Carl H. Clark

The small launch descrihed in the present article is of the extreme speed launch type and is intended primarily for use on sheltered waters, such as lakes or rivers. With skilful handling, however, the boat will stand a considerable sea, but is hardly to be recommended for use upon other than quiet waters. It should appeal very strongly to those who are fond of canoeing, offering, as it does, a type of boat very similar to a canoe, but with far greater speed and endurance qualities.

TABLE OF OFFSETS FOR 20-FOOT SPEED LAUNCH.

Number of Moulds.

Bow.

1

2

3

4

5

Stern.

Height of gunwale

2' 0 1-2"

1' 10 1-2"

1' 9 1-8"

1' 8 3-8"

1' 8 "

1' 8"

V 8"

" " keel bottom

0' 7-8"

0' 3"

6"

" " No. 1 section

0' 4 3-4"

0' 1"

0' 3-8"

0' 1 3-8"

0' 31-4"

0' 6"

" " No. 2 section

0' 4"

0' 1 1-2"

0' 2"

0' 4

Half breadths deck

1' 0"

1' 5 3-4"

1' 8"

1' 7 1-2"

1' 3 3-4"

0' 10 3-8"

Half breadths w. 1. 4

0' 9 3-4"

1' 4 1-2"

1' 7 3-4"

1' 7 3-4"

1' 4 3-4"

Half breadths w. 1. 3.

0' 8 5-8"

1' 3 1-2"

1' 7 1-8"

1' 8"

1' 4 1-2"

Half breadths w. 1. 2

0' 7"

1' 1 3-4"

1' 6 1-8"

1' 7 1-4"

l'3 1-2"

Half breadths w. 1. 1

0' 4 1-2"

0' 10 3-8"

1' 3 1-2"

1' 4"

Waterlines are spaced 3" apart. Sections are 6" apart.

No. 1 and No. 5 moulds are 3' 0" from ends of w. 1., other moulds are 3' 3" apart.

To be successful, the boat must be very lightly and yet strongly built, all unnecessary weight must be done away with and all parts as strongly connected as possible. The canvas covered type of construction has been chosen, as it gives to the amateur a very easy method of boat building and at the same time the lightest possible boat. The general system of construction is very similar to that described in the recent issues of the canvas covered tender. The construction is, however, much lighter and simpler, as the launch is not likely to be subjected to as hard usage as the tender.

The small power required, 1 to 2 h. p. is a very attractive and economical feature, as it is both cheap in first cost and economical to run, a similar launch having attained a speed of 11 miles per hour with a 1 1/2|h. p. engine. Referring to the lines it will be seen the general shape is not unlike a canoe except for the increased size and the full stern above water. The general dimensions are:

Length on top 19' 6"

Length on water line 19' 0"

Beam at deck 3' 4"

Draft as designed 0' 6"

The actual draft of the boat will, of course, depend upon the lightness of construction and upon the weight of the crew carried, but this draft should easily be obtained with two persons and with three she will trim lower in the water. The maximum speed will, of course be obtained with the lightest possible load.

To transfer the lines and make ready for building, the usual table of offset is given. As explained in previous articles, the measurements given under " heights" are measured vertically above the base line on the mould corresponding with the number at the top of the column. Those under "half breadths" are measured horizontally out from the center line on the water lines corresponding with the numbers of the moulds given at the top.

The shapes of the several moulds are laid out on thick brown paper, the water lines being spaced 3 in. apart from the base line, a center line is drawn square with the base line, and the two fore and aft section lines parallel with the center line and spaced 6 in.

apart. The object of these section lines is to locate points below where the waterlines are useful, for example, in the body plan. Fig. 4, the two points on mould No. 4 below the lowest water line are located by the section lines.

Referring in detail to mould No. 4 in the top line of the table, the measurements given opposite the half breadths are laid off on the proper waterlines and the deck, the " height of sheer" is then laid up, locating the curve below w. 1. No. 1, and lastly, the "height of keel bottom " is set up, locating the center line point. The points should be laid out on both sides of the center line and the curves struck in with a slender batten. To allow for the thickness of the plank, a second curve should be drawn inside at a distance of 3-16 In. The other sections are laid out in the same way. It will be noted that the sheer and level from the stern to mould No. 3, where it rises toward the bow.

The actual outline of the stern is shown by the dotted outline in Fig. 4, and the offsets are:

Deck 0' 1 8/8"

W. L. 4 0' 1 1/2"

" 3 0' ll 3/4"

This outline is laid out the same as the others. The outline of the bow is also laid off; it begins 6 in. forward of a vertical at the forward end of the low water line and has a slight outward curve; the curve below the 1. w 1. should be similar to that shown. This completes the laying out.

The method of construction is very similar to that of the canvas boats already described in the previous issues. The moulds are constructed to the outlines already laid out, and of comparatively rough stock, but accurately shaped and with the load water line and the sheer line marked upon each. The sternboard is also gotten out of 1/2-in. stock to the shape laid out, but a small amount must be allowed for the bevel of the sides, about 1/4 in. on the sides and 1/2 in. on the bottom will be sufficient. The two sternboards are joined with a cleat at the center-line, and through fastened with brass screws. The angle between them is obtained as in Fig. 9, by measuring out from the center line 8 in. and forward 4 in. on each side; a templet would best be made for setting these, as the shape given is only correct when they are set at this angle. The two boards are bevelled at the joint; the cleat is also bevelled at the correct angle, and the whole fastened together. In addition to the outline laid out, the upper edge of each board should have a curve or curvature of 1 1/2 in. and the grain should run horizontal.

The stem is 3/4 in. thick, cut to the proper shape; it should be about 1 1/2 in. wide and of pine or other light wood.

For the centerpiece inside, apiece of pine 1/4 in. thick, 4 in. wide and the length of the boat is needed; the stem is fastened on at one end and the board is tapered down to the thickuess of the stem at the extreme forward end.

A foundation is now built, consisting of a board cut to the shape of the keel and set up about 2 ft. above the floor. The proper outline for this foundation is obtained from the laying off table in the line of "height of keel " by measuring them up on the correct mould points, as laid out by the given spacing. The keel, from mould No. 3 forward, is straight.

The centerpiece, with the attached stem, is now laid upon the foundation in the proper position, and bent down into place and held by shores from above. The mould and stern points are also marked on the center piece. The stern should be shored so as to stand exactly plumb when looking at it from forward. The two connected stern boards are now to be attached to the center piece. It is to be noted that from the last mould point to the after end of the stern, outside, is 3 ft. The after end of the center piece is bevelled to the proper angle of the sternboards, and under the cleat joining the latter, which is bevelled off to receive it. The stern boards may now be fastened in place, and should be shored, taking care that the after side of the joint is at right angles to the base line and in line with the stern, fore and aft. The moulds are set up in place at the mould points; those forward of the middle being placed with their after faces on the mould point, and those aft with their forward faces on the mould point. They must be set exactly at right angles to the base line and square with the center line, and the middle points of the cross braces must be in a straight line from the center of the stern to the point of the stern. The setting of the moulds is one of the most important operations concerned in the building of the boat, as any inaccuracy in the setting will result in the two sides being unlike. When correctly set the moulds should be well braced.