Silver fin was designed primarily as a family day cruiser with adequate beam to insure a stable boat, a large deep cockpit for safety, high freeboard for dry-ness in rough water and generous shel­tered space for weather protection. With only a slight modification to include addi­tional lockers for stowing a small amount of additional equipment, Silver Fin be­comes a satisfactory camping cruiser for two, especially in tidewater areas where it is impractical to sleep ashore.

Silver Fin was deliberately designed with little detail to the interior due to many possibilities that only the ingenuity of the builder can develop. It might be suggested that the back of the driver's seat and the companion seat be fitted with lockers having doors that hinge down to form a cooking and working area as indi­cated on the construction plan.

While Silver Fin has been designed to be capable of speeds up to 30 miles an hour with outboards up to 60 horsepower, the transom cut-out has been laid out to suittwo 30 horsepower outboard motors for added safety, especially when used in semi-open water as found in large bays.

This 20-foot day boat may be built of plywood and equipped with twin engines.

To suit the modern trend you will note the two tail fins as seen on many late model cars and even smaller outboard boats, with an adjustable stern light mounted on one fin as shown. These optional tail fins are not structural members of the boat and their only purpose is to partially hide the motors in profile. Their omission will not affect Silver Fin's performance.

Although the kind of plywood is not specified on the plans, should mahogany plywood be used it is important that all the plies be mahogany, not just the two-face layers, as there have been many cases where the center cores that were not mahogany have dry-rotted away, leaving only a thin shell which eventually col­lapsed. Only the marine grade or equiv­alent quality of plywood should be used.

The construction of Silver Fin requires waterproof glue and screw fastenings to make proper contact between the surfaces.

Fastenings spaced sufficiently close to­gether along the edges provide pressure to squeeze out the air from the pockets and insure tight faying surfaces. The man­ufacturer's instructions should be followed completely for the use of the glue.

Silver Fin should be built upside down. For that reason the offsets are all given to a base line located above the sheer and to the inside of planking and underside of decking. It is most advisable to lay down the lines of the boat full size. It is a lengthy operation, but is the only way to find slight errors in the hull form or clerical mistakes in the offsets that are not apparent to the eye when working on a small drawing. Plenty of time must be allowed for this portion of the work and the builder should construct the boat mentally as he lays out his full-size plans.

Each frame should be laid out for both sides instead of the usual procedure as each bottom frame is a single piece from chine to chine across the centerline of the boat. From these outlines templates can be made for marking off each part on a plank so that the grain runs as long as possible on the turns. Cut out these parts and smooth up the inner edges, but do not cut any notches or bevels until the frames are set up. After checking each part on the full-size frame layout, the frames are assembled; across the top add a temporary cross brace to hold the frame together.

On a clear level floor lay out the center-line and frame lines at the locations shown and finish up the transom. After checking each frame for symmetry all parts can be set up, taking care that the centerline of each frame lines up with the centerline on the floor and that the entire framework is thoroughly braced together and all parts lie fair and in proper relation to each other.

Band the keel in place, locating it in the notches provided, and bolt it to each frame and the stem on the centerline with i^-inch diameter carriage bolts. Then by using battens long enough to go over at least four frame spaces, the outer edges of the frames, keel and stem can be beveled. At the same time notch for stringers, clamp and chine logs. There is no rab­beting on the chine or clamp, which sim­plifies the work a good deal. These members together with the stringers can be added and fastened to the frames with long wood screws.

The entire frame should be carefully checked for bevels and fairness. See that all bolt and screw heads are recessed wherever necessary. The boat is now ready for planking the topsides. It is sim­pler to use a thin sheet of inexpensive ply­wood as a template, checked for a fit on both sides and then laid out on the good plywood. After cutting and fitting each side drive the alternate screws. When all has been satisfactorily done back out the screws, apply glue to all contact surfaces, replace the plank and redrive the screws as well as those previously omitted (this is the best method). Plane off the bottom edge flush with the chine log so the bottom planking fits close together along the edge.

The bottom planking can be done in a similar manner and the outer edge should be planed flush with the outer surface of the side planking. Then the spray strips, outer stem and outer keel can be fitted. Before finally fastening in place, bed these well in seam composition so that all re­cesses will be filled. All screw heads should be recessed slightly to allow for filler over the heads before painting.

The boat can now be removed from the floor, turned over, the frame projections cut off, and the deck beams, brackets, deck stringers and the various blocking fitted. The decking can be added in the same man­ner as the planking, and the guard rails, coamings, seat risers, floorboards, joiner-work and shelter added.

She is now ready for painting, which should be carefully done with the best ma­terials in accordance with the manufac­turer's recommendations. The surface to be painted must be smooth, dry and clean. At least two coats of plywood sealer should be applied before giving her at least three coats of paint or varnish.

If the materials specified are not avail­able in your area see what the local prac­tice has been and substitute accordingly. Watch the weight, however, and don't spoil things with the idea of improving the hull form or construction. Scantlings and pro­portions are about right and must be re­tained if maximum performance is desired.

Specify that all the wood listed is to be used for boat building and is to be air dried to a maximum of 15 per cent moisture con­tent. All lumber should be free from checks, warps or wanes. Only tight knots not over ½inch in diameter are to be per­mitted. All hardwood is to consist of first, second or select grades only. All soft­wood is to consist of A and B grades only. For salt-water use, bronze or Monel metal fastenings are recommended. For fresh water, hot-dipped galvanized steel fasten­ings are adequate.

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