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Old 04-05-2015, 06:48   #391
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Re: The criteria of "blue"

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Originally Posted by Jon Eisberg View Post
I'm guessing few who have ever put the spreaders of a cruising boat in the water offshore would make such observations so casually... :-)

Here's what Evans Starzinger had to say a few years back about the centerboarders they had encountered "Down South"...
It mentioned the contessa 32 was going over more frequently.

"A contenssa 32 we know got spreaders in the water 7 times from the Falklands to Cape Town, and that's a pretty stable boat for her size."

The contessa has an avs of (155) which is very high. It kinda show that if you spread your righting moment over a wider angle it is easier to go over because you have not got your maximum righting forces where they are really needed - at around 50 - 60 degrees. You simply cant have it both ways.

You pray to the initial stability God or the AVS God. I want my maximum defence a long ways before 155 degrees. 60 seems to be the norm but the contessa 32 gives it's peak at 80. Why? Not sure I understand this because at 60 you lose most load from the sail anyway.

To be honest I can see why the contessa would be flat lining a lot based on its stability curve. It provides for a lot of momentum to be carried to that 80 degree mark undermining it's peak counter righting force at that mark. Seems silly to me.
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Old 04-05-2015, 06:51   #392
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Re: The criteria of "blue"

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Most of the fin keel cruisers have low AVS..
Might be so but it's got nothing to do with the fin keel itself. What affects most to AVS is the CG, the height and the volume of the top sides and the cabin. In this regard pilothouses are a big bonus. Remember CB is dynamic ie allways on the move..
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Old 04-05-2015, 07:35   #393
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Re: The criteria of "blue"

Lets be honest. A lot of people want a catamaran because of the initial stability it gives. However, that same lot of people are put off because it can not self right in the event of a capsize but if it could self right lets face it, it would also not be in the space of 30 seconds either. But.. Just that little notion of can would be the difference for a lot more people moving to a cat as their preferred choice.

I would much rather have a boat that gives a lot of resistance to going over in the first place that would take longer to self right than a boat that goes over too easily and comes back up fast - This would provide something a bit too wobbly for me in general use.

A boat that did the former that could also provide protection for crew and boat whilst inverted with a method that could be followed for self righting to me would be more "blue" than the latter.

We simply can not build sailing boats like motorised life boats with big bubbles of buoyancy in the center line of the coach roof. If we could we would see them sailing but we don't
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Old 04-05-2015, 08:09   #394
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Re: The criteria of "blue"

If you can give me a boat that has its maximum righting force at between 55 and 65 degrees but also has an AVS of 155 and a fin keel of course I will take it, but don't think it exists and that would stop me showing off my party trick in the Bahamas of being able to cruise in 3 foot of water.
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Old 04-05-2015, 08:18   #395
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Re: The criteria of "blue"

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It mentioned the contessa 32 was going over more frequently.

"A contenssa 32 we know got spreaders in the water 7 times from the Falklands to Cape Town, and that's a pretty stable boat for her size."

The contessa has an avs of (155) which is very high. It kinda show that if you spread your righting moment over a wider angle it is easier to go over because you have not got your maximum righting forces where they are really needed - at around 50 - 60 degrees. You simply cant have it both ways.

You pray to the initial stability God or the AVS God. I want my maximum defence a long ways before 155 degrees. 60 seems to be the norm but the contessa 32 gives it's peak at 80. Why? Not sure I understand this because at 60 you lose most load from the sail anyway.

To be honest I can see why the contessa would be flat lining a lot based on its stability curve. It provides for a lot of momentum to be carried to that 80 degree mark undermining it's peak counter righting force at that mark. Seems silly to me.
As a foot note I would suggest that this contessa 32 boat would be a real pain to self right beyond 155 as well because if you look at the curve it seems to have a lot of reserve buoyancy high up on each side. So those 50 degrees of inversion look quite stable to me but I am using amateur eyes and knowledge so could be totally wrong.
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Old 04-05-2015, 08:41   #396
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Re: The criteria of "blue"

The ISO Stix test is performed against the most adverse dynamic. This means a boat with a lifting keel will have its righting force and AVS measured with the keel "up" so in the real world you will have better capability with the keel down such as crossing an ocean.


Maybe this better than the feel 44 http://www.southerly.com/yachts/sout...imensions.html
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Old 04-05-2015, 11:16   #397
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Re: The criteria of "blue"

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The ISO Stix test is performed against the most adverse dynamic. This means a boat with a lifting keel will have its righting force and AVS measured with the keel "up" so in the real world you will have better capability with the keel down such as crossing an ocean.
And why assume keel down?

I thought one of the benefits of a lifting keel is the skidding factor. You drop the keel, you lose the skidding befefit.

Now I say in real world you will have way less as in a boat without deep bilge all your cruising stuff will be likely stored well above the center of gravity of the factory calculated boat.

Not to say the boat is no good, only to point out that our assumptions should be realistic rather than best scenario.

