U789
Part 3
- Kapitan Bill Thomas
 

Kapitan Bill Thomas reveals all about successful model
submarine construction and operation.
 


U789 in the 'chop'. Even in moderately rough conditions, attempting to run submerged is a waste of time, as the boat is impossible to see. But these boats enjoy such conditions!
 

   Investigating Blowing Techniques
  Full size submarines use compressed air to expel water from their ballast tanks in order to rise to the surface. I have heard of models using Freon gas or carbon dioxide, but I discounted these as being too expensive and probably inconvenient, Compressed air, however, was worth considering. I soldered a car tyre valve into a small WD40 aerosol can (about 2in din x 6in. tall), and pumped it up to 80lbs per square in. in easy stages, and with caution. However it displayed no signs of distress. took an empty plastic transparent turpentine bottle and fitted it with a vent tube and a longer tube reaching right to the bottom, 3/16 ' in dia. copper. I connected the aerosol to the turpentine bottle (capacity .75 litre, filled with water), and pressed the valve, gently, hoping that water would he expelled from the bottle in a nice orderly fashion.

  I was staggered and petrified by the ferocity of the jet which emerged! It blasted all over the ceiling, and bounced back down again drenching everything. My brain flashed a message to my index finger: "Release the valve, stop the jet!" My index finger replied: "Who, me"", and all the time the water was everywhere. I uttered a hoarse cry of dismay, and hurled the apparatus into a corner. I then ran into the bedroom. "What's going on'?" other members of the family shouted?" But I am master in my own house, and I would not come out from under the bed. Later, I tried to blame the dog, who was even more terrified than myself, but the state of the ceiling gave me away.



  I'm not saying you can't use compressed air. The pressure I used was too high, and the valve was not sensitive enough. After about three dives the compressed air would rim out anyway, in the amounts I was contemplating. I could later only use it as an emergency method of blowing a sunken model to the surface. possible, operated by a timer.


  So that was Mode 1. An undoubted success, being simple, requiring only three channel gear and reliable. The disadvantages were, too high a speed required to prevent its natural buoyancy raising it to the surface and connected with this, a high current drain.

  One evening at the lake, 1 had had my 25 minutes. the batteries had indicated that they had had enough, and 1 was sitting gloomily surveying U789 lying stopped at the waterside, and chewing anti depression tablets. "Himmel", I said, "I've got to get more running time out of this boat." I started fastening pieces of lead pipe to the keel with elastic bands. Soon the boat was trimmed right down with the decks awash. The gentlest of downward shoves with a finger-tip was sufficient to send it right down. At first I thought it was going to stay down, but she gradually floated up again. I set the planes to dive position and gave a gentle push forwards. The boat went under with scarcely a ripple. I hurried home and weighed the lead. 12oz. I cut a piece of 1/2 in. square mild steel bar, abut 10in. long which turned out to be about right and clipped it to the keel. Out came the hummingbird motors and in went a couple of much smaller motors. they were not standard Monoperms, but they were of similar dimensions and performance, made in Germany, possibly an industrial equivalent of the Monoperms. I don't knew for sure. They have proved ideal. when propelling the boat, the combined ampage they pull only 1.8 amps. I added another D cell to the main pack, lifting the voltage to 7.2v, and fitted 30min dia. two blade brass props of my own manufacture. The Tamiya speed controller was now redundant, and simple ahead stop astern switching was used, with micro switches.

 

   Mode 2
  The following Sunday 1 was at the lake early, with the heavily modified U789, which I now regarded as being in Mode 2 operation, First I tried the boat on the surface, without the steel bar on the keel. It was acceptable I brought it in, and clipped the bar in place, then carefully deposited the model in the water. It sank down until the deck was awash. I took a quick swig of Phyllosan and started the motors. The result was pure magic. It responded superbly, sliding gradually under the surface in the deliberate way that the full sizers have. The response to the controls was much better.

