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Old 08-01-2012, 07:10 PM   #1
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Cored vs. Solid Hull

Having just read a thread that used the terms "solid" and "cored" hull, I realized that I don't know the difference or why it is important. I've also seen the terms used in describing the floors of some boats with flying bridges. Is it something to be wary-of in looking at (older or newer) boats?

Gary
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Old 08-01-2012, 07:22 PM   #2
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Coring, whether it be cored hull or cored decks refers to the construction technique of sandwiching lightweight but strong materials in between layers of fiberglass. Many, many, many boats, i.e. almost all boats, have cored topsides either in the form of cored decks, cored cabin super structure, etc. Some have coring below the water line, some don't. There are multiple materials used for coring with the most common material being balsa. It is strong, durable and lightweight as long as it is not exposed to water and then it turns to mush. Modern coring utilizes synthetic materials that do not obsorb water and don't rot. The typical compromise is no coring below the waterline but then use coring on decks, etc. to save weight. Coring is not a bad thing as long as it is appropriately utilized and protected from water intrusion.
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Old 08-01-2012, 11:44 PM   #3
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Originally Posted by MilShooter View Post
Having just read a thread that used the terms "solid" and "cored" hull, I realized that I don't know the difference or why it is important. I've also seen the terms used in describing the floors of some boats with flying bridges. Is it something to be wary-of in looking at (older or newer) boats?

Gary
If it be below the waterline... Don't do that. Above is very common.
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Old 08-02-2012, 01:15 AM   #4
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Originally Posted by Woodsong View Post
Coring, whether it be cored hull or cored decks refers to the construction technique of sandwiching lightweight but strong materials in between layers of fiberglass. Many, many, many boats, i.e. almost all boats, have cored topsides either in the form of cored decks, cored cabin super structure, etc. Some have coring below the water line, some don't. There are multiple materials used for coring with the most common material being balsa. It is strong, durable and lightweight as long as it is not exposed to water and then it turns to mush. Modern coring utilizes synthetic materials that do not obsorb water and don't rot. The typical compromise is no coring below the waterline but then use coring on decks, etc. to save weight. Coring is not a bad thing as long as it is appropriately utilized and protected from water intrusion.
Tony, as you know both your Bayliner 4588, my 4788, the 5288, and the 5788 utilized a vaccume bagged foam core in the hulls. This practice was continued into the meridian lineup as well.

The fleet is approaching 30 years of service for the older units, and as far as I can tell, there has never been a documented case of a hull delamination on these large Bayliners.

Not a bad record.

There's another advantage. Even in the cold waters of Alaska, with our muggy summers, these hulls do not sweat like the non cored hulls are known to do.
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Old 08-02-2012, 02:17 AM   #5
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Kevin- you are absolutely correct.
Many brands use coring below the waterline. Cruisers Yachts, Inc., Sea Ray, etc. Coring is not a bad thing in and of itself- typically the problem comes from an owner down the road deciding to make adjustments, add a thru hull or something of that nature and they don't seal things properly and then you have water getting to the core. With synthetic that is not a good situation but it is not catastrophic. A balsa cored hull though....now that can be a problem.
Solid fiberglass is not necessarily the answer either. LOTS of solid glass hulls have lots of blister problems in a big way. I've got a good friend right now with his 50' Taiwanese built trawler on the hard right now due to dinner plate sized blisters. Or you can have hatteras which will blister like clockwork but they are so solid it's not really an issue.

