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Old 26-06-2015, 03:57   #766
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Re: The criteria of "blue"

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Originally Posted by NevisDog View Post
I'd just like to clear up some obvious misunderstandings here.

Extending a backing plate beyond load area is an inefficient method of supporting and transferring the concentrated loads from heavily loaded fittings. Just as a cored deck fails when the core breaks down and allows outer layers to slide and flex independently, so it is with a large backing plate (except directly in way of bolts): the plate outer edges can move independently of the next layer, so much of the stiffness is lost. A better engineered solution is to build in that backing (whether aluminum or plywood) within the last few bottom layers, so they become an integral part of structure, increasing stiffness without increasing thickness/weight.

How you determine "load area"? Integrated backing plates work in theory but are hard to inspect and replace

Muckle's fear of ply or timber core is sometimes well justified: because the ply is supposedly encapsulated, some builders will use inferior plywoods, they may skimp on sealing the bolt holes against water ingress, and may use the wrong resins (most resins adhere well to end-grain but only epoxy holds permanently to timber or ply). So timber/ply core used anywhere demands quality build. But then so does balsa (think of the number of boats with failed balsa-core decks) and any other core material creates equally serious issues over time, if quality of build/maintenance is lacking.
So true..

Let me know if you find someone offering solid glass hulls built entirely with epoxy - except for hi-tec, weight-saving, one-off racing machines (never designed for longevity, and more likely to be cored), they must be rare as hen's teeth. Not sure it offers much advantage in strength either (unless you want to minimize thickness - never a great idea in a non-cored cruising hull). Only the water absorption is prevented, and that can be done with epoxy outer layers alone.
Dunno any solid GRP boats produced today thou I'm not been seeking them either. The difference in costs however would be allmost insignificant, maybe few % of the total price

I think that's a fair assessment but feel free to correct anything I missed.
Sorry it did take some time before I got to answering you.. Agree with the most you say above, thou a few exceptions (comments)
If you can get a copy of Dave Gerr's "The Elements of Boat Strength" there's construction details and scantlings for Deck-Hardware-Mounting-Areas on pages 68 through 71. There isn't much, actually next to nothing in other sources in literature what I'm aware of (Chapelle, Larsson&Eliasson, Skene, Birmingham, Nicolson etc..)
Anyway I have my doubts over ply as It's used in most production boats, and there are better solutions..

BR Teddy
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Old 26-06-2015, 05:43   #767
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Re: The criteria of "blue"

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Let me know if you find someone offering solid glass hulls built entirely with epoxy - except for hi-tec, weight-saving, one-off racing machines (never designed for longevity, and more likely to be cored), they must be rare as hen's teeth. Not sure it offers much advantage in strength either (unless you want to minimize thickness - never a great idea in a non-cored cruising hull). Only the water absorption is prevented, and that can be done with epoxy outer layers alone.
Sounds like Tartan Yachts at least come pretty close...

Hulls & Decks Are Infused With Epoxy Modified Vinylester | Tartan Yachts
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Old 26-06-2015, 07:28   #768
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Re: The criteria of "blue"

Passport and Outbound use solid glass.

They sell it as a plus point, but I think it is simply because the hulls are made in the east and they don't have the expertise to core properly. It could be their philosophy of choice but solid is far quicker and easier to do. Far less steps involved so you could forgive a yard for following this construction path.

I am with the school of thought that is in favour of cored laminate use though. It add's a lot of value being able to dissipate energy through that core. Tests according to Gozzard do show that this cored construction is stronger in many ways with the right core material and top product such as core-cell seem to be able to negate osmosis and ultimate de-lamination issues.

To lay up a hull with core-cell takes a lot of time and for me provide the best theoretical build method if done "properly".

Gozzard use core laminate in their builds and I agree with the rational and logic that they subscribe to on their page. I don't think solid can be better but it is the next best thing if you don't have the skill in house or want to lessen the labour overhead.

Reading between the lines I think solid just means we don't have a core lamination skill in our work flow to be able to do a proper coring job and manage to stay within our cost margins. IMHO
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Old 26-06-2015, 11:15   #769
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Re: The criteria of "blue"

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Passport and Outbound use solid glass.

