"calculations of moderate length, with which all naval architects are familiar, and of laying down no 66 hampering rules to interfere with the freedom of the designer's fancy as to form." A good deal of the question that has been discussed since I came into the room has been as though there was some real difficulty in ascertaining the displacement. If I may make a diagram, I will show you one thing which has not been touched upon yet. I should not like to destroy the illustration of Mr. Harvey, because it seems to me to prove in the most conclusive manner that I have been eminently right in one thing, namely, that the present rule of measuring the stern-post instead of taking in the counter was utterly insufficient. I did not expect that anyone who objected to what I said would so entirely prove my case as it is proved by that drawing. One of the great points which we want to get at is that the architect shall be as little as possible hampered in his design. Therefore displacement is a good thing; but I maintain that with displacement this is the section which we shall have beyond all possible doubt. [illustrating it]. That shows an absurdly small displacement, and we shall have this enormous vessel. There is obviously no accommodation in that vessel. I think nobody can have any doubt that a vessel with a good deep keel will have all the qualities of an ordinary centre-board yacht, but she will be, beyond all reaching, fast in smooth water on any point of sailing; but she will also be very bad in a sea-way; and with a head wind she will bob about and go up and down, and will not go on. I maintain that displacement inevitably produces that form in a yacht, in spite of all that has been said as to its allowing anything to be done. It prescribes that, and that is really my main objection to displacement. Mr. WELCH: It is a good form.

Mr. STERLING: For certain purposes; but it has not got the comfort which is important in a yacht, and it is not a good vessel for sea-going in rough weather.

Mr. J. SCOTT RUSSELL: And not a weight-carrying ship.

Mr. LIGGINS: Not a fine sea-going vessel.

Mr. STERLING: It is very difficult, indeed, to say with that what sort of relation the two vessels bear to one another. One man will contrive to overhang as much as that.

Mr. LIGGINS: It is a racing machine.

Mr. STERLING: It will, as has been said long ago, make the vessel all deck and dead-wood. In fact, it will be little else than a raft with a deep keel; and surely that should not be the thing to which we ought to tend. I am very sorry, I confess, that the whole Discussion since I came into the room has gone on the question of displacement; and that no gentleman has objected, as I hoped he would-and given his reason for objecting-to the Corinthian Rule adopted by the New Thames Yacht Club. That has been simply put aside, and the whole question has turned on the question of displacement. I think it is very unfortunate that not a word has been said with regard to the Corinthian Rule. That is really the only practical effort that has been made to alter what many of us believe to be a thoroughly bad rule; and I must say I did not expect that question would be shied, as it is so apt to be among yachtsmen. It has been said, as we all know, that the Royal Thames Yacht Club Rule is the best; and I was in hopes that some reason would have been given here to show why the other is bad.

Mr. J. SCOTT RUSSELL: I do not think you could have heard what I said, for I certainly did not shirk the question.

ON A NEW STEERING GEAR.*

By G. L. WATSON, Esq., Naval Architect.

[Read at the Seventeenth Session of the Institution of Naval Architects, 8th April, 1876; the Right Hon. LORD HAMPTON, G.C.B., D.C.L., President, in the Chair.]

I HAVE Considerable diffidence in submitting to such a body as the Institution of Naval Architects any scheme purporting to be an improvement on the method of steering vessels; for I am aware that among those present there must be many who have given their careful attention to this particular branch of naval tactics, and are therefore better able to deal with the subject than I can be. At the same time, while all naval architects are more or less interested in the manoeuvring of vessels, but a few have busied themselves in examining the means by which they are to be manoeuvred; and while they have investigated the nature of the rudder's action on the water, have left the study of the steering gear's action on the rudder to the engineer or practical shipbuilder. This I am sure has been a mistake. For while these gentlemen have produced machines, which are more or less perfect, for turning a shaft on which there is a constant load, they have apparently overlooked a fact of which we are all aware-viz., that the resistance increases enormously as the rudder is put over to its extreme angles; and although in one or two of these gears the power brought to bear on the rudder at any angle is as the difference between the secant of that angle and that of the secant of the angle immediately adjoining it, the resistance on the rudder increases so very much more quickly, nearly as the sine, that the gain by this method is unappreciable until large angles are reached. Now the very alphabet of mechanics teaches us that a machine is a combination of appliances whereby we are enabled to perform work which with our unaided hands we could not attempt, and that it is more or less perfect as it performs exactly the work we require, or falls short of or exceeds that work. But however good the ordinary gear, it is evident that if it is made to have just the right amount of power to turn the rudder from 0 to 5 degrees, it will require five or six men at the wheel to move it from 40 to 45 degrees. Or again, if the

* Received 10th March, 1876.

gear be made sufficiently powerful to enable one man to put the rudder hard must be uselessly slow at the more central angles.

If the preceding conclusion be admitted, it follows that the only perfect steering gear is one in which the power brought to bear on the tiller increases in exact proportion to the pressure of the water on the rudder, and (although in small vessels this is not of much moment, for the gear may be powerful enough for the extreme angles and yet be decently fast at the more central ones) it becomes an important consideration in any vessel over 1,000 tons. This is no mere supposition. Every day we hear of collisions more or less disastrous; and in the majority of these cases if the whole helm could have been given either of the vessels the catastrophe might have been avoided, but before the steersman can summon assistance to put the helm hard over the mischief is done. Again, every large steamer now building and even some of the better class of river boats are being fitted with steam-steering gear, showing that the gear at present in use although all very well for plain sailing is useless in an emergency. In proof of this I may say-and I have no doubt but that

similar instances have come under the notice of most present—that on the trial trip of a not very large steamer (some 1,800 tons) we could not get the rudder past 10 degrees even with four men at the wheel. Farther, I was told by a Clyde shipbuilder that on trying to turn one of their large steamers by hand gear they got the rudder over some 6 degrees, when on putting more men to the wheel they broke it.

