The Newest Navigation
(See page 680, June, 1927, Proceedings)
Commander Archer M. R. Allen, U. S. Navy.—The idea of this paper is excellent and the use of the method described is heartily recommended by the Department of Navigation, U. S. Naval Academy, except for sights within an hour and a half either side of the meridian. It is not used as a basis for instruction because every effort is made to teach methods which are as exact as possible, as there is a constant tendency towards greater tolerance in the accuracy of position, unless a rigorous method is adhered to. This eventually leads to errors on the part of the midshipmen which are very difficult to find when approximate methods are used.
I think that more navigators are using H.O. 203 and 204 each year and we see to it that each midshipman is instructed in the use of these tables before he graduates.
The careless use of the term “Marcq Saint-Hilaire” in this paper and to a certain extent in the service at large should be corrected. In H.O. 203 the method of solution is the Marcq Saint-Hilaire and this term applies to any method where the altitude difference is used regardless of the method employed for the solution of the astronomical triangle. What the author means in this case is the “cosine-haversine” method which is at present the standard type of solution taught the midshipmen for the above reasons.
The time required for the two solutions checks remarkably closely with the results obtained by the writer some two or three years ago in making similar investigation.
The error of position by H.O. 203 or Aquino will be within one mile but the ease of solution more than compensates for this and in the vast majority of cases both the
rigorous and approximate methods will give identical positions.
That method of solution, in which the processes of multiplication and division are least, and the results can be obtained by addition and subtraction, or by inspection, will in the long run prove the least liable to error in solution. For this reason the writer prefers Aquino’s method using the interpolation table for minutes of “b.” An inspection of Ball’s Tables in which a similar table is furnished and the fact that the Nautical Almanac includes Table IV show that practical mathematicians have appreciated this fact for many years. It is to be hoped that a similar table will eventually be printed in H.O. 203. The value of ease in solution both for the greater speed and the lessening of mental fatigue can only be fully appreciated by the navigator who has covered a long mileage under constant pressure, when the mechanics of solution have become almost automatic, and the line of position on the chart is the only consideration. As long as a solution requires intense concentration and mental gymnastics the result is sure to be in doubt and the amount of useful work reduced.
The author states that the moving bridge throws sights off, but this error should not be considered great as an inspection of the dip table shows that for a change from twenty to forty feet in height the difference is only 1.8 miles in position, and the ordinary observer on the bridge seldom varies half that much in his relative position to the horizon at the instant he takes his sights. Tenths of seconds of time should be used, but the nearest tenth of a minute of arc (6") is a proper standard of accuracy.
His caution in regard to plotting is excellent. With approximate methods as he says this becomes the greatest source of error. The error which he does not mention is time. In these days of the radio tick every navigator should have an excellent time basis and the two factors to concentrate on in solutions are accurate time, and accurate plotting.
A suggestion is offered here that the slide rule be employed for the interpolation in H.O. 203. A preliminary investigation seems to indicate its possible value but its real
value can only be found by test under actual operating conditions.
In the solution of problems for comparison such as are given in this article it is always better to give the latitude and longitude as computed for each method and compare the computed instead of the graphic positions on account of the impossibility of checking plotted positions accurately.
