11th Experiment.
Torpedo:—112 lbs. of gunpowder, enclosed in a cylindrical case of 3/64" steel, placed in a 3/16" steel case, with 223 lbs. of buoyancy. Ignition effected by a glass igniting bottle. It was placed 5·75' from No. 5 frame, 9·25' below the surface of the water.
Effect of explosion:—There was but little upcast of water outside the ship, but a great upcast through the ship. She immediately lurched to starboard, and on boarding her five minutes after, the target was found full of water.
The effect on the target was as follows, above the 2nd longitudinal frame, where strengthened by the wing passage bulkhead:—Outer bottom blown away from the 4th to the 6th frames for a length of 8 feet and a height of 4-1/2 feet, and bent in 6-1/2 feet. Inner bottom bent in and broken through between the 4th and 5th frames, with an irregular hole 8' square, and between the 5th and 6th frames, a similar sized hole. Wing passage bulkhead was bent in 2" to 3", and riven for a length of 29'; in the water-tight middle bulkhead athwartships the rivets in two vertical joints were completely torn away.
Between the 2nd and 3rd longitudinal frames, and below the wing passage bulkhead, both the inner and outer bottoms were completely blown away for a length of 12 feet and a height of 4 feet. The vertical and horizontal frames between the two bottoms had kept their position unchanged, and excepting that the bracket plate by frame No. 6 was bent, cracked, and torn away, the damage they had sustained was limited to some comparatively slight bending. The open hole formed in the target measured 76 square feet in outer bottom, and 60 square feet in inner bottom.
Comparing the effect of this torpedo with the 7th, 33 lbs. of dynamite; with the latter charge the breach was made at the cost of the bottom plates as well as the vertical and longitudinal frames, which were completely torn asunder and strained; with the gunpowder charge, only the bottom plates were broken through, whilst the plates whose directions were nearly parallel to the lines of explosive effect were but little affected.
Experiments at Portsmouth, England, 1874-75.—The object of these experiments was to ascertain the effect of 500 lbs. gun-cotton torpedoes exploded at various distances from a target representing the double bottom of H.M.S. Hercules.
They were carried out in Stokes Bay, under the supervision of officers belonging to the torpedo department of the Royal Engineers, and a torpedo committee, composed of naval and military officers.
The Oberon, the vessel chosen for these experiments, was fitted with a double bottom, representing as nearly as possible that of the Hercules without the armour; also with a surface condenser, and its connections; a donkey Kingston feed-valve; and athwartship water-tight bulkheads, which divided the ship into seven water-tight compartments. The outer skin was composed of 3/16" and 7/8" iron plates. In her starboard side at different points were fixed forty-four crusher gauges, and over each side were suspended six shots, each fitted with a crusher gauge.
Displacement of the Oberon about 1100 tons.
The ship was anchored head and stern. Her mean draught of water during the experiments was 11 feet.