|Notes on "Fenian Ram" - Cont'd|
There is scarcely anything required of a good submarine boat that this one did not do well enough, or fairly well. It could remain quite a long time submerged, probably three days; it could shoot a torpedo containing a 100 pound charge to 50 or 60 yards, in a straight line, under water, and to some uncertain range, probably 300 yards, over water, I got somewhere about 200 yards range with 120 pounds pressure. It could act just like a porpoise, exposing from only 9 in. of its turret to one-fourth of its body, according to its speed. Exact tests were never made of its efficiency in anything. The boat was unfinished when my partner stole it. All the experiments made were with a view to testing or correcting some part of the apparatus, preparatory to a series of efficiency tests when the machine would be finished. I may be able to include most of them by giving a sketch of what let to features in its design, and of what was done in the way of testing the apparatus, so far as I can remember them.
Boat No.1 had water chambers equal in vol. to the space surrounding the operator, who was to be clad in a diver's suit so that he could, by expending a little compressed air, fill the space around him with water from the chamber and come out of the boat, without changing its buoyancy, or want of buoyancy, and without having to lift the manhole cover against pressure. Another set of chambers were provided so that buoyancy might be destroyed, if desired.
It was intended that the operator should be provided with one of those diving helmets and connected appts. that afterwards took the form of a knapsack, much as they employed in the Bristol Channel tunnel - I think it was called the Severn Tunnel, so that he could leave his boat on the bottom when it was not too deep, and fasten a torpedo on a ship, or else open the cover and direct and despatch an automobile torpedo - one of the two to be towed after the boat - against the vessel. The operator would close the cover quickly when this was done, and change the water to the outer compartments as quickly as possible to avoid the effect of the concussion from the explosion.
This was not explained, if I remember rightly, in the specification I sent to Washington during Robeson's reign in Feb, 1875. Commdr. Barber told me the papers are now in the library of the Torpedo Station in Newport. I can remember scarcely anything of what I described, but I know I held a good deal back, and described something I didn't want to do, as I believed they would have no regard to my desire for secrecy. I was right in this point for Commdr. Barber published the drawings and an abstract of the specifications, believing they were patented, or that there was no objection to using them, as they were exposed publicly.
The vitiated air was separated from the rest, to be pumped out at intervals. The separation was made by a loose diaphragm, so that there might be no difference in pressure.
The boat described in the specification was not built, but a larger one, which was, by an after thought, fitted with a pair of petroleum engines. These proved a failure, but the experiments were not prevented. I hired a steam launch and took steam through a hose from its boiler. By towing the launch alongside or behind I was able to do considerable experimenting.
The first thing I found out was that it was folly to be bothered with either respirators or air purifying appts. They need lots of attention that can't be spared for them, and a fair supply of compressed air, that can be easily stored, render them superfluous.
The trouble and care required to handle things in the boat satisfied me that although the plan of opening the top to send off a torpedo looked nice on paper, one man could never manage it. He could not be quick enough, and as he couldn't afford to miss anything, it would not be satisfactory.
Therefore I determined to employ a gun that could do better work more rapidly and reliability, and with less trouble and risk. The danger of an explosion, or the blow of a heavy shot in the neighborhood that might explode my torpedoes, help to condemn my plan. Even though the gun rendered it necessary to provide a larger boat and to have two or three men, it appeared to be far preferable.
Besides the engines, the most signal failure was the method of going under water - a pair of balanced rudders on a transverse axis at the center of buoyancy. They were positively no good, and showed no result at the best speed I could get, about 3½ miles. When turned at a considerable angle, the speed dropped to next to nothing. On studying that point afterward I saw that the power for the submerged run, with any motor requiring air, would be all wasted in overcoming even a little reserved buoyancy. The equivalent of this plan - downhaul screws - is just as expensive in power, and more objectionable because more cumbersome, even though the boat is pulled down while lying still. More water ballast does the same thing and does it much better; every gradation of gravity being obtainable by employing compressed air and valves operated by water pressure, and it may be done automatically. Yet this was the subject of one of Nordenfeldt's Laws of Submarine Navigation, as promulgated by his friends in Engineering. My experiments were made in May 1887, in the Passaic River at Paterson, N.J. The longest time spent under water in this little boat was one hour.
