AN ELECTRIC LAUNCH
THE little electric launch to be described is of very simple
construction, and when finished it will provide the builder with a very
shipshape little model from which he will be able to derive a good deal
of pleasure. It has a speed of from 2-1/2 to 3 miles an hour when
equipped with dry batteries or storage batteries. The hull is of the
Sharpie type, and this offers very little trouble in cutting out and
assembling.
The general appearance of the boat and hull will be gathered from the
drawings. The pieces necessary to assemble the hull are shown in Fig.
58. Only five pieces are necessary: two side pieces, a stern piece, a
bow piece, and a bottom piece. The length of the boat over all is 40
inches with a 7-inch beam. The widest part of the boat is 1 foot 10
inches from the bow.
After the pieces that form the hull are cut they are thoroughly
sandpapered to produce a smooth surface. The heavy imperfections in the
wood can be taken out with coarse paper, and the finishing can be done
with a finer paper. It is understood that sandpapering should always be
done with the grain, never across the grain. The sides of the boat are
cut about 1/4 inch thick, but they are planed thinner in places where
the bend is most pronounced. The side pieces are 2-3/4 inches deep at
the stern and 2-1/4 inches at the stern. There is a gradual curve from
the bow to the stern, which is more marked toward the head.
The stern piece is thicker than the side pieces, being made of 1/2-inch
wood. It is cut to the shape shown at Fig. 58, and beveled along the
bottom edge to enable it to be fixed on the slant. The bow piece is a
triangle 2-3/4 inches in length.
After the parts are thoroughly finished with sandpaper the stern piece
is fixed in position. In making all the joints on the boat the builder
should see that plenty of fairly thick paint is run in while the joint
is being screwed up. This will help greatly in making the boat
water-tight. Plenty of 3/4-inch brass wood-screws are used in assembling
the hull. All the holes for the wood-screws should be countersunk so
that the heads will come flush with the surface of the hull. Now one of
the sides should be screwed to the stern piece, at the same time bending
the bottom and side to meet. This is done gradually, inch by inch, and
screws are put in place at equal distances. When the bow is reached, the
side piece is beveled to fit the bow piece, which should already have
been screwed into place. The other side of the boat is treated in a
similar manner, and the young worker should take care to keep the side
and bow piece perfectly square and upright. This may sound easy on
paper, but it will be found that a good deal of care must be exercised
to produce this result.
After the hull has been assembled it is given a good coat of paint
inside and out. When the first coat is dry the holes left by the
screw-heads are carefully puttied over, and the hull is given a second
coat of paint. This procedure will produce a perfectly water-tight
hull.
[Illustration: FIG. 58]
[Illustration: FIG. 59]
[Illustration: FIG. 63]
The stern tube is 3/8 inch, outside diameter. A hole is bored in the
bottom of the boat to receive the stern tube. This job must be done
cautiously; otherwise the bottom of the boat may be ruined. It is best
to screw a substantial block to the inside of the boat. This block
should be cut to fit the bottom and will act as a support for drilling.
It will also help greatly to make a water-tight joint around the tube.
The distance from the point where the stern tube passes through the
bottom to the stern should be about 12-1/2 inches. The stern tube should
be mounted as nearly parallel with the bottom as possible, since on this
depends the speed of the boat. As the angle of the propeller-shaft
increases, the speed of the boat will decrease. In drilling the hole the
boat-builder should be careful to keep the drill running along the
central line of the boat.
As before mentioned, the stern tube is a piece of brass tubing 3/8 inch
in diameter and 8 inches long. It is filed square at both ends, and a
brass plug is fastened with solder in each end. The tube is then filled
with melted vaseline, which is allowed to cool. The hole in the hull
around the tube is then well smeared with thick paint. When this is
done, a layer of red lead or putty is placed around the joint both on
the inside and the outside of the boat.
While the putty is drying the spray-hood or turtle-deck can be made.
This is bent to shape from a piece of tinplate and extends half way
down the boat. When the turtle-deck is finished, it is best to lay it
aside, before finally fastening it in place, until the entire boat is
completed.
The wooden part of the deck is made of 1/8-inch wood and scribed with a
sharp knife to represent planking. This method of producing planking was
described in detail in Chapter II.
Toward the stern of the boat and just behind the motor a hatchway is
fitted to give access to the batteries and starting switch.
The finished Sharpie hull without its driving batteries or motor should
weigh about 1 pound 3 ounces. The hull being finished, let us consider
the electric propelling equipment.
A 1/8-inch cold-rolled steel driving or propeller-shaft is used. The
shaft is 13 inches long and a gear-wheel 1 inch in diameter is fixed to
one end of this shaft. This gear-wheel meshes with a brass pinion on the
motor-shaft. This forms a 3-1/2 to 1 reduction gear, which produces a
greatly increased speed of the boat. The other end of the
propeller-shaft rests in the skeg bearing. In this present case this
consists of a tube about 1/2 inch long, which is made for a revolving
fit on the propeller-shaft and supported by a sheet-metal bracket. This
is shown in Fig. 63. The end of the propeller also revolves adjacent to
the bearing in the skeg.
[Illustration: (C)_Jack Sussman_
GETTING READY FOR A TRIP
Heating the blow-torch to a point where it will burn automatically]
The propeller is a three-blade affair with a diameter of 2-1/4 inches.
It is attached to the propeller-shaft with a set-screw. The motor is a
very simple type obtainable in the open market. It is similar to one
shown in Fig. 41. As before mentioned, either dry or storage batteries
may be used as a source of current. The writer strongly advises the use
of storage batteries if possible. The initial cost of these batteries is
greater than that for dry batteries; but, on the other hand, the small
storage battery can be charged repeatedly and will outlast many dry
batteries. If the boat is used much the storage battery will probably be
the more economical of the two.
The steering gear of the boat is very simple. The rudder works in a
bearing that is screwed to the stern piece. The end of the rudder-shaft
is tapped, and a brass screw is used to clamp it in position after
setting it with the fingers. The rudder-shaft is a 3/4-inch brass rod.
The lower end of this rod is slit with a hacksaw and the rudder is
placed in this. Solder is then flowed along the joint.
[Illustration: (C)_Jack Sussman_
ALL READY TO GO!
A little boat with steam up, ready for a trip when her owner releases
her]
[Illustration: FIG. 60]
Of course, the builder may paint his boat whatever color he may select;
but a maroon hull with a white-enameled spray-hood or turtle-deck makes
a very pleasing combination. Fig. 60 shows a rough plan of the general
arrangement of the power machinery. Figs. 61, 62 and 63 will do much to
give the reader a clear idea of the method of construction which could
not be gained by reading a description.
[Illustration: FIG. 61]
The general appearance of the boat can be improved materially in many
ways. For instance, a little stack or ventilator may be added to the
turtle-deck, and a little flag-stick carrying a tiny flag may be placed
on the bow and on the stern.
[Illustration: FIG. 62]
The motor current should be turned on only when necessary, for dry-cells
deteriorate rapidly when in use, and small storage batteries quickly
lose their charge, although they will last much longer than dry-cells
and give much better service.