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Old 13-04-2021, 18:15   #1
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Sailboat calculations questions

I’ve been researching sailboats for a few years now and am curious how the sailboat calculations you would find about a specific vessel stack up to real world cruiser experience. As an example I’d like to use the beneteau 36 cc

Per sailboatdata.com

Calculations


S.A./Disp.: 18.09

Disp./Len.: 195.19

Comfort Ratio: 21.61 [ 20 - 30 indicates a coastal cruiser does this mean the vessel is absolutely not suitable for any ocean crossing? Would it be suitable for a trip through the Caribbean or even a coconut milk run?

Capsize Screening Formula: 2.12 [ “the boat is better suited for ocean passages if the result of the calculation is 2.0 or less” I assume this means with full sheets out so in anyone’s expert opinion would this boat be “suitable” for ocean passages with a good captain sailing conservatively at 80%?

Also interested in any other opinions/experience on all sailboat calculations

Sorry this is long winded Thanks for your help!

Fair winds
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Old 13-04-2021, 18:30   #2
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Re: Sailboat calculations questions

The main users of those numbers are journalists having to write something clever about any new boat they've only seen shortly at best and armchair-sailors. Better go out sailing instead of w*nking over ranking lists with those numbers.
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Old 13-04-2021, 18:53   #3
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Well I have solo'd a Bene 321 (2.11) from the Caribe to the UK non stop and a Bene 331 (2.08) from the Caribe to Portugal..
I reckon it'll be just fine..
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Old 13-04-2021, 19:16   #4
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Re: Sailboat calculations questions

Quote:
Originally Posted by Saltandsea View Post
I’ve been researching sailboats for a few years now and am curious how the sailboat calculations you would find about a specific vessel stack up to real world cruiser experience. As an example I’d like to use the beneteau 36 cc

Per sailboatdata.com

Calculations


S.A./Disp.: 18.09

Disp./Len.: 195.19

Comfort Ratio: 21.61 [ 20 - 30 indicates a coastal cruiser does this mean the vessel is absolutely not suitable for any ocean crossing? Would it be suitable for a trip through the Caribbean or even a coconut milk run?

Capsize Screening Formula: 2.12 [ “the boat is better suited for ocean passages if the result of the calculation is 2.0 or less” I assume this means with full sheets out so in anyone’s expert opinion would this boat be “suitable” for ocean passages with a good captain sailing conservatively at 80%?

Also interested in any other opinions/experience on all sailboat calculations

Sorry this is long winded Thanks for your help!

Fair winds
I'll comment on the Comfort Ratio. "Sea Kindly" behavior has always been very important to me, because I enjoy sailing boats long distances. A long trade wind passage is a delight on a good boat, and a miserable experience (for me) on one without good behavior.

I have a couple of boats that I have experience with, and that I have strongly formed opinions about how comfortable they are at sea. I did not know ahead of time what their "Comfort Ratios" were.

Here are the boats and my editorial comment on their sea kindliness:

Cabo Rico 38--Superior
Hughes 40-- Excellent
Hans Christian Cristina 43-- Excellent
Amel Super Maramu 53-- Very Good
Jeanneau Sun Odyssey 49-- TERRIBLE.

Now, the Comfort Ratio for those boats:
Cabo Rico 38-- 40.4
Hughes 40-- 41.1
Hans Christian Cristina 43-- 39.9
Amel Super Maramu-- 32.8
Jeanneau Sun Odyssey 49-- 26.8

For me, the "Comfort Ratio" looks like a useful tool for putting boats into broad categories. But small differences aren't really telling us anything useful.

It can be important to understand what it is that makes a boat "uncomfortable." It is the tendency to "jump" up out of the water when a wave hits the bow, and then (worse!) the tendency to come back down into the water with a SLAM! instead of a gentle Whoosh...

Many of the modern production boats have the kind of broad, flat bottoms, with a very large waterplane area, that I find miserable at sea. Fast and fun for a run across the bay, but most of these boats will teach you very quickly why they call it "beating" when you go to windward in the ocean.

For the boats in my list, the Cabo Rico NEVER pounded. Of course one of the reasons for this was it did not rise quickly to waves, so the deck could be as wet as a half-tide rock. The Hughes would rarely pound down on a wave. Maybe two or four times in a day of upwind work it would smack down hard. With the Amel, it might be every other hour. With the Jeanneau it was SMACK! down into EVERY SINGLE WAVE. Just a miserable ride. You basically were forced to bear off to avoid knocking the filings out of your teeth.