Boat No.2 was begun May 3, 1879, at the Delameter Iron Works, foot of W. 13th St., New York. The ends of the boat were made air holders because their stupid engineer was quite certain he could make then absolutely air tight, and it was not practical to get large tubes that could be fixed up to do the work without great expense.
The empty ends just suited my plans. The tubes would have to go in the middle and spoil my engine room. The curve of weights did not correspond with the curve of displacement but was greatly bulged at the middle and lean on the ends, - just what I wanted to make the boat "lively" and give great longitudinal stability. The transverse stability was small, and she rolled next to nothing when on the surface in the trough of waves.
The air tanks at the ends were built for 300 lbs. working pressure, but I never used over 250 pounds. The firing charge was held in a tank good for 1000 lbs. but the highest I ever put on it was 495 lbs. The machinist shot a nail keg from the gun against a large casting while it was in the shop, using waste for a gas check, and it made matches and powder of the keg.
The boat was not launched until April, '81 on account of the failure of the builders to make the tanks air tight.
In June, '81, we made the first dives in water only 14 feet deep and did not touch bottom. The manhole in the bottom was opened while the boat was afloat in order to test the automatic valves operated by air and water pressure. The water rose inside only 4 or 5 ins. and subsided again to about 3 inches.
The first dive gave me my first surprise. As the water was quite muddy everything looked yellow when an inch or two of water covered the top light. The compass was no use as every inclination of the boat disturbed the needle, the end that was highest attracting the near end of the needle and swinging it. The movement of the steel shackle bars of the engine and of the levers near it that could not be compensated, helped to keep it dancing or varying most of the time.
My first dive cured me of the idea that it was possible to find my way under the bottom of a ship even if she were alongside, and either boat or ship were moving. If the water were clear as crystal I suppose things might have been different. I had a strange experience in this respect. When the boat was lying on the bottom I could see the underside of ships and air bubbles a few feet above, but it was like looking at the bottom of a cup from under - nothing could be seen a few feet away.
The boat was lying against a pier and the side lights of the turret were about two feet out from the spiles. The water was so clear on this occasion - high tide at Bay Ridge - that clam shells on the bottom could be seen by those on the pier. The day was very clear with bright sun light, and nothing could be distinguished a few feet away. Everything appeared to be hidden by a fog - I suppose the sun light reflected from the muddy particles in the water. Even the piles two feet away could not be distinguished. To be sure. they were a little in the shadow, the sun shining on the other side of the dock chiefly, but as it was early in the afternoon, the boat lay where it was shining. I told the men on the dock it was too muddy to see anything and they showed me the clam shells where it was ten feet deep.
The next day we went down to regulate air valves, and someone offered a bet that we couldn't remain one hour below. To convince him we remained two hours and one-half submerged, until the tide had nearly uncovered the top of the turret. Then I could see a crowd has gathered and that they were preparing to pull the boat up, thinking we were smothered; so, we floated up. The man that wanted to bet was satisfied and badly frightened. During this submergence I found that we could manage to remain about three days below, by first exhausting one-half of the air - one tankful - and then passing the contents of the other through it, and employing a diaphragm, as in my first project.
Until I fixed a temporary contrivance for controlling the rudders there was no telling where I was going when I went down; therefore the precaution was always taken of going several hundred yards offshore, or running in circles when inshore in the Narrows, when diving.
When passing under a boat, even in the comparatively clear flood tide water at the Narrows, nothing but a dark shadow could be seen overhead unless we went close enough to risk striking it, This convinced me of the folly of expecting anything from the class of boats that Lt. Kimball calls gropers. It would be no small feat to fasten a torpedo to a ship anchored in clear water, but the existence of a current would render it a tough job. I wouldn't undertake to do it if the ship were moving; the boat would run the risk of being chopped up by the ship's wheel. Even when the vessel is anchored it is not easy to avoid knocking against her and carrying away something or fouling on the mooring chains.