  More movement on the planes was needed, and I could still improve on the balance, The endurance improved out of all recognition. Now, the receiver batteries were getting exhausted before the main batteries, after only 60 or 70 minutes as it happened. I1 thought I had faulty batteries. I changed them. No better, still just 60 minutes We were talking about it in the pub, and the point was made that the boat was now spending almost all its time under the water and the hydroplanes were in literally continuous use. The plane servos were giving the receiver battery a bushing. I replaced them (they were normal pen cell size) with Sub C cells The endurance of the boat rose higher again, now over 2 1/2 hours, by which time I was exhausted, and the model was still going strong. I did try running the radio gear off the main propulsion pack, but the receiver wasn't having any of that, and I went back to the Sub C's.


  If you find space at a premium in the submarine, and wish to dispense with receiver batteries, a voltage regulator can be used. Lieutenant M. Young uses one with complete success. My own Rx dislikes the apparatus. however, and I still use a battery pack. As we submarine commanders always say: "There is room for everything in a submarine except a mistake."

  Though control was much better, there was still a lot of room for improvement. What I needed was independently controllable fore and aft planes. This meant 4 channel radio. I asked around in the club, and no of the offers was a set of Digimax for 30. Old gear, but top quality. None of 'yer paper circuit boards or pot tracks'. Soon I had independent fore and aft planes. Progress was thrilling. Depth keeping is never going to be dead easy, but viable control was now an established fact, "We have the technology!" Practice with the system was the order of the day. I soon tired of the iron bar on the keel, however, and started to think about fitting tanks and pumps to achieve surface trim and diving trim by radio. Mode 3 was just over the horizon.

Questions
An integral part of the model submarining is the questioning. These boats arouse far more than the normal interest shown by passers by ....

'Does it Dive?" is the favourite.
"Does it come up?" is a close second.
"Is it water proofs?"
"Why isn't it yellow like a proper submarine'?!."
 "Did you know your boats just sunk. Mister?"
"How doesn't the water get in those slots?"
"Has it got a motor?" (they can see it moving along under the water)!
"Is it remote controlled?" '(you're standing there working the transmitter)!!
"Can you make it torpedo that noisy boat?" (I wish I could)!!'
"Has it got an underwater camera?" (there is precisely nothing on the bottom of the lake worth photographing!).
If you think these questions are gormless, you should hear some of my answers!!!.

Now and again an intelligent kid, not always a boy, will follow you for a while, and then ask a string of pretty good questions. These you answer properly. My favourites are the seafarers, who know there is usually something worth looking at on Tynemouth lake, and who stroll by now and again. They know what to ask. When you've satisfied their curiosity, you let the boat lie stopped on the surface, and get them talking. It's all part of the enjoyment.

   Tactics
  The Type IX family of U Boats were very successful. Relatively few were built compared to the Type VII, as they were larger, and did not lend themselves so readily to mass production. Of the six top scoring U-boats of the war, three how ever were Type IX. They took longer to submerge, as well, and were thus more vulnerable when on the receiving end of a sudden radar guided aircraft attack which became increasingly common as Allied .scientists started winning the electronic war, and when escort carriers came on the scene. The long range Catalinas, Sunderlands, Liberators and Wellingtons were also a source of fear to the U Bouts as the war progressed. The U boat Command tried fitting additional anti aircraft guns, and instead of diving and being hunted, they started staying on the surface and slugging it cut with the aircraft. These fights were conducted with extreme ferocity on both sides. and the outcome could not be foretold. The aircraft were often large, low speed types, who came in close to try for accurate attacks and did not present impossible targets. Many were shot down.

  On the surface. Type IX boats were also an awkward customer for a small escort to tackle, such a., it Corvette. which with their speed of 18 1/2 knots they could out run in any case The deck guns they mounted, 88mm or 105mm were roughly equivalent  to the 4inch guns of many, of the escorts, and the
low lying sub did not offer much of a target. On the other hand. they could not readily sustain much damage without serious effect. A four inch hole in the pressure hull might be impossible to plug because of the maze of pipe work and other gear which lined the inside of the boat. When forced to the surface. U-boats did not frequently get the chance, to retaliate. As soon as they appeared on the surface, probably damaged and shocked. they were, attacked with a fusillade of gunfire of very calibre, torpedoed, rocketed and rammed, such the fear and loathing they inspired among the merchantmen and escort crews they attacked, and the U-boat crews were usually gunned down long before they could
get to the deck gun. Most Type IX U Boats lived and died violently, often in remote parts of the world by virtue of their long range of about 12,500 miles.

