tidtugconstruction

The Royal Navy, by its very function, was and is a big user of tugs. It is probably correct to say that they have built and owned more of this type of vessel than any other organisation. Many of their tugs were designed by that little known Naval organisation, The Royal Corps of Naval Constructors. At the outbreak of W.W.l, a rescue tug was designed, drawing heavily on existing civilian technology, but with the needs of the fleet in mind. The resulting vessel was designated the Saint Class with 46 being built. By the start of the Second World War 15 were still in service, while others that had been disposed of to private interests were recalled. During the building of the Saint Class a much larger ocean going tug was also built as the Rollicker Class. While the foregoing is by no means a comprehensive list of naval tugs, it serves to suggest that the Royal Navy has a lot to offer to the tug enthusiast.

T.I.D. Class tugs of the Royal Navy.

W.W.2 saw further requirement by the Navy for a general purpose tug with the ultimate intention of using them to tow prefabricated harbours to the landing beaches of Normandy. The Constructors Corps came up with the very much prefabricated T.I.D. It was built in sections by inland engineering concerns and then transported to the coast. There the sections were welded together to form a hull 70’ x 17’ which was then fitted out for service. The first batch were steam powered but as time progressed diesel engines became available and these were installed in place of steam. The first batch had had open bridges and very basic fittings. Over 180 T.I.D.s were built during a period of about three years. There has been some dispute over the exact meaning of the nomenclature T.I.D. but I am happy with the generally accepted 'Tug Inshore Defence'. The tugs were disposed of very quickly at the end of the war, mostly into civilian employ. A short history of these vessels appeared in the Tugs and Towing supplement to the October 1998 issue of Marine Modelling magazine, and at the time of writing only a handful are known to exist.

Modelling the T.I.D.

A T.I.D. must be the ideal starting point for any tug modeller. Its simple chine hull and box like superstructure makes for one of the easiest models to build, yet it will display all the charisma of its civilian brethren. Some years ago I built a T.I.D. using the Marine Modelling plans. The hull was built to 1:24 scale using 1.2mm ply throughout. A simple 540 electric motor provided the power through an electronic speed controller and 7.2 volt ni-cad packs. Two function R.C. gave excellent control and many hours of good sailing. Nothing was changed in its lifetime, just the odd collision damage touch-in and one or two fittings glued back on! In 1998 a Maxwell Hemmens Caton steam plant came into my possession and it was decide to convert the T.I.D. to steam power. Nothing seemed more simple, but it was not to be. As the model had only used small battery packs a fair amount of lead had been bonded in to ballast the model correctly. It was obvious that nothing was going to shift it! The only course open was to salvage all the fittings together with the one piece superstructure, and start again, but using a new hull.

As stated the hull is a simple project and the Marine Modelling plans explicit, but time was valuable so a simple alternative was chosen, a ready made hull was purchased from Kingston Mouldings.
This supplier offers the option to have the hull moulded in heavier glass mat should the modeller so desire. Although not strictly necessary it is aimed at the builder who intends using steam. I have but one criticism of this supplier; the mouldings are really too perfect for this type of vessel! On delivery the hull was as expected, moulded to a consistent thickness and accuracy, with a beautiful and flawless black gel coat finish. At this stage it is important to assess the all up weight the hull will carry, bearing in mind that a steam plant is quite heavy and that other ancillaries such as water tank, gas tank, batteries and servos increase the weight. Adhesives and paint also tend to put on quite unexpected ounces.

To establish the weight required to achieve a correct water line, the bull was floated in the domestic test tank. It was gradually filled with water from a pint milk bottle, The schoolboy table, 'A pint of pure water weighs a pound and a quarter', established how much weight the hull would sustain while floating correctly. The superstructure, engine, boiler with water and all the fittings and ancillaries were then weighed coming to a total of just under 12 pounds. This total was subtracted from the ‘pints x pounds' total which had suggested the hull would need some 14lbs to bring it down to its correct waterline. The 2lb deficit was made up by pouring lead shot into the bottom of the huII and then pouring in some resin to secure it. In fact, slightly less than the two pounds needed was bonded in. The completed model could then be finally trimmed using self adhesive weights as used in car wheel balancing. Once the bonding had cured it left an even platform for the engine bed. Before work was started on installing the steam plant the inner surfaces of the bulwarks were covered with car body filler, and then cut back with 'wet and dry'.This task is best carried out early in the build so that other fittings are not damaged.

Engine Installation.

