50' to 70' Skipjack Types
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General Concept
Dockside wags may well ask, "Why did you bother fooling around with a dowdy old-fashioned sailing type, and one that was not even intended for open ocean sailing...?"
- First: I wanted to start with a traditional type that could be easily built in steel or aluminum or any other flat sheet material, thus having a single chine hull shape for ease of 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.
- Second: I was told in no uncertain terms by another Naval Architect that a Skipjack would never be safe as a yacht, nevermind a yacht that is intended to venture offshore... Well, of course with the original flat, shoal body, wide, low freeboard Skipjack form - I agree totally! But never say never..!
Naturally, I took exception to the notion that the Skipjack type could not be adapted to a new purpose and made into quite a seaworthy yacht... One that would be safe in the open ocean, yet one that would preserve the outstanding aesthetic character of the original Skipjack types. Thus, I developed the 50' to 70' Skipjack design series illustrated here (and on our 100' Bermuda page) more or less as the result of the implied 'bet' that I could not...!
My goal in doing so was to create a classic sailing yacht that could travel the oceans of the world; that preserved the original character of the Skipjack type; and that could be simply and economically built in steel,, aluminum, or other flat sheet material.
Seaworthiness...?
Is the result faithful to the aesthetic of the original Skipjack types... Yes, very much so! In order to become a good yacht though, our design has included the following changes:
- Our Skipjack design is less wide in proportion to its overall length;
- The hull has been made deeper;
- The topsides have been given considerably more freeboard (to the weather deck).
This latter trick was accomplished without aesthetic penalty by raising the deck up to the height of the rather substantial bulwarks characteristic of the original Skipjack types, and then introducing a bulwark above that.
In order to check out the seaworthiness of this modified Skipjack design, I have calculated the hydrostatics according to the rather rigorous criteria of the EU-RCD, specifically the STIX criterion as outlined in ISO-12217. The result...? Provided that the VCG can be as I have estimated, the Skipjack model shown here achieves a STIX 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 quite 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 avoiding being tripped by a sea.
In steel or aluminum, the ballast is easily located in the hollow box-keel, so is therefore located as though it were "external" ballast. If desired for the sake of improved windward sailing, a centerboard could be added in order to provide additional 'bite' to windward.
Alternately, if the keel were shaped somewhat differently, the ballast could be lowered further. This would not necessarily make the keel deeper overall, it would just become level on the bottom, but still raked back at the forward end. In other words, starting aft, the keel would remain at the full depth of the rudder heel for approximately 2/3 of the keel length, and then would slope upward to the depth of the stem forward. With that configuration it would no longer be a temptation to use a centerboard, vastly simplifying the whole thing.
The overall benefit of the Skipjack shape is its highly 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 slightly more wetted surface, therefore more sail area is provided, making it the equal of a rounded hull in light airs. 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 surfing down wind, the chine shape is actually faster due to being able to develop substantially greater dynamic lift.
The single chine shape has other advantages... primarily it is quite simple to build, therefore requiring considerably less labor. If thought of in terms of "boat speed per dollar" it becomes obvious that one can afford to make a single chine vessel longer than one could afford to do with a rounded or multi-chine hull form, thereby realizing real performance gains.
Sailing Rig
For the rig, in order to make good use of modern materials and to reduce labor and hardware costs, the spars are intended to be fabricated using welded aluminum pipe. The sail materials are to be Dacron, and a performance oriented sail cut is intended to be used.
Of course the rig should be kept rather low-aspect for this kind of hull, but it need not be at all shy on sail area. Possibly the rig would be something like a modified Bugeye, or maybe a modified Bahamian schooner.... Aesthetically, this is entirely a matter of successfully pulling together various traditional elements that will create just the right blend. Check out our 100' Bermuda design, which is exactly this hull form stretched to 100 feet on deck, then given a three mast Bermuda-style rig.
Summary
Overall, this is precisely how the US 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. Then, whether it is an "exact" replica of a fat old oyster boat... no one will care. Nor will anyone even notice...! For an understanding of the rationale being applied here, please see our article on New Materials vs Classic Design.
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. In my view, all of those goals have been superbly met.
For more information, please inquire.
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