Cored Hull Underwater
- Thread starter BruceK
- Start date
The friendliest place on the web for anyone who enjoys boating.
If you have answers, please help by responding to the unanswered posts.
If you have answers, please help by responding to the unanswered posts.
There wasn't just one either. Some sank. Some were towed back to shore. Major issues and multiple lawsuits and/or settlements.
Those boats did not have core below the waterline.
sunchaser
Guru
- Joined
- Apr 9, 2008
- Messages
- 10,195
- Location
- usa
- Vessel Name
- sunchaser V
- Vessel Make
- DeFever 48 (sold)
The B 40.7 was built using a "monolithic Fiberglas " process. Many hundreds were built this way. So I guess the question is what the heck is "monolithic fiberglas"?
The picture I saw of the B 40.7 Cheeki Rafiki with its keel gone sure looked like torn up core, but ??
Last edited:
This is a complicated issue. There are a lot of variables. There are steel, aluminum, solid fiberglass, combination below-the-waterline solid with upper cored and fully cored.
Oy - what a dilemna. Let's consider the first thing - the reputation of the builder. A good builder puts a lot of money into their product. The Beneteau Group builds more than trawlers - it includes Monte Carlo yachts and Prestige amongst other brands. Their R&D lab is huge. As big as they are - if every hull failed there business would literally go under water. Does that preclude an isolated failure? No more than any other technique or builder.
That said - A Swift is half the price of a Nordhavn, Outer Reef or even more than a Fleming, to name a few.
Does that mean that the Swift is a bad boat? No. But it's a different beast with pod drives that aren't protected like the shafts of a higher end boat. It also has a CE Rating of "B" versus the others at "A", "Ocean Class".
I don't think you should have a concern about the quality of the boat. Certainly a solid fiberglass hull below the WL is a work of art in the right hands. I've seen Hatteras' magic and it's die and go to heaven stuff. But a 60 footer for near 2.5 million? Not in check book.
Keep in mind your cruising. Most don't go past 100 miles offshore. We can choose our weather mostly. The Swift can outrun many a storm. I think their new boats are stunning. I'd steer from the 50, though. It's being refreshed to match the rest of the line. It's very dated.
I hope this helps. It would be a good idea to re-review the video if you haven't lately:
https://www.boattest.com/oem/3211533/library/2613/4/off/640x360
Slider70
Senior Member
QUESTION: Why does a "state of the art" boat get blisters?
There are a number of reasons why a hull can blister.
One way is as follows. I was patching my recently purchased Bayliner that had minor blistering below the waterline. i.e. Not migrated into the fibre glass, just between the glass and the gel coat. Along side of me working in the yard were two retired fibre glass boat builders. These guys just happened to be the manufactures of the last vessel I owned. They used to make a line of vessels that were well known in BC. Canada.
They looked at my blisters and commented that they were minor and told me how to do a simple, lasting repair. They further said that this minor blistering was caused by the guy doing the 'cop application with a cop gun.' They said when you shoot cop you should start the flow on cardboard then swing the gun onto the hull. If you stop at anytime you need to again start your flow of chop onto a sheet of cardboard then swing the flow onto the hull. If you don't do this a small drop of risen can accumulate on the tip of the gun and be blown onto the hull. Years later this drop will migrate to the gel coat and blister.
I have taken the vessel out to do the bottom and the patches from two years ago look great.
There are a number of reasons why a hull can blister.
One way is as follows. I was patching my recently purchased Bayliner that had minor blistering below the waterline. i.e. Not migrated into the fibre glass, just between the glass and the gel coat. Along side of me working in the yard were two retired fibre glass boat builders. These guys just happened to be the manufactures of the last vessel I owned. They used to make a line of vessels that were well known in BC. Canada.
They looked at my blisters and commented that they were minor and told me how to do a simple, lasting repair. They further said that this minor blistering was caused by the guy doing the 'cop application with a cop gun.' They said when you shoot cop you should start the flow on cardboard then swing the gun onto the hull. If you stop at anytime you need to again start your flow of chop onto a sheet of cardboard then swing the flow onto the hull. If you don't do this a small drop of risen can accumulate on the tip of the gun and be blown onto the hull. Years later this drop will migrate to the gel coat and blister.
I have taken the vessel out to do the bottom and the patches from two years ago look great.
Blisters really (suck). Pacemaker was notorious for them. In that day they were still experimenting with formulations. I was looking at a 47'. I've always believed in a good survey. We hauled the boat out and they quoted me $1000 a foot to take care of the blister issue with NO guarantee that they would not come back. Even Hatteras had some issues way back then. Of course they only make mega-expensive boats and their hull process is insane with epoxy coats and paint as well. Ain't 'nuthin getting in there ;-)
That is quite true. I said way up thread that a cored hull requires more care than most ordinary production builders can supply. Nevertheless we should not condemn a good material because of poor construction practices.
BruceK: I just googled "cored boat hull sinking". It returned 1,390,000 results. Among them you should find some of interest.
