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  #21  
Old 07-22-2012
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Re: Balsa cored hulls

I think one of the main reasons for not coring a hull below the waterline is that a cored hull has far less puncture resistance than a solid glass hull. With all the junk floating out there from Fukashima a little extra puncture resistance might be nice now!

Gary H. Lucas
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  #22  
Old 07-22-2012
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Re: Balsa cored hulls

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Originally Posted by GaryHLucas View Post
I think one of the main reasons for not coring a hull below the waterline is that a cored hull has far less puncture resistance than a solid glass hull. With all the junk floating out there from Fukashima a little extra puncture resistance might be nice now!

Gary H. Lucas
That depends on the hull. Would you rather have a typical solid glass hull that is 1/4" or 5/16" thick, or a cored hull with 3/8" balsa sandwiched between glass with a total thickness of two inches?
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Old 07-23-2012
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Re: Balsa cored hulls

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Originally Posted by Night_Sailor View Post
That depends on the hull. Would you rather have a typical solid glass hull that is 1/4" or 5/16" thick, or a cored hull with 3/8" balsa sandwiched between glass with a total thickness of two inches?
Huh?
Why would you bother with a 3/8" core if the total thickness was 2"? Why would you compare that to a single thickness of 1/4 to 5/16"? The purpose of using a core is to space the two loading carrying surfaces further apart thus making a stiffer beam. It does get much stiffer, but it actually loses strength against a puncture. Core only makes sense if the core thickness is a large percentage of the total thickness.

Gary H. Lucas
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Old 07-23-2012
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Re: Balsa cored hulls

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Originally Posted by SimonV View Post
From what I have seen and please correct me if my observations are wrong, but I have yet to see a production boat, other than pure race boats to be completely foam cored. ...
FWIW, in the Hinckleys, at least the Southwester 42' is all Airex, based on my observation of a friend's fully peeled hull. One expensive job...l
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Old 07-23-2012
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Re: Balsa cored hulls

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Originally Posted by GaryHLucas View Post
Huh?
Why would you bother with a 3/8" core if the total thickness was 2"? Why would you compare that to a single thickness of 1/4 to 5/16"? The purpose of using a core is to space the two loading carrying surfaces further apart thus making a stiffer beam. It does get much stiffer, but it actually loses strength against a puncture. Core only makes sense if the core thickness is a large percentage of the total thickness.

Gary H. Lucas
I was responding to the comment that cored hulls were not a good, or as good as cored hulls. I felt the comment was nonsense comparing apples with oranges. I responded in kind.

The purpose of a cored hull is to save weight and gain strength. The one advantage of a solid hull is longevity and ease of maintenance at the expense of weight.

Regarding the layup mentioned. I am talking from experience. My Ericson 46 is literally bulletproof. It is literally as described or thicker. You would need armor piercing ammunition to penetrate this kind of layup. As I have already stated, back then builders thought fiberglass needed to be as thick as wood.

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Old 07-24-2012
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Re: Balsa cored hulls

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Originally Posted by Night_Sailor View Post
back then builders thought fiberglass needed to be as thick as wood.
Old wives tale - for a quick bit of truth about the early days of glass read "Heart of Glass" by Daniel Spurr.

They knew what they were doing back then - lab testing to destruction etc. They were thick because it was cheap & easy, much like the huge, thirsty engines in the muscle cars of the time.
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Old 02-11-2013
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Re: Balsa cored hulls

I bought a 1978 C&C 38 Mk1 in 1999. It has a cored hull. I have had blister repair done on the hull just after purchase (not caused by the balsa core) that required grinding into the core in several places. The work was done at the Mystic (CT) Shipyard and it has been blister free for the past 12 years. They also cured the classic C&C keel root "smile" by rebedding the keel and bolts. I had the boat awlgriped last winter and it looks and sails in spectacular fashion. This beautiful boat has been part of our family for 13 years and I have never regretted taking a chance on a somewhat neglected older boat.
When I look at the new C&C 38s is see ugly and a $225,000+ price tag! A solid 38 of my vintage can be had for less than $50.000.
Get a good survey, get necessary work done at a reputable yard and enjoy one of the fastest, most beautiful boats ever made!
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Old 02-11-2013
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Re: Balsa cored hulls

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Originally Posted by SimonV View Post
From what I have seen and please correct me if my observations are wrong, but I have yet to see a production boat, other than pure race boats to be completely foam cored. What I have observed is the foam finishes at the waterline and the underwater part of the hull is solid glass. I do know that Ben, Dahl, Jano and Bov, did look at at some point look at totally foam cored and did make a few boats in all core, but went back to solid glass below the waterline. It may have to do with the fact they all use bolt on keels.
I was looking to buy a 1990 Pearson 34 until I discovered that the entire hull was balsa cored, and observed two dish sized circular cracks in the bottom paint just below the water line. I checked the hull with my moisture meter, and found very high moisture at these circles, and from there down to the keel stub.

Here is a pic;


My theory is that something impacted with the hull below the waterline, enough to crack the outer skin, and allow water penetration to the core. Water traveled down the through the core, and would soon begin to delaminate the hull. Whomever bought this vessel was going to have to pay for a VERY expensive bottom job.
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Last edited by eherlihy; 02-11-2013 at 03:51 PM. Reason: added pic
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