|Topic Review (Newest First)|
|08-26-2010 12:04 PM|
|seabreeze_97||I was just recently reading an article by Yves Gelinas about his sailing adventures. He invented the Cape Horn Windvane, and since 1973 has sailed an Alberg 30 named Jean-du-Sud. Several Atlantic passages, a circumnavigation and trip around the Horn and he says she will not make another bluewater passage..... Unless one of his grandchildren is as seduced by the sea as he was. Meanwhile, he's still sailing the east coast. Of note, he states his final Atlantic passage was rough, with winds 25-35 knots and big northerly swells, he was unable to carry full sail for more than 24hrs and managed an average of 142 miles per day. It'd been 20 years since he'd left Saint Malo, and while the people didn't recognize him, they said the boat hadn't changed, confirming in his mind that fiberglass ages better than man. Draw what conclusions you will, but I'd say if you buy a good old glass boat it'll probably outlive you.|
|08-26-2010 11:03 AM|
Would an older, (60's) unframed boat that has been sailed very gently throughout it's life, still retain a considerable reserve of flexure, or is the loss of such, purely a function of age?
Could an older boat that appears in fine shape be successfully reinforced with some framing?
Might smaller boats, with smaller panels be less prone to this fatigue?
|08-26-2010 10:53 AM|
As much as neither of us would ever expect to see these words, I agree with Seabreeze97 100%. I do not believe that early fiberglass boat designers did not know the properties fiberglass. (I apologize that most of what follows was cut and pasted from drafts of articles that I had written for other purposes.)
As I have said here before, earlier boats had heavier hulls for a lot of reasons beyond the myth that designers did not know how strong fiberglass was. Designers knew exactly how strong the fiberglass of that era actually was. The US government had spent a fortune developing fiberglass information during WWII and by the early 1950ís designers had easy access to the design characteristics of fiberglass. (Alberg, for example, was working for the US Government designing F.G. composite items when he designed the Triton and Alberg 35) Based on conversations that I have had with designers from that era, I believe that the reason that the hulls on these early boats were as thick as they were had more to do with the early approach to the design of fiberglass boats and the limitations of the materials and handling methods used in early fiberglass boats.
Early designers and builders had hoped to use fiberglass as a monocoque structure using an absolute minimal amount (if any) framing which they felt occupied otherwise usable interior space. Along with decreased maintenance and reduced potential for leaks, the added useable interior volume was a major selling point in the fiberglass boat literature of the day.
But without framing, there are important structural reasons why these early boats has such thick hull laminate. On its own, fiberglass laminate does not develop much stiffness (by which I mean resistance to flexure) and it is very dense. If you try to create the kind of stiffness in fiberglass that designers had experienced in wooden boats, it takes a whole lot of thickness which in turn means a whole lot of not very useful weight.
Early fiberglass boat designers tried to simply use the skin of the boat for stiffness with wide spread supports from bulkheads and bunk flats. This lead to incredibly heavy hulled boats and boats that were still comparably flexible compared to earlier wooden boats or more modern designs. (In early designs that were built in both wood and fiberglass, the wooden boats typically weighed the same as the fiberglass boats but were stiffer, stronger, and had higher ballast ratios)
The large amount of flexure in these old boats has proven to be a real problem over the life of the boat. Fiberglass hates to be flexed. Fiberglass is a highly fatigue prone material and over time it looses strength through flexing cycles. A flexible boat may have plenty of reserve strength when new but over time through flexure fiberglass loses this reserve. There are really several things that determine the overall strength of the hull itself. In simple terms it is the strength of the unsupported hull panel itself (by 'panel' I mean the area of the hull or deck between supporting structures), the size of the unsupported panel, the connections to supporting structures and the strength of the supporting structures. These early boats had huge panel sizes compared to those seen as appropriate today and the connections were often lightly done.
This fatigue issue is not a minor one. In a study performed by the marine insurance industry looking at the high cost of claims made on older boats relative to newer boats and actually doing destructive testing on actual portions of older hulls, it was found that many of these earlier boats have suffered a significant loss of ductility and impact resistance. This problem is especially prevalent in heavier uncored boats constructed even as late as the 1980's before internal structural framing systems became the norm. The study noted that boats built during the early years of boat building tended to use a lot more resin accelerators than are used today. Boat builders would bulk up the matrix with resin rich laminations, and typically used proportionately high ratios of non-directional fabrics (mat or chopped glass) in order to achieve a desired hull thickness. Resin rich laminates and non-directional materials have been shown to reduce impact resistance and to further increase the tendency towards fatigue. The absence of internal framing means that there is greater flexure in these older boats and that this flexure increases fatigue further. According to this study, apparently, there are an increasing number of major marine insurance underwriters refusing to insure older boats because of these issues.
