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6 Most Common Problems With Wooden Boats
Wood-Epoxy Construction. Plank-on-frame boats still have a strong cult following and a relatively large number of older wooden yachts are sailed and maintained by devoted owners. Some new plank-on-frame yachts are also built from time to time, and a few boatyards�the most prominent are probably Gannon & Benjamin on Martha�s Vineyard and Rockport Marine in Maine�even specialize in this sort of work. But the most exciting wooden boatbuilding these days is done with composite wood-epoxy construction.� Furthermore, a wood-epoxy hull forms a one-piece monocoque structure that cannot leak unless punctured. In most cases, to improve abrasion and impact resistance, the hull and deck are also sheathed in one or more layers of fiberglass cloth. Boat building basics. Prior to the development of fiberglass construction techniques, boats were built of wood, steel, and other materials, by assembling pieces and parts into a structure which was then sheathed with a hull. With fiberglass boat building, however, the major components of the boat � the hull, deck, liner, and large parts like consoles�are molded from fiberglass. Usually, this means starting with a female mold. The mold is first sprayed with gelcoat, then fiberglass cloth is applied, and then resin is used to saturate or �wet out� the fiberglass. When the resin cures, you have a. Boat hulls vary significantly in shape, size and design, which often determines their best application. They can be made out of various materials including fiberglass, aluminum, wood or steel. Although there are many variants, below are the major categories of hull types: Flat bottom hulls: A hull that has almost no deadrise (angle between the horizontal plane at the keel and the surface of the hull). Flat hulls are stable (in calm water) and usually have a very shallow draft (i.e. depth or distance between the waterline and the bottom of the hull. Deep-V hulls: A wedge-shaped hull.

This essay proposes to fill the alleged gap by offering a general discussion of how to approach the survey of a wood hulled vessel. I also recognize that in this day and age when very few wooden boats are being built, and most have gone the way of buggy whips, there's not much opportunity to gain experience in wood vessel survey.

Yet the overriding feature of the surveyor's art is just that: experience. And since the Coast Guard is reported to survey over wood vessels annually, certainly no one has a better opportunity to gain that experience rapidly and amass a large body of comparative data rapidly. As their own studies and data has shown, the U.

Because of that, the of accidents like EL TORO are likely to increase unless the CG does not only a better job of surveying them, but also of mandating repairs or condemning them once structural deterioration has reached the point of no return.

Let start with the point that most independent surveyors I know are no longer in the business of performing prepurchase surveys on wooden boats and the reason is simple. Surveyors have learned the hard way that surveying wood boats is very difficult and fraught with risks.

As private individuals, marine surveyors cannot fall back on lame excuses such as not having adequate guidance, or not finding any evidence or being inhibited in one way or another at locating serious safety defects. The civil courts charge us with the utmost degree of care in conducting that survey, and we are held accountable when we fail, an accounting that more often than not destroys our careers.

This is not to say that serious structural defects cannot be found with relative ease if one knows what he's looking for. In my 30 years experience with wooden vessels, its a maxim that structural problems always manifest telltale signs.

The difficulty is that the inspector must be expert, and must have a great deal of experience in knowing what to look for in order to find them. It should be recognized that the following discussion covers only the most basic aspects of wood hull surveying. It would require an entire book or series of books to address the subject in its entirely.

Before getting into the heart of the matter, lets first consider the nature of the materials that we are dealing with, for this will give us a far better understanding of why severe problems frequently go undetected.

Wood is a natural, organic material that has no consistency from one species to another, or within a species. Each tree grows differently and yields different qualities of wood. Consistency may or may not exist. There are literally hundreds of varieties of species wood used in construction, and these species also have an equally wide range of strength and other characteristics. Of all these species, only a very few have the ideal characteristics of good strength and resistance to deterioration.

Woods like teak, cypress, fir, long leaf yellow pine, mahogany and only two of hundreds of varieties of oak fit the bill. But over several thousand years of boat building, these most desirable species have been consumed and all but disappeared, causing builders to have to utilize ever lower grades of material.

This can damage the wood in ways that aren't easily detected. It causes minute splits in the fibers which will make the wood more porous and cause a plank cut from that tree to rot much quicker. This is why we often find just one plank on the whole vessel that rots badly with no apparent explanation for why.

Teak and cypress, among others, are highly valued for their fungi resistance. That resistance comes from certain chemicals in the tree that are toxic to fungi and man as well. These trees can also grow in soil where those chemicals are absent, meaning that they will not be present in the wood and therefore not be rot resistant.

This also explains why rotten planks and frames will appear in places where it is not expected. Strength of Wood is degraded by a variety of factors: soaking in water for 10, 20, 30 or more years, micro-organisms, shipworms, ants, termites, the normal stresses imposed on the hull, sunlight, constant wetting and drying and chemicals introduced into the interior of the hull such as spilled battery acid, petrochemicals, detergents and chlorinated cleansers, etc.

In other words, unlike materials such as fiberglass and aluminum, wood is degraded by a large variety factors. Metals Wood construction, of course, must utilize some sort of metal fasteners to hold it together.

As with the quality of the wood, the quality of the fasteners used in the trade can run from very poor steel to fairly good silicone bronze to excellent monel. As with everything else in this world, the higher the quality, the more it costs.

Thus, the ever-present tendency to reduce quality to reduce the cost of the product. This is one thing the surveyor should never loose sight of, for it can also come back to bite him if he does. Metals , of course, are all subject to corrosion, a phenomenon which is subject to much myth and little understanding. In industry, corrosion is still one of the most highly studied areas of metallurgy. Even after billions of dollars of research, all of its causes and effects are still not fully understood.