They sell it as a plus point, but I think it is simply because the hulls are made in the east and they don't have the expertise to core properly. It could be their philosophy of choice but solid is far quicker and easier to do. Far less steps involved so you could forgive a yard for following this construction path.
Pacific Sea Craft builds solid cored hulls, also did it that way when the factory was in California.

Valiants were built that way up through 2011 in Texas.

Island Packets are built in Fla. with solid hull layups.

Catalina Yachts build their boats with solid layup hulls, in Ca.
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Old 26-06-2015, 11:53   #770
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Re: The criteria of "blue"

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Pacific Sea Craft builds solid cored hulls, also did it that way when the factory was in California.

Valiants were built that way up through 2011 in Texas.

Island Packets are built in Fla. with solid hull layups.

Catalina Yachts build their boats with solid layup hulls, in Ca.
Yeh, I noticed America builds solid. Not absolutely sure why. Must be opinion that solid is better by the buying public. The industry there seems polarised to me. Solid hull builds one end and advanced carbon nano tube builds the other end but not much technology choice in between. - Not that I can determine anyway.
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Old 26-06-2015, 12:07   #771
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Re: The criteria of "blue"

Maybe blue boats could be built of this stuff very shortly.

Arovex® Prepregs — Zyvex Technologies
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Old 26-06-2015, 14:06   #772
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Re: The criteria of "blue"

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Sounds like Tartan Yachts at least come pretty close... Hulls & Decks Are Infused With Epoxy Modified Vinylester.
Not even close.

Muckle wanted a solid glass hull entirely in epoxy. Tartan build high quality yachts for sure but they are famous for their cored hulls - why would they step backwards from that skill now? Besides, their ad says only that the first layers behind the gel coat are laid down with 'epoxy modified vinylester' - not epoxy, but a perfectly reasonable blister-prevention barrier in any production boat. In every ad we must read the small print.

Plenty of solid hulls around, but no one is offering solid epoxy - epoxy is brilliant for wood-core, for barrier coats, or for ultralight, cored raceboats.
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Old 26-06-2015, 17:04   #773
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Re: The criteria of "blue"

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Not even close.

Muckle wanted a solid glass hull entirely in epoxy. Tartan build high quality yachts for sure but they are famous for their cored hulls - why would they step backwards from that skill now? Besides, their ad says only that the first layers behind the gel coat are laid down with 'epoxy modified vinylester' - not epoxy, but a perfectly reasonable blister-prevention barrier in any production boat. In every ad we must read the small print.

Plenty of solid hulls around, but no one is offering solid epoxy - epoxy is brilliant for wood-core, for barrier coats, or for ultralight, cored raceboats.
Ooops, you're absolutely correct...

Total brain fart on my part, for some reason I was thinking Tartan was still building them the old-fashioned way...

;-)
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Old 26-06-2015, 18:20   #774
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Re: The criteria of "blue"

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Not even close.

Muckle wanted a solid glass hull entirely in epoxy. Tartan build high quality yachts for sure but they are famous for their cored hulls - why would they step backwards from that skill now? Besides, their ad says only that the first layers behind the gel coat are laid down with 'epoxy modified vinylester' - not epoxy, but a perfectly reasonable blister-prevention barrier in any production boat. In every ad we must read the small print.

Plenty of solid hulls around, but no one is offering solid epoxy - epoxy is brilliant for wood-core, for barrier coats, or for ultralight, cored raceboats.
I did not think that would be possible Nevisdog. Would that not be like concrete with no rebar?
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Old 26-06-2015, 19:39   #775
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Re: The criteria of "blue"

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I did not think that would be possible Nevisdog. Would that not be like concrete with no rebar?
Okay, okay - by solid, Muckle and I both mean we don't want a cored hull/deck - not one missing any kevlar/glass/carbon fibers in there - now that would be novel!
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Old 27-06-2015, 07:32   #776
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Re: The criteria of "blue"