  Only one still exists, as far as I know. The story of its capture by a U.S. hunting group is told in 'Clear the Decks', by Admiral D. Gallery who commanded the force, the centre of which was the carrier 'Guadalcanal', I recommend it as a very readable book indeed. The U-boat, is in it museum in Chicago. and when I win my fortune on the football pools, I in heading for Chicago in rapid order, because I would dearly like to see that boat. That is. if I can get through US, Customs. Maybe they'll think I'm an Undesirable Alien! If they read this, I wouldn't blame them.


http://www.msichicago.org/exhibit/U505/U505home.html

   Three Dimensions

  The orthodox boat modeller accustomed to two dimensional control, is almost certain to find the use of a third function awkward in the initial stages, as I did. I became intrigued with the problems associated with up and down control to the extent that I constructed a model aircraft and learned how to fly it. The experience is helping me to obtain better control of the submarine. One habit I have picked up from aeromodellers is worth mentioning. They continually check the condition and functioning of their models. Not just a quick look now and again, but frequently, to an extent that I have never observed boat modellers to use. It's a good habit, and one that I have got into, and on two occasions it has saved me from acute embarrassment and irritation with U789!

The first milestone in the careers of we U-boat Commanders is our first submerged trip of 2 or 3 yards. When you achieve this feat, you may apply to me for your Certificate. On receiving it, you will be officially entitled to place the letters B.Sc. after your name (British Submarine Captain). The whole thing is done "in the best possible taste!" In addition. you in are entitled, here it says on your Tax Form 'state Your occupation', to put 'U Boat Commander'. Of course. if your tax man, its is likely, is ex Royal Navy ", and served on Corvettes in the, Atlantic 1939-45, you might well run into difficulties with your taxes over the next year or so, but doubtless this is a risk you will be glad to take. ( NB. To cover administrative  expenses and overheads, your application for your Certificate should be accompanied by a substantial remittance' There is no need to prove your achievement. just send the money. I really mean that most sincerely.)

   Dive! Dive! Dive!
 
When attacked on the surface, U Boats were desirous of disappearing as rapidly as possible. In addition to flooding the tanks and applying dive to the hydroplanes, they used a third expedient. All crew members not actually manning the controls would rush to the, fore end (or 'bow' as we experts call it). the diesels would thunder at full bore until the water was about to pour down the hatch, at which point, the diesels would be shut off, the hatch slammed shut and the electric motors cut in. If the timing was not quite right, either a large amount of water entered the boat, or a large amount of air was sucked out by the diesels, with painful results. to eardrums, etc.

  Once a submarine was forced to dive, it lost most of its performance, being dependant on batteries for propulsion. A typical limit was 80 miles at about normal walking pace, or maximum speed submerged, about 8 to 9 knots, which could only he sustained for a matter of about two hours. Schnorkels were devised, basically v breathing tubes projecting above the surface which enabled the diesels to run with the boat under water, at periscope depth. Speeds of 6 knots were about the limit. In rough conditions, a cut off valve prevented water getting down the trunk of the schnorkel. and also air, which made the method very uncomfortable for the crew. because the diesels sucked in air regardless, causing severe variations in the air pressure inside the boat.

Without the schnorkel, submerged endurances of more than 1,5 hours became unhealthy, as oxygen was consumed and carbon dioxide emitted by the crew With the severe condensation and humidity, oily fumes from the engine room, emissions from the vast lead acid batteries, rind the odour from bodies which could not be washed for weeks at a time, the interiors of submarines were a horrendous environment for the human system. Toilet facilities must have been nightmarish, There were two on Type IX boats, for a crew of 50 to 55 men. However, one was almost invariably used as a store, as was every possible nook and cranny in a small boat already infested with machinery, pipes and equipment of every type

