Pros and cons of steel sailboats - Page 202 - SailNet Community
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post #2011 of 5317 Old 10-31-2013
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Re: Pros and cons of steel sailboats

Jabber:
I would think that is a good question for your designer and not the internet.

Marty:
The design team, me, Tim O'Connell and Jody Culbertson is hot on the new project now. We ared we3ll into the 3D modelling and working on deck structure details now. But I'm going to let the client decide when to let the project loose. There is no sense and a hell of a lot of frustration being asked to explain and defend details when the boat is still in a preliminary form. Just be ready to see something a bit different.

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Last edited by bobperry; 10-31-2013 at 10:14 AM.
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post #2012 of 5317 Old 10-31-2013
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Re: Pros and cons of steel sailboats

Bob,

That is all I need, I was looking for the thread on SA the other day, did not see anything. I knew the owner would let it out of the bag. Was wondering if I had missed it.

Anyway, have a happy halloween, and off to work with me.......may try to check out sliver if I get over there today.

Marty

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I drives me dinghy!
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post #2013 of 5317 Old 10-31-2013
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by Jabberwock View Post
That's very interesting! I read something years ago like that. It's interesting to me now because I'm currently having a boat designed with a lifting keel and I was wondering if would ever be a good Idea to the partially lift the keel up in a storm. I could see it putting less stress on the boat but the question is would it actually be a strategy to reduce the chance of roll over? If it is, it's kind of counter intuitive.

Edit: Mehhh, I guess I should have read down a bit. But it's still a question in my mind.
It depends on the type of hull and if the keel is ballasted or is just a centerboard without any considerable weight. If it is a beamy hull I would say yes, assuming you are talking of a centerboard and the ballast is not on the keel.

That is the recommendation that the manufacturesrs of French aluminium center boarders make to their clients.

Regards

Paulo


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post #2014 of 5317 Old 10-31-2013
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Re: Pros and cons of steel sailboats

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Originally Posted by PCP View Post
It depends on the type of hull and if the keel is ballasted or is just a centerboard without any considerable weight. If it is a beamy hull I would say yes, assuming you are talking of a centerboard and the ballast is not on the keel.

That is the recommendation that the manufacturesrs of French aluminium center boarders make to their clients.

Regards

Paulo
Hmmmm? Well in my case she's a narrow boat and the ballast is on a bulb down low, so maybe that's a "no". However hauling weight up the mast is not exactly what you would expect either so who knows. Hopefully I won't get the chance to find out.
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Re: Pros and cons of steel sailboats

The worst boating experience in my life was motoring the J24 with the mast OFF THE BOAT from Greenport to Riverhead

Who would think not having a 70 pound stick would make a boat that much MORE unstable
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post #2016 of 5317 Old 10-31-2013
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Re: Pros and cons of steel sailboats

Bob- At work but recall LPS is 128 degrees. Remember an interesting article ( think it was in Ocean Navigator) discussing small boat (below 100') behavior in severe storms. The point about broaching and tripping on the keel was stressed. The impacts on behavior of boats floating on the water versus in the water was discussed. Still know I prefer having some of the boat in the water. Was in a moderate storm on a tri and have been in much more severe stuff in various monohulls. Behavior of the tri was pukeogenic and every one was bruised on the outsides surfaces of arms and legs whereas in a good monohull you can just weather on. My unscientific impression is on boats more dependent on form stability the ride is worse when things pipe up as well.
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post #2017 of 5317 Old 10-31-2013
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Re: Pros and cons of steel sailboats

My understanding of the weight up the mast was that it was allowed to swing through a reasonably wide angle. The concept was that it acted like a counter balancing pendulum, similar to the counterbalance weights on radio towers and tall street light poles.

Like most things the right amount of roll moment of inertia is a matter of doing things in a reasonable manner. The current thinking seems to be that if you end up with too much roll moment of inertia that will take the boat out of phase with the waves and so the kenetic rolling loads will be larger resulting in an over swing (continuing to roll past the point that the same boat with a lower roll moment of intertia might roll to), similar to excitation roll.

The problem of overswing is further exacerbated when the weight is up high, raising the vertical center of gravity and reducing the boat's tendancy to right itself.

I am always amazed at the sheer amount of attention paid to the likelihood of a capasize. There is a huge pile of factors at work such that its hard to have a one size fits all general rule. Take the debate about deep keels in big waves. In theory the surface of the wave is moving faster than its core. This creates a sheer which wants to rotate the boat, and the deeper the keel, the more sheer it is likely to experience. But most deep keels are also short chord and so stall easily, and that since the sheer forces are at a steep angle, the deep keel is also likely to stall and produce less side force. But even the reduced force is likely to heel the boat, but as the boat heels, it reaches a point where the keel has less penetration in the wave and so the force is further reduced, that is unless the boat starts to slide sidewards on the wave face in which case the velocity of the boat will add to the force the boat experiences and since a shallower keel is more likely to slide, its velocity is greater, and therefore the unit force is likely to be greater, and since a longer chord length keel does not stall as easily it is also more likely to produce a greater rotational force.

In other words, the specifics of the boat's shape and its loading, the wave height and ist shape matter more than theoretical advantages and disadvantages.

Jeff


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post #2018 of 5317 Old 10-31-2013
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by outbound View Post
...Behavior of the tri was pukeogenic and every one was bruised on the outsides surfaces of arms and legs whereas in a good monohull you can just weather on. My unscientific impression is on boats more dependent on form stability the ride is worse when things pipe up as well.
"pukeogenic"
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post #2019 of 5317 Old 10-31-2013
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by Jabberwock View Post
Hmmmm? Well in my case she's a narrow boat and the ballast is on a bulb down low, so maybe that's a "no". However hauling weight up the mast is not exactly what you would expect either so who knows. Hopefully I won't get the chance to find out.
I don't think that in your boat would be a good thing to raise the boat CG and diminish righting moment in bad weather but as Bob had said: Talk with the boat designer.

Regards

Paulo


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post #2020 of 5317 Old 10-31-2013
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Re: Pros and cons of steel sailboats

"What is the LPS of your boat? I would guess 128 degs. Maybe 126 degs. "

That is me quoting me.

So what you are saying Out is my guess of 128 degrees was spot on. Got it. Allow me to be a pompous, egocentric, know it all, ass for a change here. I knew I was very close. I am very good at guessing stability numbers. I have been looking at them for 50 years and I have slowly honed and refined my ability to look at a boat and make a very good seat of the pants guess. It's a tool of my trade. I think Paulo looks at a lot of these numbers also and he can smell BS when he sees it when it comes to stability. After all, there is reality and there is non reality, fairy land.

This is just to preface the argument that is sure to erupt when Brent finds out we are calling BS on his G-Z curve. It's bound to come but he has shown over and over that his grasp of naval architecture is rudimentary at it's best.

I am ready.

Out:
Your pukeogenic observations are spot on. Funny too.

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