he
fittings of the boat are not too heavy.

A suitable power motor for small boats, which will run with either one
or two dry-cells, is shown in Fig. 41. The connections for the motor are
given clearly in Fig. 42, and a suitable switch to control the motor is
shown at Fig. 43.

Owing to its greater power, the storage battery is to be preferred.
Dry-cells are extremely heavy and occupy considerable space. They are
also costly, since they do not last long and cannot be worked too hard
unless they polarize.

[Illustration: FIG. 41]

[Illustration: FIG. 44]

[Illustration: FIG. 43]

[Illustration: FIG. 45]

A very suitable method of mounting an electric motor is illustrated in
Figs. 44 and 45. It will be noticed that the motor is inverted. A small
pinion or gear is mounted upon the armature-shaft of the motor. A larger
gear (about three times the diameter of the small one) is placed upon
the propeller-shaft. This gives a speed reduction of three to one. It
will be seen that the propeller-tube is strapped within a strip of brass
to a small cross-piece nailed to the bottom board of the hull. The hull
is of the built-up type, and the other three boards that go to make it
up are not shown. When the three boards are glued in place, a brass
strip is run across the top board and the base of the motor is screwed
to this. This holds the motor rigidly in place so that it will not move
when the power is turned on. The brass strip used should have sufficient
thickness to hold the motor rigid. It will also be seen that the motor
is tipped slightly so that it will come in line with the
propeller-shaft.

[Illustration: FIG. 46]

[Illustration: FIG. 47]

[Illustration: FIG. 48]

It is not always possible to obtain small gears. For this reason the
model boat builder may find it necessary to use a different method of
fastening the propeller-shaft to the motor. A very good method of doing
this is shown in Fig. 46. Here a coiled wire spring is used. This is
wound to shape on a rod, and a drop of solder holds it to the propeller
and motor shafts. In the method of propulsion shown in Fig. 44 the
armature-shaft of the motor must be perfectly in line with the
propeller-shaft, or the gears will bind and unsatisfactory operation of
the motor will result. With the little spring the motor will not have to
be mounted exactly in line with the shaft, and it will also be possible
to mount the motor standing up. Of course, if the motor is m