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Old 07-11-2015, 03:30   #151
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Re: Most boats have liners; which ones do it best?

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Originally Posted by minaret View Post
Yes, peace and elephants. But, I assure you, boats that don't have core problems are also brought to me. Because I don't just fix rotten core, or just fix broken boats for that matter. The majority of the work in any boatyard is always maintaining boats that are in good shape. You'd be amazed how often people with boats just like yours, which they are certain are in perfect condition, come in for bottom paint and hull polish. Then I pick it apart and find all the failures they weren't aware of, and we fix it. Extremely common.
Sounds like a good business model!
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Old 07-11-2015, 03:43   #152
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Re: Most boats have liners; which ones do it best?

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Originally Posted by minaret View Post
Yes, peace and elephants. But, I assure you, boats that don't have core problems are also brought to me. Because I don't just fix rotten core, or just fix broken boats for that matter. The majority of the work in any boatyard is always maintaining boats that are in good shape. You'd be amazed how often people with boats just like yours, which they are certain are in perfect condition, come in for bottom paint and hull polish. Then I pick it apart and find all the failures they weren't aware of, and we fix it. Extremely common.
My boat resents resembles that remark!

Having ripped her apart internally to drop the keel and fix a few known issues under the water tanks it was quite remarkable what we found... I still wake in the night... screaming.... what with a 'boat buck' now being $2k with inflation and all.

1986 solid core heavy layup Westerly.

Sob....
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Old 07-11-2015, 08:04   #153
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Re: Most boats have liners; which ones do it best?

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Originally Posted by Dockhead View Post
That's news to me -- never seen such a thing other than on racing boats. But if you say so. Considering the high cost of doing it right, I would certainly avoid a cored hull on an inexpensive boat.



How exactly does one "do it right", in your opinion?
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Old 07-11-2015, 08:42   #154
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Re: Most boats have liners; which ones do it best?

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Originally Posted by Dockhead View Post
Did I really write that? You are of course right, and I thank you for the correction.

Obviously it's not true that wooden cores never rot. There is always a risk even with a quality job. But what I should have said is that the risk is very, very small with the latest techniques, done by quality builders, and without someone having come in later and bodged a penetration.

I know, for example, that there were lots of problems with Hinckley and Morris cores in the 70's and 80s. But I've never heard of a single case of a rotten core on a Hinckley or Morris built with SCRIMP, not caused by someone's bodged through-hull, have you? These techniques are very, very reliable.

Dollars to doughnuts, that Oyster deck is plain, non-infused, non-encapsulated, and probably not even end-grain balsa. Older boat, am I right? And even so, I bet the rot was caused by a later retrofitted penetration, not so?

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Certainly it was end grain balsa, and indeed I found that that fact tended to limit the damage quite significantly, as the grain wicked vertically, not horizontally. For the same reason the areas of marine ply were in bad shape over a large area, as the grains are lateral. You are also correct, certainly in that case, that the rot was due to deck penetrations, but in most cases not retrofitted but original. Most had been effectively sealed, but this was an older boat, and seals are only effective for so long… the best materials and techniques of course improve failure ratios and are to be well considered… however as Cromwell said: "Stone dead hath no fellow." And I prefer non cored hulls for this reason. Meantime, here's a bit of Edwin Muir for you to consider, 'cause I am in the mood tonight (for gold reconsider bioactive saltwater):

The Castle by Edwin Muir

All through that summer at ease we lay,
And daily from the turret wall
We watched the mowers in the hay
And the enemy half a mile away.
They seemed no threat to us at all.

For what, we thought, had we to fear
With our arms and provender, load on load,
Our towering battlements, tier on tier,
And friendly allies drawing near
On every leafy summer road.

Our gates were strong, our walls were thick,
So smooth and high, no man could win
A foothold there, no clever trick
Could take us in, have us dead or quick.
Only a bird could have got in.

What could they offer us for bait?
Our captain was brave and we were true...
There was a little private gate,
A little wicked wicket gate.
The wizened warder let them through.

