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U789
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| All waterborne craft, from the dock tug to the majestic battleship have their own particular appeal to the onlooker. Of them all, the submarine must rank as one of the most fascinating and intriguing. The story of their origins and development, and their war record, is one of sudden disaster, incredible danger and hardship, extreme ferocity and unbelievable courage, with appalling losses being both received and inflicted. |
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Having said this, the job is not a pushover. Good, sound building is essential. Like the full-sized counterparts, model submarines are more prone to accident than normal surface craft. I suppose the submarine is, to the model boat builder, what the helicopter is to the aero modeller: more complex to build, and more critical to operate. I am really aiming at the modeller who has a track record of say half a dozen successful surface models to his credit, who knows how to build a straightforward hull, and install the appropriate ironmongery. You do not of course need to be a genius, though I personally found this attribute useful at times. I really mean that most sincerely. On a more serious note, in case I forget to mention it later, lead acid batteries should not be used in the confined hull space of a submarine. These batteries give off hydrogen. Motor commutators spark. The combination is explosive, in the literal sense ‑ remember the airship Hindenburg. It can happen. Long‑time readers of Model Boats will recall the sad episode of USS Perch, which blew up, almost causing serious injury to her owner. Sealed lead acid batteries may be a different matter, and the manufacturer's advice should be sought if you think of using these. |
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Glasplies; 2 Crowland Street, Southport, Lancashire, PR9 7RL ‑ Telephone: 01704 540626. Fax: 01704 537322;
K.
R. Whiston; New Mills, Stockport ‑ metals, (available in small
quantities) tools. Both firms publish very useful catalogues. The other items I used, motors, batteries, pumps and other hardware are all readily obtainable at most well stocked model shops. I have in the past found it annoying when reading model‑building articles to find the author recommending the use of exotic, ridiculously expensive or simply unobtainable items. I plead not guilty to such a practice. U789 is built with commonplace gear throughout. In addition to GRP materials, a radio outfit with at least three channels, and preferably four or five, you need the usual hardware, prop shafts, couplings, and a few elementary model engineering tools such as drills and taps, and there is of course your supply of tranquilisers, headache treatments, anti‑depression pills, your nerve tonic and your fortified health wines, most of which are available through your family doctor. What's that? You don't need these things. Well, we'll soon see about that, after you've made a start. Having made the decision to become a submarine commander, you now need to recall the principles employed by submersibles to dive and surface. This is accomplished by two methods in conjunction, flooding or emptying ballast tanks, and using control surfaces, hydroplanes, which are similar in principle to the control surfaces of an aircraft, that is, they tilt the craft up or down, as the case may be. The diagrams show this. We can then consider these principles, and how they can be adopted or adapted to suit model purposes. |
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Into the cellar. The periscope, 'lain. diameter snake tube used for linkages, tells the depth of the boat. Note that even in slight chop, the boat becomes difficult to see just under the surface. |
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Conventional submarines spent most of their time on the surface, at 'Surface Trim,' with the hull well out of the water, Fig. 1-1. In this trim, they were efficient sea boats, and could cope with very bad conditions. Their keel cavities were filled with iron bars, and this, together with the very small superstructure, gave tremendous stability. |
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Diving was achieved by two principles in conjunction: (1) Ballast tanks, with a capacity of, typically 150 to 200 tons of water, would be flooded, and this brought the boat down to 'Diving Trim, ie. with the deck awash. Fig. 1-2. The boat now had little or no positive buoyancy, and could be thrust down by a flow of water over its control surfaces ‑ hydroplanes ‑ which tilt the submarine in a manner similar to an aircraft's elevators. The angles of the planes are as shown in Fig. 1-3. |
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To surface the boat, the planes are angled as Fig. 1-6. |
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From the diagrams, you may think, that all you do is set the hydroplanes to the dive position, then when you get to the required depth, you level out and finally apply up hydroplane in order to surface. Well, that may be true in theory. In practice, you are attempting a most difficult balancing feat. Though, under ideal conditions, the model may seem weightless in the water, it still has mass, and therefore momentum, up and down as well as backward and forward. Thus when you move the hydroplanes, they take time to overcome momentum. When the bow starts swinging into the required angle, you have to check well before you reach it, by putting on opposite plane angle at the right amount, and at the right time. You always have to be a couple of moves ahead of the submarine, because of the delay in response to the controls. Visualise a baulk of timber, about 4ft. long by say 4in square, balanced like a seesaw on a pivot at or near to its centre of gravity, free to swing up or down. Thus, the fullsizers used compressed air to blow the water from their ballast tanks. Modellers can use air, or other gases, such as CO2 or freon. For reasons which I will outline later, I discarded this idea. Instead, I opted for Mode 1, and subsequently progressed to Modes 2 and 3 of operation. Each has its pro's and con's.
