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post #30 of Old 06-30-2013
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Re: 6 Americans, 1 Brit vanish at sea

Okay- allow myself to defend my logic.
Here is the complete work up including designs, construction, and history of the Nina- it can be found here:
Sailing, Seamanship and Yacht Construction - Uffa Fox - Google Books

Martinez said the vintage schooner had survived storms before.

"That boat's taken a lot of damage, but it's always limped back to port," she said. "The thing is born to sail."

Blakemore said plane searches earlier this week covered a wide band of ocean between New Zealand and Australia. He said searchers were considering their options for the weekend.

He said the logical conclusion is that the boat sank rapidly, preventing the crew from activating the locator beacon or using other devices aboard, including a satellite phone and a spot beacon. He said that unlike many locator beacons, the one aboard the Nina is not activated by water pressure and wouldn't start automatically if the boat sank.

Surveyors have learned the hard way that surveying wood boats is very difficult and fraught with risks.

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.

"Wind shakes" are a phenomenon caused when a tree is hit by high winds, causing the whole trunk to twist. 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.

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.; all work to take their toll on wood. In other words, unlike materials such as fiberglass and aluminum, wood is degraded by a large variety factors.

On wooden boats, galvanism is rarely a factor except in small isolated areas.

Oxygen Starvation This is the primary cause of corrosion to hull fasteners, also known as crevice corrosion. 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.

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. i.e., air flow. The chemical reaction of oxidation of the metal robs the water of oxygen and turns the water to an acid.

Climate The effect of climate on wood vessels simply cannot be understated.

The other great enemy of wood are very damp and rainy climates, especially moderate and tropical climates.

Hull Stress The deep bilge of course is always the first place the surveyor looks for bad fasteners, for it is here where there is a constant source of water. Yet boats are not monolithic structures and they are subjected to stress and thus work and torque and wrack and twist in all directions. Often not enough to be visually detectable, but enough that all the seams and joints are indeed moving. Projected over thousands of cycles over the years, this creates the potential source for water entering virtually any seam in the hull bottom, not once but hundreds of times.

Any surveyor who has spent a significant part of his career surveying wood boats knows that, other than the garboards, wasted bottom fasteners can occur anywhere, and just about any point in the life span of the vessel.

Because a plank is no longer a living organism, it has lost much of its ability to transmit water along its length. Eventually it reaches what is known as equilibrium level and will absorb no more. Complete saturation of the open cells will only occur a short distance from the end grain unless rot sets in and then it will advance further.

When it comes to fasteners, the effect of this point should be rather obvious: fasteners near the ends of planks are the ones most vulnerable.

The most important thing to understand about wood hulls is that they are in no way similar to any other material as far as aging is concerned. As wood hulls age, they deteriorate and weaken generally. The constant destructive action of stress, working, weakening of the wood and corrosion of the fasteners means that the hull is getting weaker and all the connections looser and looser.

Now I will post the physics
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