Oh then our maze of tunnelled stone
Grew thin and treacherous as air.
The cause was lost without a groan,
The famous citadel overthrown,
And all its secret galleries bare.

How can this shameful tale be told?
I will maintain until my death
We could do nothing, being sold;
Our only enemy was gold,
And we had no arms to fight it with.
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Old 07-11-2015, 12:38   #155
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Re: Most boats have liners; which ones do it best?

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Originally Posted by minaret View Post
How exactly does one "do it right", in your opinion?
As far as I know, the state of the art is still vacuum infusion, with the core in individual blocks (if it's balsa). SCRIMP and similar processes, as used by Hinckley, Morris, Discovery, Contest, Swan, etc.

http://tnyachts.com/wp-content/uploa...mp-Process.pdf


I believe most of the high end European makers use Gurit and Conyplex systems, which are similar to SCRIMP.

Here is how Contest hulls are molded using balsa and Conyplex vacuum infusion technology: Conyplex Contest 55 - Vacuum Infusion - Polyworx

Here is a Swan 601 being molded with a Gurit foam core: http://www.composites.com/seminar/pr...%20Prepreg.pdf
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Old 07-11-2015, 12:45   #156
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Re: Most boats have liners; which ones do it best?

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Originally Posted by Muckle Flugga View Post
Certainly it was end grain balsa, and indeed I found that that fact tended to limit the damage quite significantly, as the grain wicked vertically, not horizontally. For the same reason the areas of marine ply were in bad shape over a large area, as the grains are lateral. You are also correct, certainly in that case, that the rot was due to deck penetrations, but in most cases not retrofitted but original. Most had been effectively sealed, but this was an older boat, and seals are only effective for so long… the best materials and techniques of course improve failure ratios and are to be well considered… however as Cromwell said: "Stone dead hath no fellow." And I prefer non cored hulls for this reason. Meantime, here's a bit of Edwin Muir for you to consider, 'cause I am in the mood tonight (for gold reconsider bioactive saltwater):

The Castle by Edwin Muir

All through that summer at ease we lay,
And daily from the turret wall
We watched the mowers in the hay
And the enemy half a mile away.
They seemed no threat to us at all.

For what, we thought, had we to fear
With our arms and provender, load on load,
Our towering battlements, tier on tier,
And friendly allies drawing near
On every leafy summer road.

Our gates were strong, our walls were thick,
So smooth and high, no man could win
A foothold there, no clever trick
Could take us in, have us dead or quick.
Only a bird could have got in.

What could they offer us for bait?
Our captain was brave and we were true...
There was a little private gate,
A little wicked wicket gate.
The wizened warder let them through.

Oh then our maze of tunnelled stone
Grew thin and treacherous as air.
The cause was lost without a groan,
The famous citadel overthrown,
And all its secret galleries bare.

How can this shameful tale be told?
I will maintain until my death
We could do nothing, being sold;
Our only enemy was gold,
And we had no arms to fight it with.

LOL, the "enemy half a mile away" being water, getting into the "famous citadel" of our hull. One of the most erudite and entertaining arguments I've ever read on here
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Old 08-11-2015, 00:32   #157
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Re: Most boats have liners; which ones do it best?

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LOL, the "enemy half a mile away" being water, getting into the "famous citadel" of our hull. One of the most erudite and entertaining arguments I've ever read on here
_
Och, aye,

An' our Muckle Flugga is a deep one!

Thanks, MF,

Ann
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Old 08-11-2015, 02:52   #158
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Re: Most boats have liners; which ones do it best?

Picture of a jeanneau ds50 grid/liner, as you can see if you get t-boned by a fisherman amidships the liner will not hide any breach.
One thing that people often forget, large mass produced boats are built at a price and maybe using cheaper methods, however they have better R&D and a large production numbers to see how structures perform in the real world. They also have very good control of the production process, they generally don't have issues with hulls being produced in unsuitable temperature and humidity environments, ask Oyster about that.

