# Balsa cored hulls - old boats



## gstraub (Sep 25, 2002)

I''ve been looking at boats of the ''79 to ''84 vintage. A couple that I am interested in have balsa cored hulls. I once had a boat with a balsa cored hull and no problems, but the boats I''m looking at are getting pretty old and I''m concerned about the longevity of the balsa/fiberglass bond, as well as the potential for a waterlogged or rotten core. Any thoughts on this issue, especially with regard to the age of the boats?

Gerhard


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## Jeff_H (Feb 26, 2000)

There is no one single right answer here. In a boat that properly constructed, properly maintained, and has not had major trauma, there is nothing wrong with a balsa cored hull. Potentially they can have an equal or longer lifespan than a boat with a hull that does not have coring or adequate framing because fiberglass tends to fatigue if it is allowed to flex a lot. 

BUT that means examining each boat on a boat for boat basis. The other problem has to do with the specific time frame that you are considering. This is the period that blister problems was at their worst. Blisters can greatly accelerate fatigue in non cored boats and delamination in cored boats by weakening the laminate and allowing moiture to migrate deeper. During this period I especially perfered boats that had substantial internal framing as it helps with both cored and non cored hulls. Internal framing reduces the stresses on and flexing within the skin and probably offers the most durable construction over the long haul. 

(That is how my current boat which was built in 1983 is constructed and was one of the reasons that I bought the boat that I did).

Jeff


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## tsenator (Nov 6, 2000)

Be vary wary.....20 year old boats have a long time for water ingress and on cored hulls the problems can be very damning. A solid hull is much less critical to water intrusion.

In any event I would get the *best* surveyor money could buy. One that has extensive experience with water intrusion into Hulls. Just any surveyor won''t do and it will be money well spent.


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## Jeff_H (Feb 26, 2000)

"A solid hull is much less critical to water intrusion" but far more prone to fatigue problems.

Jeff


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## gstraub (Sep 25, 2002)

Thanks for the detailed comments, Jeff and all. I was hoping you folks would make my decision easier!!

Gerhard


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## paulk (Jun 2, 2000)

We are dealing with this issue right now, as a yard preps our 1981 boat for painting the topsides. They are claiming that high moisture content in the core, especially along the top edges, near the toerails, mostly midships, will affect the longevity (and appearance) of the awlgrip. We are having samples taken to determine how "wet" the core is in different places. Overall, the hull appears sound, though there are a few blisters under the waterline. The problem is that wet core often preceeds delamination and rot. It is sounding like we need to dry things out a bit -- difficult on a boat!


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## tsenator (Nov 6, 2000)

Paul,

Where are you located? Do you haul your boat every winter or are you in warm water and just haul for maintenance? Have you owned this boat for the full 20 years?


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## sailingfool (Apr 17, 2000)

I suggest you review the material about cored hulls on www.yachtsurvey.com. The author is pretty vociferous about this subject, but certainly backs his opinions with a lot of engineering data. Our decision was no cored hulls need apply.
Good luck.


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## Jeff_H (Feb 26, 2000)

Actually, I find that there is a whole lot of hyperbole on that site that really is not borne out in the literature nor in my research with other experienced surveyors, yacht designers and marine engineers. Also much of the limited data that appears on that site seems to reflect practices really not used in sailboat construction. 

Jeff


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## paulk (Jun 2, 2000)

We bought our cored-hull knowing the potential for problems was there. The previous owners had raced her hard, moved fittings around without bedding them properly, hit things, had people hit them - the whole show. We fixed the cabintop, which had become a soggy mess of balsa, from the inside. Six seasons later, we still race her pretty hard (10knots with the chute up in 25 knots of breeze) and the yard has taken core samples that show one area of wet delamination that we think was caused because the previous owners screwed holes into the interior liner aft to secure wiring , and then added water by not packing the rudderpost stuffing box. The quarterberth plywood facings held the water over the screwholes, and voila! We expect to fix that this winter. Getting the deck to drain better in the way of the toerail should help dry out the topsides. With any luck (knock on wood!) we hope to have another 10 years with our 1981 baby.


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## TSOJOURNER (Dec 16, 1999)

Our present boat, Teacher''s Pet III was one of the first balsa cored boats, we had to import the logs and have a mill cut the strips for the hull, not like the squares.
She was built in the 1968-69 period. The resin was very good then. She has never had a leak and when surveyed the surveyor said she was in better condition then any boat of the same period he had surveyed. Balsa Core is O.K., maybe even good, our boagt does not sweat, is dry, cool in the heat and easy to heat when its cold. I get tired of hearing "experts". except for Jeff H shooting their mouths off.
Gene Koblick


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## tsenator (Nov 6, 2000)

There are obvous pro''s and con''s to cored hulls. If I had all the money in the world, I would probably own a custom built cored hull boat.

I suggest you read some of Calders Books like Boatowner''s Mechanical & Electrical Manual. I think he goes over some of these issues in a non-biased format.


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## sailingfool (Apr 17, 2000)

Gene,

Can''t bite my tongue on this... I,m glad a cored hull has worked out for you. I''m no expert, however I''ll share my personal experience, for whatever it''s worth. 