This comparison by computation is given below:
| By H.O. 203 |
|
|
|
D.R. | L ii°-53'-oo"N. | X | 78°-45'-oo'' | 'W. |
Assumed position | L i2°-oo'-oo"N. | X | 79°-34'-45" | 'W. |
Computed point | L I2°-o7'-3o"N. | X | 79°-29'-33'‘ | 'W. |
Course. | Dist. N. |
| E. | Dio. |
35° | 9 7-5 |
| 5-i | 5-2 |
U | to O 6 CD 6 0^ >* |
| 79°-34'-45"W. |
|
| 7'-3°" |
| 5'-I2" |
|
l2 | i2°-07,-30"N. X2 |
| 79°-29'-33"W. |
|
Latitude factor f = .68 | By Cosine-Haver sine. |
|
|
|
D.R. | L ii°-53'-oo"N. | X | 78°-45'-oo"W. |
|
Computed point | L ii°-43'-oo"N. | X | 780-52'-i8"W. |
|
Course | Dist. N. |
| W. | Dio. |
2150 | 12.3 IO.I |
| 7.0 | 7.2 |
La | ii°-53,-oo"N. |
| 78°-45'-oo"W. |
|
| io'-o6" |
| 7'-12" |
|
l4 | ii°-42'-54" |
| 78°-52'-i2"W. |
|
Diff X2 79°-29'-33"W. |
|
|
|
|
X4 78°-52'-i2" |
|
|
|
|
o°-37'-2i" x | .68 = 25.4 |
|
|
|
L2 I2°-o7/-3o"N. 25'-24"S.
L5 ii°-42,-o6,,N. L4 ii°-42'-54"N.
Error of H.O. 203 = 48"S.
In addition, the following minor errors in the solution are noted which in no way affect the value of the writer’s argument.
The exact value of the equation of time is 13nw56s-7 but using this in no way affects the resulting longitude.
In correcting the altitude, the sub-correction was omitted. As this amounts to one- fourth of a mile it should be included making the proper correction for the observed altitude 10-39 instead of 10-24. As many as possible of these small errors should be eliminated, as when they all happen to have the same sign the accumulated error may be as much as one mile.
A Destroyer Leader for the U. S. Fleet
(See page mi, June, 1926, and page 325, March, 1927, Proceedings)
(Editor’s Note: Dr. Mendl, a Roumanian naval architect of Bucharest, has long been one of the Naval Institute’s distinguished foreign associate life members.)
Dr. Ing. Wladimir V. Mendl.—First of all I want to state that I don’t know anything about the adopting date in the Swedish Navy of the “spidery yards and triatic antennae,” as adopted for the design, but I remember very clearly that I noticed a very similar arrangement for the first time with the German Nassau class launched in 1908. I am not aware whether this same arrangement has been adopted in older Swedish vessels too. I know of it for the Sverige class, the first unit of which seems to have been launched as late as 1914.
Mr. Prendergast’s design is an efficient one. I hope that some Navy or other will not fail to embody the features outlined in one of its future vessels.
But as to the massing of the armament on the forecastle I cannot very well see how a destroyer leader could reasonably be compared to capital ships such as the Nelson. I am sharing the views of Mr. Pren- dergast and his British friends that a vessel designed for attack should have the possibility of firing efficiently ahead.
British capital ships of the Nelson class are intended as “spear heads” and from this point of view the arrangement is fully justified. But .... will the age of a vessel not become an obstacle for her being used as spear head? Will her place not be taken later on by newer vessels? And what is going to happen then with a specially designed ship? Is she to be replaced by scrapping? It would be a rather costly experiment. The massing of the armament forward seems more justified for a leader than for a battleship. The leader’s life is shorter and even if she is to be scrapped at a future date the cost involved will not be so onerous.
Firing astern does not mean in all instances turning heels and trying to escape. Such a costly weapon as a capital ship should be able to fight in any direction for one cannot foresee under what conditions she will have to fight. Think one moment of a vanguard vessel in a long battle line having passed her enemy long before the rear guard is abreast—but all of us will certainly remember Admiral Beatty’s retreat during the Battle of Jutland when he tried to draw the Germans into the arms of the Grand Fleet.
A leader is quite a different proposition and what may suit her may be objectionable for a capital ship. Therefore why should we compare both types of vessels and make the latter type an advocate for the first one. The design of a war vessel has two sides: a military-technical one and, last but not least, a financial one. Every navy must know what it is able to afford, whether it can pay the luxury of special vessels or whether it has to act according to the buy- a-Ford-and-spend-the-difference principle and build all round vessels.
