Foam Core Hull

[daletournier]

Originally Posted by rourkeh

There is no way I would own a hull that is manufactured with core below the waterline. It is a disaster waiting to happen, and because you cannot see it does not mean water ingress has not occurred.
This is an excellent summary of why not to use coring below the waterline.
Cored Hull Bottoms
it is the end to any argument in favor of this idea.

I didn't even google the site you mentioned, I knew it would be David Pascoe, it used in the argument everytime.
The best argument for cored hulls is just to look at the huge numbers of cored boats out there successfully cruising and have been for a very longtime. My last boat is 32 years old and still going strong.

Sent from my vivo Y35 using Cruisers Sailing Forum mobile app

[double u]

...I'm in the process of reading up on surveying fibreglass boats, & what I find concerning cored construction is unanimously damning. obviously cored decks will be unavoidable, but the books all agree to be ultracautious with cored hulls, particularly below the wl. I am happy to discount anecdotal evidence ("My last boat is 32 years old and still going strong." etcetc.) in favour of surveyor's experiences.

[daletournier]

Originally Posted by double u

...I'm in the process of reading up on surveying fibreglass boats, & what I find concerning cored construction is unanimously damning. obviously cored decks will be unavoidable, but the books all agree to be ultracautious with cored hulls, particularly below the wl. I am happy to discount anecdotal evidence ("My last boat is 32 years old and still going strong." etcetc.) in favour of surveyor's experiences.

And discount that top designers and builders around the world use composites?

Sent from my vivo Y35 using Cruisers Sailing Forum mobile app

[double u]

it's the reason they do it, that matters: it's light, stiff & cheaper to produce than adequately stiffened single skin, not more durable, easier survey- or repairable. any number of "cored hull tragedies" to be found! (tragedies only because of the core!)

[smj]

Originally Posted by double u

it's the reason they do it, that matters: it's light, stiff & cheaper to produce than adequately stiffened single skin, not more durable, easier survey- or repairable. any number of "cored hull tragedies" to be found! (tragedies only because of the core!)

Cheaper to produce? You sure about that?

[Polux]

Originally Posted by double u

it's the reason they do it, that matters: it's light, stiff & cheaper to produce than adequately stiffened single skin, not more durable, easier survey- or repairable. ....obviously cored decks will be unavoidable

What is adequately stiffed single skin? A boat as stiff with single skin than a boat with a good cored hull? For that you would need a hugely thick single skin and a hugely heavy boat. Excessive weight is not desirable on any sailing boat.
Besides that extra thickness and weight would not add much in what regards safety because fiberglass is brittle.

Regarding to be chapear to built you are just wrong. That's why most mass production boats don't have cored hulls and more expensive ones have the hulls cored.

Yes, you are right about cored hulls to be unavoidable since they are the best way to built a strong, stiff and light hull.

[Mike OReilly]

Originally Posted by double u

...I'm in the process of reading up on surveying fibreglass boats, & what I find concerning cored construction is unanimously damning. obviously cored decks will be unavoidable, but the books all agree to be ultracautious with cored hulls, particularly below the wl. I am happy to discount anecdotal evidence ("My last boat is 32 years old and still going strong." etcetc.) in favour of surveyor's experiences.

I’d be curious to get some of these references b/c when I did my search years ago I only found this Pascoe fellow claiming problems. I guess I missed something.

As I mentioned, I own a cored hull boat. She is now 40 years old, and like many of her siblings, have been well used. As far as I can tell there are zero issues with the hull. And I’ve never heard of any issues, anywhere.

As another anecdotal point, spend any time spent on these online forums and you’ll hear about hull problems due to osmosis, poor construction, gel coat problems, blisters and related delamination. I can’t recall one single discussion about hull problems due to core issues. When I use the search tool (which is pretty crappy, I know) I can’t find any threads.

I don’t doubt that cored hulls can produce problems, just like any other aspect of a boat. And I’m sure construction and design quality matters — just like with any other aspect of a boat. But if they were a specific issue I’m pretty sure there would be tons of chatter here and other places.

[Cheechako]

-Considered buying a 51 foot boat 7 years old. Found out it had already failed a survey, much of the cored hull was saturated in 7 years.
-Did buy a 44 ft boat with coring supposedly only above the waterline. In reality it was several inches below the waterline. One side was saturated. Cost $30K to fix that and related issues.
-Freedom 33 I considered had wet core.
-Wet core not uncommon on J35's I hear, but no actual experience with that.
-Mega 30 has cored wide strips for strength, talked with a guy who was tearing it all out and replaced it due to wet core... strangely, no thru penetrations on that core. The Mega had no thru fittings below the waterline.
-Many foam core rudders are saturated, it must leak in from the shaft? I've had two, Both were 7-8 years old.