So when we think that we have some understanding about the nature of corrosion, we should think twice. The final consideration of materials leads us to consider how they all work together, and it is here where the general understanding of wooden vessels usually falls short.

Corrosion is a natural process that works to degrade all materials, whether its gold, rock, plastic or steel.

Corrosion occurs in many forms, most of which are not common knowledge, even in the marine industry. The ones we experience most often are oxidation reduction, galvanism and electrolysis. I will start with the last first because it is so misunderstood. Electrolysis is the same identical process used in electroplating.

It occurs only with DC current and essentially moves material from an anode to a cathode. Theoretically, electrolysis cannot occur from AC current, although in reality stray AC current can be converted to DC current through naturally occurring diodes such as salt crystals.

That's why electroplating can only be done with the very expensive process of using DC current. Otherwise, plating would be cheap and not as expensive as it is. Electrolysis only occurs on boats when there is a ground fault and it is leaking current, usually from bad wiring. Small current leaks are commonplace and are rapidly dissipated in surrounding metals without doing damage. Larger current leaks, as when a significant part of a large conductor has a ground fault, can produce very damaging corrosion.

People often see heavy pitting on propeller blades and rudders and attribute this to electrolysis when, in fact, it is usually the result of yet another form of corrosion, erosion corrosion caused by fast streams of water laced with air bubbles. Erosion corrosion is strictly a mechanical form of corrosion.

Galvanism This is a from of corrosion caused by a current flow generated between two materials with greatly differing electrical potentials. Contrary to popular belief, galvanism does not occur just between two different metals; it can occur between other materials, such as carbon rubber and a metal. Carbon rubber mated against aluminum, for example, is a disastrous combination that will destroy aluminum very quickly. This is often found in carbon rubber hose joined to aluminum or copper pipes and is often referred to as electro-chemical degradation ECD.

On wooden boats, galvanism is rarely a factor except in small isolated areas. When two dissimilar metals are mated electrically, they generate a very small amount of current that has little power. That means that the electricity generated has little capacity to flow very far before being dissipated. Wood is an extremely poor conductor, and sea water wet wood is not much better, although it will conduct current for short spans before being generally dissipated.

For this reason, stray current in a wooden hull does not have the capability to generally damage hull fasteners, even when underwater metals are bonded. When zincs are attached to the system, all potential for galvanism is eliminated so long as the zincs remain effective. Bottom fasteners, of course, are not normally exposed to water, and thus their chance of being affected by stray current or galvanism is even further reduced. Thus, galvanism rarely, if ever, is a factor in hull factor corrosion.

Stray Current is the cause of true electrolysis and can cause damage to fasteners if the leaking voltage is high enough, has sufficient power flow amperage and continues long enough under ideal conditions. However, I have never found a case where stray current damage to fasteners was not also accompanied by severe corrosion damage to exposed, submerged metals such as propellers, shafts, sea cocks and the like.

Absent such damage to exposed metals, there is no Wood Boat Hull Construction Key reason to suspect stray current damage to fasteners as fasteners are the last to become damaged in the chain of events. The effects of stray current are usually unmistakable. This is the remnant ofa zinc anode attached to a bonding system that was subjected to a full twelve volts, leaving an obvious burn pattern.

The zinc did its job and. Electrolysis, or stray current corrosion is usually notable by the very bright appearance of the corroded metal. When the pitted part of the metal is bright, that means that the corrosion is so rapid that oxides have no chance to form. That's particularly true with all copper-based alloys like brass and bronze. When the surface is dull, but still brightly colored such as pink or orange, this tends to indicate a less rapid rate of corrosion, but stray current nevertheless.

Oxygen Starvation This is the primary cause of corrosion to hull fasteners, also known as crevice corrosion. Oxygen starvation is not the simple form of chemical reaction with water that causes rust or other surface oxides, but the result of water being trapped in a small, confined space where the oxygen supply is cut off.

Surveyors are familiar with this phenomenon on aluminum fuel tank bottoms mounted on a wet plywood deck that results in rapid and severe corrosion pitting. What most surveyors have never understood is that this same phenomenon occurs with metal fasteners joining two pieces of wood together, or any other material for that matter. By the time a surveyor has pulled a thousand bronze screws out of hull bottoms, it becomes readily apparent that the wastage of the screws, or necking as its sometimes called, always starts at the center of the screw.

This coincides with the interface between the plank and frame. The reason it does is because the seam between plank and frame is subject to the capillary effect which, as we know, is the tendency of water to follow along cracks, seams or fissures.

Now, the screw, being spiral threaded, creates the tendency for that water to follow the treads right up and down the shank of the screw. Occasional wetting of the fastener is not, of course, a problem in and of itself.

But once the fastener is wetted a few times, it acquires a slight layer of soft and very porous oxides. Normally, these oxides would serve to protect the screw from further corrosion, but something else interferes. The oxides on the screw surface further enhance the capillary effect the same way that beach sand absorbs water.

Thus, once the corrosion process starts, it can only accelerate. Corrosion of stainless bolts by crevice corrosion or acid attack. The prominent feature is that the active corrosion. Unfortunately, yet another factor gangs up on our poor fasteners: crevice corrosion. The water entrapped within the screw cavity or interface between the planks does not have a good oxygen source. The chemical reaction of oxidation of the metal robs the water of oxygen and turns the water to an acid.

So what we now have is first, oxidation followed by acid attack which really does the most damage. These processes are endlessly repeated over the years, at an ever accelerating rate until the fastener is finally destroyed. The feature that often leads surveyors and investigators to the conclusion of galvanism stems from the fact that oxidation reduction or acid corrosion usually leaves the eroded metal bright-looking and without the usual covering of granular oxides.

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