PHRF versus approx. passage times on dif. boats?

[hellosailor]

Just a reality check here.

If two 38' boats are planning to make the same longer passage, say 600 miles, and one boat has a PHRF of 100 while the other is rated 160 (or 80 vs. 140, pick your own pair) then that would mean the boats have relative speed ratings that are different by 60 seconds per mile sailed? SO, one minute per mile, or one hour per 60 miles sailed? So a back of the envelope figure would be that they boats would arrive 10 hours apart a the end of 600 miles, all else being equal and the one not holding back to keep with the slower?

Basically 1/2 day apart, dawn versus dusk, on a 600 mile run, and a full 24 hours apart on a 1200 mile passage?

Or do I have my PHRF ratings all mixed up again? (And yes, I know, those are of limited value for specific conditions only, but it beats "Gee, I think we can make six maybe seven knots" as a starting point.)

[Paul L]

It's in the ballpark, but remember that PHRF ratings are based on a triangle course covering upewnd, downwind and a reach. Your 600 mile passage might be all downwind where one boat may shine over the other despite the rating.

[Don C L]

That is my understanding of it, though I don't claim to be an expert. BUT given the necessity of "all things being equal" I'm not sure it beats out the "gee, I think I can make 6 maybe 7 knots" to predict what will really happen in real life. More importantly, how upset will the owner of the lower PHRF boat be if he or she ends up showing up later than you?

[Jim Cate]

Don't forget that PHRF ratings are derived from boats that were actively racing in official events. This implies that the skipper and crew were staying involved full time with trim, sail selection etc. Extrapolating these figures to cruising conditions, where lots of folks don't pay much attention to trim, is kinda problematical.

And then, some boats need more tweaking than others for max performance, and that too plays a part.

So, while the PHRF ratings do give a general picture of the boats capabilities, there are far too many other variables to make the kind of calculations that you propose. Short of a full velocity prediction workup by a NA, the ol' PHRF may be the best informal yardstick available to you, but that does not make it very accurate (ask anyone who races under the system why they don't win all the time!).

Jim

[osprey877]

Also, dont forget that although the base rating difference is expressed in seconds per mile, in practice the actual handicapping of boats is based on time on time, not time on distance. Obviously 6 seconds a mile is totally inadequate if your 600 mile race is a three week drifter, as opposed to a 3 day downwind sleigh ride.

[Singularity]

FWIW the thread below from 2011 discusses some of the dynamics at play in addressing the question at hand:

PHRF as Estimate of Passage-Making Speed

[Adelie]

Evans Starzinger and Beth Leonard published a formula for estimating daily passages based on SA/D & LWL. Using a database of boats including PHRF ratings I did a regression analysis and found their formula corresponds very well with PHRF ratings. The values their formula gave we’re about 2/3 to 3/4 of what the Rating gave.
I don’t have the formula handy but will look it up tomorrow.

The formula for PHRF is 360sec + rating in sec = sec/nm. Working that out for daily progress:
86,400sec/day / (360s/nm + rating) = progress in nm/d.

[gjorgensen]

As a former local PHRF chair I'd like to correct a couple things people have said. The original post is correct as to use of the handicaps - they're designed to be time on distance, so you're just looking at the difference between the two as seconds per mile. PHRF is almost always handicapped and scored time on distance, not time on time. In many areas the handicap is basically a mash of windward/leeward and random leg formats. In Southern California we actually assign 3 handicaps: W/L, Offwind aka OWC (at least 2/3 of course expected to be offwind), and Random Leg aka RLC (neither W/L or OWC). The handicaps are not typically based on a triangle course.

As others have said, there are enough variables, especially with cruising boats, that the handicaps should be looked at more as a general notion of comparative performance and not precise. PHRF generally handicaps expecting the boat to be in optimal racing condition and at minimum weight, so once loaded down with cruising gear the performance can change radically.

[Fore and Aft]

If you are buying a boat based on PHRF rating alone for cruising you are going to be disappointed. The crews and your ability plays a huge role in how fast a yacht can go.
Cheers

[SailRedemption]

All things equal covers trimming sails and tweaking. A boat that is sailed easily, not trimmed hard or tweaked regularly, with a lower rating will still be faster than a higher rated boat trimmed the exact same.

[Montanan]

Originally Posted by hellosailor

Just a reality check here.

Basically 1/2 day apart, dawn versus dusk, on a 600 mile run, and a full 24 hours apart on a 1200 mile passage?

Or do I have my PHRF ratings all mixed up again? (And yes, I know, those are of limited value for specific conditions only, but it beats "Gee, I think we can make six maybe seven knots" as a starting point.)

Reality check, okay. It appears you are describing a buddy boat situation and a reasonable distance of cruising the sailed boats, i.e., not planning on providing for motor sailing.

If you desire to buddy up, then you match the vessels speeds to accommodate the slower vessels capability and / or desires, end of discussion. If you are sailing from two different locations intending to meet at a common destination, then the two boats will traverse a different course so their arrival is anyone's guess.