I passed under two long tows of canal boats opposite Communipaw and knew nothing about it. They had turned in from the river towards the Cove while I was passing down the river, but it was after sunset.
I felt persuaded that a boat should be, if possible, as smooth as a bottle, so as to avoid catching or being held by anything. The shaft and screw gearing on the Detroit boat look nice; they certainly are very ingenious, but I shouldn't like to go near a ship's netting in her.
I think you will agree with me in believing that I had reason enough for saying that a submarine boat, in order to be effective, must be able to steer straight under water, to act quickly and to attack from a distance.
My boat could act quickly, - come to the surface for a few seconds to take a bearing, and dive again like a porpoise - steer a straight course in still water, and attack from a distance.
There was never any tendency to stand on end because the ballast water was near the middle, the after water tank being chock full; the forward tank nearly full, allowing a little to compensate for changing weight, as oil consumption, etc. This made a practically immovable center of gravity, wanting which, so many attempts at submarine navigation have failed. The longitudinal stiffness being quite considerable for so small a boat, the movements fore and aft in the small space available had no effect on the trim.
With regard to steering, it was found that the boat swung too much for each movement of the rudder owing to the want of a keel. This might have been remedied by reducing the rudder surface, but that was not done, in order to save expense.
The first attempts to dive by the aid of the diving rudders were failures because the space between the forward, or balancing end of each of them was only ½" from the edge of the skeg in front of it. This made her dive, but clumsily, by tipping the forward edges down instead of up. When they were cut off so as to leave a space of about one foot open in front of them, they worked properly. The boat would dive without touching the rudders if she happened to be lying still awash when the engines were started. This was caused by the water piling over the forward end and depressing it, the after end being uncovered at the same time. As soon as both ends were covered, the boat stood level. During this operation the turret would not be submerged over two feet, sometimes less. The horizontal rudders had to be depressed by hand, before coming to a level during a dive, or the boat would rise just as she descended. When the rudders were set to dive ordinarily, the turret was submerged about 4 feet; the boat vibrated up and down a few feet for some time and then ran level. The bow must have been slightly depressed but I never could detect it although I intended to test it with a level.
There was never any trouble in running at say, 18 feet deep or in changing the level 2 or 3 feet either way.
I did a good deal of checking with dummies under water and very soon found that one of the chief causes of want of seaway was compelling the air to follow the projectile until the latter left the muzzle of the gun. It appeared, somehow, to interfere with the direction by pushing the tail of the projectile downward or sideways. The air generally followed the projectile 30 to 40 feet after leaving the muzzle and when fired at the side of the dock it appeared like a continuation of the projectile back to the boat, but it swelled quickly and broke the surface about 30 feet away from the boat. I allowed the air to escape before the projectile was all out, and I always had perfect shooting afterwards.
Capt. Ericsson did not appear to have noticed this point, but attributed it to some irregularity in the projectile or to an unsuitable position of its center of gravity. The remedy he adopted - great length of projectile - would of course, help cure it on account of the hold on the water by the great length of projectile that had already punched its way into it, but the trouble was there all the same, and is there still, because Mr. Laine never noticed it or thought of it. I was going to get a patent on my method at one time but I felt that the money spent would only be sent to keep company with the time and money I have already lost, and I got enough of that. The most important thing in the Pneumatic Gun Co's. patents is the intermediate air reservoir between the air tanks and the gun. Geo. H. Reynolds got a patent on that in 1884, and sold it to the Gun Co., but in 1879 he superintended the construction of the same thing in my boat.
