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A 100' Cargo Carrying 'Skipjack'
Large Aft View | Large Fwd View | Large View AboveCopyright 2008 - 2011 Michael Kasten
General Concept
Based on a request for a classic shoal draft charter yacht of around 100 feet on deck (approximately 31 meters) with an easy to handle rig (no gaffs or tops'ls), I developed the 100' Bermuda Skipjack prototype. Then, based on another inquiry regarding the possibility of a 100' cargo-yacht, I developed the prototype shown above. This "Cargo Skipjack" makes use of the same hull form, but adds a cargo hold in place of the original cabins and adds a pilot house aft. As a cargo-yacht, the idea was to employ a more modest sail rig and a motor-vessel sized engine in order to take advantage of the synergy offered by motor-sailing.
Given the single chine shape inherited from the original Skipjack types, this design will be ideal for aluminum or steel construction. The Skipjack is perhaps the ultimate in terms of being an aesthetically refined traditional sailing vessel which has always had a single chine hull shape. No one argues with the shape, since these vessels have never been otherwise.
Could the original flat, wide, low freeboard Skipjack hull form actually be made suitable for the open ocean..?
Not if taken too literally. In order to make this work, I adapted the hull to a new shape for its new ocean-going purpose, but without violating the aesthetic character of the original Skipjack types. My goal in so doing was to create a charter-worthy cargo-yacht that could be sailed with confidence on the oceans of the world; that preserved the original character of the Skipjack type; and that could be very simply built.
The first concepts in this design series were my 51' to 70' Skipjack prototypes. Taking those concepts a few steps further first led to my 100' Bermuda Skipjack prototype, and here has led us to a competent cargo-yacht having the same hull form.
Seaworthiness
In order to be a good cargo-yacht suited to the open ocean, the original Skipjack hull form was made much less flat and wide for its overall length; the hull has been made deeper; and the topsides were given more freeboard. This latter trick was accomplished without aesthetic penalty by raising the deck to the height of the rather substantial bulwarks of the original types, and then placing a bulwark and toe rail above that.
Per the rigorous requirements of the EU-RCD, specifically the STIX criterion as outlined in ISO-12217, as long as the CG can be kept low, the adaptation of the Skipjack shown here has proven to score well within Category A, i.e. all ocean.
Hull Form
Given that this design still has somewhat more beam than would a typical yacht, the righting moment is excellent, providing for stiff sailing without excessive depth of keel. The long straight keel, with slight 'drag' over its full length, provides for the ultimate in tracking at sea, while not offering too much keel below. This combination is the very best at being able to avoid broaching or being tripped by a sea. With this keel configuration a centerboard could be used in order to provide more 'bite' to windward. But as a "motor-sailor" there is really no need to do so.
The overall benefit of the Skipjack shape is its refined traditional aesthetics, combined with an economically built and easily driven hull form. Inevitably comes the question then... 'Isn't a rounded hull faster..?'
We answer this question the same way every time: A single chine shape has very slightly more wetted surface, therefore more sail area is indicated making it the equal of a rounded hull. In section, the single chine shape has just a bit more 'shoulder' below the waterline which allows the boat to carry that extra sail area without penalty in terms of heel. At speed, in particular when sailing fast down wind, the chine shape is actually faster due to being able to develop greater dynamic lift.
The single chine shape has other advantages... primarily that of being quite simple to build in metal, therefore requiring considerably less labor. In terms of speed per dollar, since one can afford to make a single chine vessel longer than one could afford to do with a rounded or multi-chine hull form, there are substantial performance gains to be had.
Sailing Rig
For the rig, in order to make good use of modern materials, the spars would ideally be fabricated using welded aluminum pipe. The sail materials would be Dacron, and a performance oriented "off-the-wind" sail cut would be used.
Of course the rig must be kept rather low-aspect for this adventure, but it need not be shy on sail area. A modified Bugeye or modified Bermuda rig would be ideal. Aesthetically this seems to provide just the right dose of tradition, while also providing excellent performance in an easily handled rig.
Summary
This is just how the working sailors of yore would have adapted such a vessel to its new purpose, i.e. that of a safe, easily built ocean sailing craft. Whether it is an "exact" replica of a fat old oyster boat is a completely silly question. Given the proper attention to detail, no-one would even notice...!
Fast cruising, windward ability, seaworthiness, simplicity of construction, ruggedness, and a reasonable cost to build and maintain... these have been the primary goals of the design. At least in my view, those goals have been superbly met.
For more information, please inquire.
Please see the Plans List page to review our available Boat Plans.
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