Seaworthiness is one of the most important boating concepts. Thus two absolutely identical boats in a showroom may be not that much similar, for instance one of them may be an offshore sport fisherman and the other - a river or inland ways cruiser. Seaworthiness involves quite a number of features: the shape of the bow, the bottom on the hull up and down aft near the transom, the shape of the 'shoulders' behind the bow and other factors ranging from the inner strength of the hull (so-called 'structural integrity') and the shape, size and style of outboard well of the transom.
The shape-structural features of the hull are of great importance. Thus water-ski boats are easy to recognize due to their sleek, pointed appearance and little freeboard - in other words the sides of the boat are not very high. Water-ski people are concerned with having a hull that will accept the most horsepower for the least expense of money and weight. A 16 ft. flat-bottom boat with a 100 hp outboard engine will be far more speedy than a 16 ft. deep-V transom boat. A flat-bottom boat tends to slide on the water surface while a deep-V hull rides through the water. This is the corner stone of seaworthiness. A flat-bottom boat goes quite jerky as the flat sections of the hull hit the water. The deep-V-hull boatat the meantime rides softly and gently as the V-hull slices through the water. Besides a deep-V boat high sides offer protection and provide comfort regarding water drops and splashes.
Considering all above-mentioned factors one always tries to reach a compromise. He wants a deep-V hull and high topsides so that his boat slices through the water and rides softly and provide safety but on the other hand he wants a flat-bottom hull and low topsides for stability and economy (as a bottom-hull is far more stable and low topsides help avoid excessive weight and windage). As there is no ideal boat one should be patient and careful when choosing a yacht. Now let's examine some of the boat's seaworthiness features.
Flare
Flare is the amount of overhang in the forward sections of the hull and is destined to block or suppress spray coming up from the bow. It is of great importance: too much flare is worse and more dangerous than too little. With too much flare the boat tends to dig into the waves; with to little flare the boat will lift out of the waves quite well but at the same time tends to throw water back over the bow.
The Shoulders
The boat shoulders are also of great importance. When having too thin shoulders the bow tends to dig too deeply in a following sea. Otherwise, if the shoulders are too broad and too far forward the boat tends to slam.
Hull Bottom
There are two different areas of the hull bottom which rub off on your boating. The forward area of the hull bottom that meets the water the hull is shaped in a curved V that twists and flattens out down towards the stern. At the stern most manufacturers use a shallow or moderate V of 15-18 degrees or a 18-22 degree deep-V. The concrete dimensions depend on the individual characteristics of every single boat. Thus if two boats have an identical waterline beam and one is 17 degrees and the other is 20 degrees the latter will have a slightly softer ride in extreme conditions, but the 17 degree hull will be more stable and require less horsepower (given that other factors such as the weight of the two boats, the type of construction, the load etc. are constant). Some of the best manufacturers use a 'variable deadrise hull' that combines the best of both: good stability at rest and a soft ride underway.
Freeboard
High topsides have always been considered the feature of a good sea going boat. Freeboard is not necessarily related to seaworthiness as the factors keeping the waves off the boat include not only the height of the boat sides.
Transom Shape
The higher and more 'filled in' the transom, the safer the boat. There are four basic transom systems:
Full width well with a high secondary transom behind the outboard
- Virtually full transom with room for one outboard motor cut out
- Full width, full height transom of the stern drive
- Full height transom with an outboard pod or bracket bolted to the rear transom wall
So as we said the more filled in and higher the transom the more seaworthy the hull.
One should check very carefully to ensure the secondary transom provided in the outboard well is as high as if a normal full height transom had been provided. Quite a number of manufacturers tend to reduce the secondary transom height on the outboard well which can cause serious problems in choppy conditions.
Thus we can conclude that a seaworthy boat has most of its characteristics in a "not too little, not too big" relationship. And now choosing a boat and knowing its features and dimensions you can determine whether it is seaworthy or not.
