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Build a Cheap 16-Foot Catamaran




Scientific American Supplement,

 Phil Bolger, for one, has sketched something very similar...

THE accompanying illustrations, taken from plans of a catamaran in service on San Francisco bay, will give an idea of how such a craft may be constructed cheaply and with little labor.

The runners, A A, Fig. 2, are made of three-quarter stuff, strengthened with internal cross-pieces; are put together with galvanized wrought iron nails, and the joints calked with white lead laid on before being put together. If carefully made there is no need of any opening for bailing; but after hard usage, if leakage occurs, they may be tapped by a small bit underneath and plugged. The runners are 13.5 ins. high, l ft. wide, and 15.5 ft. long.


The scow shape at the bow and stern is adopted because easier to make, and practically it makes little difference as to resistance whether the runners are sharpened in this way or laterally, while the continuation of the straight longitudinal lines is an advantage as regards weatherliness, and the upward sheer at the bow helps to keep the craft dry. In putting the runners together, set the side pieces, bottom side up, on a true surface, nailing on temporary cleats to hold them in position. The bottom board, which should be a little thinner than the other parts, is then placed on the sides, having been previously dressed into shape as closely as possible.

Begin nailing at the center and work toward the ends. When the point where the bend begins is reached, place several thicknesses of wet rags upon the bottom board and pass a hot iron over them. This expedient obviates the necessity of a steam box. Before finishing the nailing the board should be firmly clamped into place, to prevent springing. When the nails are all in, the clamps may be removed.

With the shape shown the total buoyancy will be about 1643 lbs., the catamaran being calculated to carry, in addition to its hamper, two persons, although in a pinch it will take four or even five. With a crew of two, the draught should be 4 ins.

The arrangement of cross-beams, BB, 2 by 4 inches. each, and of the mast-step, C, open platform, D, etc., will be easily understood from the diagram, Fig. 2.

The space between the runners is 8 ft., and the outside beam is therefore 10 ft. This extreme width is not required for stiffness, but is convenient in giving more room, and materially assists the purchase of the stays. The cross-beams are secured to the upper surface of the runners by bolts and lags, or wood-screws, which pass through heavy longitudinal battens (see Fig. 3) inside the runners.

The center board, E, is pivoted by a lag near its forward end and is forced down when needed by a halliard secured at the upper a fore corner and led aft to a cleat in a convenient position.

The hull thus being accounted for, the motive part of the craft, in this case of decidedly peculiar but effective arrangement, is next to be considered. One of the most important points is the proper staying of the mast, it being evident that the step only secures the heel and assists very little in keeping it upright. When the enormous spread of canvas I and its strong but unsteady lateral pressure are considered, it will be seen that the stays, upon which alone reliance can be had, must be carefully set up.



At the four points F F F F stout wrought iron straps are let into the wood of the runners, and four wire stays, 3/8 in. diameter, are led from the collar on the mast to within 18 ins. and tautened by lanyards. If the stays are perfectly taut when in use, the mast will be kept sufficiently rigid. [Stays in side view: see Fig. 1]

The sail, which is of the original Malay type with a few Yankee innovations, is 17 ft. on the boom, 9 ft. on the gaff, and 18 feet hoist. It has five slats of pine, 2 inches diameter at the middle and tapering at the ends, which answer the double purpose of flattening it and of obviating the necessity of ordinary reefing gear. The four lower slats are placed at intervals of 2 ft., the lowest the same distance from the boom, and the fifth is intermediate between the slat below and the gaff. The sail has 2 inch bands of heavy canvas sewed across it where the slats come, and the latter are made fast by fishline passed through pairs of eyelets at suitable intervals. A four-part lazy jack, G, which also acts as a topping lift, receives the sail and slats when lowered, and the whole comes home as compact as though reefed or furled in the ordinary manner. The halliard is of single purchase and rigged kite fashion to the gaff; the hauling part is passed through a fair leader at the foot of the mast and led aft. The sail slides on the mast by loose rope beckets, which permit the jib portion to swing forward when sailing free and throw the sail aft when close hauled.

This greatly assists the steering, which is done by a sweep hung by a lanyard to the after cross-beam. A sweep is preferable to a rudder, as it can be used to paddle the catamaran about or as a scull when the sail is down. [You'll need a tack line or tack purchase at (a), for some reason it's been left out of the original diagram.]


A sail made on this principle is so flat that it admits of a course less than three points off the wind. In beating to windward its superiority is unquestioned, and the ease with which it may be shortened in an emergency commend it to use on other vessels than catamarans. Notwithstanding its queer appearance it is destined to become a favorite among yachtsmen when its merits are better understood. Slats may be added to any fore-and-aft sail along the lines of the reef-points with good results; or may be made to extend over the after half of the sail only, if convenience in shortening sail merely is desired. As regards the utility of flattening the sail as much as possible, every sailor understands the question practically ; but perhaps a clearer conception may be afforded by a glance at Fig. 4, in which the common and slat sails are combined, as applied under the same conditions.

In the slat sail the line B shows the contour of the baggiest portion, i.e., between the slats, and the line C follows the curve of the belly of a common sail hauled well home. It will at once be seen that, the direction of the wind being as indicated by the line H, the portions E and I are worse than useless in propelling the boat, the former being a back sail and the latter part lying too close in the direction of the wind. Very frequently sails are so carelessly set as to belly much more than shown in the diagram, and with the utmost care the curve cannot be less, without support. This the rigid slats give. In the orthodox Malay rig a series of vangs hold each slat and the gaff in an exact line with the boom. For small craft such nicety requires too great a complication of running gear and is not necessary.

This form of catamaran is adapted only to comparatively smooth water and light winds. It may be used to advantageously in shallow water and in hunting, or exploring creeks, etc. In a sea way the runners have a tendency to dip under, and the craft is wet. The former obstacle can be obviated by making the runners higher out of water forward, with a sharp sheer, or by adding a lifting plane between them; and the latter may be removed by building the platform solid and higher, with a washboard if desired. A movable bench may also be added. From these hints, by aid of the engravings, the reader may construct for himself a powerful and efficient craft, modifying the plan according to whether it is intended as a racing machine or simply a cheap and comfortable boat.

Phil Bolger's similar cartoon
of a sharpie catamaran from
Messing About in Boats.
Back to the Top

[And what the heck, this was in the original: ]


"George Roahr, of New York, is at present busily engaged in building a catamaran for his own use. The craft, which is nearly completed, is composed of two outrigger boats, each 30 feet in length, 2 feet 3 inches depth of hold, and 2 feet 2 inches beam. The platform is 8 feet wide and 14 feet in length, and is fixed midway between the two outrigger boats, which are fifteen feet apart. The catamaran will carry a jib and mainsail rig, and when loaded will only draw nine inches of water. Mr. Roahr is finishing his craft in a most superb manner and expects that she will take no mean place in the forthcoming yacht races."

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1.0 10/15/99