Although many European and Australian and NZ manufacturers had used internal framing very earl on, by the 1970's US manufacturers began experimenting with a variety of internal framing systems, with Ericson, being one of the first US companies to produce a production boat with a molded "force grid" internal framing system. With the common use of internal framing, the weight of hulls were able to be reduced while their strength and stiffness increased.
Like any other period in boat building, the 1970's has its own issues. While many manufacturers were adopting better material handling practices, better lamninating schedules and adding internal framing, not all were, but most were beginning to lighten laminate schedules so that many of the issues of the 1960's can be found more extremely on some boats from the 70's.
Probably the biggest issue with boats from the 1970's was the blistering issue. By the mid-1970's this was an across the board problem within the US built fleet. The problem remained serious well into the mid- to late 1980's, depending on manufacturer, with the worst period for blister prone laminates being the early 1980's.
Once you get past the 1980's, the basic engineering and lamination of boats improved greatly across the board. But then you start getting other issues, which depending on make or model might include such dubious practices as glued structural components rather than tabbed, outward flange hull to deck joints, full interior liners being used to transfer working loads to the hull, poor qualitycontrolled cored hulls, and under-engineered hull to keel structures.
Which is to say, that using broad generalities there is no one period that automatically better than all the others. Each had period had some well built boats and a whole lot of not so well built boats. The good news is that you are only buying one boat. If carefully research the makes and models that had reasonable build practices, and find a good clean example, you should be fine. There are no easy answers here.
|08-26-2010 10:05 AM|
|killarney_sailor||I would also be leery of boats built just before a company went into bankruptcy (most did unfortunately). There is just too much chance of corners being cut as a company attempted to get a boat out the door to maintain cash flow. You would have to check the history of individual companies but this was a common problem in the late 80s and into the 90s.|
|08-25-2010 05:44 PM|
Originally Posted by seabreeze_97 View Post
quickly to the structural properties of fiberglass. The engineering
that went into the early Cal boats like the Cal 20 & 24 has clearly
proven to be pretty spot on fifty years later. In most cases, any
structural failures in these boats is due wooden support structures
rotting away. There are of course many builders, past and present,
that have substituted over building with massively thick lay ups
for solid engineering.
|08-25-2010 05:03 PM|
|seabreeze_97||I keep seeing that explanation about "them" not knowing how much fiberglass was needed. Now, this isn't aimed at any one person, but I just don't buy that. The first high temperature plastic composites had already been in use for several years in the SR-71. We were already well into the space program. When you consider the precision of the mechanics of so much that already existed, it doesn't make sense. Maybe they didn't know how little they could use and still have something hold together for a few years, but if they didn't know how much to use, why would the amount they decided to use have been enough? Why not twice as much? Granted, time and real-world experience bring information that, even now cannot be fully simulated, but it's pretty insulting to the whole industry of the time to say they didn't know what they were doing. Is it really believable that "they" would build with this new material without at least having some basic understanding of the strength of said material? I mean come on.|
|08-25-2010 02:21 PM|
Happened with sailboats. Years to be particularly concerned about are mid-70s during the energy crisis. Changes in resins and layups to save money during that time resulted in a lot of "iffy" build quality depending on the builder.
Also varies by builder and ownership of said builder. Builders are always looking for ways to save money and will change layups and hull design to reduce laminate. Some worked, some didn't.
Late 60s and early 70s boats are generally built like tanks because they didn't know how much glass was needed. They thinned out considerably through the 70s and had mostly sorted out by the 80s. I tend to avoid boats built between 74-76. Sticking with well-known builders tends to work better.
In the end you need to do research and know the model of boat you're looking at. For example, I will *never* touch an O'Day 30 despite being very happy with an O'Day 22 and like the O'Day 37.
|08-25-2010 01:55 PM|
Good Years and Bad Years
Just wondering if there were time periods when sailboat manufacturers really stepped up quality or when quality seemed to suffer. I know this has happened with motorcycles, motorboats, etc. but I wasn't sure about sailboats. Thanks.