THE DE BAY PROPELLER.

Hawke's Bay Herald, Volume XXI, Issue 5833, 19 November 1880, Page 3

THE DE BAY PROPELLER.

From, the following particulars gleaned from a valuable article in the Engineer of the 20th August last, it would seem that a wonderful revolution is about to be effected in our steam ships by the adoption of improved screw propellers. The article in question, after briefly adverting to the wastefulness of the ordinary propeller, and to the fact that a perfect propeller had not yet been produced, thus speaks of the De Bay propeller : — " This propeller is not a screw. Each part would separately act as a screw, but their contrary direction of rotation prevents the water caught between them, from following the direction of either, and the resultant of their combined direction being coincident with the axis of the screws, the water acted upon is thrust directly astern. This propeller was first tested on the screw collier Elaine and afterwards on the yacht lolair, and with the latter vessel a series of experiments were carried out. The general result of these were that the lolair, which with the ordinary propeller had made a moan speed of 7 miles per hour, had her speed increased to 8 3 miles per hour. With the old screw, however, the engines indicated 45 horse-power, but with the new propeller they indicated 58 horsepower. The new propeller has since been fitted to the steamship Cora Maria, a vessel of 831 tons net register and 2800 ton 3 displacement, on a draught of 18 feet, and thus sufficiently large to give a decisive test to the value of this invention. In this case it was found that the mean speed obtained with the ordinary screw was 8 73 knots, while with the De Bay propeller it was 11*28 knots, or in the proportion of 100 to 129 2, or an actual gain in speed of 292 per cent, with practically the same expenditure of power. With the old propeller the vibration of the vessel was excessive, causing the leading rods and chains from the wheel to the rudder to make a continuous knocking on the deck, while with the De Bay propoller the ship was as steady as if under sail. " From the accompanying drawings, this new propeller seems to consist of fans revolving on a strong shaft, and alternately shaped like an extended thumb and forefingor, and like half a fishes' tail with a square piece cut out of the centre.