a cruising guide, as said above. You might use the PHRFs to compare, or get some relative idea between several boats.

One good source for cruising boats is the Pacific Puddle Jump crossing time reports in Latitude38 (online too) each year (during the summer issues?)...

Some real pigs out there. But surprisingly not so much correlated with the boat but rather the crew and style....
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Old 29-04-2011, 04:18   #11
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Re: PHRF as estimate of passage making speed

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Originally Posted by boatman61 View Post
The thing about cruising is... it aint around the bouys...
Statistics tend to go outa the window...
+1

Most cruisers I know allow for about 100 miles a day for offshore passages. Over a couple of years probably isn't far out unless you are one of the wealthy ones who motors for 100's of miles when the wind dies.

But most don't really bother trying too much at putting a timescale on passages. It takes as long as it takes, looking at a calendar just leads to frustration.

Take plenty of good books instead
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Old 29-04-2011, 05:40   #12
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Re: PHRF as estimate of passage making speed

Quote:
I understand that PHRF is based on time around the buoys with an unladen boat.
You answered your own question perfectly!

If you are not laden you are not cruising. If you are headed toward a finish line it means you are about to sell the boat. For passage speed it's pretty hard to beat a long water line. It tends to conflict with your bank account so the art of compromise is paramount.

If you are in a hurry then you probably are not cruising either. It's also a bad habit that can get you killed.
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Old 29-04-2011, 06:06   #13
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Re: PHRF as estimate of passage making speed

As Paul suggests, waterline length is the more pertinent factor.

As a "rule of thumb" plan on making 75-80% of the boat's theoretical Hull Speed as an overall average for long passages. That's held true for me over around 9,000 nm in offshore passages, and some folks I know with many more miles than me seem to agree.
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Old 29-04-2011, 09:09   #14
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Re: PHRF as estimate of passage making speed

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Originally Posted by FecklessDolphin View Post
When shopping for a boat that will be used for a two-year cruise, is it valid to use the listed PHRF as an estimate of passage-making speed. I understand that PHRF is based on time around the buoys with an unladen boat. For example, would one expect a loaded down Alden 46, with a PHRF of 84, to be a faster passage-maker than a similarly loaded Mason 44, Passport 40 or Valliant 40, all which have a PHRF's around 140.
G'Day FD,

Now that everyone has told you how useless the PHRF ratings are, lets try to answer your specific query. I for one would bet the farm that yes indeed, the Alden 46 would be a faster passage maker than the PHRF 140's when similarly loaded and similarly driven. I think that comparisons where the delta between the PHRF ratings are large would be quite reliable. But not so for fine tuning... say where the differences are like 120 to 140 or so.

And to say that since PHRF ratings include windward performance in their establishment they don't apply to cruising isn't right IMO. Sadly, our cruising experience has included lots of windward miles, even though we planned differently! And really, if a boat is quick to windward, it will likely be quick downwind as well.

Having said that, I wouldn't try to use a PHRF as a quantitative indicator of passage times. As others have said, there are too many variables in a given passage to make accurate predictions. Again as others have said, LWL is a reasonable predictor. In fact, in their first (I think) book, "A Circumnavigators Handbook" or something like that, the Dashews final recommendation was to buy the longest LWL that you could afford, and reckoned that this was the most important single factor in selecting a cruising boat. (I hope that I haven't misquoted here... it has been long since I read it!).

There are cruisers and wannabee cruisers who loudly say that sailing performance isn't important to them, and they are welcome to their views. From your questions, I suspect that performance is important to you (as it is to Ann and I), and so questions like yours are appropriate. These folks often raise the issue of comfort, saying that the lighter boats suffer from some sort of motion that will be bad at sea. Here I think we must realize that comfort is pretty individually defined. We find that our "performance" cruiser, with a L of around 125 and SA of around 20 is, for us, far more comfy at sea than our previous, much heavier boat. YMMV, and I'm sure that no one will convince the "heavy" advocates that their opinions are wrong, or that ours could be right... for us!

The issue of performance degradation due to loading has been raised as well. I'd like to point out that for the boats that I have sailed the first place that overloading seems to affect is quickness to surf. While such reluctance reduces the pleasure of downwind sailing for us, in reality, it does not much affect passage times, for the auto pilot isn't too good at following waves! On most points of sail the reduction is less obvious and less of an influence on passage times. My final comment on this subject: while a "performance cruiser" may be more affected by loading than a "traditional" cruiser, it will still be faster!



Good luck with your search

Jim
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Old 29-04-2011, 09:34   #15
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Re: PHRF as estimate of passage making speed

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Originally Posted by Hud3 View Post
As Paul suggests, waterline length is the more pertinent factor.

As a "rule of thumb" plan on making 75-80% of the boat's theoretical Hull Speed as an overall average for long passages. That's held true for me over around 9,000 nm in offshore passages, and some folks I know with many more miles than me seem to agree.
This checks out with my experience. So far my boat has averaged 162 nm per day during passages where I'm sailing around the clock. This means I'm averaging 6.75 knots. This happens to be 79% of my theoretical hull speed.
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