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Random Quote: It's a boat, it's supposed to leak money.
Structurally sound, or a ticking time bomb?
After reading Pascoe's article on fully cored hulls and the Sea-Ray debacle(in his words), I am curious about the long-term integrity of hulls cored below the waterline. Does anyone have any personal experience--good and bad--with owning a boat that has a fully cored hull? I have done some extensive research on the subject and have discovered that there are plenty of reputable builders who make a quality boat with fully-cored balsa hulls, and there are more than just a few out there(many 40 years old and more).
I know of the extra precautions taken when making a through-hull penetration, and that many manufacturers have solid fiberglass surrounding the factory through-hulls.
To listen to Pasco tell it, it's a gamble and you are holding a losing hand if you purchase a boat with a hull that's cored below the waterline.
I'm not looking to flame any particular make and model, but would like to hear some knowledgeable first-hand accountings of positive and negative experiences.
Where I agree with Pascoe on this is that I can't find any valid reason to do it in the first place!
It does not save THAT much weight, and weight down low is good for stability anyway. So what's the point of doing this, when the risks are known - and extreme?
Stiffness is the reason and the weight change can be quite a bit more than you would think. The stiffer the bottom of a boat the better the ride, speed and efficiency along with the fact that any hull flex no matter how small will lead to hull fatigue it's just a matter of how many years or decades.
Does it increase problems or make a boat better? Depends on if the people building the boat do everything right, one small mistake and it's trouble. Cored bottoms are more of a problem with Production builders than the smaller because with production you have.... well a production system, a set time to get things done, people get sick, quit, guys not fully capiable fill in, etc. Cored bottoms are not the problem, the builder is.
As for Pascoe, well it's no secret that I often disagree with him.
__________________ Remember now curiosity killed the Cobia................
The valid reason IMHO...was to find a cheaper way of doing it while retaining the same integral strength.
I have a 1972 31 Uniflite all hand layed up...and it rides like a tank.I contend that the pre 74 Uniflites were the toughest fibreglass hulls ever built.Even the Bertram guys will confess [usually after a glass or two] ....that Uni's have a tougher hull than Berties.
To hand lay up a 31 footer today with a couple of inches of glass ,all around ,would cost upwards of 1/4 million US dollars.But you wouldn't be able to penetrate the hull will a hammer like you can with a Bayliner or a similar cookie cutter.
I don't think cored hulls are cheaper - I have been having some discussions with semicustom builders who will do the bottom with either solid glass construction or CoreCel - your option - and the solid glass was the cheaper option.
__________________ When blithe to argument I come, Though armed with facts and merry; May Providence protect me from, The Fool as adversary. Whose mind to him a kingdom is, Where reason lacks dominion; Who calls conviction prejudice, and prejudice opinion.... ;-)
I know of some older Carver-nightmares.
I've read the Pascoe thing.
Then I read Viking is going to the cored bottom on the 65, and I believe the 74, maybe all the new hulls?
And I read here how the technologies have improved so much over the last 25 years.....
BUT, then I read of FINNSEEKERS "NIGHTMARES" on this board, with I believe a 1998 38' cored hull. Possibly a Rampage? Not sure of the brand, but I don't get the cored below the waterline thing, period.
I also believe there's one of those older Searays locally in a boneyard cause the jackstands went through the bottom, cored hull (or maybe just stringers) but this "water intrusion" being such a big issue- IT'S A BOAT, IT GOES IN THE WATER! I prefer to have something that will not rot or decay below my feet when I'm offshore.
Just my 2 cents...
I think of them as a big sponge, with a minimal amount of glass on either side, just don't let them get wet or else........
Use of core material in boat constuction needs attention in application. Not done properly equals chances of future delamination. This can render a boat junk depending on the extent of failure.
Below the waterline use is a long standing debate and preference. The bottom of a hull endures the most vibration, stress, flex, etc. and with any poor core application delamination is on the way. If this occurs, the motion through the laminates will disinegrate balsa or foam without water intrusion. Now you have a dry but spongy weak hull bottom.
Bertram 630 sf built to take heavy water packing high hp, solid glass as they learned a serious lesson years ago with the 72' sf.
ali'i kai - 10/3/2006 2:08 PM...
Bertram 630 sf built to take heavy water packing high hp, solid glass as they learned a serious lesson years ago with the 72' sf.
