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Old 05-21-2016, 03:10 PM   #21
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Larry, you surely are not talking about Sealife's plywwod fore deck are you?! But yes my old mainship had balsa and limited migration, my Krogen is ply and it ran a lot further, of course the slope of the front deck probably didnt help.
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Old 05-21-2016, 04:10 PM   #22
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years ago I got a piece of foan from a boat builder and submerged in water for six months. It did not absorb any water. try that with balsa.
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Old 05-21-2016, 06:26 PM   #23
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I once saw a KK in the yard for a very long time because the balsa core was saturated. IMO the boat was probably totaled but the entire bottom was removed and rebuilt. I have no idea of the cost.


It is my strong opinion that balsa coring does not belong anywhere on a boat. Synthetic coring that will not rot and wick water from a failure site to elsewhere is a different story.


I agree with the above statement that the two crashes don't prove anything about either type of construction. I have seen solid FG smashed and pushed in and it didn't break into pieces like glass but did leak.


You could argue that the bottomless KK I saw doesn't provide any proof either however it was apparent that rot had migrated across large areas of balsa. Supposedly with proper wetting out the balsa blocks are separated by resin but that puts us back to the manufacturing process control again.


There is great value for an engineering standpoint to cored construction. Like an I beam it is stronger and lighter than a solid structure, in normal use.


The big problem with coring is proper control of the manufacturing process and what must be greater expense of synthetic core vs balsa.


Personally I would never buy a boat with balsa core below the water line.
I will NEVER buy a boat with ANY end grain balsa in it ANYWHERE. Been there never, never again.
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Old 05-21-2016, 06:49 PM   #24
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It's somewhat moot for me. We took some possible risk buying our boat in regards to the cored hull but a later model KK42 was well over our budget. I certainly have no professional or educated position in the debate. Only that the possible benefits on the one side and the possible risks on the other side might be over stated by both camps.


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Old 05-21-2016, 11:18 PM   #25
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My 50 foot James Krogen designed 1972 model trawler has balsa core below the waterline. I have all of the blueprints, one of which shows the coring, where and how much . The hull below the waterline is minimum 1 1/2 inch thick, mostly 2 inches, with 3/4 inch balsa coring. But, it was built by Charley Morgan in Florida, and construction was personally overseen by James Krogen, not as an afterthought of Art Kadey. This boat has no water intrusion to the coring. It was built to specs and sealed correctly, meaning that the core was properly saturated so as to not allow water to migrate thru. Anything going thru the hull is solid layup or saturated plywood, depending on needed strength. James Krogen designed a really good boat, but it was to expensive at the time to compete with those built over seas. Art Kadey was the beginning of competitive priced Krogen designed boats. Mostly they were OK, but still, corners were cut (dauntless, what about tank baffles ?) and when supplies were short acceptions were made. Mostly no one was there to say otherwise. But, back to the originall post, if coring is done properly it is preferable, and stronger than solid layup. Its just difficult to find "properly" done so solid seems preferable. Hard to screw that up,,, but they did sometimes !!!!
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Old 05-21-2016, 11:23 PM   #26
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I have a 1982 KK, hull 23. My hull is cored with synthetic, not balsa.
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Old 05-22-2016, 06:08 AM   #27
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I can assure you 100% Krogen hull #42-61 was synthetic core! I would know, I exposed every inch of the bottom.
Thanks for the clarification. I had thought there was some issue, but clearly not this one.
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Old 05-22-2016, 06:11 AM   #28
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My 50 foot James Krogen designed 1972 model trawler has balsa core below the waterline. I have all of the blueprints, one of which shows the coring, where and how much . The hull below the waterline is minimum 1 1/2 inch thick, mostly 2 inches, with 3/4 inch balsa coring. But, it was built by Charley Morgan in Florida, and construction was personally overseen by James Krogen, not as an afterthought of Art Kadey. This boat has no water intrusion to the coring. It was built to specs and sealed correctly, meaning that the core was properly saturated so as to not allow water to migrate thru. Anything going thru the hull is solid layup or saturated plywood, depending on needed strength. James Krogen designed a really good boat, but it was to expensive at the time to compete with those built over seas. Art Kadey was the beginning of competitive priced Krogen designed boats. Mostly they were OK, but still, corners were cut (dauntless, what about tank baffles ?) and when supplies were short acceptions were made. Mostly no one was there to say otherwise. But, back to the originall post, if coring is done properly it is preferable, and stronger than solid layup. Its just difficult to find "properly" done so solid seems preferable. Hard to screw that up,,, but they did sometimes !!!!
Thanks for the information.