When it comes to older boats though it is hard to say one method is better than the other. Brand and to a certain extent, construction methods, become not as important as how well the vessel has been cared for over the years. I can show you solid glass hulled boats that are absolute train wrecks due to neglect and I can show you cored hull boats and even balsa cored hull boats that are very old and the boats are wonderful in wonderful shape. Most boaters (ok, not trawler folk but boaters in general) "love" sea rays yet how many of the 1990's model sea rays have water logged stringers? Of note too is that while lots of trawlers may have solid glass hulls, they often also have wood stringers wrapped in fiberglass which are very much capable of rotting from within.
My Monk 36 had a fair # of very small blisters when we bought her and began the refit yet my bayliner 45 that had not been hauled out in about 4 years didn't have a single blister on her at all this spring when we hauled her out for repair and refit and new bottom paint.
Saying all the above I'd still probably suggest that it's best to minimize one's probability of having issues so choose your individual boat wisely- not just on brand and construction method- but actual condition, upgrades, and evidence of long term maintenance. Would I want a balsa cored hull- not me personally. Synthetic core- acceptable for me personally.
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Old 08-02-2012, 10:42 AM   #6
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Kevin- you are absolutely correct.
Many brands use coring below the waterline. Cruisers Yachts, Inc., Sea Ray, etc. Coring is not a bad thing in and of itself- typically the problem comes from an owner down the road deciding to make adjustments, add a thru hull or something of that nature and they don't seal things properly and then you have water getting to the core. With synthetic that is not a good situation but it is not catastrophic. A balsa cored hull though....now that can be a problem.
Solid fiberglass is not necessarily the answer either. LOTS of solid glass hulls have lots of blister problems in a big way. I've got a good friend right now with his 50' Taiwanese built trawler on the hard right now due to dinner plate sized blisters. Or you can have hatteras which will blister like clockwork but they are so solid it's not really an issue.

When it comes to older boats though it is hard to say one method is better than the other. Brand and to a certain extent, construction methods, become not as important as how well the vessel has been cared for over the years. I can show you solid glass hulled boats that are absolute train wrecks due to neglect and I can show you cored hull boats and even balsa cored hull boats that are very old and the boats are wonderful in wonderful shape. Most boaters (ok, not trawler folk but boaters in general) "love" sea rays yet how many of the 1990's model sea rays have water logged stringers? Of note too is that while lots of trawlers may have solid glass hulls, they often also have wood stringers wrapped in fiberglass which are very much capable of rotting from within.
My Monk 36 had a fair # of very small blisters when we bought her and began the refit yet my bayliner 45 that had not been hauled out in about 4 years didn't have a single blister on her at all this spring when we hauled her out for repair and refit and new bottom paint.
Saying all the above I'd still probably suggest that it's best to minimize one's probability of having issues so choose your individual boat wisely- not just on brand and construction method- but actual condition, upgrades, and evidence of long term maintenance. Would I want a balsa cored hull- not me personally. Synthetic core- acceptable for me personally.
Its, a little off topic, but on the subject of coring...

When we started looking at trawlers one of our biggest fears was getting a boat and finding out a couple years later that we had to replace the decks due to balsa waterlogging. Possibly that was a somewhat irrational fear, but it just scared the heck out of me.

Because of that fear, part of our boat search criteria was no teak decks. Not because of the teak itself, but because of the hundreds of hidden hull penetrations waiting to fail.

Again, it might be irrational but, thats one of the reasons we went with a newer boat, the 4788 with its foam cored decks. I really like the 4588's due to their interior teak. I also liked the prop pockets. We seriously considered buying a 4588 that had been recently repowered with Cummins Naturally Asperated engines. In my opinion that platform is and would have been an almost perfect coastal cruiser.
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Old 08-02-2012, 02:06 PM   #7
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The big problem is anything can be considered a "core".

While there are many fine core materials , some folks will claim a boat is a composite , with house plywood covered with a slather of GRP.

"Cored" is like HI FI was , sounds great but has little substance.

First question on a cored boat is WHAT IS ? the core.

Second is how the hull or deck was created , there are great core building methods and rotten ones.

FF
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Old 08-02-2012, 02:46 PM   #8
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The big problem is anything can be considered a "core".

While there are many fine core materials , some folks will claim a boat is a composite , with house plywood covered with a slather of GRP.

"Cored" is like HI FI was , sounds great but has little substance.

First question on a cored boat is WHAT IS ? the core.

Second is how the hull or deck was created , there are great core building methods and rotten ones.

FF
It would be nice to have the lamination schedules from the original manufacturer.

We have them for the Bayliner Motoryachts.
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