Transactions of the Society of Naval Architects and Marine Engineers Volume 5 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1897 Excerpt: ...in the variation of the other features as noted above, viz., pitch or pitch ratio, and slip or revolutions. The investigation of the influence due to gradual variation in the area was not one of the fundamental purposes of these experiments, and the information relating to this point was restricted to the results arising from a reduction in the number of blades from 4 to 3 or 2, their shape and size remaining the same throughout. In the experiments to be hereafter described, an additional variable element--that of the amount of area--is to be introduced. In these experiments, therefore, diameter, speed of advance, and shape of blade as well as number of blades, are kept constant; while amount of blade area, pitch or pitch ratio, and revolutions or slip, are subject to variation. The essential feature of the present investigation is therefore the relation of the amount of area to the performance as a whole. There seems to be reason for believing that the influence due to change of area includes that due to change in number of blades, or, in other words, that with given area and usual proportions the performance is but slightly dependent on the number of blades. This may require further examination at a later point, but in the meantime no serious error will be made by accepting the above proposition as substantially correct. We shall not here enter into any detailed discussion of. the utility or propriety of model experiments. In the last twenty years experiments of this character have steadily advanced in scientific standing, and have won for themselves a secure place in the development of our present knowledge Transactions Institute of Naral Architects, Vol. XXVII, p. 250. of ship resistance and propulsion. It will be sufficient to note that in the case of ...