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  #1  
Old 07-26-2014
Mr. Bill
 
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PHRF Rating Vs Miles/Day

When reviewing all the criteria for a good cruising boat, is there a loose correlation between a PHRF rating, to an average 24hr daily distance made good?
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Old 07-26-2014
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Re: PHRF Rating Vs Miles/Day

A very loose one at best I would think. A PHRF rating I think includes all points of sail and would certainly consider windward ability. When you are doing long distance cruising you generally are well off the wind. So a boat rating 120 will be faster than one rating 150 but not particularly by 30 sec/mi, could be more, could be less.
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Old 07-26-2014
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Re: PHRF Rating Vs Miles/Day

I've been following Webb Chiles latest voyage in his Moore 24, rated at 150, which is equal, if not faster than many cruisers. Without plotting his actual progress, it looks like he's averaging around 135 miles/day.
So I guess my question is, what's a reasonable 24hr mileage, and how did I evaluate different performance based boats.
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Old 07-26-2014
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Re: PHRF Rating Vs Miles/Day

Some body posted an article link the other day, where DWL is probably the most important factor to how well/fast one can go vs other factors from a distance per day cruising. 135 per the article, IIRC was actually pretty ave to slightly above ave. 200 miles seems to be the perverbial this is what one shoots for, but with leeway, having to not do the actual straight line course etc, this does not work unless you can always go 8+ knots IIRC 24-7, which one needs a 60+foot WL to equal that. Yeah a 36-40' boat has a deisp speed of 8+, but can one go the full speed ALL the time? probably not, so the actual "sq root of wl" vs "sr x 1.34" is probably a better hourly speed one can go.

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Old 07-26-2014
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Re: PHRF Rating Vs Miles/Day

PHRF makes a lot of assumptions about the condition of the boat and crew. It assumes good sails, clean bottom, proper sail changes, a full crew and so on. Few cruising boats come close to meeting the expectations implied by the PHRF. In reality there can be differences between the performance that might be anticipated from the rating when comparing one boat to another. Generally boats with easily driven hull forms and a long waterline relative to its length overall will have an easier time sailing closer to its rating than boats with a lot of drag or a shorter waterline.

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Old 07-26-2014
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Re: PHRF Rating Vs Miles/Day

Something else to think about for long distance cruising is that expectations matter a lot. When I had a 35 footer (Niagara 35) I would do my planning using 100 miles per day. In good, off the wind conditions I would generally do 120 or more (5 knots). Sometimes we would do much better. We once did 191 but we had a favourable current, perfect waves for surfing, you name it. This was faster than our theoretical hull speed but it was one of these perfect condition times - I actually was doing all I could to slow down, without much success.

With the new boat, a heavy solid 45 footer with a large rig, I use 120 mile days for planning but in trade wind conditions we generally do 130 to 170 days. Our best was 211 in the Indian Ocean but I think we had a good knot or more of current. Going from Norfolk to USVI we averaged more than 170 for more than a week, but it was 30 knot plus winds from a great direction. We also wanted to get south quickly before a big depression got any worse so were pushing it a bit with a crew of four. If it had been just June and I we would have slowed down a bit.

In general, you compare your progress to boats that are similar. There is no point in comparing our boat to a Westsail 32 on one side or an X-50 (something) with a crew of about six young strong guys that we saw in Mauritius.
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Old 07-26-2014
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Re: PHRF Rating Vs Miles/Day

"is there a loose correlation between a PHRF rating, to an average 24hr daily distance made good? "

In the simplest sense, yes. A boat with a faster rating will typically cover more miles per day.

Some boats are notoriously off their ratings under some conditions, though. A boat which normally races with a crew of six--and uses three of them as live ballast--will not be able to keep level and maintain that speed if only two people are cruising on it. That's the kind of stuff that makes PHRF a bad way to make comparisons, unless you are aware of the limits.

PHRF also measures boatspeed as an average, on and off the wind, as you'd have in a typical triangle course. And again, some boats are notorious for having one point of sail that really skews the average.

And as has been suggested, of course cruisers tend to be loaded down more, with older sails, that are not being trimmed as intensively and perhaps simply not as critically. They won't be diving on the bottom every week, or longboarding it every haul.

So generally? If you're looking for a boat that will cruise ### miles per day, find cruisers who have routinely logged that, in that boat. If you're just trying to get a sense of "is this boat faster than that boat?" then PHRF isn't a bad way to start.
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Old 07-26-2014
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Re: PHRF Rating Vs Miles/Day

Thanks everyone. I know there are a hundred factors that make a great cruiser, with speed just one of the many variables, and compromises. And I souse that if your longest passage 3 weeks, a couple days one way or another won't matter.
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Old 07-27-2014
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Re: PHRF Rating Vs Miles/Day

If you run the numbers...

Taking two similar boats a J-35 and a J-30. Both are former race boats, and have a phrf split around here of 63sec/mile (75 and 138). Assuming the J-30 in a day will do 100 miles, then the numbers indicate that the J-35 will have sailed that 100miles in 22:45:00. Now the J-30 would have sailed at an average of 4.1666knots. The J-35 would have sailed at 4.3956 knots. So over the course of the day the J-35 would have sailed ~105.5nm.

Others have pointed out that there are a lot of other things that come into play, and I will point out a few more... Planning hull boats will absolutely destroy their phrf numbers in a downwind course, but will sail much slower than it going upwind. Something like an Open 60 is absolutely capable of 500nm days downwind, but will be no faster beating than any other 60' boat. So it is important to understand the specific boats in question.

There is also load carrying. If you assume that you will need to bring 10lbs of food/water/stuff per person per day, a large boat has a few advantages... One they can absorb the weight much easier. Just because their lb/in immersion is going to be so much higher. So on a large boat a few thousand pounds may not matter much, while on a small boat it may be an appreciable amount of total displacement. The extra speed from waterline also means you don't need to carry as much, which makes you faster still.

There is also a crew issue. Long distance sailing on small boats is uncomfortable. The boat is constantly moving up and down waves, speeding up and slowing down, heeling over as a gust hits, ect. The larger the boat the less these small variations effect the boat, which makes it more comfortable. This means the crew is fresher, more likely to keep their head in the game, better rested, ect...


All in all for distance sailing a bigger boat (to a point) is more comfortable, and much faster. PHRF may indicate this, but does a poor job making allowances for it.
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Re: PHRF Rating Vs Miles/Day

Quote:
Originally Posted by e-27 sailor View Post
Thanks everyone. I know there are a hundred factors that make a great cruiser, with speed just one of the many variables, and compromises. And I souse that if your longest passage 3 weeks, a couple days one way or another won't matter.
Like everything else, it depends. Unless you are one of those who enjoys being at sea more than getting to your destination it is nice to get there. We met a guy in Fiji who cruised on a Pearson 36 and only used his working jib (not jib and main, just the jib). He figured on 50 miles day and was happy since he said he had lots of food, water, and books. Of course he eventually lost his boat. The longer a passage takes the more risk there is from weather and the more wear and tear on boat and crew. The general wisdom is that when you go from Tonga to New Zealand you are going to get one pasting. If your boat is really fast, perhaps you can get a weather window and avoid this. If your boat is really slow you may get two (three?).
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