PHRF as Estimate of Passage-Making Speed

[Jon D]

I think Jim Cate summed it up well, PHRF ratings can serve as one data point, just as water length will etc. I also found Sail Area/displacement ratio was also valuable. Boats without enough sail area don't move well in light air or they are forced to use very large overlapping headsails.

I too have found using 75% or so of waterline hull speed works well for passage estimating.

[zeehag]

do you want comfort while passage making or speed---LOL.. good luck..i prefer comfort.

[FecklessDolphin]

Thank you for all your thoughtful comments regarding PHRF's. The Alden will probably stretch our budget too much, but I do like its lines and the low PHRF has seemed attractive compared to that of the Mason which also has beautiful lines to me. The Passport and the Valliant seem like good choices when I am being level-headed, but share the higher PHRF. Like Jim Cate, I am interested in sailing performance. Not that I am in a hurry to get anywhere, just that my boats so far have been a Laser (at age 14 I saved enough), a Hobie 18 and a J/27 (which my son and I lived on for a week). Safety will far outweigh performance given that this boat will be used for a family cruise, so I end up dreaming of a boat like an Alden which seems like a solid boat that will still be fun for dad to go out and single-hand for a week's vacation and which can still beat away from a lee shore and which might not break up right away if we end up on a reef. I am still probably 5 years out from an actual purchase (wife is pregnant with our second, so probably no trips for a while) but we are putting away money in a boat fund (invested in treasury bonds) and I am always trying to figure out if I will have saved enough for a boat and a couple years off work.

[FecklessDolphin]

i guess my question regarding Zeehag's point is whether you can get both comfort and speed by paying enough. Does spending the money for, say an Alden or an Oyster, buy you a low PHRF as well as comfort? And if so what are the design features that would enable having both? (Displacement and length both cost more, of course.) Are these boats overpowered, leading to a lower PHRF, but seldom cruised under full sail?

[boatman61]

Originally Posted by FecklessDolphin

i guess my question regarding Zeehag's point is whether you can get both comfort and speed by paying enough. Does spending the money for, say an Alden or an Oyster, buy you a low PHRF as well as comfort? And if so what are the design features that would enable having both? (Displacement and length both cost more, of course.) Are these boats overpowered, leading to a lower PHRF, but seldom cruised under full sail?

Its basically down to how one sails the boat... on long crossings I sail with two reefs in the main maybe 80% of the time and every night from sundown... just use the Genny for power and the main as a steadier... furl as required to maintain comfort/speed ratio..
My last solo in a Bendi 331 took me 23 days St Martin to the Azores so I averaged over 100 comfortable miles/day...
Just half a knot less can make life so much better sometimes...

[S/V Alchemy]

This was precisely the logic we used in deciding on a steel sailboat that is shading into "motorsailer" territory. We can carry a fair bit of sail in a stiff wind and have a comfortable ride at 7 knots, and we HAVE to carry ALL sail below 15 knots apparent if we hope to stay above 5 knots, although I am planning to carry a large crusing spinnaker to increase light air performance.

The argument that going around the world at 10 knots is better than 5 knots ignores the existence of jet planes. A boat is about the process. I would prefer a faster smaller boat, because there's a limit to the food, water and fuel capacities, so you will trade comfort for "range" and zip from point to point. At the 40 foot plus point, however, the argument in favour of Slow(er) but Steady begins to dominate. Outside of whole gales, we won't often choose to heave to, and we will arguably be better rested just plugging along.

100 miles a day is indeed comfortable, and if you can do that EVERY DAY averaged out, you'll not be far off so-called faster boats.

It's important to realize, though, that apart from planing, massively canvassed ocean racers, the difference between a $750,000 new French 45-footer and a beat-up Westsail 32 is the difference between a fast jog and a slower jog. I know which boat is cheaper to own. Me, I wouldn't have either boat for distance voyaging, but they define the outliers of what is desirable and affordable.

[estarzinger]

Originally Posted by FecklessDolphin

comfort . . . speed . . . what are the design features that would enable having both? l?

Three quick comments:

1. First, just to set your absolute expectations correctly - ALL cruising boats are slow and uncomfortable at sea. If comfort and speed are high in your life priorities I would suggest a cruise ship or a plane.

ok so its all about relative discomfort and slowness.

2. Second, on relative slowness - We did a bit of a study on actual real world passage speed and the best model we found was actual knots achieved = 2.62 + 0.066*SA/D ratio + 0.051*LWL in feet. That seems to be pretty good +-5%. But do realize the sailors have as much (if not more) to do with actual speed acheived as the vessel.

3. Third, on relative discomfort - This is much more subjective. For physical comfort many would say the more waterline (first priority) and the most displacement (second priority), and the more systems (from nice hot showers to roller furling to radar) (third priority) you can buy and maintain the less the discomfort. Of course each of these costs extra money. But 'mental comfort or piece of mind' might be found in other factors (like smaller, simpler, stronger).