There are examples of cored sailboat hulls losing their keels, and in a few cases it was due to under engineered or poorly constructed cored structures. In most cases it is due to under engineered or poorly built keel structures, having nothing to do with core. Beneteau in particular has had a few lost keels, and those cases indicate weaknesses in engineering and construction, not necessarily core problems. Beneteau is not one of the production builders I would want to buy a cored boat from. They are poorly thought of in the sailboat world, sometimes derogatorily referred to as "Bendy Toys". They are considered a lower end or "value brand" there. Plenty of fans, and perhaps a good value for the money, but no one thinks they are the best examples of construction.
The 40.7 was built with a solid hull (in the failed area) and a bonded in "grid liner" consisting of stringers and floors. Like coring, this requires attention to detail when bonding in the liner; and like coring, it is more or less uninspectable once built. If incorrectly built, or subsequently damaged by grounding, you likely won't know it until it fails. The loss of the Cheeky Rafiki was probably due to that effect.
IslandTractor
Veteran Member
As a past owner of a J36 I can confirm that their balsa cored hulls were/are a big problem. I lost mine when the yard determined it was not safe enough to relaunch and I had two independent surveys to confirm their findings and assessment. I ended up selling for a pittance to someone who wanted to take the time to do the repair himself. Not an economical repair at a decent commercial yard.
MichaelB1969
Guru
- Joined
- Oct 15, 2016
- Messages
- 679
- Location
- USA
- Vessel Name
- Speedy Charlotte
- Vessel Make
- Beneteau Swift Trawler 44
BTW, the inference here is that cored boat hulls sink a lot, but the Google search does not accurately support this inference because if you actually search for the exact phrase "cored boat hull sinking", it returns zero results. Not a single one.
A better related search strategy is one that contains the word "sinking" AND one of the following phrases:
"steel hull" 25,700 results
"fiberglass hull" 34,400 results
"solid hull" 7,460 results
"cored hull" 6,530 results
"cored fiberglass hull" 990 results
What does this all mean? Not much I'd argue.
That said, by searching these terms you will obviously find a lot of information. But the search volumes are meaningless in my opinion.
Mike
MichaelB1969
Guru
- Joined
- Oct 15, 2016
- Messages
- 679
- Location
- USA
- Vessel Name
- Speedy Charlotte
- Vessel Make
- Beneteau Swift Trawler 44
BTW, I am a 2014 ST44 owner (boat is for sale if anyone is interested) who researched this issue of cored vs. solid quite a bit prior to purchasing.
At the end of the day, I felt comfortable that the hull was strong and sound given their manufacturing process and the sheer volume of boats out there on (top of) the water. In their process, the balsa is cut into small rectangles, each of which ends up getting encapsulated in vacuum-infused resin thereby limiting the spread of any water damage that might occur if the hull were to be compromised.
Unlike smaller manufacturers, Beneteau has a huge R&D budget and engineering team along with 130 years of experience behind them. Given their massive volumes, any problems related to hull manufacturing or materials that led to boats sinking or other major problems would be WIDELY known at this point, and their reputation would suffer greatly. And a multi-billion dollar company would likely go under.
Yet every time I go out on SF Bay I see tons of Beneteaus, some quite old, with seemingly happy owners enjoying their time out on the water...cored hull and all.
Note: if anyone is interested in a 2014 ST44 with low-hours, check out https://www.denisonyachtsales.com/y...ft-Trawler-44-2014-Oakland-California/6903722
At the end of the day, I felt comfortable that the hull was strong and sound given their manufacturing process and the sheer volume of boats out there on (top of) the water. In their process, the balsa is cut into small rectangles, each of which ends up getting encapsulated in vacuum-infused resin thereby limiting the spread of any water damage that might occur if the hull were to be compromised.
Unlike smaller manufacturers, Beneteau has a huge R&D budget and engineering team along with 130 years of experience behind them. Given their massive volumes, any problems related to hull manufacturing or materials that led to boats sinking or other major problems would be WIDELY known at this point, and their reputation would suffer greatly. And a multi-billion dollar company would likely go under.
Yet every time I go out on SF Bay I see tons of Beneteaus, some quite old, with seemingly happy owners enjoying their time out on the water...cored hull and all.
Note: if anyone is interested in a 2014 ST44 with low-hours, check out https://www.denisonyachtsales.com/y...ft-Trawler-44-2014-Oakland-California/6903722
Last edited:
The photo on page 53 of the report does look like coring was torn away...maybe the very small area where the keel bolts up is solid laminate. Clearly the bonded in "grid" is essential for hull rigidity. I found the report to be lacking a comprehensive engineering analysis and lab testing of the most probable failure sequences...a conclusive failure modes and effects analysis in the aviation world.
https://assets.publishing.service.gov.uk/media/55408664e5274a157200005b/MAIBInvReport_8_2015.pdf
Last edited:
I find that question interesting just because there are various good quality boats with certain regular issues. We didn't have the problem, but Sunseeker is notorious for after a few years in the sun a lot of spidering in the gelcoat. Nothing structural, just ugly. They claim it's because of temperatures and humidity during build but they have the problem solved. I had to ask then why Princess, also built in the UK didn't have the issue. They may really have the problem solved now and I hope so. But it was something they were doing wrong.