Now, what is it about those baffles? They make no sense to me. Why would you install them and then cut them out??
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Old 05-22-2016, 06:13 AM   #29
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Larry, you surely are not talking about Sealife's plywwod fore deck are you?! But yes my old mainship had balsa and limited migration, my Krogen is ply and it ran a lot further, of course the slope of the front deck probably didnt help.
That's the deck that was replaced in Dauntless some years ago.
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Old 05-22-2016, 07:45 AM   #30
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"when a boat hits a rock it is more likely to be holed if the hull is cored than if it is solid glass, assuming the two hulls were built to the same stiffness specification."

A cored hull built to the same stiffness would barely have any glass at all.

Most cruising cored boats will have about the same layup weather cored or not.

If 1/2 inch thick in single skin a layer of 1/4 on the outside and almost the same inside is used.

There will usually be a bit less glass on the inside as surfacing tissue outside to stop print thru is not usually inside

Better quality builders may use a layer of mat inside to make cleaning and painting easier.

Core is a general term that means nothing until you know what core material was chosen.

Some TT claim their house ply deck is a core , NOT!

The Navys of the world and the Pilot bot guys usually have the best standards ,
its their lives , but not their money.

Most specify AIREX as the foam core.
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Old 05-22-2016, 09:20 AM   #31
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[quote]I will NEVER buy a boat with ANY end grain balsa in it ANYWHERE. Been there never, never again. [quote]


sounds like the voice of experience. Some details might help others understand the issue.
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Old 05-22-2016, 09:30 AM   #32
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A way to tell if a section is cored is to shine a bright light on the outside while looking at the same space inside. Balsa blocks will be apparent as very regular shaped shadows.


I know it works for balsa on gel coated, unpainted, surfaces. Have no idea if it works with other cores or through paint.
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Old 05-22-2016, 02:23 PM   #33
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[QUOTE=bayview;445064][quote]I will NEVER buy a boat with ANY end grain balsa in it ANYWHERE. Been there never, never again.
Quote:


sounds like the voice of experience. Some details might help others understand the issue.

Look at end grain balsa mats at the fiberglass store. Then imagine what happens if you have water intrusion. If it is a vertical surface the water will drain to the low spot and rot there. If it is a horozonal surface, like a deck on a boat the water will run to the low spot stay there until the trim changes. The gaps between the balsa gives the water canals and "freedom to move around the country" setting up rot everywhere.

While EGB is light, stiff and properly applied and maintained it is excellent but one non thinking, ignorant or don't give a damn individual works on the surface then failure is eminent. Case in point, the Mainship 34 MKI, II, III. 78 to 85. Boats were shipped to dealers, bridge furniture, ladders, deck rails, bridge shield and other attachments were slapped on. No hole saw and filling beforehand where drilling was to take place, just 'git er done. That is the beginning, and I bet you know the rest of the story.

I took 5 or more Home Depot buckets of saturated mush out before recoring the bridge, similar on the cockpit and various soft spots on other decks. Every one of the Boats in that 7+ year production run I have encountered had exactly the same issues. Never, never again.
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Old 05-23-2016, 06:31 AM   #34
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"Some details might help others understand the issue."

"Then imagine what happens if you have water intrusion"

Water intrusion is either a poor build or more usual poor or no maint.

If kept "perfect" wood , balsa , ply, whatever would not be a danger.

In the real world folks prefer to rely on blobs of goop , rather than lift and rebed as required.
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Old 05-23-2016, 08:47 AM   #35
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FF does not the "blobs of goop" break down over time and lead to the results I described?
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Old 05-23-2016, 09:42 AM   #36
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Sure it does and things come loose for a variety of reasons.


Poor workmanship is a fact of life, even at new construction or attaching options. Using a product like balsa where the smallest screw leaking can cause massive damage is just irresponsible.
You have a nice tight deck then someone comes along and installs snap fitting for your bimini or a nice carpet and penetrates what was a solid deck. Guess what happens next.
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Old 05-23-2016, 09:47 AM   #37
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Could not agree more.
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Old 05-23-2016, 01:14 PM   #38
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FF" does not the "blobs of goop" break down over time and lead to the results I described?"

Sure bit All the sealants do not last forever.

Stanchion bases , water fills, diesel fills ,window frames, Everything that is an attachment has a sealant ,,,with a limited life.
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Old 05-23-2016, 02:04 PM   #39
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http://s-www.leprogres.fr/images/AEC...1450251431.jpg

it's no scientific test here, and may be outside thread...
it's about accident between Balearic grp non cored hull (Menorquin or Majoni about 43') cruising downstream Rhône-River and heavy steel barge going upstream, cored hull at places.
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Old 05-23-2016, 02:11 PM   #40
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FF" does not the "blobs of goop" break down over time and lead to the results I described?"

Sure bit All the sealants do not last forever.

Stanchion bases , water fills, diesel fills ,window frames, Everything that is an attachment has a sealant ,,,with a limited life.
That is why a quality build will have solid fiberglass at the places where those things are attached. Unfortunately, it is more expensive to do it that way so many builders didn't/don't.
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