[S/V Alchemy]

Evans, you forgot the discomfort factor inherent in "more systems": more time spent upside down in the bilge attempting to tighten a hose clamp in a gale because something put in a spot inaccessible to a greased contortionist has shaken loose due to normal conditions.

If you start from the idea that cruising is "assisted camping", with limited (footpump/shower bag on boom) water and limited (has the sun shone/did the wind blow? OK, we get a DVD tonight) electrical use, you can enjoy what you have.

In fact, I recommend a month in the woods with a 10 mile hike to town as a reasonable simulation of camping. If you emerge reasonably clean, only slightly bruised and less than 10 pounds lighter, you are going to find even a stripped out cruiser luxurious (your books will stay drier and the butter won't melt in the ice box as quickly) and the possibility of a bear attack goes way down.

The "mental comfort" idea is too often ignored when choosing a cruiser. Money and a heavy load of maintenance can indeed make a floating condo in which a cold beer, microwave popcorn and very small loads of laundry can be produced, but you have to service a miniature power station, a tiny water purification plant, a Munchkin sewage facility and we haven't even sailed the boat yet.

If you want to go sailing, I believe simplicity and a liking for "freedom from amenities" is key. If you like spending weeks rolling at anchor until some critical expensive part is shipped to your tropical paradise so that you can replicate technologies found in the meanest of student digs, go for it. I'll need to make money on passage, and over-equipped fellow cruisers are a good place to start.

[Jon D]

Originally Posted by FecklessDolphin

i guess my question regarding Zeehag's point is whether you can get both comfort and speed by paying enough. Does spending the money for, say an Alden or an Oyster, buy you a low PHRF as well as comfort? And if so what are the design features that would enable having both? (Displacement and length both cost more, of course.) Are these boats overpowered, leading to a lower PHRF, but seldom cruised under full sail?

Yes is the answer. FWIW we routinely sail with a full main and working jib, boat is under control easy to reef down and see 7.5 knots often. Avg passages are in the 150-175 mi/day depending.

[chuckr]

we learned from some old cruisers a long time ago to throw all the ratings out the window when cruising --
1st we sail a 2001 jeanneau ds40 and she can be quite fast if we get things right and we have been out 4 years
BUT - we calculate all passges on 5k regardless of where we are going - we would rather arrive early and lay off than late have a real problem - we usually do a lot better than 5k but for us it works -
if plan on faster speed and don't make it, as paul put it you could end up with a real problem that you do not want to consider

just our opinion and how we do things
chuck patty and svsoulmates
rio dulce guatemala - outbound in 9 days toward points south wx permitting

[perchance]

Originally Posted by chuckr

we learned from some old cruisers a long time ago to throw all the ratings out the window when cruising --
1st we sail a 2001 jeanneau ds40 and she can be quite fast if we get things right and we have been out 4 years
BUT - we calculate all passges on 5k regardless of where we are going - we would rather arrive early and lay off than late have a real problem - we usually do a lot better than 5k but for us it works -
if plan on faster speed and don't make it, as paul put it you could end up with a real problem that you do not want to consider

just our opinion and how we do things
chuck patty and svsoulmates
rio dulce guatemala - outbound in 9 days toward points south wx permitting

That is a very good strategy for maximizing the life of the sails and rigging. The harder you drive the boat the more stress you put on the gear.

[Adelie]

There are 2 basic extremes to consider.

On a long passage if you have good consistant winds LWL is going to be a good predictor of how you do relative to other boats on the same passage.

The other extreme is having light winds in which SA/D (D being 1/2 load displacement) is going to be the better predictor.

Reality is likely to be a mix of both with occasional heavy air conditions thrown in for good measure in which case there is a different set of measures still that you want to consider.

[zeehag]

comfort is not the number of systems and amount of STUFF ye has--is how the boat moves in the water and thru it---- you will learn....eventually!

[estarzinger]

Originally Posted by zeehag

comfort is not the number of systems and amount of STUFF ye has--is how the boat moves in the water and thru it---- you will learn....eventually!

I shall wait to be instructed by experts such as yourself!

A hot shower and a cold fresh squeezed orange juice rate pretty highly on my 'comfort' index.

[Hud3]

Originally Posted by estarzinger

...We did a bit of a study on actual real world passage speed and the best model we found was actual knots achieved = 2.62 + 0.066*SA/D ratio + 0.051*LWL in feet. That seems to be pretty good +-5%. But do realize the sailors have as much (if not more) to do with actual speed acheived as the vessel...

Evans, I was curious how your formula would work for my boat, so I ran the numbers through your formula, and came up with 5.5 knots, which is 72% of the theoretical Hull Speed.

Our actual average SOG on offshore passages (~9,000 nm) was 6.3 kts, which equates to 83% of Hull Speed. Most of that sailing was broad or beam reaching, with with maybe 20% close reaching. For passage planning, I always used 75% of Hull Speed, slightly above the speed your formula yields.