You are cruise sailing - duration of journey varies based on conditions and course more than boat type or boat handling. It will be what it will be.

Lest we forget, they are sailboats, they inherently will not travel fast. A half day, full day, or additional days is of what real world consequence in the scheme of the trip? Just enjoy the sailing, more time laying a wake on water and less at anchor or marina the better. If I have to reef down to slow to keep pace for another boat or boats that just makes for greater comfort onboard and more enjoyable time onboard my boat. Similarly as to whether to reef down my boat, I just instruct everyone onboard to just do it if they feel the inclination, there is no debating, or permission expectations, and if they don't know how to reef, then they are just to suggest reefing for others to thence promptly accomplish. The passenger or crew that desires a slower, more level boat sets the tempo on my boat and I am keen on looking out for any discomfort or uneasiness of all onboard, particularly as to providing for the newbies. Simple rule: Destress the boat to destress the persons on the boat or on another's boat. If conditions require to hove-to and not proceed, or to sail away from my intended destination then that is what is to be done, schedules do not come aboard. Similarly as to my business-related or private flying, intended destinations are always optional and as to day or hour of arrival those are not defined. All takeoffs are optional, whereas a landing [somewhere]within a certain framework of hours eventually is a requirement. Whereas a boat one can just wait at sea with the water keeping you up. I prefer to not buddy fly, keeping watch out for another plane is hazardous, putting considerable distance between planes is much preferred; they really don't do well occupying the same hole in the air.

Having found the joy in long distance and of simple day cruising is why I gladly gave up any and all racing habits a long time ago and even longer ago gave up racing against boats of different class, typage, sizes, equipping and crew size or training. The last boat back to the marina is the one who enjoyed spending more time on the water and less time in the club bar. Kind of like playing golf, the person with the highest score garnered more from their golfing experience then the person with the fewest. Particularly if you play like I do, whereby when I tee off I will often attempt to position the ball into a tough lie so as to require the next shot to be more challenging, than say setting cleanly and boringly in the middle of the fairway. So love purposefully putting the ball into a chosen difficult sand bunker to require a skill shot to chip to the green, instead of just chipping to the green. The golf game ends up becoming a skilled called game of golf like calling your shot when playing billiards, why take the easy shot when there is a more challenging shot to be had. Just the opposite of sailing, I don't go looking for rough challenges when boating.

[roland stockham]

This strikes me as rather like looking at the lap times a car makes on a race circuit and then using that to predict how long your daily commute to work will take!!!
If you can get some numbers for noon to noon runs during an ocean crossing that may give you a guide to passage planning speed for different boats. It is still only a guide however as different passages will have very different sea and wind conditions plus all will depend on crew capabilities.
Also remember that most race data will be gained from inshore waters, typically with winds of F3-4 with seas of less than 3/4ft whereas offshore winds are more likely around F5 with 6/8ft seas. One boat may be a flyer in inshore waters but then have to slow significantly offshore to avoid damage to the boat or crew!
Another significant factor is loading. Under race conditions the boat weight will be kept to the absolute minimum. Cruising you will be carrying substantial additional equipment and supplies. On some designs this will have a minimal impact on passage times, with others it can change them drastically or even make the boat unsafe.

A much better point to start would be to look at events like the transatlantic rally and see how the boats perform there.

[SailRedemption]

You guys are missing the "all things being equal". That means weather conditions and loading vessel. That's what that means. A faster PHRF boat will be faster than an equivalent slower PHRF boat driven the same, same sails and trim, loaded the same, in the same weather conditions.

[thomm225]

The PHRF System works pretty well on shorter windward/leeward courses but for an overall distance race or cruise, it doesn't work that well especially if there is only a windward leg or say a reach or just downwind all the way

This is why I liked the downwind starts on distance races with my last boat because it was just as fast as the larger beachcats which had much lower ratings but couldn't stay with them upwind especially if that wind was close to 18, 19 knots

You'd have to know the boats involved, their strengths off the wind and beating, the conditions of the cruise as far as wind direction, etc

Also, as was mentioned, the PHRF Rating especially on boats that race a lot is many times hard to match which is why you sometimes hear folks talk "sailing to it's rating" on certain boats

Then there are boats (and Skippers) that sail better in light winds vs heavy etc

Which is why for many racers we prefer one design.........then all you have to watch for is the guy that tries to bend the rules a bit with unauthorized sails, rudders, masts, daggerboards etc

[roland stockham]

Originally Posted by SailRedemption

You guys are missing the "all things being equal". That means weather conditions and loading vessel. That's what that means. A faster PHRF boat will be faster than an equivalent slower PHRF boat driven the same, same sails and trim, loaded the same, in the same weather conditions.

That would be true ONLY if you add 'sailing in the same conditions of wind, weather and loading as the PHRF was derived in'



So yes handicaps derived from coastal racing work for coastal racing and ones derived from ocean racing work in ocean racing. The point being made is that neither give useful guide to likely cruising performance which involves sailing is significantly different conditions. Hence my suggestion to look at rally performance which is closer to cruising conditions. As far as I know there is no PHRF data set for cruising.