[a64pilot]

Cored decks are not un-avoidable.
There are even some type of deck cores that will not absorb water, Island Packet is one example, They call it "polycore" I suspicion its microballons and resin, but do not know. I am sure they are not the only one.
I have seen too many wet deck nightmares, I don't want to go down that road, way too much work and or money for this old man

[TeddyDiver]

There are a lot of excamples both good and bad. Unfortunaltely it's difficult to know if a boat you are looking into has problems or not. Some things can indicate the risk of core problems like polyester resin, handlaminated in a mould, low end boatyard, DIY hardware installations, repairs etc.. Some indicates towards healthy core like epoxy resin, vacuum bagged or infuced, high end boatyard, One-Off..
But boat on the hard and a couple of days tapping with a light mallet will tell..


BR Teddy

[Tortuga's Lie]

I had a 1977 Tartan 37 for 20 years with balsa coring and she never showed signs of water penetration, plenty of small blisters, but no wet coring. She had solid glass where bulkheads were tabbed into place as well as through hull fittings. Several 37's have circumnavigated and are still above the waterline!
My new (to me) boat is also a Tartan that utilizes coring. I am not concerned one bit about the integrity of these hulls. I recently drilled a hole about 6 inches above the WL for the air conditioner discharge and the outer skin measured 5/8", 1/2"core, and about 3/8" inner skin making for a total thickness of 1-1/2"! I couldn't imagine how heavy a solid glass hull that thick would be.....

[Typhoon]

This boat is lovely, except for when you ground it .

Epoxy Kevlar , with ceder core .

Lyman-Morse Boatbuilding - Waianiwa - Bill Dixon - Thomaston, Maine

Regards John.

[Jim Cate]

Originally Posted by ColdEh Marine

This boat is lovely, except for when you ground it .

Epoxy Kevlar , with ceder core .

Lyman-Morse Boatbuilding - Waianiwa - Bill Dixon - Thomaston, Maine

Regards John.

interesting, but this strip planked vessel has no similarity to foam core FrP hulls such as are being discussed in this thread.

Lyman Morse is to be commended for this restoration of a hugely damaged yacht.

Jim

[leftbrainstuff]

Originally Posted by Polux

Here a good answer by a surveyor:

"Designers and builders of boats know that cored composite fiberglass structures have better characteristics than solid fiberglass structures. The general boating public does not. We tend to believe that solid fiberglass is stronger and less likely to suffer damage from water saturation, and the latter is true. Virtually every high performance racing sail or powerboat is cored....

The boating public became aware of the problem and many builders started advertising “solid fiberglass hulls”, likely beginning the boating public’s opinion that this was a better way to build a boat. It’s not. It is however a way to eliminate concerns about water intrusion into core...."
Cored vs Solid Fiberglass Structures

and a more technical information:
Getting To The Core Of Composite Laminates : CompositesWorld

This so called piece of expert advice requires a firm response by an engineer.

The general statement that cored is better is typical of a comment not based on any evidence.

Lets list some pros and cons

Cored layup
1) cheaper especially for carbon laminate
2) lighter
3) cheaper to manufacture and this has been the big driver since the 70s oil crisis up to today where only high volume manufacturers survive
4) poor penetration resistance
5) subject to delamination of foam to composite interface leading to substantial loss of bending, shear and compression stiffness
6) poor delamination detectability
7) more challenging to repair and meet the original design strength
8) core to laminate interface integrity testing requires destructive testing to validate load derating

Solid layup
1) more expensive
2) heavier
3) can be manufactured and repaired with good quality by relatively low skilled labor
4) much better penetration resistance
5) no loss of shear, bending or compression strength over time
6) issues due blistering readily detectable and can be repaired piecemeal
7) no complicated jigs or fixtures needed to carry out repairs. Self supporting
8) load testing by simple non destructive deflection testing.

In summary cored hulls are cheap and quicker to build and ideal where lightweight for performance is the primary design driver. Or to minimize build cost.

Solid layup for longevity and field repairability.

30 years of building and repairing motorsport and aerospace composites calls bs on the surveyors wisdom.

[smj]

Thank you for your firm response. Now why should I trust your opinion above actual marine professionals that deal with this daily?