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Mode 1 |
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Mode 3 Ballast tanks are fitted, fore and aft. Electric pumps flood or drain them by radio control, though on the surface, normally taking about 45 seconds, with the boat on the move if required. Having tried this mode of operation, I would not consider going back to Modes 1 or 2. |
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| U789 under way, under the surface and under control. The most beautiful part of this photo is the tiny wake from the periscope, called the feather. |
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Imagine this is your submerged model. Visualise that you can tilt it, by radio, by shifting small weights, situated about 6in. in from each end, just as the hydroplanes are positioned. You can't shift them much, only say, 3in. each. This is the nature of the problem. You have to strive to keep the bulk of wood horizontal, by shifting the weights. You would most likely find that until you had a fair amount of practice, that the timber would tilt inadvertently very easily, and that once it starts tilting, it goes out of control, i.e. your model has either surfaced contrary to your wishes, or it has hit the bottom. It's quite a tough problem, but like all tough problems, you feel all beautiful inside when you start getting it right. You don't sail submarines, you fly them, odd though it may sound. Welcome to the Third Dimension. Both delight and despondency await you. |
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Decision time Which submarine? I opted without hesitation for a Type IX U Boat. To the modeller who enjoys hull making, submarines are truly glorious subjects, the pleasing fishy shapes, the bulges, blisters, bumps and lovely knobbly bits and pieces are all there to be enjoyed in a leisurely fashion. But as a prospective submarine commander I wanted a 'now' boat, with clean, simple lines. The knobbly boat could wait for a while. So I came to the Type IX for more than one reason. The size had to be right, that is, it had to fit into my bath at home. This is a vital consideration. There is a great deal of testing, both of equipment and of flotation, there is balancing, mostly done by trial and error, and all this is time‑taking. Moreover it needs to be done in comfort, lest you are tempted to skimp the job. You need good light. You can't do sensitive checking with the wind howling round your jowls. Then there is transporting the model. My models have to share an average sized car with a family of four and a rather large dog with a low IQ. Hence it must fit in the luggage compartment. Those readers with swimming pools and pantechnicons of course can think bigger. I felt 46in. would be about right. A large bonus is the shape of the Type IX. Not a. bulge in sight. Just a long, lovely sweeping curve from the shark like stem to the long slim stern. If you have never planked a hull in your life, you couldn't find a better one to start on. No blocks at bow and stern to carve. The shape is classic, with tumblehome nearly the full length. I built mine, inverted, on a plank about 4ft. long by 6ft. wide by 1 in. thick, without really trying. Then I made a fibreglass mould from the finished hull. Once you have the mould, you can turn out hulls of immense strength, inexpensively, for a couple of hours of working time. A 30p tinlet of No. 53 Humbrol paint can be added to the resin mixes. This is a dark grey colour with a satisfyingly sinister dull sheen about it. The hull could of course be made of wood, or ABS or metal, depending on personal preference. I have not regretted my decision to use GRP (Glass reinforced Plastic or Fibre-glass - Mayhem). |
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U789 shown in mode 1. The slots in the deck are over scale and would create havoc for the crew. This fact caused the author many sleepless nights, however the important‑thing is to let the air escape when diving. |