The distribution of the machinery with the boiler rooms between the machinery rooms seems liable to discussion. Is it a good proposition to pass a propeller shaft under the boilers, especially in vessels of destroyer type, in which head room seems to be lacking? So the electrical drive proposition may be the only one to be taken seriously. One must not forget, however, that with the longer cables for transmitting the current to the motors the possibilities of something going wrong, be it hits from shell fire or anything else, is greater too.
While Air. Prendergast mentions that the sketch given is only an “idea-diagram,” I shall have to insist one moment upon dimensions. It is stated under the heading, “Machinery,” that the funnels are stepped amidships “so as to keep the bridge clear of smoke-interference.” This measure taken seems very wise, but if one has in view that electric drive will probably be the only possibility for putting the boiler rooms between the machinery rooms, it must be borne in mind that the electric drive turbines will rotate at very much higher rate than the direct-drive turbines and consequently are to be shorter. From a summary consideration of the design it may be deduced that the length of the machinery and boiler rooms have been dimensioned for direct drive. Therefore it is probable that for electric drive the forward turbine room will be shorter. Will the funnels still be as far from the bridge as should be desired and if not will the same purpose be attained with a stepping and inclining of the funnels as in certain modern Japanese cruisers ?
As to signalling, it has been stated that the “hoisting and lowering of long tacks of signals .... has been found to interfere considerably with range-finding, fire-control.” Now a single mast behind the bridge has been avoided. But it would seem to me that if the guns are able to fire only forward there will be no possibility for rangefinding, etc., astern and therefore I am not quite sure as to how the signals behind the bridge could interfere with these latter. A possibility would be that for the destroyers led by the leader themselves some stern fire is considered. But in this case the question arises whether it is to be recommended to give the leader another arc of fire than the destroyers led.
The telescoping mast seems a very useful proposition, be it a single mast or twin masts stepped to the right and to the left. However, with the ordinary type of masts and the antennae rigged, the length of these latter is changed during the lowering or hoisting operation. For this reason they may get entangled. I propose a mast curved along the line of a circular arc, the middle of which is located, the other fixed point of the antennae on the top of the mainmast. With such a mast the length of the antennae will remain the same whether the mast is hoisted or lowered and only the length of the wire connections to the wireless cabin will have to be changed, which seems a very much easier operation. Still there is one disadvantage in the proposal; the mast is not perpendicular on deck and you will know that we naval architects have a strong and most times not unjustified aversion against oblique intersections. In order that the mast may be perpendicular on deck it would be necessary that the fixed point of the antennae should be on deck too. This is rather difficult to realize, but it could be approximated if the after fixed end of the antennae were made as low as possible.
A Destroyer Leader for the U. S. Fleet
(See page 325, March, 1927, Proceedings)
Brockholst Livingston. —Maurice Prendergast has reopened the discussion of Captain Taussig’s article by submitting an entirely new design based on his study of the matter. It seems that the new design will bear question in that it is rather radical according to American views.
Air Prendergast is correct, in this writer’s estimation, when he says: “What is wanted is neither a trimmed-down cruiser, nor an inflated destroyer, but an entirely new type of vessel, expressly and specially designed to exercise the function of sea- leadership in the very highest sense.” However, while an entirely new type is needed the mission of the leader and the company it must keep are not to be overlooked. Leading destroyers and acting jointly with them in every way are the two points to be brought out in the design. Accordingly, the design submitted must embody these points and fulfill the requirements, having consideration for the limitations imposed.
One might mention that the American Navy has long since broken away from what Mr. Prendergast calls the “conventional ideas regarding a particular class of warship.” Our designs of recent craft are far more non-conventional in many respects than those of other countries. Our light cruisers may be used as an example. It could be added, also, that Captain Taussig in my mind, is one of the most radical of our officers, par example, his personnel ideas.
