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  #1  
Old 02-07-2008
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artbyjody is just really nice artbyjody is just really nice artbyjody is just really nice artbyjody is just really nice
Just an interesting article

Link

Interesting read...
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  #2  
Old 02-07-2008
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Thanks for the link Jody...great article and some other good reading there too.
I like where he says:
The point here is that what we had here was in-product testing, e.g. using the product as R&D. And unfortunately, we still have a lot of that going on today.

I think that those looking at buying composite hulls for cruising would do well to read this article.
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  #3  
Old 02-07-2008
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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.

Respectfully,
Jeff
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Old 02-07-2008
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Quote:
Originally Posted by Jeff_H View Post
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.
Another factor is that powerboats need a high power to weight ratio to get into planing mode. Extra weight also subtracts directly from top speed, which will reduce the boat's marketability.

Quote:
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.
I had checked with Bob Adriance who's been editor of BoatUS Marine Insurance Damage Avoidance Program's Seaworthy magazine for a bunch of years, but he hadn't heard of such studies. It'll be interesting to try to track this work down. Well, interesting for some 'classic plastic' boat owners, anyway

Cheers,

Tim
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Old 02-08-2008
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That's funny, I thought that one of the places that I first encountered mention of the study was on Seaworthy, BoatUS's magazine. I am pretty sure that the first time I read the studies there was a link either here, on Sailnet, or over on the Cruisers Forum. I also think that Professional Boatbuilder may have also had a brief write up on these studies.

Jeff
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Old 02-08-2008
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Quote from the Article: The techies in the aerospace industry had their eye on reinforced plastics and began diddling around with it. The more they diddled, the more they liked it. Glass fiber wasn't strong enough, but they knew that DuPont had come up with a new fiber called Kevlar, and a lot of work was being done with carbon fiber.

I worked for DuPont in R&D during this time period. My job was destructive testing of different laminates. My father-in-law was DuPont's chief scientist for composites. I can verify most of the numbers that the author uses for delamination and flexing. For you golfers out there, I helped invent the graphite golf club with Paul Norman. My father-in-law invented the graphite tennis racket and I still have the first prototype.

Coring material. I did what was called the peel test with different laminates. Foam was worthless, I can attest to that. Why I don't like it. The aerospace industry at the time also didn't like Balsa like the marine industry does. What they used and still do according to my brother-in-law( who still works there) is honeycomb material made out of varies materials; aluminium, coated paper, high density plastic and a very strong fiberglass composite. These materials are both cheaper and easier to lay-up than what the marine industry uses. Why they have never went to honeycomb material is beyond me. Now back to the peel test. With solid laminates like balsa and plywood the peel test was around 200-500 psi. In honeycomb material I would get up to 1000 psi or more depending on the resign and coring material. Epoxy resins did the best at the time. There was another problem with solid coring; it was the bonding of resign to the actual material like plywood and balsa. There is another test I did that simulated the flexing of a piece around its horizontal axis. Boats flex a lot like airplanes. What I found was once a solid core started to delaminated the piece lost all of its strength properties. To get to that failure point didn't take all the much flexing or strength. In honeycomb material, it would flex all day long without losing its strength nor delaminated as easily. If it did delaminate, the fracture would be contain in a small area therefore it retain some of the strength because the honeycomb material would retain it attachment point along where it didn't delaminate.
They aerospace industry did use plywood believe it or now. It was used in the floor on airlines. Why? Three words. Women's high heels! At the time, 1970-1982 (when I worked there) the PSI in a woman's high heel was extremely high. I forgot the numbers. Flight attendants at the time were required to wear high heel shoes. Honeycomb materials main fault at the time was small footprint compression failure point.
Kevlar and carbon materials. At the time I was in the business it was pretty radical stuff. Both strength properties were threw the roof. I can remember getting new testing equipment because the equipment I was using couldn't fail the Kevlar. The main problem with Kevlar was it affinity to water. The water molecules would sit up on the fiberglass strands and not adhere to the resign and prevent the bond. We would have to dry the Kevlar fiberglass before coating it with resign. Carbon fibers problem was it didn't like UV. It would break down the bond between the resin and carbon fibers. Talking to my windsurfing buddies, they think this is still a problem. They break sticks all the time. I believe Alex had a problem with his boom once. Not sure what causes his problem.
Melissa
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Old 02-08-2008
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I have enjoyed reading the articles of Pascoe, as well of those from Jeff and Melrna. While I am sure there are certain disparities in his arguments, I see a common thread in the discussion so far, and that is the problem: consistency of quality.

When I read the post from Melrna, and words like 'aerospace industry, chief scientist, radical materials' come up. These are high tech industries with lots of know-how, and with it come costs. And I believe that this is one of the points that Pasoce was trying to make. The moment the complexity of the material/structure increases, the skill level of the individuals who are involved also increases. To use these complex materials gives very little room for error, so increased supervision is required. Therein lies the conundrum. This additional education, training and complex material increases costs, the very thing a manufacturer is trying to avoid, because his competition is still using low skilled labour, and more than likely low tech products.

I see parallels in the industry that I work in. The Client is always on the lookout for a minimal investment, but high quality product. Well, that isn't going to fly, because yes we can build you this structure from Carbon Fibre, but you don't have the cash in the bank. So, we build it out of concrete. Why? Because we know how to make it. We can keep our strength delta to minimum, and we can keep out labour costs down to a reasonable level, and we can assure quality. Quality means reliability and achieving design life, not premature failure. Having said that, Concrete Technology is very complex with an enormous amount of variables. The whole chemical reaction and the hydration process is not yet fully understood, however I digress.

I guess what I am trying to say, that is all well and good to provide new materials and procedures, but in the end, will the Client pay for it? And I see this as the reason why manufacturers are going to automisation of the construction process to achieve consistency and reduce labour costs. As for the actual laying up process becoming automated, I think there are other more qualified individuals whom could give a answer on that one.

My apologies for having digressed from the thread...

Bloke
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Old 02-08-2008
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Bloke and others.

I have a problem calling composites new technology. It has been around since the late 60's. I also have a problem with quote "skill labor"! Those workers that did the actual work at DuPont making the actual composites weren't any more skilled at the time than what I believe is in the yacht builders factories now. All were just high school graduates, that were taught how to lay up. Even I, that worked in the R&D, only had a high school diploma at the time ( I was working my way thru college at the time). The engineering behind composites is out there, the manufactures just have to ask for the technology. I know for a fact, that yacht builders can order fiberglass impregnated with resin on large rolls to their specifications. The French yacht builders are doing this as we speak, not sure any American builders are. The quality control from by using pre-impregnated fiberglass is built it. Perfect resin mixing, perfect resin to fiberglass content to mention a few benefits. It takes the technology for the most part out for those builders that are afraid of it. I truly believe it is the builder's "fear" that keeps them from incorporating this technology. When I have talked to a few yacht manufactures at boat shows, that is the impression I walk away with. Furthermore, it is a huge time saving in man hours in lay up.
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Old 02-08-2008
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"They aerospace industry did use plywood believe it or now."

They certainly did, as in this example:
http://www.diggerhistory.info/pages-...d/mosquito.htm
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Old 02-08-2008
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John I know they did until 1950 or so in building airplanes. What we are talking about is modern day building techniques, specifically composite materials which weren't available back than.
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