Join Date: Feb 2000
Location: Annapolis, Md
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I had seen that article before, and there is actually an old thread that greatly refutes or redirects much of what Pascoe says as it applies to the sailing industry.
Pascoe is a surveyor whose primary work is on powerboats. He has a lot of experience and there is great value in his observations but his articles tend towards over simplification for the sake of marketing his business. Much of what he says has a grain of truth, especially in the powerboat industry where the large volumes of boats produced (typically 75 to 100 times the numbers of sailboats built in year) encourages the kind of corner cutting that leads to the conclusions that Pascoe reaches. Which is not to say that these conclusions have universal accuracy especially when applied to the way that sailboats are built.
He also jumps to conclusions that may have been different if he had done a bit more research. Some of these are simple errors. For example, take his paragraph:
"In 1961 nobody knew much about fiberglass. The Navy had been doing some work with it ever since the end of W.W.II. At first they made life boats with it. In fact, even John VanHoboken, Design Chief at Chris Craft didn't know much, and I'll tell you how I know that. My father purchased a 1965 Chris Craft 38' Commander. When we drilled a hole in the bottom to install a transducer, it was OVER one inch thick. It was so heavy, we jokingly said that it wouldn't get out of its own way. Only four years later, that very same model was laid up right down to the failure point. The first boats that were over an inch thick, were now around 1/4" and they were breaking."
That somewhat reflects the 'common wisdom' of today but from my own conversations with actual sailboat designers of that era, they knew a tremendous amout about the strength and bending properties of fiberglass. (The information was widely available in published form). What designers had not figured out was how to deal with fiberglass's propensity toward high flexibility.
Early sailboat builders wanted to use fiberglass without any internal framing. Much of the literature of the era described the roominess of frameless fiberglass construction. The result was that in engineering without framing, designers ended up addressing the need for stiffness by adding a lot of thickness to the laminate. The problem with that approach came in how that thickness was actually added, with non-linear and high resin content laminates. The result was stiffer sections at a greatly reduced puncture and fatigue resistence. But that's another story.
Hulls became lighter and stronger as, in the 1970's, designers began to use internal framing systems, and boat builders began to use better construction techniques.
While much of what Pascoe says about foam coring is true for the low grade foams used in the power boat industry, there are very high grade foam materials out there that have excellent properties all around, and while they are more expensive and heavier than balsa core materials with similar strength characteristics, these are long lived materials with excellent behavioral properties.
Of course, there are other ways to go when one builds a boat besides using coring. My own boat has almost no coring in the hull or deck relying on a fairly extensive system of closely spaced frames. The short coming of this technique is that this is a labor intensive way to build a boat.
As you and I have alluded to in our PM exchange, much of this kind of discussion, in citing broad opinions based on anecdotal evidence, the applicability of the generalization often comes down to the care of execution and the specifics of the example chosen.
So as many times as I have observed 40 plus year old balsa cored decks without rot, it is also easy to cite the 10 year old boat with extensive deck rot. While I pesonally owned a 25 year old boat that lived a tough life and still had perfect condition high modulus foam cored hull and deck, I am sure we can find the kind of examples of failed foam core decks.
As I mentioned in the case of my current boat, there are very limited areas that were cored. Last haul out I had to replace the core in one of them, (the one with plywood coring) but the other areas are all intact (those being the ones with balsa coring), so that even within a single boat, there can be anecdotal exceptions to the rule.
In any event, there are some very good scientific studies of the use of coring and laminate. Probably one of the best of these was a series of Marine Insurance Industry studies that are now about 10 years old in which they went back and examined panels taken from older boats. Unfortunately the last time I looked these articles were no longer available online.