I think enough has been said as to the advisability of making the means at every point adequate to the work to be performed in turning the rudder, and it remains only for me to describe this means. I am aware that the machine is not altogether perfect, but cost, compactness, and other items must be considered to a certain extent. As far as may be seen from a large scale model it works perfectly; but of course this is a very different test from a winter in the Atlantic.

E

In the diagram L is the rudder-stock on which is keyed the tiller F carrying at its outer end the pin H; on this pin is a brass or gun-metal roller I fitting the curved

groove EE formed in the lower side of the travelling table, which is driven to and fro on the parallel guide rods G G by a screw turned by an ordinary steering wheel. When therefore the curved groove E E is driven directly fore and aft, the roller I and the pin H and with them the tiller F must accommodate themselves to the altered position of the groove by moving laterally, thus putting the rudder over to port or starboard. And the curve of the groove EE is so constructed, that supposing the resistance on the rudder, when at an angle of 20 degrees with the centre line of the ship, to be double what it is at 10 degrees, the travel of the table required to move the tiller one degree in the former position will be just double what was required in the latter; and consequently, as the same power-that is the steersman's effort-acts through double the distance, his power over the rudder at that particular angle is doubled, and similarly with all other angles.

It may be objected that the resistance on the rudder does not increase exactly as the sine of the angle to which it is put, but I have merely adopted this approximation in the meanwhile, until I can get authentic information as to the precise increase of pressure which takes place. I understand Mr. Froude has given this some attention, but I have been unable to find any account of his experiments in that direction.

As to the construction of the gear the sketch almost explains itself. The stands are of cast iron; the guides of malleable rod iron turned up true; they are screwed down at the ends a trifle smaller than the rest of the rod, so as to form a collar on which to heave up the nut. There are diagonal tie rods to prevent rocking, as the strain is not balanced as in the equal armed gear. The table and groove are of cast iron, and so made that along with the guide rods and screw they would form a kind of lattice girder, resisting any lateral kick of the tiller; the roller of gun-metal and pin of malleable iron (unless it seemed advisable to use steel). The gear can be instantly disconnected by withdrawing it.

The only objection I can see to this gear is that the roller I will be apt to wear, but as it is a very small part of the machine it could easily be renewed; in fact two or three spare rollers might be sold with each. However, inventors are notoriously the blindest of parents when the failings of their offspring have to be viewed, and it is more than likely there are faults in the construction which I have not observed, or have under-estimated, and which I shall be glad to have pointed out, as it is possible that they may be overcome.

DISCUSSION.

Admiral J. H. SELWYN: I have no doubt whatever that, as a means of applying great power, the screw is one of the best, as it is the slowest; giving, therefore, the time that is gained by long leverage in another form; but I confess that my objections to all this kind of steering gear, which has been recently used, in consequence of other difficulties, is that it tends to throw a still greater strain on an already overburdened portion of the rudder. The head of the rudder can be twisted off; but you cannot always, at high speeds, force the rudder over. There is a great difficulty there. I think the object can be better effected by changing the form of rudder than by changing the steering gear; but the improvement in steering wheels, and the application to them of screws would be much greater if the constructors always considered the jolting motion caused by the intermittent beat of the screw on the ship. On the rudder there is a jarring jolt which transmits itself to any machinery employed in connection with the rudder head, and which makes it very difficult to preserve those surfaces in perfect order, so that on some occasions when it is most required the rudder will fail to act. I think that difficulty should be closely investigated by those who make gear for rudders.

Mr. WIMSHURT: In 1835 I built and fitted a vessel with a screw apparatus similar to that, and the difficulty there arose-as has been stated-from the jerking motion; and when it got to be a little loose the noise was very great indeed. We found it better to take away that machine, and put the common tiller ropes; but you must be aware, that with the sea running under the quarter, and the screw not only beating against it and catching as it generally does the broadest part of the rudder under the counter, the blow is very great; and if it is so rigid that there is no possibility of the rudder head moving, something must give way. Therefore I consider that screw machinery for steering is rather dangerous than otherwise.

Mr. J. SCOTT RUSSELL, F.R.S.: I am anxious-as there are many who have given their thoughts to this very important subject, especially at present with relation to war vessels-to have the opinion of one or two Members present on the principles which it is safe now to follow out in steering. Now, two modern improvements have been introduced, one of which has just been properly mentioned, namely, the introduction of the screw into steering apparatus. That is a very tempting system, because the screw has for that special purpose this great value, that you can get enormous power in very little space, without complexity of mechanism; therefore I think that has led so many people to adopt the screw. I wish to ask those gentlemen present who have studied this subject, whether it is or is not a disadvantage to the screw that it has so much power and so much friction that when it is struck it does not yield to the blow? I wish to ask you sailors whether you think it more desirable or more undesirable that there should be so much power in the mechanism that you can hold it fast in spite of the sea, or whether you do not think that a source of danger; and whether you would not rather that it was not so strong, and that the sea compelled you to let it go and yield? I know I have often, in steering a smaller class of ships, found that I saved mischief from being done by letting the wheel run away. Then the other point I wish to ask your opinion upon-as so many able men are here who have studied this subject-is, whether you like or dislike the terribly short levers which compactness and the force of this screw enables you to act with; and whether you do not prefer the rather clumsier longer levers of old-fashioned ships; and, in