I fear that you will have much difficulty in making head or tail of this mixed up, rambling history, but my only chance of doing anything at all was to write while I had time and felt good, and to trust to your kind consideration to overlook the absence of order or want of proper description enough to brace ourselves against something and avoid hurts. I think you will agree with me, and disagree with those naval gentlemen who wish to see a good big one, that a small submarine boat has all the chances of being most effective in its favor. There is a limit to smallness in my opinion, and that is where a submarine gun cannot be carried that will give, say 20 yards effective range with torpedoes carrying 100 pound charges submerged after breaking through a net, and, say 200 yards as serial torpedoes. A boat of 10.5 tons weight, 12 tons displ't., will do this and have about 12 knots speed and 30 hours endurance at full speed. Boats of that kind will be substitutes for automobile torpedoes in many cases. A fleet carrying one on each ship could clear an enemy's harbor of torpedoes while the ships are 50 miles away, and even knock their shore batteries to pieces, enjoying perfect immunity, because one submarine boat is no defense against another.
When speaking of ventilation I forgot to say that it was secured in the F. R. by permitting the engine to pump its supply of air from the engine room. That of course, compelled us when doing so, to have the same pressure inside the boat as outside, but it would have been different when the boat would be finished, - a special pump would have taken care of the ventilation and the engine would have been supplied direct from the tanks, leaving the air regulating valves to maintain atmospheric pressure in the engine room.
In considering the design of the Fenian Ram I had in mind what I had noticed in experiments with No. 1, that a boat should be short in comparison with her diameter in order to maneuver reasonably well. This proved correct in the F. R.; 4 HP. acted about the same in No. 1 as 10 HP. would in No. 2 (F.R.), the speeds of these powers being about 3½ or 4 miles in one case, and about 6 miles in the other, but with 20 HP. the larger boat acted splendidly. This is confirmed by the reported action of Goubet's boat which is said to tilt longitudinally when a man on board extends his arm. The longitudinal stability should have been greater in that case. His boat was far too sensitive. She'd be a nuisance to operate. Good steerageway is essential, it covers very many defects, in fact it is all important.
The Fenian Ram was so named by the newspapers on acc't of the nationality of its designer, but its ramming power, 49 to 50 foot tons delivered by a sharp point against the thin skin of a ship - before double bottoms were common - was far from contemptible. The boat was strong enough to endure it, being built of 11/16" charcoal flange iron. We had a partial demonstration once by running into the end of our pier at about six miles speed owing to my bad steering or forgetfulness of the tide. We split a 12" spile and lifted a horizontal tie having a load of 4 feet deep of stone ballast over it, and hurt nothing but the engineer's respect for good English. There was just warning.
This was done only two or three times altogether while adjusting the valves, but we could not do it all the time for want of the pump. There was no trouble with any valves but the checks, outboard, on the exhaust pipe. They could be heard humming always unless when we dived. When on the surface they were nearly one foot submerged. The expansion of the ship would in this case be effective in the engine and lengthen the dive. Our longest dive lasted nearly ¼ of an hour and we spent about 150 pounds of the pressure in the air tanks.
Our course under water could not be traced by bubbles from the exhaust unless in dead still water. There was scarcely any sign, as it was mostly absorbed, and the boat was some uncertain distance ahead of where they were seen when she was only 4 feet down.
The deepest dive was within 3 feet of the bottom opposite Castle Point, Hoboken, I forget whether it was 37 or 47 feet, but we went within 3 feet by gauge of what the chart shows. The engine worked well at that depth but the pressure was unreasonably high, to balance the back pressure. We stopped put about 30 pounds air pressure over the water in the tanks, and we were on the surface in about one minute, with the air roaring out through the kingston valves on the bottom.
The best speed we made on the surface was nine miles per hour. I never measured the diving speed, but observers said invariably that it appeared to be greater, the boat always rising farther away, in short dives, than where they expected. There is no telling for certain but I think it was no slower than the surface speed.
There may be many other points on which information is desired that I cannot now remember, but should anything further be required I shall be most happy to send it.
Yours very sincerely,
John P. Holland