(To the Editors of the Annals of Philosophy.)
Bushey Heath, Stanmore, Sept. 13, 1824.
DEAR SIRS,
The readers of the Annals of Philosophy will be gratified to learn,
that the Admiralty, in addition to the improvements already introduced into
the navy, have given orders for building three vessels (the Orestes,
Champion, and Pylades) upon different principles, suggested, I
believe, by Prof. Inman, Capt, Hayes, R.N. and Sir Robert Seppings. As these
ships have nearly equal length, breadth, and tonnage [1] and as great theoretical knowledge and ability will be exercised in
giving to every vessel that form which each individual considers the most
advancement of naval architecture may be expected from the above collision of
intellect.
When these ships proceed to sea for the purpose of comparing their
respective qualities, it is possible considerable difference will be found in
their sailing. This inequality may proceed from dissimilarity in the length of
the masts and yards, and consequently in the size of the sails. The bow of one
may be better adapted than the others for dividing the water, or the after
part may possess a more efficacious shape. The stowing of the ballast, the
smoothness of the bottoms, or superiority of seamanship, will also severally
produce a disagreement in their rates of sailing. The latter can, however, be
detected, by chainging the officers from ship to ship. An alternation in the
distribution of the ballast will produce a correspondent fluctuation in the
merits of each vessel; the best sailor becoming worse, and the dull better;
but with respect to the fore and after bodies, how far the particular form of
each contributes to the fast sailing, it will be impossible to judge from want
of sufficient knowledge of the resistance of non-eleastic fluids. This branch
of mechanical science being very imperfectly understood, it cannot be expected
that the shape of vessels can be advantageously altered, until the improvement
is founded on the solid basis of experiment. Then, and not before,
constructors will be able to give satisfactory reasosns for adopting one form
in preference to another.
To place in a conspicuous point of view the various opinions which writer
on naval subjects entertain respecting the resistance of water, I will
commence with the remarks of Monsieur Romme, Correspondent de l'Acad‚mie des
Sciences de Paris, et Professeur-Royal de Navigation des Eleves de la Marine.
This gentleman, in the year 1787, published a quarto book on naval affairs;
and therein states, that the resistance a vessel meets when sailing is almost
independent of the form of the bow; the impulse of the water being the same,
provided the greatest vertical section remains unaltered. And this theory is
represented as, confirmed by experiment, made with two models of a
seventy-four gun ship; one model had the bow formed in the usual manner with
curved lines; the other had a similar midship bend, but the bow consisted of
strait lines; yet notwithstanding this great dissimilarity of shape, both were
equally resisted when moving with equal celerity. M. Romme could not discover
that these models experienced more or less resistance effected when the
vessels were cut in two, and the head of one joined to the tail of the other.
Mr. Stalkartt, in his Treatise on Ship
Building, recommends the segment of a circle as best adapted for dividing the
water; and others prefer the parabola. Such contrariety of opinions only
prove, how little we know on the subject; and the importance of estanblishing
some more correct rule for drawing the water-lines of vessels, than the mere
fancy of the draughtsman.
The tonnage of the Royal navy in round numbers may be estimated at 450,000;
the expense of building, taking one vessel with another at 20 l. per
ton; the value of all at nine millions. To the expense of the hulls must be
added the cost of the masts, yards, sails, cordage, and many other et ceteras,
requisite for the equipment; this doubles the amount, making 18,000,000 for
the primary sum laid out on men of war. The durability of the ships in time of
peace may be now calculated at 14 years; during war at 10 years; the average
is 12 years; consequently 1,500,00 l. of money is annually expended in
keeping these bulwarks of the nation in an efficient state.
Every one will assent that the construction of such costly machines should,
in the first instance, be as perfect as possible; hence arises the question,
how, and at waht expense, is so desirable an end to be accomplished? The
increase of 1/18000th part on the annual expenditure, would secure this point;
for the application of the comparatively small sum of 100 l. in making
a complete set of experiments, in all probability, would be attended with most
beneficial results for the future constructure of ships.
Let it be borne in mind the sums of money which are year after year laid
out to encourage a superiority of far less moment to the United Kingdom than
the excellence of the navy: there are plates, sweepstakes, and purses, for
breeding fleet horses; in a national point of view, it is of little
consequence whether the average rate of a racer be 37 or 38 miles in the hour;
but widely different is the case, if the sailing of our men of war be
increased one knot, or half a knot, in the same space of time. By such
improvement an enemy's fleet may be taken, or an island captured, or a colony
preserved; and who would not rather read in the Gaszette a dispatch from an
Admiral, stating that in consequence of the superior sailing of his fleet he
had come up with, and captured the enemy, than peruse in the public papers
that at Newmarket, or an other celebrated racing ground, after a well
contested run, one horse was declared the winner by half a neck, and the prize
adjudged accordingly.
If the union of capacity with quickness of sailing be deemed impracticable,
the error of such opinion is fully demonstrated by reference to the engravings
accompanying a work on the Elements and Practice of Naval Architecture, by Mr.
David Steel; who there gives the draught of a London trader particularly
distinguished for capacity and velocity; -- a circumstance the more remarkable
in a merchantman, as the variety of the cargoes would be tantamount to
alteration of stowage; and consequently if the same vessel, under such
circumstances, continues to remain a prime sailor, it is evident this
superiority depends on the curves that divide the water.
Discoveries are continually making in chemestry, magnetism, and galvanism;
improvements are introduced in chronometers, and mathematical instruments; all
these advantages proceed either from experiment or observation, and it only
requires the powerful influence of my Lord Melville, to expel, by simlar
means, the mist that at present envelopes the science of hydrodynamics; and to
place this negelected branch of knowledge in the elevated situation it so
justly merits from its importance to a maritime nation.
I remain,
Dear Sirs, yours very truly,
Mark Beaufoy.
1)
Orestes. Champion. Pylades.
Feet In. Feet In. Feet In.
Length on deck . . . . . 109 11 . . . . . 109 6 . . . . . 110 1
Breadth extreme . . . . 20 6 . . . . . 30 6 1/2 . . . 30 1/4
Depth in Hold . . . . . 7 6 . . . . . 7 8 1/4 . . . 8 3
Builder's tonnage . . . 460 0 . . . . . 456 0 . . . . . 433 0
Light draft of water Afore.
8 6 . . . . . 10 8 . . . . . 8 8 1/2
Abaft.
11 0 . . . . . 10 10 . . . . . 10 11
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