If the experiments upon the friction of surfaces turn out as I
hope, and give us reason to expect a very much less resistance from
a copper surface than that now created by painted iron, I suspect
we may be led rather to increase our length and diminish the
proportion of beam; but this is a very serious question, not
entirely dependent on the consideration of the form of least
resistance including friction, but also materially affected by the
consideration of the advantages of the extreme steadiness of motion
which length seems to give. It is a subject which must be well
discussed and well considered, with the assistance of all those
whose opinions and experience are likely to be of use to us. My own
impressions, I confess, derived from considering the cases which we
have, even after the striking result of the ‘Ocean Queen,’ are that
positive length, independently of relative length, has much to do
with it. When I see that the ‘Great Britain,’ although with a beam
of about one-sixth of her length at the water line, and a midship
section favourable to rolling, is nevertheless steady, I must
conclude that positive length may compensate very greatly for a
relatively wide beam. Now, we shall unquestionably have abundance
of positive length. We must then be careful not to sacrifice much
to keep a small beam, without being very sure that there are very
great advantages; and, except for the assumed advantages of the
long parallel or equal bearings, the form of least resistance,
including friction, with a draught limited to 24 feet, and a
required displacement of 21,000 tons, would, I apprehend, give us a
beam nearer 90 feet than 70 feet. I should like to know exactly
what the proportion would be without regard to the theory of the
long narrow parallel forms; and then let us consider how much, if
anything, should be sacrificed to attain the advantage assumed to
be attained by relative length.
Let us therefore have at once the draft of a vessel of 21,000 tons
displacement at the 24 feet water line, and of such form as will in
your opinion give the greatest speed in smooth water, without
seeking to make it narrow.
We must, of course, also bear in mind the comparative weakness of
form caused by length, and the consequent increased thickness of
material required, besides an actual increase of surface, involving
a very considerably greater quantity and weight of material in the
ship, which last consideration is very greatly in favour of breadth
of beam; for I think you will find that the quantity of iron in
two ships of 600 and 700 feet in length respectively, with the same
displacement and the same ultimate strength to resist strains, will
be fully in the ratio of their length.
_Report to the Directors on Mode of Proceeding._
Public-domain text, read in full here on John Shaqi.
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