  To operate the flushing system was not simply a matter of pulling a chain. A sequence of valve operations, involving the use of high pressure air. was required, and if not performed correctly a geyser of unspeakable material would deluge the entire compartment and its luckless occupant. The apparatus could not be used below a depth of about 200ft. or when the boat was under attack. in which case buckets were used. The effect of these in an already hideous atmosphere can only be imagined. The interiors of these submarines were not lovely places. They were bad enough during normal running. When they were being depth charged it must have been pure undiluted hell. It took a special breed of man to be a submariner, to withstand the cloister, phobia, the boredom, and the fear. The amazing fact is that there was no shortage of volunteers for submarine service in any of the navies of the nations involved in the conflict. In round figures, the Germans for example. built 1,100 U boats, of which they lost 780 (They sank 2.500 ships), Yet at the closing stages of the war, their morale was still high



   Mode 3
  Loafing around in the model shop, my beady little eyes latched on to some M.F.A. pumps, as used for pumping glow fuel in and out of tanks. I bought one and hurried home. On 7 volts, it emptied my turpentine bottle in rapid order, pulling .8 of an amp. It is a good product, no piston or cylinder, just a couple of gearwheels. a-la car oil pump. Next, came the installation of ballast tanks in U789. I ascertained the approximate size by experiment, and fitted the tanks. The ends were of 20swg aluminium. the tops transparent acrylic sheet. I needed to know m hat was going on in those tanks. The aft tank required two tunnels for the plane and rudder rods. and these were of 1/2in. aluminium tube. The adhesive was Stabilit Express. The tank tops had two circular hatches, tin. diameter, and the vent tubes were fitted to these. I purposely made the tanks oversize.



  Experiments started in the bath It took 1 1/2 minutes to fill both tanks, rather a long time. Worse, the tanks did not fill evenly. One always filled first, then vented, with the other half full. I fitted restrictors and valves into the quicker filling tank, but it wouldn't come right. Sobbing miserably, I went back to the model shop and bought a second pump, This transformed the situation. I could now fill the tanks in 4,5 seconds, and I could balance the boat at will. When the required diving trim was reached, i.e. with the deck awash, there was, as expected still air remaining in each tank. This would have been bad news if allowed to remain, because when the boat submerged, that air would be compressed. and more water would enter the tank thus altering the trim. Control is oil difficult enough without trim alterations happening Thus, corks mere inserted through the 1in hatches mentioned above until the airspaces were completely removed. "Da ist gut. Bill!" I said to myself completely feeling that I had now licked the trimming problem  - wrong again!



  I had failed to take water temperature into account, In warm water, the boat will lie deeper. This is worth remembering when you are experimenting. In colder water the boat will be reluctant to dive. To overcome this. I planted a vertical a1/8in diameter brass rod in each of the free flooding spaces, fore and aft. I made a couple of dozen in diameter discs of 3/16in. thick sheet lead, with ,a 5/8 in, hole in the centre These little weights could be dropped on to the rods or easily removed with a little wire looped gadget, and they served in, the final adjustment of the trim. The job could have been done rather more smoothly by admitting further water to the boat, but like many 'lashups', this little disc system works well enough.

  The MFA pumps have proved to be robust and reliable, but they must be protected led by filters. It is net fair to expect gear type pumps to digest water containing grit, sand and other foreign material. Each pump should be protected by an easily accessible filter at both inlet and outlet, l e two filters per pump, of the type (in line) used fly i/c engine modellers to filter their fuel

  I have heard yarns about model submarines using bicycle pumps to pressurise their boats. Fair enough, but it is rather like using a sledgehammer to knock a tintack in. If you blow down the silicone tube vent, fairly hard. then plug the end, with the tube nipped between finger and thumb, you will have all the pressure in the boat you need. U789, without wishing to tempt providence, is far dryer than the flatties (multi speed boats) I have been racing over the years. But keep checking for leaks, especially after you have been rimmed. These low-profile submarines blend into the background too well for their own safety, and other modellers, perhaps with poor vision or not vigilant will occasionally clatter into your submarine. until you learn the arts and craft, of like experts such as myself!
 

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