Sorry to derail, but what's this about? I never heard of this issue.
__________________ 30' Chris Craft Tournament Sportfish
the why's are listed (less resin/glass/labor=less$$) for production builders. but remember almost every 'carolina' boat has a 'cored' hull. the coring is just okume or similar ply instead of foam. with proper construction and attention to all penetration sites i wouldn't have a problem with it. And i may be crazy but i still think the cold molded carolina hull i used to have gave a completely different feel/ride than all glass, and raised fish like dynamite.
I can tell you this, Corecell is NOT cheap. Any problems you're having are in the builder. If done properly there will be no water intrusion- you can't knock all fiberglass mfg's b/c one had a delamination problem.
You never heard about the Bertram problem because they took back the boats and cut them up. It was a problem with tramsom coring. I did hear one went to OZ where it was stretched and repaired.
I used some cored hulls in my boats that I design. Now with that said, I do this very carefully, the builder has to be top notch like a Boston Boatworks type place, or a Jarret type. I will not farm out my projects to mediocre builders for the specific reasons above. I have also experimented with Coracel and it is ok, but expensive. I will say without a doubt, cold mold is my favorite, its expensive laborous but top notch all the way.
You never heard about the Bertram problem because they took back the boats and cut them up. It was a problem with tramsom coring. I did hear one went to OZ where it was stretched and repaired.
Only five were made. If one went to OZ, two currently for sale in CA maybe only two got scrapped.
In my experience there are two types of cored hulls. One is where a production builder tries to use core to make a cheaper hull - to save money. This usually ends badly.
The other is builders using cores to make custom or semi-custom high performance hulls. This type of production is harder and costs more than straight glass. Core-Cell is one of the expensive high performance cores. Even Pasco concedes it may be the way to go: http://www.yachtsurvey.com/ATC_Core-Cell.htm
Quote! "The entire balsa cored hull was stripped and replaced with Divinycell foam coring" End Quote!
I was actually gonna start a thread a few weeks back when I saw these comments on yachtworld, I was looking at Bertrams and of course the biggest ones come up first. Anyone wanna chime in as to how this repair could have possibly been done? Either the entire interior was removed or the hull was cut from the outside? Read this!
In 1990 Bertram launched it's huge 72' and only five were built. This was the largest sportfisherman ever put into production at Bertram and the novel design and meticulous engineering put it ahead of it's time in many ways. "name deleted" has undergone a tremendous amount of improvements in the last two years both inside and out. The entire balsa cored hull was stripped and replaced with Divinycell foam coring and the interior decor and layout totally updated and improved. She has all new electronics and appliances and the stabilizers and machinery have been recently overhauled. "name deleted" is definately a yacht with palatial accomodations yet she continues the Bertram tradition of being a seaworthy fishing machine!!
Now, the other one on yachtworld makes no mention af a repair. Must have been a big problem, and an even bigger repair. I can't imagine what the yard bill was for this! How the heck can you get to every square inch of the coring? Maybe there's hope for finseeker after all......
The valid reason IMHO...was to find a cheaper way of doing it while retaining the same integral strength.
I have a 1972 31 Uniflite all hand layed up...and it rides like a tank.I contend that the pre 74 Uniflites were the toughest fibreglass hulls ever built.Even the Bertram guys will confess [usually after a glass or two] ....that Uni's have a tougher hull than Berties.
To hand lay up a 31 footer today with a couple of inches of glass ,all around ,would cost upwards of 1/4 million US dollars.But you wouldn't be able to penetrate the hull will a hammer like you can with a Bayliner or a similar cookie cutter.
If you're saying that your Uniflite has a couple of inches of glass in it, then you probably have the strongest hull ever made, by anybody.
As most have mentioned it comes down to the builder knowing how to properly core a hull. As with anything you will find cored hulls with issues and you will find non-cored hulls with issues. I don't think a boat builder would chose to properly core a hull to save money. I also wonder how many cored hull issues are due to the boat owner and not the mfg.
I've seen a 50ish Searay with core samples taken out showing decomposition due to hydraulic action. I would not want to be on the ownership end of that nightmare. I think this discussion reflects some general principles about the boat building industry rather than an inherent flaw in the use of cores below the waterline. The moral of the story is that I would not buy a fully cored hull from a large scale production builder.
__________________ Carpe Diem
01 Tiara 2900 Coronet
Cored below the waterline...... 
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