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post #1 of 10 Old 05-23-2010 Thread Starter
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Best hull material?

I believe that some or most hulls have Bulsa Wood in them. This tends to be a problem if the gel coat cracks. Who in your opinion is currently making the longest lasting and most durable hull?
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post #2 of 10 Old 05-24-2010
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I'm not sure about hulls having balsa cores but there was a time when decks had end-grain balsa as a core - very strong but also quite absorbent. I don't know if it is still widely used.


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post #3 of 10 Old 05-24-2010
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Wood seems to work out pretty well. Schooner Lewis R. French - The Oldest Active Schooner in the U.S.

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post #4 of 10 Old 05-24-2010
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Quote:
Originally Posted by Omatako View Post
I'm not sure about hulls having balsa cores but there was a time when decks had end-grain balsa as a core - very strong but also quite absorbent. I don't know if it is still widely used.
Almost all decks have been and continue to be, constructed with balsa core.

Originally all FG hulls were solid glass, over the last 30 years some manufacturers started to core their hulls, for cost or performance reasons, so perhaps half or so of newer FG boats have cored hulls.

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post #5 of 10 Old 05-24-2010
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There is no such thing as a best hull material. Each has its own merits and liabilities, and each is best suited for a particular application. I also do not think that there is a particular builder who is building "the longest lasting and most durable hull". Most builders do a good job at building long lasting and durable hulls. It is often the decks and the details of construction such as how the structural components of the interior are installed that dictate the long term durability of the boat.

As to the best hull material, of the most common boat building materials:

Fiberglass offers a lot of strength for its weight and the ability to produce a lot of boats with a minimum of labor. I high tech form can be very rugged and durable, or press the limits of 'just enough strength to finish the race" depending on the design goals for the boat in question.

Wood offers a range of building techniques, some very low maintenance and some not so low maintenance but highly maintainable almost forever. Wood can be very strong for its weight, or not so strong for its weight depending on build technique and materials used. Wood offers some of the least expensive ways to build a one-off design.

Steel and Aluminum are comparatively inexpensive ways to build a one off design, and has some real advantages for bigger boats. Steel offers great abrasion and impact resistance but it comes at the price of being a heavy material for the strength, but also high maintenance and with a shorter lifespan than some other choices.

Ferrocement offers comparatively inexpensive and readily available building materials, but requires high skill levels to build and finish well.

I would like to address your comment," I believe that some or most hulls have Bulsa [SIC] Wood in them. This tends to be a problem if the gel coat cracks."

Many, if not most, production boats have balsa coring in the decks. This has been true since the some of the very first fiberglass boats (Bounty II, New Horizons 26 and Galaxy 32 for example) Balsa is used because of its strength to weight, its resistance to fatigue and horizontal sheer, and because end grain balsa, if properly installed, is very resistant to rot. It is a comparatively expensive way to build a boat. There is a potential problem that can occur when balsa coring is not installed properly, and also in cases where the core is not properly sealed where fastenings for deck hardware penetrate the deck. This can be a particularly common problem on boats built before the 1980's when proper installation procedures were not fully understood.

Cracking of the gelcoat has nothing to do with the core rot. Gelcoat is merely a cosmetic finish whose sole functional purpose is providing UV protection for the reinforced laminate (the reinforced portion of lay-up that makes up the structural portion of a fiberglass reinforced composite). There are multiple layers of reinforced laminate between the gelcoat and the core and it is this reinforced laminate that protects the core from rotting not the gelcoat.

Jeff


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post #6 of 10 Old 05-24-2010
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Quote:
Originally Posted by Jeff_H View Post
Cracking of the gelcoat has nothing to do with the core rot. Gelcoat is merely a cosmetic finish whose sole functional purpose is providing UV protection for the reinforced laminate (the reinforced portion of lay-up that makes up the structural portion of a fiberglass reinforced composite). There are multiple layers of reinforced laminate between the gelcoat and the core and it is this reinforced laminate that protects the core from rotting not the gelcoat.
Jeff, I agree 100% with everything you said except for this.

While you are correct that the gelcoat is the cosmetic finish to the structrual laminate below, a crack in the gelcoat will often accompany a crack in the underlying laminate, as whatever caused the gelcoat to crack will often cause the laminate below it to crack as well (impack or stress), or vice-versa where a fatigue or failure in the structrual laminate below the gelcoat causes the gelcoat to crack.


Either way many cracks in gelcoat are cracks where moisture can get into the cored material and thus should not be ignored.

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post #7 of 10 Old 05-24-2010
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DropTop, I see where you are coming from and to some extent this may be purely a matter of trying to explain things within the limits of the internet. As I read the original post, I understood him to say that balsa coring is a problem if the gelcoat cracks. I was trying to explain that gelcoat is not the structure of the boat and even if the gelcoat cracks, it may not lead to core rot.

I was trying to say that gelcoat develops cracks for a lot of reasons many of which do not involve the structural laminate such as improper mixing or application of the gelcoat itself, or storing a wet object on the deck year round which then had cycles of freeze and thaw, both of which could leave the core perfectly intact.

On the other hand, I completely agree there are reasons why the gelcoat would show cracks that are more serious and may be a reflection of damage to the structural laminate, and so may also potentially reflect damage to the core.

I think my main point is that there is nothing inherently wrong with balsa cored decks if they are properly constructed and sealed from deck leaks.

Jeff


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post #8 of 10 Old 05-24-2010 Thread Starter
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Great reading, thanks guys. I am learning.
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post #9 of 10 Old 05-24-2010
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Wink snb25 joni

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post #10 of 10 Old 05-24-2010
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Jeff

I probably should have been clearer myself. I understood your intent and didn't think that you didn't know what I wrote, I was just trying to clarify for Jay2 what you wrote. I just thought you only told part of the story while you were explaining that some cracks are nothing to be concerned with, you forgot to mention the exception to that, plus I wanted to interject my feelings that he is often right to be concerned with a gelcoat crack, and reaffirm what you said is still valid.

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