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Old 08-06-2012, 06:26   #121
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Re: Capsize Ratio's

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Originally Posted by sneuman View Post
(...) If you don't believe me, take a look at the results any given year from the Carib 1500 or similar rallies where boats of various designs - ranging from out and out racers to catamarans and heavy cruising designs - are in the pack. The results are illuminating. When you strip away a few outliers, what you find is that the bulk of the mom and pop crews sailing conservative designs do just as well as the same kind of folks sailing those sleeker, more extreme designs.
OK.

I actually meant a different aspect - the actual sailing skills necessary to sail these two different types of designs. Off course, in the end, this leads (should lead) to results when trying to go fast.

So to say, I mean that if you take a mamma and pappa crew sailing a racing design, they will jump into the cruising design and sail her to somewhere. But when you put a m&p sworn cruising crew (no experience with racing boats whatsoever) into a racing design, they will be lost. Maybe the boat will be lost too! ;-)

And I would not 'strip the outliers' either: for they too may be sailed by m&p crews - so, statistically, it is safer to leave them in the picture and see how they performed, then form theories that describe the whole picture.

Anyways. There are so many ways to look at things so we are happy to have this many kinds of boats to chose from.

Hug,
b.
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Old 08-06-2012, 06:33   #122
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Re: Capsize Ratio's

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Originally Posted by barnakiel View Post
OK.

I actually meant a different aspect - the actual sailing skills necessary to sail these two different types of designs. Off course, in the end, this leads (should lead) to results when trying to go fast.

So to say, I mean that if you take a mamma and pappa crew sailing a racing design, they will jump into the cruising design and sail her to somewhere. But when you put a m&p sworn cruising crew (no experience with racing boats whatsoever) into a racing design, they will be lost. Maybe the boat will be lost too! ;-)

And I would not 'strip the outliers' either: for they too may be sailed by m&p crews - so, statistically, it is safer to leave them in the picture and see how they performed, then form theories that describe the whole picture.

Anyways. There are so many ways to look at things so we are happy to have this many kinds of boats to chose from.

Hug,
b.
Fair enough. I see your point. For the record, I am the guy on any daysail or cruise that is annoying the hell out of everyone else because I am constantly tweaking things instead of saying "well, that's good enough." That comes from my days of racing - inexpert as they were.

I'd still argue that a sensible look at how people actually cruise (as opposed to how they say they do) would have you removing the rally outliers. There's really not much difference between catamarans, monos - fin keel/light displacement, full keel/heavy displacement - when you look at how they're crewed and how they place. I realize that cruising class in a rally is not a race per se, but I would argue that most people try within their skill set and comfort level to make the fastest passage possible. I've never been aboard a boat in which the crew didn't desire to get from point A to point B as fast as is practical - it's just human nature.
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Old 08-06-2012, 06:37   #123
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Re: Capsize Ratio's

Read Peter Bruce's "Heavy Weather Sailing" this is the definitive book on heavy weather. Note his comments on what it takes to capsize a boat. The Commission that studied the Fastnet Race came to the conclusion that keel design, weight and depth hard very little influence on Capsizing. Beam had a lot to do with it.

The problem with multihulls is that it takes a lot to tip them over, but once they are over it takes a lot to tip them back again.

Any modern blue water cruising boat should have an AVS of over 140 degrees. less than that and you're asking for trouble.
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Old 08-06-2012, 07:03   #124
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Re: Capsize Ratio's

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I'm not buying this. I have raced and cruised. There is a huge difference in how much the crew is willing to put into the effort day in and day out that has little to do with design and a lot to do with fatigue and comfort.

Within the context of a beer cans race, sure everyone focuses 100% on getting everything out of the boat. Within the context of an offshore race, a crew of dedicated racers put everything into winning, but even that is subject to the fatigue factor.

That is not the same at all as a couple going cruising. Even if that couple is dedicated to keeping the boat well-tuned, they just won't be able to endure getting beat up on a daily basis as they plow through their passage at 9 knots. That makes them a slave to every whim and whiff and frequently is going to make for a lack of comfort. When taking it a bit easier is an option, that's what they'll opt for.