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"Ho!" says Captain Fastidious, "what right has he to talk of Type IX U‑boats when he has wilfully scorned authenticity in this callous manner?" Well, these are not so much alterations as improvements! U‑789 is what Type IX boats should have looked like. Indeed, it was truly fortunate for the Allied cause that Germany did not have men of my technical superiority designing their boats for them, or the Battle of the Atlantic would have taken a very different course. I really mean that most sincerely. Anyhow, there never was a U‑789. Numbers 780 to 790, due to be built Wilhelmshafen, were all cancelled. |
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The watertight compartment The construction of this compartment is shown in the diagrams. The bulkheads and hatch rim should be tacked in position with dabs of top grade adhesive. I prefer Stabilit Express (www.pattex.de/ - Mayhem ), which sets hard in 20 minutes. Naturally, the hatch rim should by this time have been tapped and fitted with the screws, of which 43 were involved in my case. Great care should be taken not to deform the hatch rim when locating it in position, by bending or twisting it. After the glue has hardened, gel can be applied with a short stubby brush, from the interior of the compartment, to make a substantial fillet right round all the joints. When hard, fit the gasket and hatch cover, and tighten the nuts, as evenly as possible. Ideally, a little torque wrench would be used, but I haven't got round to that yet. Over tightening will damage the gasket. Test the compartment by plugging the end of the bilge pipe, immersing the hull in water, and blowing down the vent. Hopefully, no bubbles will appear. The next items are the propeller shafts and tubes, 8in. long. They should be drilled 3/32" and have a ˝” length of 3/32" brass or copper tube soldered into them, 1 ˝”. from the motor end. This is so a length of silicone tube can be fitted, down which you can blow a quick squirt of WD40, or LPS1 or whatever your favourite water disperser / lubricant may be. To completely prevent water entering the boat through the propeller tubes is not easy, unless of course you pack from solid end to end with grease or petroleum jelly, in which case a lot of drag is caused. Initially I used oil, but even a single drop of this escaping causes a noticeable oil slick on the surface, and makes a bad impression. I tried emptying the tubes altogether, except for regular spurts of WD40. Water entered at the rate of lee per minute, i.e. a teaspoonful every five minutes. Only just acceptable. Then I injected a few cc's of petroleum jelly. The current drain, both motors running, props out of the water, rose from .4 amp to .8 amp. I. settled for this as a reasonable compromise. Water does seep in, however, in very small quantities. I used 35mm three blade red plastic props. They did the job well enough, though they didn't pull very well astern. The red plastic irritated me after a while, and when I came to fitting smaller motors to U‑789, I made a pair of two bladed brass props, 30mm diameter. I like brass props, because you can alter the pitch easily to suit your motors. Captain Fastidious stands back in amazement. Two‑bladed props! On a IX Type U‑Boat! What heresy is this? Well, the fewer blades a propeller has, the more efficient it is, in my experience. |
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| Bottom.. the plug for the GRP mould in wood. Centre is the left side and top the right side of the mould, with the hull shell still in place. Two halves are bolted together when the hull is being made. |
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But you
must not have stuff sculling around loose inside. Battery packs must be
gently but firmly restrained from any movement. Finally, build light. You
can always add extra weight, if necessary, to the keel, where it's going
to do the most good. Getting rid of surplus weight is a tougher
proposition altogether.
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U789 Mode 1. Stand / tool tray is a must. Two screwdrivers, one crosshead and one normal. Two syringes ‑ one to apply petroleum jelly to seal hatch ‑ this was before a gasket was fitted ‑ and one to suck water out of bilge via tube on right, silicone plugged with a 1/8" diameter. Tubular spanner is a must, but use finger tight only without a Tommy bar. Tweezers are useful. The tool in front is a 48A socket grub screw wrench for the large number of grub screws. Jar contains 68A nuts. All photos by the author. |
