Twin-boat.
A boat or deck supported on two parallel floating bodies, which are placed some distance asunder.
The floats are usually long, pointed at each end, and circular in cross section.
They are called
spindle or
cigar shaped.
The object of the construction is stability and speed, the former being secured by the lateral extension, and the latter by diminished submerged section.
The wheel is usually in the space between the spindles.
The idea may be founded upon the outrigger boats of the Indies, or upon some form of raft.
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Twin-boat. |
Twin-boats have found their principal employment in ferries, the central portion being used for the wheel and the machinery, and the platform on each side for the vehicles and passengers.
The largest boat of this construction, of which we have seen any mention, was a vessel constructed to run on the
Hudson River.
The spindles were 300 feet long, and in the center, or thickest part, were 8 feet in diameter, tapering in a regular parabolic curve to a point at each end. The paddle-wheel, which was 30 feet in diameter, worked in the space between the spindles.
In the sectional view,
a a are the staves, 26 in number and 3 1/2 inches thick, to each of which is attached an iron bolt,
b b, 26 inches long, passing through the staves, and countersunk on the outside of them.
These bolts pass through an iron ring
c, on the inside of which they are screwed up by nuts
d d; sufficient room is left in the center for a man to enter and pass fore and aft, to examine the bolts.
In the plan,
a a are the spindles;
b, the paddle-wheel;
c c c, the boilers;
d d, the cross-beams, which cross the spindles, and reach to the outside yards;
e e, f f, the diagonal bracing.
This vessel was built at New York for a
Hudson River passenger-boat.
She was said to have run 21 miles in 61 minutes, to have averaged on the river 20 miles per hour, and 14 miles per hour at sea. Her draft of water was 24 inches. She was wrecked after making a few trips.
Snodgrass twin-boat,
English patent, 1837.
The spindles are of
sheet-iron, and are cylindrical for the middle one-third portion of their length.
They are divided into apartments, by bulkheads, which divide each spindle into air and water tight sections.
Longitudinal beams and transverse braces supported the platform, or deck, upon which the boilers, engines, and cabin accommodations were placed.
The single wheel rotated in the interval between the spindles.
Gemmell's patent, about the same time, had exterior side-wheels.
Symington's steamboats.
1789-1802, were twin-boats, in which the single paddle-wheel was revolved in the central space.
A large twin channel steamer, the “
Castalia,” has lately been put upon the
Dover and
Calais ferry,
Europe.
Each hull is 234 feet long, 16.4 beam, 12.6 hold; distance between hulls, 25.2.
She has paddle-wheels between the hulls, each driven by its own engine.