In the beginning I will say that Mr. Prendergast has certainly not, in his design, left out any detail of armament or arrangement but in endeavoring to embody all these into one vessel he has, it seems, designed a craft which would be so crowded as to hinder its carrying out the mission assigned.
The designer of the Canandaigua has produced a fair looking craft, not much like the ships which have come to be known on the Seven Seas for their trimness, but, nevertheless, not an eye-sore. We may forgive the change in appearance since we have come to the tripod mast and “wayside water tank” control towers of the newly modernized battleships. The Texas certainly “ain’t what she used ter be,” in more ways than one. Why question the appearance of the Canandaiguaf One point which should be gained from the design is the coat of arms on the bow. Would not this little trimming add to the fairness of all our ships? Especially would the “monster’s face” of our clipper bow battleships be improved by this addition.
The armament of a destroyer leader is a questionable matter. Since the leader must meet the same types as the destroyers she leads, should she not mount the same guns as the latter? Captain Taussig desired six- inch guns on his “idea-diagram.” The main question, it would appear, is, what guns will our replacement destroyers carry? And this brings us back to the old question, why don’t we build some of each type that we may keep abreast of the improvements? The gun arrangement proposed by Mr. Prendergast may be a good one but I hate to see a good gun stuck away behind another. Not that it is ever necessary to fire dead ahead but because of the principle. This arrangement, however, seems to he gaining in favor. Perhaps the American Navy may adopt it.
The rig suggested by Mr. Prendergast is novel hut apparently needlessly so. Personally, I think the writer studied each new warship design in an endeavor to find something singular. He found many. There appears no good reason for adopting the tripod mast, nor the double, telescopic mast suggested for signalling.
Searchlights should be carefully placed although the present writer doubts if they would be used very much in the vicinity of the enemy. With the precautions taken to darken ship it is doubtful if a searchlight will be turned on except in extraordinary cases. However, it is better to have them away from the bridges. Captain Taussig probably meant his two bridge searchlights to be used for signalling only. There is a point which may be noted while on this subject. What effect would searchlights at close range have upon the secondary batteries of the enemy ships? Would it not be possible to temporarily blind these crews?
We may be glad Mr. Prendergast did not attempt to defend his heretical idea that leaders and destroyers should relinquish the torpedo arm to planes, submarines and coastal motor boats. In passing we might ask what purpose the destroyers would have in the fleet as an attack ship if this arm were abandoned. Of course one knows the many duties which fall to the destroyers before and after the attack but nevertheless, the idea of giving up the arm which first brought the destroyer’s predecessor (the torpedo-boat) into existence, is indeed heretical, to say the least.
The torpedo armament of Canandaigua embodies two novel features—we might, sarcastically, say only two. The question of two sizes of torpedoes was answered by Captain Taussig. His conclusions were, it seems, correct. The “fixed discharging troughs” on the stern of the design do not seem to be adaptable to such large vessels as the destroyer leader must be. In fact, I am afraid more stern-discharged torpedoes would find their mark in a quarter of the ships discharging them than in the vitals of the enemy. The danger to the carrying ship would be too great to warrant their being fitted.
I might call Mr. Prendergast’s attention to the fact that Captain Taussig provided four, not two, triple tubes and a single catapult.
The design of catapult used in Canandaigua would not, I believe, answer tbe purpose of the catapults now in use in the American Navy. An examination of the length and rigidity of the present catapults would preclude any such light affair as is suggested by Mr. Prendergast.
The point of laying a number of depth charges while leading a squadron and thus endangering her own brood is well taken. However, if we do away with the stern torpedoes we might substitute depth charge racks for such occasions as independent service and good visibility'.
In answer to the writer's question “Or is she (Canandaigua) simply an impossible freak?” we must reply that she is not, neither is she, in our estimation, an entirely “worth-while ship.” She embodies many good points which are useful in discussing the matter of destroyer leaders and yet she does not appear entirely perfect.