propeller wheel so that the blades stand horizontally, the boat can be hauled up and down the sandy beach as it comes in or goes out through the surf. In some localities, these boats are known as beach skiffs. They have a flat bottom and are something like a dory, but are fuller in body, have more beam aft and far less rake to the stem and transom. Their proportions are 20 feet long by 5 feet wide, and as a rule they are fitted with about a 5-horsepower motor, which is enclosed in a box-like cover to protect it from spray.

26.

Stern-Wheel Boats. On the Mississippi River and its tributaries stern-wheel boats are used considerably. These boats have a wide flatbottomed hull, the deck is generally extended out over the side of the hull, and is square or has a very full curve forward, as many landings are made by running the bow of the boat up against the river bank and dropping a gang plank to the shore. The deck houses on these boats are of all

descriptions according to the size and the use to which they are put. The river packets that carry freight have the deck clear and open except for a pilot house and a square boxlike house aft over the motor to shed the water splashed up by the big stern wheel, which is carried on beams stuck out aft on either side. Both marine and stationary types of motors are used on these stern wheelers and the power is transmitted to the axle or wheel shaft either by sprocket wheels and chains or by gears.

So shallow and low are these hulls and so liable to twist out of shape that wire, iron-rod, or chain guys are set up tight over upright posts to strengthen the hull. Owing to the fact that the bottom amidships has the largest area and consequently the greatest sustaining surface, it is the ends of the boat that are

FIG. 26

likely to drop or sag. If the ends of a boat stick up and the middle drops, the boat is said to sag. If the middle rises and the ends droop, the boat is said to be hogged. As these chains, etc. are arranged to prevent the ends sagging, which is the more likely of the two evils to happen, they are called hog chains. In steamboats, where this support is framed of huge timbers, it is known as the hog frame. In Fig. 26 is shown a 16-foot stern-wheeler, with a 3-horsepower gas engine, used in shallow water for towing duck boats.

27. Tunnel-Stern Boats.-Another form of shallowdraft boat is the tunnel-stern boat, which is a style largely built in England for export to foreign countries for use on such rivers as the Nile, the Amazon, and the rivers of China. In the United States, a similar type is extensively used on the shallow Florida and Mississippi rivers. The name is derived from the

fact that there is a trough-like tunnel built in the boat's bottom from about amidships aft, in which is placed a propeller. This

FIG. 27

tunnel is made so large that the blades of the propeller do not extend below the bottom of the boat. A large propeller is used by building the top of this tunnel considerably above the boat's water-line as shown in Fig. 27. When these boats were first built experiments demonstrated that an arched tunnel built in so that it just cleared the propeller, Fig. 28 (a), was more efficient than a tunnel built square, as in (b), but owing to the gain in efficiency being slight compared to the difficulty and

expense of construction, most small boats are built with the

square or box-section tunnel. It is of far

more importance to build the tunnel in its fore-and-aft shape of such a sweep that the water can flow easily up into the tunnel and not be retarded at its after end. Some builders tried to increase the speed of their boats by building the tunnel straight aft from its highest point where the propeller works to the stern, as in Fig. 29. This plan, however, was not successful because the air that was thus admitted prevented the water from rising and submerging the propeller, which merely churned around half in air and half in water. By hinging a door to close the after end, Fig. 30,

00g

FIG. 29

this difficulty was overcome. But after the propeller had ejected the air and the boat was going fast enough to start a

solid stream of water following up the sweep of the tunnel, this door could be hoisted up flat against the upper part of the

L.W.L.

Door

FIG. 30

tunnel and the propeller remain submerged. For this reason, the tunnel

stern boats have the after end of the tunnel down even with or nearly

even with the surface of the water.

28. Rift Climbers.-In some sections of the United States shallow rapids are called rifts and a type of tunnel-sterned or tunnel-bottomed boats constructed on the foregoing principle

are called rift climbers.

FIG. 31

(a)

These boats are built on the flatbottomed skiff model with a square tunnel, as shown in Fig. 31. An iron grating across the tunnel protects the propeller from hitting anything and a removable square plate in the top of the tunnel gives access to the propeller so that it may easily be repaired or even replaced should it become damaged. The tunnel is built on straight lines, and is of such height as to take in the entire diameter of the propeller, allowing no part of it to extend below the bottom of the boat. It has a long,

(b)

FIG. 32

easy front slope, thereby reducing resistance to a minimum, and giving the water a free and unobstructed flow to the propeller.

29. Viking Skiff.-For use as a tender to yachts and other boats ascending shallow rivers where extreme low water prevents landing from the yacht itself the viking skiff is a valuable craft. Its light construction, wide beam, and small draft makes it an ideal tender in which to make landings, carry out anchors in case of grounding, and to fetch in game shot from the yacht and which without the skiff would be inaccessible. It is shown in Fig. 32 (a) and (b).

CLASSIFICATION WITH REFERENCE TO CABIN AND DECK ARRANGEMENTS

30. In addition to the classification already given, motor boats used as pleasure craft are arranged into various classes according to the use to which they are to be put, with no regard to the model whatsoever. The boat may be round- or flatbottomed or skipjack, the hull may be a square-sterned, canoesterned, or any other shape, and the bow may be of any form whatever. This classification deals wholly with the living arrangements of the boats and the way the cabins and decks are built.

31. Open Boats.-Strictly speaking, open boats are only such boats as rowboats, skiffs, canoes, whale boats, skiffs used

to go through the surf on the Jersey beach, St. Lawrence river skiffs, and in fact all boats that have little or no decks that serve as a shelter. The term open boat is, however, often applied to what are, strictly speaking, half-decked boats, such as the old naphtha launches for instance, although these carried a light roof supported on stanchions with canvas drop side cur