I think what you will find is that people who own boats with "bad" comfort ratios will tell you that the number doesn't mean anything.
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Old 13-04-2021, 19:31   #5
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Re: Sailboat calculations questions

I'd trust Boatie's real world assessment over any raw numbers or calculations.

We've had this discussion here before... the basic numbers and calculations are useful as a first-level look, but all boats are more than the sum of their specs. So the basic numbers and calculations only provide a very limited picture of what the boat is actually like.

One way to use these specs is to start with a boat you know well, and compare it against other similar designs. But as the design range increases, it becomes less and less meaningful. So they're useful -- but only to a rather limited point.

This database is a fun one to play with if you want to do some comparisons, or possibly find a boat that is worth serious investigation (and keeping in mind all the provisos): Sail Calculator Pro v3.54 - 3200+ boats
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Old 13-04-2021, 21:01   #6
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Re: Sailboat calculations questions

Bill, I certainly believe what you have posted here, but I must ask one question: what were the relative speeds of the various boats and what were the actual wind angles achieved?

I suspect that one reason the J was more uncomfortable was that it was going faster and at a smaller AWA than the other boats. When you say you had to bear off, were you then sailing at a similar AWA to the "comfortable" boats when they were pressed up as far as they would go?

Our semi-modern boat will go pretty fast upwind, and in a chop she bangs now and then... whilst making 8-9 knots STW and at 30-32 deg AWA. When that becomes tiresome falling off to ~40 deg AWA and reefing to slow down to ~6-7 knots eliminates pounding and the ride smooths out to pretty comfy. I bet those numbers are not too different from your subject vessels normal upwind-in-a-breeze results, but correct me if I'm wrong on that.

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Old 13-04-2021, 21:32   #7
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Re: Sailboat calculations questions

I think the comfort ratio is pretty useless. Having owned 3 boats that I sailed on offshore passages, the correlation of 'comfort' to Comfort Ratio was closer to inverse than meaningful.
Alberg 35. CR 35
J37. CR 22
Outbound 44 CR 32

No cruising sized boat is comfortable in offshore conditions. We are just talking less uncomfortable. Of the boats above:
Outbound - by far the most comfortable and coincidentally the longest.
J-37 - not bad, but lively
Alberg - pretty uncomfortable in any seas and winds

For me, the Comfort Ratio is meaningless. It was created by Ted Brewer and this is what he said about it:
"This is a ratio that I dreamed up, tongue-in-cheek, as a measure of motion comfort but it has been widely accepted and, indeed, does provide a reasonable comparison between yachts of similar type"
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Old 14-04-2021, 01:37   #8
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Re: Sailboat calculations questions

Greetings and welcome aboard the CF, Saltandsea.
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Old 14-04-2021, 06:17   #9
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Re: Sailboat calculations questions

Quote:
Originally Posted by Jim Cate View Post
Bill, I certainly believe what you have posted here, but I must ask one question: what were the relative speeds of the various boats and what were the actual wind angles achieved?

I suspect that one reason the J was more uncomfortable was that it was going faster and at a smaller AWA than the other boats. When you say you had to bear off, were you then sailing at a similar AWA to the "comfortable" boats when they were pressed up as far as they would go?

Our semi-modern boat will go pretty fast upwind, and in a chop she bangs now and then... whilst making 8-9 knots STW and at 30-32 deg AWA. When that becomes tiresome falling off to ~40 deg AWA and reefing to slow down to ~6-7 knots eliminates pounding and the ride smooths out to pretty comfy. I bet those numbers are not too different from your subject vessels normal upwind-in-a-breeze results, but correct me if I'm wrong on that.

Jim
Jim,

There is a some truth in what you say, after all a Cabo Rico 38 is NOT in the same sped class as an Amel 53 or a Jeanneu 49. BUT... it is a much smaller boat, and usually small boats pay a large penalty in the calculation of the Comfort Ratio.

That said, if I was facing 1000 miles of windward work in the boats listed, the Jeanneau 49 would be my very last choice. It IS a bit faster in light air, than even the larger Amel might be, and maybe a bit more weatherly in calm water. But, my experience in the Jeanneau was that in a lively offshore chop (say beating from Monterey to San Francisco) the amount you had to bear off for comfort was WAY more than the few degrees of pointing performance she had over the other boats.

Of course this whole thing is personnel preference. I might just be a whimp. All those offshore miles might have just beat the piss and vinegar out of me and left me wanting a cushy boat.

Just as an example of how personnel this is, the idea posted above that a J37 is a "comfortable" offshore boat, is--to me--pretty funny. It might be a CAPABLE boat, but comfortable on a long beat??? The poster even described it as "lively", which I guess he doesn't understand is exactly the very opposite of "comfortable."

