CANOEING, SAILING AND MOTOR BOATING
LIEUT. WARREN H. MILLER U.S.N.R.
D. APPLETON-CENTURY COMPANY INCORPORATED
COPYRIGHT, 1917, 1919, 1928,
But the best small racing craft of all for boys is the knockabout. In the old days designers used to build a yacht with sharp vertical bow and a long bowsprit that overhung like a spar. Such a boat always slowed up in a head sea, and, when running before the wind, was apt to dig her nose into a wave and "broach to," that is, slew around on her nose until broadside to the wind, when she would generally capsize. These were bad points, and the short body of the yacht made good sharp entrance lines impossible. So, why not have the bowsprit part of the boat hull itself, so that it would lift her up in a heavy sea and make it easy also for the designer to give her long, easy entrance lines -- In a word, the knockabout model of today.
SAIL PLAN OF A 26-FT LOA KNOCKABOUT
Another thing: most boats sail on their sides, not on their bottoms, and the formula for speed says that, other things being equal, a boat is faster in proportion to her length. Now a knockabout on an even keel will draw only, say, 15 to 25 feet of waterline, but when she heels down on her side she puts all of her shell into the water for its full length, 25 to 40 feet respectively, and thereby increases her speed, besides giving her good lifting power when her nose hits a wave. And so the knockabout came to stay, and, as it beat the older models all to pieces and was much safer to sail, the latter went out of existence entirely. In general the knockabouts are built with rather shallow sections and a deep fin keel; the overhang fore and aft when on an even keel is very large, taking the place of the bowsprit and stern outrigger of early days; the jib is entirely inboard so you do not have to crawl out over the pickle and get soused with salt spray in furling it (as I had to when a boy) ; the mainsail is of the modern shape, with gaff cocked well up and center of effort kept low -- and how she can sail! I've seen the large Class Q knockabouts raced against the famous
THE POPULAR 15-RATER KNOCKABOUT
Our illustrations show the smallest of the knockabouts, the 16 feet L.W.L., 26 feet over all. The beam is 7 feet 5 inches, so you see she is not so narrow; the draft, including fin, is 4 feet 6 inches or about three feet to the bottom of the boat measured from the taffrail. They carry about 1700 pounds of lead ballast in the keel, and of course are too complicated for youthful carpenters to attempt. The best way to acquire one is to buy them secondhand in the fall, when their rich owners are willing to part with them for a few hundred dollars, having usually built the boat solely to enter some one-design races.
The sail area of the boat shown is 330 square feet, which is a good deal more than double that of the 16-foot catboat just described, and a third larger than that of the sail skiff. The boom is 19 feet 6 inches; gaff, 18 feet 4 inches; hoist, 10 feet; and leach, 32 feet. Jib has 18-ft. hoist; 14-ft. luff and 7 ft. 10 in. foot. A spinnaker with 18-foot pole completes the sail set. A little house or cabin aids in making her a good weather boat, besides providing a cruising shelter, of sorts. This boat is primarily for racing, but modern designers have worked up cruising knockabouts that are better cruisers than any of the older designs of cats and sloops.
In the design you will note that the matter of strength in mounting and staying the mast has received especial attention. The two weak points in any boat are the mast step and the shroud anchorages. These, with the mast itself, constitute a triangular truss that must withstand the enormous sail pressures. No ordinary mast step will do; note that the step used in knockabouts is a heavy oak timber, secured to half a dozen ribs as well as to the stem for'd. The ribs and mast partners are braced at the mast sections with knees, and doubled ribs are put in here to give a stout anchorage to the chain plates. Note also a new rope in the rigging that you have not seen before. It runs from the masthead back to a cleat about amidships on each side, and is called the backstay preventer (or rather preventers as there are two of them, to port and starboard).
One or the other of them is in use when broad reaching or going dead before the wind with spinnaker set in both cases. The ordinary drive of the mainsail is taken care of by the aft pitch of the main shrouds, but, with the spinnaker added, the pressure would pull the mast over forward if it were not for the preventer backstay. The lee preventer is slacked off its cleat and the weather one belayed as the boat comes about so there is always one of them working.
While the design of a knockabout looks hard, I believe that a simplified model, with centerboard (as many of them are designed), and the planking covered with canvas, would not be out of the question for four youths of 18 to 20 years of age to build. I would suggest a 2 x 12-inch oak keel, steam bent to fit the lines shown and take the place of the stern hook on the usual three-piece keel of larger craft. A natural bent 3 x 6-inch oak stem and a stern knee of 3-inch stock serve for your main members. Oak stern transom of 1-1/8 inch stock; planking of 7/8-inch white pine with No. 00 duck canvas skin. An 8-foot board will be plenty for this boat, and the bottom of centerboard trunk logs are rockered to fit the sweep of the keel. The logs would be of 2 x 12-inch hard pine; upper boards of 1-1/8-inch yellow pine; centerboard of 1-7/8-inch willow oak.
Both board and trunk are through-bolted with half-inch iron rods. You would need a skeg and rudder post, and the boat itself ought to be a foot wider beam than the dimensions of the one shown with keel, and the ballast, about 800 pounds of it, in sand bags in each bilge behind the cockpit seats making 1600 pounds in all. Ribs of 1 x 7/8-inch oak stock, steam bent. A heavy sawed frame every third rib, gotten out of 2-inch stock, makes a stiffer boat of her, leaving the work of pinning the planks firmly together to the thinner steam-bent ribs.