OP
OP
BruceK
Moderator Emeritus
- Joined
- Oct 31, 2011
- Messages
- 13,347
- Vessel Name
- Sojourn
- Vessel Make
- Integrity 386
Thank you for posting. I found myself balancing similar considerations. My unresolved concern was how well each thru hull was sealed. That Beneteau had not managed to seal the bow cabin portlights was a concern.In many ways we really liked the boat, electing not to proceed was a tough decision.
The subject boat was an early one, 10 years older than yours. In 2005 Beneteau began injection moulding the hull builds, doubtless there were many other improvements between the respective build dates.
I wish you every success with your sale.
gsholz
Senior Member
- Joined
- Nov 2, 2016
- Messages
- 484
- Location
- Northwest
- Vessel Make
- Sold-GB 52 Europa, Queenship 59, Tolly 45
I looked at one of Beneteau/Jenneau's Prestige 46 power boats at a recent boat show. Boat show special reduced from > $1M to 800k. I was not impressed. It felt there were many corners cut just below what you could see and touch. Every floor we walked on creaked and deflected like they used 3/8 inch ply. Most surprising was the bow thruster installation. The builder simply cut out a triangular wedge of the bow section below the water line, installed a small tube and then just caulked the tube/wedge back into the hull. No fiberglassing just caulk. I have never seen anything like that.
MichaelB1969
Guru
- Joined
- Oct 15, 2016
- Messages
- 679
- Location
- USA
- Vessel Name
- Speedy Charlotte
- Vessel Make
- Beneteau Swift Trawler 44
Thanks Bruce!
Jeff F
Guru
- Joined
- Nov 5, 2015
- Messages
- 2,435
- Location
- Canada
- Vessel Name
- Escapade
- Vessel Make
- 50` US Navy Utility trawler conversion
I haven't looked in detail at the new STs, but the recent larger Beneteau sailboats have thrusters that live in a molded cavity in the hull. There are removable fairing assemblies for access. Looks like a really smart design. I suspect that's what you saw.
Here's deets on the sailboats: http://no-frills-sailing.com/bow-thruster-hole-in-the-hull/
No inference. the poster wanted information, there is a lot to be had. Cored boats are actually a bit less likely to sink, since the hulls are buoyant.
When I had my sailboat custom built I could have specified any construction. I specified cored, including below the waterline. But it must be done with due care, and I'll repeat that few production builders exercise sufficient care for me to be comfortable.
The fact that balsa is built up in small blocks does not prevent water channels between them that can run the length of the hull. This is easily provable by cutting one apart. Infused boats have a small chance of filling these with resin but usually don't achieve that. Hand laid up, no chance.
I tried to search this one and couldn't weed through the results. Can you elaborate a little or post a link?
In the bottom of my cereal box I found an injection molded hippopotamus. I can't make the jump from the hippo to the boat.
Here's one link:
https://www.cruisingworld.com/how-its-made-injection-molded-decks
Guessing quality control could be far better with injection molding.
Does anyone make an injection molded one-piece core?
Last edited:
My concern with a cored hull, isn't sinking, its possible blistering and delamination. I think these concerns multiply for an older boat that spends most of its time in the water (maybe even full time). May be less of an issue for a newer boat or one that spends only part of the time in the water.
Jim
Jim
I am not aware of any reasonable sized cored hull boats where the bouncy of the coring would come close to 'floating' the balance of the equipment and machinery.
They may very well sink slightly slower - I am sure it would not be measurable or relevant.
There are numerous cases of both powerboats and sailboats floating for months after capsize due to cored hulls. Monohull sailboats which lose their keel and flip, catamarans that flip. For example, the Beneteau 40.7 referred to above was found floating upside down and flooded several weeks after the capsize. Largest sailboat I'm aware of was an 80' that lost it's keel, was recovered in a couple of days and salvaged. Powerboat may depend on the specific model but certainly it happens. On my own sailboat, there is 900 sq ft of cored surface in the hull, 650 in the deck, and 1110 in the interior. That is enough to float the hull it if lost the 11,000 lb keel.
It isn't a big advantage, it will float very low in the water and likely be unsalvagable on recovery.
It isn't a big advantage, it will float very low in the water and likely be unsalvagable on recovery.
Comodave
Moderator Emeritus
- Joined
- Jul 2, 2015
- Messages
- 21,280
- Location
- Au Gres, MI
- Vessel Name
- Black Dog
- Vessel Make
- Formula 41PC
The March 2019 issue of Boating magazine has an article about drying out a wet core. Interesting technique on how they dry out a wet core. It was expensive but cheaper than other methods maybe.