Yes you hear about the odd structural failure but as a percentage of total production I guess it's a lot less than than some of the custom builders where a single issue is statistically significant.
So statistically you are less likely to have a keel fall of a beneteau/jeanneau than an oyster, ....probably.
Yes I would love a new oyster but all I can afford is a new jeanneau. Choosing a boat purely on grid or not seems strange to me, as price wise it's Ford or Bentley, not a fair comparison.
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Old 08-11-2015, 03:49   #159
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Re: Most boats have liners; which ones do it best?

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for gold reconsider bioactive saltwater
I'd go for complacency instead. It applies to a lot of scenarios.

A nice post and a refreshing change.
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Old 08-11-2015, 03:55   #160
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Re: Most boats have liners; which ones do it best?

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Yes I would love a new oyster but all I can afford is a new jeanneau. Choosing a boat purely on grid or not seems strange to me, as price wise it's Ford or Bentley, not a fair comparison.
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I think you are wrong in your assumption. A new Jeanneau is the same price as a used Oyster. I did the comparison when I bought mine.
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Old 08-11-2015, 04:33   #161
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Re: Most boats have liners; which ones do it best?

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Originally Posted by Abgreenbank View Post
. . .
Yes you hear about the odd structural failure but as a percentage of total production I guess it's a lot less than than some of the custom builders where a single issue is statistically significant.
So statistically you are less likely to have a keel fall of a beneteau/jeanneau than an oyster, ....probably. . .
Hmm, I don't know about that. As far as I know, there have been zero point zero keel failures on Oysters since production started in the '70's.
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Old 08-11-2015, 04:56   #162
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Re: Most boats have liners; which ones do it best?

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I think that discussion of all of the benefits and disadvantages of cored versus uncored hulls is way off topic here.

But to the narrow question of strength, which is what you were commenting on --

Cored hulls, pound for pound, are without the slightest doubt stronger than uncored ones, and not only stiffer. For the same reason that a steel I-beam is stronger than a flat steel bar -- it's simple geometry.

The main disadvantage of cored hulls is higher cost, and the other compromises are obvious enough that with the single exception of Oysters, all modern high end boats have fully cored hulls these days -- Swan, Contest, Wally, X-Yachts, Discovery, Hallberg-Rassy -- you name it. And Oyster is starting to go gradually to fully cored hulls, too, although massive uncored hulls (needing to be truly massive to make up for the loss of strength), and full skeg rudders, was their trademark for decades.

/thread drift
Your statement about cross section of steel (beams) is not entirely accurate not telling the whole story. Beam action is increased by moving the "mass" of steel... for tension and compression away from the neutral axis but a strong web is required to connect the two making them act as a composite. I believe axial strength for non slender columns is driven by cross section area. Buckling is very much related to the end condition of a column.

+++++

As far as the topic is concerned.... My boat and I believe most of the boats of similar size manufactured by Conyplex have a cored molded deck and hull. Parts of the hull are solid glass, parts of the deck have plywood cores. My boat as several structural tabbed in plywd bulkheads. There are separate non structural GPR head liners between bulkheads. Between the headliner and the deck conduits are install for wiring. The hull has no liners... either hull inside is hidden and finished and inside of joinery, wood paneled or carpeted when visible from the interior.

There is no creaking or movement of joinery or bulkheads, no oil canning of the hull in my boat even in the roughest conditions. I assume this is because the construction is adequately stiff.
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Old 08-11-2015, 05:05   #163
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Re: Most boats have liners; which ones do it best?

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I'd go for complacency instead. It applies to a lot of scenarios.

A nice post and a refreshing change.
Thanks, and of course the poem is in part about complacency.
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Old 08-11-2015, 05:09   #164
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Re: Most boats have liners; which ones do it best?

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Hmm, I don't know about that. As far as I know, there have been zero point zero keel failures on Oysters since production started in the '70's.
That is my understanding as well, and it has to be said that the Oyster I gave as an example with deck problems had absolutely zero problems with the (solid and uncored) hull, after more than 20 years afloat.
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Old 08-11-2015, 05:13   #165
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Re: Most boats have liners; which ones do it best?

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I think you are wrong in your assumption. A new Jeanneau is the same price as a used Oyster. I did the comparison when I bought mine.
Very true. And I have zero doubt you are very happy with her!
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