I am not trying to say that somebody should obsess over two boats that has a comfort ratio of 24 versus 28. But the idea that a boat with a comfort ratio of 25 can have a similar motion at sea to one with a comfort ratio of 40 is just ignoring basic physics.

It is hard for me to imagine anybody ACTUALLY making a boat buying decision based on something as fuzzy and imprecise as the Comfort Ratio. I just can't see ANYBODY coming down to having a hard time picking between two boats, one with a CR of 25 and one with 41. They are just too different in too many other ways.

If I ever have to choose another sailboat to buy, the chances that one with a comfort ratio of less than 30 would show on my menu is vanishingly small, but not because I did any calculations. Boats of that shape just don't have what I want in a long distance cruising boat. Similarly, the chances of me bidding on a long passage delivery of a boat with a CR of less than 23 are also pretty small. I just am not interested in that trip. It's not that I would do that calculation, it is just not a kind of boat I enjoy sailing.

I am not saying that low comfort numbers make bad boats. I am not even saying that boats with uncomfortable sea motions are bad boats. I am saying those are bad boats FOR ME.

A lot of sailors are out there buying boats who have never sailed anything except the typical modern charter boat, and then think they have experienced "different" boats because they have sailed a Jeanneau, a Bendy-toy and a Bavaria. They have no idea what a truly sea-kindly hull sails like. They can insist that the boat THEY own is comfortable, but just have no real idea.
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Old 14-04-2021, 06:24   #10
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Re: Sailboat calculations questions

a lot of the ratios having to do with "comfort" are meaningless if you compare boats build in the 70's to model designs that carry longer waterline length
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Old 14-04-2021, 06:41   #11
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Re: Sailboat calculations questions

Quote:
Originally Posted by BillKny View Post
......

Just as an example of how personnel this is, the idea posted above that a J37 is a "comfortable" offshore boat, is--to me--pretty funny. It might be a CAPABLE boat, but comfortable on a long beat??? The poster even described it as "lively", which I guess he doesn't understand is exactly the very opposite of "comfortable."

....
It maybe pretty funny to you, but its reality to me. I would far rather spend 7 days on passage on my J37 than 10 or 12 days on my Alberg 35. When the J got uncomfortable going to weather we just cracked off bit. We would still be pointing as high or higher than the slow boats and sailing faster with much less sail up(less pressure on everything, more upright), but now it was 'comfortable'. If you'd rather spend another 3 days offshore heeled over on your ass and say this is comfort, then go for it,
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Old 14-04-2021, 06:55   #12
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Re: Sailboat calculations questions

Quote:
Originally Posted by Saltandsea View Post
I’ve been researching sailboats for a few years now and am curious how the sailboat calculations you would find about a specific vessel stack up to real world cruiser experience. As an example I’d like to use the beneteau 36 cc

Per sailboatdata.com

Calculations


S.A./Disp.: 18.09

Disp./Len.: 195.19

Comfort Ratio: 21.61 [ 20 - 30 indicates a coastal cruiser does this mean the vessel is absolutely not suitable for any ocean crossing? Would it be suitable for a trip through the Caribbean or even a coconut milk run?

Capsize Screening Formula: 2.12 [ “the boat is better suited for ocean passages if the result of the calculation is 2.0 or less” I assume this means with full sheets out so in anyone’s expert opinion would this boat be “suitable” for ocean passages with a good captain sailing conservatively at 80%?

Also interested in any other opinions/experience on all sailboat calculations

Sorry this is long winded Thanks for your help!

Fair winds
You can get a lot from those numbers if you know what to look for.

Example.

The boat I'm looking at now is a Southern Cross 31 PHRF 222

SA/Disp Ratio of 12.60.

Disp/Len of 388.57

CR: 37.62

Capsize Screening Formula: 1.59

So it's a heavily built boat and very seaworthy plus has minimal Sail Area so good in a blow especially after reefing etc.

Now contract that with an Olson 30 PHRF about 108.

SA/Disp: 26.5

Disp/Len: 77.28

CR: 10.24

Capsize Screening: 2.40

The Olson 30 has completed multiple Single Handed Transpac Races from San Francisco to Hawaii which is about 2100 miles but if heavy weather were to occur in the middle of that the boat to be on would be the Southern Cross 31.


This is what the numbers tell you. I used extremes for effect.