If you don't believe me, take a look at the results any given year from the Carib 1500 or similar rallies where boats of various designs - ranging from out and out racers to catamarans and heavy cruising designs - are in the pack. The results are illuminating. When you strip away a few outliers, what you find is that the bulk of the mom and pop crews sailing conservative designs do just as well as the same kind of folks sailing those sleeker, more extreme designs.
If you have cruised and raced you know that a performance boat has a lot more stability than a cruising boat. It needs that extra stability to be able to carry a lot more sail and go faster.

If you race a performance boat and are utilizing their potential at 100%, for that you need a crew and regarding that what you say is right. But when you cruise alone or with a short crew you are not going to sail the boat at 100% but at 75% or 80% of its capacity.

That will turn that demanding boat in a boat that will be way faster than any heavy cruising boat but that will also be an easy and stiff boat to sail with lot's of reserve stability.
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Old 08-06-2012, 07:09   #125
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Re: Capsize Ratio's

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If you have cruised and raced you know that a performance boat has a lot more stability than a cruising boat. It needs that extra stability to be able to carry a lot more sail and go faster.

If you race a performance boat and are utilizing their potential at 100%, for that you need a crew and regarding that what you say is right. But when you cruise alone or with a short crew you are not going to sail the boat at 100% but at 75% or 80% of its capacity.

That will turn that demanding boat in a boat that will be way faster than any heavy cruising boat but that will also be an easy and stiff boat to sail with lot's of reserve stability.
In ideal conditions, that might be true. In any kind of a slop, especially on a beat, probably not. Regardless of how much ballast there is below, a light displacement boat is more likely to pound into a seaway. Racers will put up with this, but most mom and pop crews will slow down to minimize it.
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Old 08-06-2012, 07:18   #126
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Re: Capsize Ratio's

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...

Any modern blue water cruising boat should have an AVS of over 140 degrees. less than that and you're asking for trouble.
That is a very partial view. The resistance that the boat offer to capsize as its dynamic stability can be a lot more important than a very high AVS.

It is very easy to make a boat with a huge AVS that will be very easy to capsize. Do you rather prefer a boat two times harder to capsize with an 120 AVS to an easily capsized boat with a 140 AVS?

When the boat capsize you lose the rig and will be in trouble anyway.

As you know the modern parameters for an offshore boat are around 120 and regarding AVS even if some have 130 almost none has 140, including Halberg Rassy.

Do you think you are in trouble offshore on a 42ft Halberg Rassy?

If the boat has at least an AVS around 120 a much more important factor (than a bigger AVS) is the proportion between the positive and negative stability and also its overall positive stability.
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Old 08-06-2012, 07:33   #127
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Re: Capsize Ratio's

I agree that the numbers are not the whole story and can be misleading. Unfortunately, without them, the only thing we have to go on is subjective - and few of us (myself included) really have enough experience in a wide enough range of boats to talk authoritatively.
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Old 08-06-2012, 09:02   #128
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Re: Capsize Ratio's

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(...) Any modern blue water cruising boat should have an AVS of over 140 degrees. less than that and you're asking for trouble.
I will disagree.

http://www.hallberg-rassy.com/filead...ilitycurve.jpg

This is the smallest of the range. I believe the figure here @ roughly 125 degs and this is for boat not loaded with cruising junk (radars, arches, solar panels, dinghies on deck, etc., etc.) that deducts from the figure (also using some water and fuel will drive the figure lower).

Hence, all HR designs (and I bet a huge majority of other major players) would be 'asking for trouble'.

Cheers,
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Old 08-06-2012, 09:06   #129
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Re: Capsize Ratio's

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Originally Posted by sneuman View Post
I agree that the numbers are not the whole story and can be misleading. Unfortunately, without them, the only thing we have to go on is subjective - and few of us (myself included) really have enough experience in a wide enough range of boats to talk authoritatively.
I am not saying that the numbers (stability data) are not important. Quite the contrary, what I am saying is that it is not the AVS that is important but all the stability data given by a stability curve, including the amount of positive stability and its relation with the negative stability, the down-flooding angle, the force the boat is making to right itself up at 80, 90 and 100 ...and of course the AVS, that looked isolated from all other data can be misleading regarding the boat stability.
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Old 08-06-2012, 09:06   #130
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Re: Capsize Ratio's

Sure if you want to sell me two IDENTICAL boats and one of them has AVS 150 and the other 110 then I may strongly lean towards the first one!