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Old 04-05-2015, 11:24   #398
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Re: The criteria of "blue"

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And why assume keel down?

I thought one of the benefits of a lifting keel is the skidding factor. You drop the keel, you lose the skidding befefit.

Now I say in real world you will have way less as in a boat without deep bilge all your cruising stuff will be likely stored well above the center of gravity of the factory calculated boat.

Not to say the boat is no good, only to point out that our assumptions should be realistic rather than best scenario.

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You mean the wifes clutter has to be above the boards coz no room under the boards? ok.. changed my mind - give me normal.
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Old 04-05-2015, 12:49   #399
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Re: The criteria of "blue"

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...Category A boat limits are ..... This means that all but a very few new monohull ballasted sailing boats sold in the EU will have had a GZ/RM curve generated, their displacement and AVS determined and a STIX calculated.
This is of great interest to me (you may have noticed) so thanks for providing specifics that I didn't want to have to read the entire standard to find out.

BUT remember those standards are a minimum for offshore - a compromise agreed by committee - Doane (Modern Cruising Sailboats) quotes other designers as recommending higher than the minimum. Some of us down here are straight out into the roaring 40s, so we can't do compromise - blue must mean 'blue'.
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Old 04-05-2015, 13:14   #400
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Re: The criteria of "blue"

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This is of great interest to me (you may have noticed) so thanks for providing specifics that I didn't want to have to read the entire standard to find out.

BUT remember those standards are a minimum for offshore - a compromise agreed by committee - Doane (Modern Cruising Sailboats) quotes other designers as recommending higher than the minimum. Some of us down here are straight out into the roaring 40s, so we can't do compromise - blue must mean 'blue'.
You are quite right. There are oceans and then there are Oceans...

I can not find any requirement that dictates a boat should be able to withstand Beaufort scale 10 and above to qualify as Cat A. There is no A+ (Maybe there should be)

Maybe some one else can find reference to storm and hurricane forces with respect to a boats sea worthiness and expectation as a written standard but I can't. It simply seems that beyond force 9 it becomes a place where there be dragons and you make your own choices about boats and say your own prayers to Neptune. I think the ocean around New Zealand is one of those places where there be dragons.
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Old 04-05-2015, 13:19   #401
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Re: The criteria of "blue"

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Maybe this better than the feel(ing) 44: Southerly 38 - Dimensions
For two superficially similar lift-keel yachts, those stats on AVS and STIX say it all - the Southerly range of yachts are light-years ahead, right up there with the (fixed keel) Nautor Swans, taking out the top rankings for stability. (It may be that the fixed keel option was the one measured but the drop keel isn't far behind.) If the other design features of the Southerly range of yachts stack up then there's no contest.
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Old 04-05-2015, 13:44   #402
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Re: The criteria of "blue"

The last thing we need is more regulation. If you had a blue water standard it would be only a matter of time before you would be banned from going to sea in anything less. People should have the right to go to see in what ever they wish. Some of us will choose a boat with blue water credentials and some will not. My boat was built in an era before reliable weather forecasts were the norm. It was built and designed to cross oceans. One survived a Cat 4 hurricane in the Pacific in the 1980s. It wouldn't be everybody's ideal boat but it is mine. I guess that's why there are so many different boats out there. Everybody has a different idea about what is right for them.


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Old 04-05-2015, 13:46   #403
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Re: The criteria of "blue"

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For two superficially similar lift-keel yachts, those stats on AVS and STIX say it all - the Southerly range of yachts are light-years ahead, right up there with the (fixed keel) Nautor Swans, taking out the top rankings for stability. (It may be that the fixed keel option was the one measured but the drop keel isn't far behind.) If the other design features of the Southerly range of yachts stack up then there's no contest.
The favourable figure is because the keel used on the southerly is ballasted. Weighs a lot. The keel on the feeling 44 however is just a fin with the ballast inside the keel so there is no negligible difference with the fin up or down with respect to righting forces.

The southerly though changes the centre of gravity when the keel is lowered which gives more righting resistance equal to that of a fixed keel.

Dynamic ballasted swing keels are a lot more money. There is a lot of heavy engineering involved over the simple fin with ballast inside the hull.
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Old 04-05-2015, 13:56   #404
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pirate Re: The criteria of "blue"

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Originally Posted by jwcolby54 View Post
BTW, one of the things that the pardeys mention is that ifshe as permittingou just continue to sail "downwind", you just stay in the storm longer. "Heaving to" if it works, allows the storm to go past you and leaves you behind it when it is over.
Wow... Talk about stating the obvious
. Cat sailors may bullshit about outrunning storms but they have t.o be pretty special to do that.. Lagoons and the like definitely do not.
Heave to.. Make a brew.. have a read or a kip then carry on when it drops to a 6.. se
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Old 04-05-2015, 13:58   #405
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Re: The criteria of "blue"

Designers just need to build a women's shoe lockers into the bilge and then there would more than enough ballast to stop a boat tipping. Designers are missing a trick
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