I raced a C&C 30 for many years in the early ''80s in a rocky coastal area. No matter how careful one was, with the heat of the battle and flying sheets and guys, eventually you made a mistake and hit a rock. The good thing was that the early C&Cs were very solid boats and would bounce over a rock at 6 knots with nothing to show for it other than a knuckle in the leading edge of the lead keel. The local owners of 24s, 25s, 27s, 30s, 33s, and 35s all shared this experience, some more than others.
C&C introduced cored hulls with the 34 which shortly showed up in the fleet. When the first 34 owner pulled his boat a few days after the introductory rock experience (just to check), the hull took several weeks to stop leaking the water it had absorbed, beginning the cycle of many years of repairs of escalating expensiveness.
So I''m no expert, but it seems to me that cored hulls can be fine unless they get damaged, in which case you can be hosed. My inexpert comment would be why take the risk if you have a choice?


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## TSOJOURNER (Dec 16, 1999)

If you are serious? TPIII is going to be seriously for sale. I''ll carry a contract on her with $7500 down on a firm 37,500 price. She is fully founded with EVERYTHING
ANYONE COULD DREAM OF FOR CRUISING.
gENE


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## Jeff_H (Feb 26, 2000)

I have seen that go both ways. I have seen none cored hulls go aground and the flexure dislodge bulkheads and delaminate the hull at high load concentration areas and I have seen cored hull boats hit bottom at very high speeds (such as my Laser 28 which hit bottom surfing at nearly 9 knots) without discernable damage. It all comes down to engineering, build quality and luck in how the boat hit. Structurally, a properly engineered and constructed cored hull should be several times stonger than an equal weight non-cored hull. That is why coring is used in the first place. 

Jeff


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## Symbol (Feb 11, 2003)

Teacher''s pet III is an entirely differently built boat than the typical balsa cored boat.
TP III was a strip plank built of balsa wood planks and then covered with glass inside and out. The cored boats have end grain balsa held together with a scrim. Since balsa is a closed grain wood, the polyester resin did not adhere well to the core--and delamination has been a problem. We hope to shortly have some ultrasonic testing gear availalbe at a reasonable cost to test these hulls. If anyone has a section taken from a balsa core boat, I would appreciate an E mail to [email protected]
Bob Austin


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## Jeff_H (Feb 26, 2000)

Bob Austin

Can you clarify your posting a bit? I understand your point about the construction technique on ''Teachers Pet III'', which is as you descibe it, especially relative to conventional cored construction. The part that I did not understand was your point about balsa cell configuration and bonding. 

Balsa like most wood species absorbs far more moisture in the capilliaries between the cells than through the cell walls. In other words, if you wet the end grain of a piece of wood, vs the side of a piece of wood it will absorb more water in a given time over a given area then the side of a piece of wood. The theory behind end grain balsa is to take advantage this capilliary action to allow resin to soak into the exposed capilliaries and to form a physical bond and at the same time seal the end grain to minimize the amount of water that can enter the capilliaries and start rot. It also in theory slows the spread of rot since water cannot flow as easy through the side walls of the cells or capilliaries. 

If properly wet out and bonded, this is a very good system since Balsa offers excellent sheer resistance for the weight and cost. Of course the big ''If'' is whether it has been properly wet out with resin and bonded. When the surface has not been properly wet out it is easy for delamination to take place. In theory Balsa should be easier to bond than closed cell foam which requires special treatment to create a mechanical bond similar to Balsa, and it takes a heavier higher density foam to equal Balsas sheer stength. 

All of that said, I still prefer a high density foam, both above and below the waterline, for its greater durability in the case where it has been exposed to water.

I do have a box of old hull corings from my boatyard working days. I used to use them for backer blocks. I have not seen them in a while but I am sure they are here somewhere. Where are you located?

Jeff


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## Maine Sail (Jan 6, 2003)

Spent over $900.00 doing three surveys (#2 & #3 were partials) on three boats with cored hulls and all the boats were mid to late eighties. Every one of these boats was in beautiful condition with loving owners but all three were basket cases below the waterline. Gave up on cored hulls and bought a solid glass hull. Never had a flex problem or any signs of it. Just my .02 cents...
Rodd C.


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## gstraub (Sep 25, 2002)

Rodd, out of curiosity, well maybe more since I''m thinking about making an offer on a boat with a cored hull, what types of boat or boats were these? You can email me direct if you don''t want to post that here.

Gerhard
[email protected]


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## sailingfool (Apr 17, 2000)

While I was in a waiting room recently I picked up an older SAIL magazine (2002/2001?) and read an article about moisture meters - their various designs, uses and limitations. As an illustration of their limitations, the author discussed a boat whose wet core had been repaired by extensive drilling/drying/filling followed by a clean bill of health from a moisture meter test. When the yard went to re-install a fixture in the hull prior to launching, water immediately began leaking from the hole that they drilled...
Might be worth looking through the library to find...


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## TSOJOURNER (Dec 16, 1999)

Workmanship makes a real difference in this question. We own a 1987 Nonsuch 30''. The 30''s and larger were cored above and below the waterline with end grain balsa. The boat was purchased two years ago at a yard in Essex that had 25 or 30 Nonsuches, ranging in age from 1979 to 1990. None of the boats had blistering problems, and there were no reports of problems with the core material.

The Nonsuch listserve, which can be found at the International Nonsuch Association site www.nonsuch.org) has had no conversations at all about either blisters, delamination, or core problems in the 8 months I have been on it. This has about 300 to 400 members from the association of perhaps 600. There were approximately 1,000 boats made.

I''ll pose the question, but I think it''s a non issue. The hulls were laid up very carefully.


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