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Old 08-06-2012, 09:07   #131
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Re: Capsize Ratio's

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Originally Posted by barnakiel View Post
I will disagree.

http://www.hallberg-rassy.com/filead...ilitycurve.jpg

This is the smallest of the range. I believe the figure here @ roughly 125 degs and this is for boat not loaded with cruising junk (radars, arches, solar panels, dinghies on deck, etc., etc.) that deducts from the figure (also using some water and fuel will drive the figure lower).

Hence, all HR designs (and I bet a huge majority of other major players) would be 'asking for trouble'.

Cheers,
b.
Does it always deduct? I think it matters where the stuff is - yes, a lot of it is going to be above the waterline, but at least fuel/fresh water tanks often are below the waterline (my 90-gallon H20 is) and that, in theory, ought to increase AVS, no?
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Old 08-06-2012, 09:20   #132
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Re: Capsize Ratio's

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I will disagree.

http://www.hallberg-rassy.com/filead...ilitycurve.jpg

This is the smallest of the range. I believe the figure here @ roughly 125 degs and this is for boat not loaded with cruising junk (radars, arches, solar panels, dinghies on deck, etc., etc.) that deducts from the figure (also using some water and fuel will drive the figure lower).

Hence, all HR designs (and I bet a huge majority of other major players) would be 'asking for trouble'.

Cheers,
b.
That's what I said you have implied

Can't you see it does not make sense?

It is common knowledge, based in many years of bluewater experience that Halberg-Rassy are very good and safe bluewater boats. I don't remember of a single one to have capsized and these boats are used extensively offshore.

Do you really think that someone that is going offshore with an Halberg-Rassy is asking for trouble?

...
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Old 08-06-2012, 09:25   #133
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Re: Capsize Ratio's

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Sure if you want to sell me two IDENTICAL boats and one of them has AVS 150 and the other 110 then I may strongly lean towards the first one!

Love,
b.
Who is talking about similar boats? The boats that have very high AVS figures normally have a lot less positive stability than boats with more moderated Avs.
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Old 08-06-2012, 09:26   #134
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Re: Capsize Ratio's

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In ideal conditions, that might be true. In any kind of a slop, especially on a beat, probably not. Regardless of how much ballast there is below, a light displacement boat is more likely to pound into a seaway. Racers will put up with this, but most mom and pop crews will slow down to minimize it.
this issue of "Pounding" in a light desplacement boat is a by-product of its speed and not its design or weight..
its like compairing a "bunt" of a baseball compaired to a hard hit.. the bunt will deliver a thud where a hard hit will deliver a crack.. same ball, same bat, but the speed of the hit will change..
the same is true with a fast boat compared to a full desplacement heavy boat..
the by product of the faster speed will cause the pounding as the speed increeses over the water.. A full keel heavyweight wont pound because it wont go fast enough to deliver the noise....
our boat, weighing in at 24k will pound going to weather at 10 to 12 knots, but if we back it off to a speed of 5 or 6, she calmly rides the waves like a full keel heavyweight..
The difference is that I can turn her off the crest about 4 or 5 degrees and the pounding stops.. and the speed goes up..
If you're sailing the boat to the point its pounding, just turn off a few degrees, its better on you and the boat..
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Old 08-06-2012, 09:29   #135
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Re: Capsize Ratio's

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this issue of "Pounding" in a light desplacement boat is a by-product of its speed and not its design or weight..
its like compairing a "bunt" of a baseball compaired to a hard hit.. the bunt will deliver a thud where a hard hit will deliver a crack.. same ball, same bat, but the speed of the hit will change..
the same is true with a fast boat compared to a full desplacement heavy boat..
the by product of the faster speed will cause the pounding as the speed increeses over the water.. A full keel heavyweight wont pound because it wont go fast enough to deliver the noise....
our boat, weighing in at 24k will pound going to weather at 10 to 12 knots, but if we back it off to a speed of 5 or 6, she calmly rides the waves like a full keel heavyweight..
The difference is that I can turn her off the crest about 4 or 5 degrees and the pounding stops.. and the speed goes up..
If you're sailing the boat to the point its pounding, just turn off a few degrees, its better on you and the boat..
Either way, the result is the same: Mom & pop dial it back, thus diminishing the advantages of the faster boat.
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