So if you are old like me and find yourself somehow offshore caught in bad weather and after a few days you are exhausted, a boat like the Southern Cross 31 can save your ass!........but not the Olson 30
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Old 14-04-2021, 07:14   #13
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Re: Sailboat calculations questions

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Originally Posted by thomm225 View Post
You can get a lot from those numbers if you know what to look for.

Example.

The boat I'm looking at now is a Southern Cross 31 PHRF 222

SA/Disp Ratio of 12.60.

Disp/Len of 388.57

CR: 37.62

Capsize Screening Formula: 1.59

So it's a heavily built boat and very seaworthy plus has minimal Sail Area so good in a blow especially after reefing etc.

Now contract that with an Olson 30 PHRF about 108.

SA/Disp: 26.5

Disp/Len: 77.28

CR: 10.24

Capsize Screening: 2.40

The Olson 30 has completed multiple Single Handed Transpac Races from San Francisco to Hawaii which is about 2100 miles but if heavy weather were to occur in the middle of that the boat to be on would be the Southern Cross 31.


This is what the numbers tell you. I used extremes for effect.

So if you are old like me and find yourself somehow offshore caught in bad weather and after a few days you are exhausted, a boat like the Southern Cross 31 can save your ass!........but not the Olson 30
And you know this from what experience? Have you been on multi day passages offshore in serious weather on any boats similar to these?
I already know the answer from your previous posts. It's no, I have no offshore experience in these type boats but I can compare some ratios that someone else cooked up.
So lets take your mythical Transpac and your mythical numbers. Based on the PHRF numbers you posted the Olson should get to Hawaii in about half the time the Southern Cross does. Now which boat is likely to get themselves into serious weather? The one that is out for 10 days or the one for 20 days?
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Old 14-04-2021, 07:28   #14
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Re: Sailboat calculations questions

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And you know this from what experience? Have you been on multi day passages offshore in serious weather on any boats similar to these?
I already know the answer from your previous posts. It's no, I have no offshore experience in these type boats but I can compare some ratios that someone else cooked up.
So lets take your mythical Transpac and your mythical numbers. Based on the PHRF numbers you posted the Olson should get to Hawaii in about half the time the Southern Cross does. Now which boat is likely to get themselves into serious weather? The one that is out for 10 days or the one for 20 days?
Nice.

I don't need the experience as I have the numbers.

Thanks Sailboatdata.

It's a good thing some of us know we don't have to sail across an ocean (boring!) to decide which boat is the right one for us.

As far as the Olson finishing first, that's nice but the scenario was it got caught in bad weather about 1000 miles offshore.

You are spinning the story to suite your argument, but the fact is the Southern Cross can take a pounding from the bad weather whereas the Olson cannot!

I do have experience though on a few boats with these numbers.

Example in video below in case you forgot the type boat I'm speaking of. (the jib isn't on it though in the video) Sounds like the Nacra 6.0 in the video is giving that ole boy a workout! I'm not sure he'd last one of the yearly 100 milers we used to race back in the day.

SA/Disp: 75.41

Disp/Len: 21

PHRF: 67

And now on this Boat

Bristol 27

SA/Disp:14.28

Disp/Len: 383.47

CR: 29.08

Capsize Screening Formula: 1.71

The boat is a total beast.......

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Old 14-04-2021, 07:40   #15
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Re: Sailboat calculations questions

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Originally Posted by thomm225 View Post
Nice.

I don't need the experience as I have the numbers.

Thanks Sailboatdata.

It's a good thing some of us know we don't have to sail across an ocean (boring!) to decide which boat is the right one for us.

As far as the Olson finishing first, that's nice but the scenario was it got caught in bad weather about 1000 miles offshore.

You are spinning the story to suite your argument, but the fact is the Southern Cross can take a pounding from the bad weather whereas the Olson cannot!

I do have experience though on a few boats with these numbers.

Example in video below in case you forgot the type boat I'm speaking of. (the jib isn't on it though in the video) Sounds like the Nacra in the video is giving that ole boy a workout!

SA/Disp: 75.41

Disp/Len: 21

PHRF: 67

And now on this Boat

Bristol 27

SA/Disp:14.28

Disp/Len: 383.47

CR: 29.08

Capsize Screening Formula: 1.71

The boat is a total beast.......
Actually you do need experience to adequately judge the meaning of the ratios to offshore conditions. Only a fool would deny that - maybe a wisefool like a sophmore.
Did you ever read the story of the two J30's that survived the 1979 Fastnet race disaster? It's interesting . Neither of the skippets wanted to be in a different boat.
https://www.jboats.com/j30-articles-...tnet-storm/amp
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