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Okay, okay - by solid, Muckle and I both mean we don't want a cored hull/deck - not one missing any kevlar/glass/carbon fibers in there - now that would be novel!
You don't rate core-cell then? It's clever stuff when used properly. You get two hulls, insulation, impact energy absorption and redistribution, plate slide instead of stretch, closed cell so no capillary action. I have yet to see a bow that can store high energy and release it with out failure that was not of composite laminate construction Nevisdog. It's natures way me thinks.
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Old 27-06-2015, 07:51   #777
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Re: The criteria of "blue"

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You don't rate core-cell then?
I suspect Muckle is looking at top-of-the-range while I'm searching bottom-of-the-market, so my reason for preferring solid fi-glass is longevity of older yachts: too many balsa-cored decks fail, an expensive business. I don't know enough about core below waterline so maybe others can discuss, but closed-cell is not immune to failure. Once the outer layers separate from the core, most of the strength is gone, and the movement will likely degrade the core. I've also seen ccfoam-cored frames soak up diesel until completely saturated, adding tons of weight to a hull.

Wood-epoxy has advantages - it's very easy to carry out repairs for one thing - so I'm still considering all options.
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Old 27-06-2015, 11:06   #778
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Re: The criteria of "blue"

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I suspect Muckle is looking at top-of-the-range while I'm searching bottom-of-the-market, so my reason for preferring solid fi-glass is longevity of older yachts: too many balsa-cored decks fail, an expensive business. I don't know enough about core below waterline so maybe others can discuss, but closed-cell is not immune to failure. Once the outer layers separate from the core, most of the strength is gone, and the movement will likely degrade the core. I've also seen ccfoam-cored frames soak up diesel until completely saturated, adding tons of weight to a hull.

Wood-epoxy has advantages - it's very easy to carry out repairs for one thing - so I'm still considering all options.
Send me that Muckle link you are reading please Nevisdog.
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Old 27-06-2015, 15:19   #779
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Re: The criteria of "blue"

The high failure rate for balsa cored decks is likely due to the dozens if not hundreds of penetrations in the typical cruising boat deck... many oof which are likely to be done by unskilled owners.

Cored hulls on the other hand have few penetrations, and they are likely done by the builder rather than an amateur. Failure is still possible, but far less likely than in the case of a deck.

In both the case of cored and non-cored hulls, the real factor is in the skill of design and construction. When those factors are well done the result is good, but either sort of construction is vulnerable to poor practice.

Jim

PS
As the owner of a strip-planked wood-epoxy hull, I'm convinced that it is an excellent choice. Ours is now 25 years of age, has done well over 100K miles and is in excellent condition throughout. No pox, no rust, no rot, still very fair. The bolt on keel (oh, horrors) is attached to a massive internal H-beam that runs from forward of the mast step to aft of the engine beds. Stronger than hell...
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Old 27-06-2015, 17:21   #780
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Re: The criteria of "blue"

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The high failure rate for balsa cored decks is likely due to the dozens if not hundreds of penetrations in the typical cruising boat deck... many oof which are likely to be done by unskilled owners.

Cored hulls on the other hand have few penetrations, and they are likely done by the builder rather than an amateur. Failure is still possible, but far less likely than in the case of a deck.

In both the case of cored and non-cored hulls, the real factor is in the skill of design and construction. When those factors are well done the result is good, but either sort of construction is vulnerable to poor practice.

Jim

PS
As the owner of a strip-planked wood-epoxy hull, I'm convinced that it is an excellent choice. Ours is now 25 years of age, has done well over 100K miles and is in excellent condition throughout. No pox, no rust, no rot, still very fair. The bolt on keel (oh, horrors) is attached to a massive internal H-beam that runs from forward of the mast step to aft of the engine beds. Stronger than hell...
I am always heartened when I hear people with good reports to tell about wood/epoxy construction.

I had a sneaky look at your boat and it has a bucket load of character. Looks a great cruiser. Love the interior.

So Jim, what are the foibles if any that you come across maintaining a wooden boat over a glass/metal one?

Do you have to do much different to look after a wooden boat?
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