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  #11  
Old 02-05-2003
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Balsa cored hulls - old boats

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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  #12  
Old 02-05-2003
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Balsa cored hulls - old boats

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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  #13  
Old 02-06-2003
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Balsa cored hulls - old boats

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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Balsa cored hulls - old boats

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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Old 02-07-2003
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Balsa cored hulls - old boats

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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Old 02-11-2003
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Balsa cored hulls - old boats

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 thataway4@cox.net.
Bob Austin
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Balsa cored hulls - old boats

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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Old 02-12-2003
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Balsa cored hulls - old boats

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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Balsa cored hulls - old boats

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
gstraub@sailnet.net
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Old 02-14-2003
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Balsa cored hulls - old boats

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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