The engine was now offered up to the hull but its location had to he precise, as the boiler flue had to line up with the funnel of the existing superstructure. Four aluminium 'feet' were made to fit the boiler base. These were tapped to accept 2.5mm screws. A hole was drilled in the hull to accept the propeller shaft salvaged from the old hull. At this stage a piece of 12mm brass bar was turned up and drilled to accept the engine shaft and propeller shaft could now be rigidly aligned by the brass bar and the whole unit located in the correct position in the hull. Small portions of resin paste located the feet of the engine bed and the whole unit was adjusted to its final position before the resin cured. The prop shaft was also bonded to the hull at this stage. This system ensures that the engine shaft and prop shaft are in perfect alignment. When the bonding had cured the engine was removed leaving the feet bonded to the hull. Further strengthening resin was now applied to the feet. The centre section of the aligning bar was cut out and the ends rejoined using a piece of thick wall rubber tubing, as used in gas appliances. This forms a flexible, shock absorbing universal joint between engine and prop shaft. Twenty four hour epoxy was used to bond the tube to the brass. This is a cheap and economical way of overcoming any slight misalignment and it is also silent when running. The single large opening gives easy access for steam power.

Controls.

A model using a Caton steam plant requires three servos to operate it, one for the steam valve controlling speed, one for the forward/reverse valve and one for the rudder. These servos could now be installed while there was room to work, but allowances had to be made for easy access should they malfunction at any stage. The answer here was to install the deck first and then the servos. This would ensure the servos could be accessed at any time. The engine was removed but first the flue position was marked on the bulwarks, then a start made on installing the deck beams. This presented little trouble and in fact the beams and deck were all fitted in an afternoon. The hull was fully decked over initially. The superstructure was then placed on the deck ensuring the funnel was aligned with the marks indicating the engine flue position. The outline of the superstructure was pencilled round and the deck opening cut out. Coamings were glued in and, after checks, work commenced on installing the servos. The steam plant was refitted and it was established that the engine control servos would both need to be on the port side, one forward of the boiler to control the steam valve, the second aft of the engine to link to the forward reverse valve. The process worked far better than anticipated. All that was needed was simple plywood servo mounts bonded vertically from coaming to the bottom of the hull at suitable distances from the steam plant. The servos are mounted so that the arm works in the same plane as the arms on the valves, but are easily removable. A plywood panel was then mounted across the hull, aft of the engine and over the prop shaft. This mounts the steering servo, water tank, refillable gas tank, RX and the receiver batteries. Provision was also made to accept disposable gas cylinders which have a greater capacity than the refillable tank. This alternative makes for flexibility during sailing. All that was left to do was set up the full radio control. A 40 meg Hitec 3 function system is used. The Hitec has trim adjusters on the TX which make for simple adjustment of the servo links. The TX has two sticks and a rotary control. Left stick controls forward/reverse and right stick the rudder. The rotary control governs speed.

The stern in detail, showing the fenders and various coils of rope.

Use of timber on bridge door and other fixtures, with splashes of red and green for the navigation lights, adds a little colour.

Note fire hoses on sides of superstructure, and well appointed mast with navigation lights and halyards.

Access, OK.

Bench testing was very satisfactory, the only drawback being that the safety valve vents straight from the top of the boiler, into the superstructure. At a later date something will have to be done about this. Because considerable thought had been given to the layout during the planning stage, engine installation/removal takes but a few minutes; the pre-planning has paid off handsomely! The engine was once more removed before final finishing of the hull. One last task was carried out and this was to coat the inside of the hull with a white fuel proof coating. Steam plants tend to throw lubricating oil around but this type of finish makes for easy cleaning. The white finish helps to lighten the rather dark interior of the hull.

Finishing the Hull.

The whole of the external surface of the hull was now vandalised by flattening with 400 grade 'wet and dry'. The prop shaft and supporting skeg were faired in using body filler which was cut back to shape. The rudder tube was also bonded in and the rudder itself fitted and set up. Weld lines were applied to the hull by placing masking tape at the appropriate points and then brushing sanding sealer up to the tape. When the tape is removed realistic lines are left. Mooring ports and wash ports were also cut at this stage. Templates were cut to the line of the bulwark and used to assist cutting the rail from thin ply. The rail was attached using cyano. Three coats of car body grey primer were used to represent Navy grey. When dry two coats of matt polyurethane were brushed over the hull. Humbrol 'deck green' was brushed on to the area of the deck indicated on the plan. All the fittings saved from the original hull were then glued to their plan locations. Most of the fittings are home made. The fenders in particular were knitted by my wife who has had only sixteen birthdays but draws a state pension!

Steaming way from the docks on her local waters.

Final Thoughts.

Performance is very similar to the original timber hulled and electric powered version but, typical of single screw models, not very handy in reverse. Visually she is much more eye pleasing, especially on a cool day when exhaust steam flows from the funnel. If I was thinking of buying a new steam plant then I would opt for the Cheddar Puffin plant, which has the advantage of requiring one servo for both speed, forward and reverse control. This would mean that a two function radio unit would give full operational control.
The Marine Modelling plan (MAR 2447) by Adrian Brewer is well executed giving all the detail for the builder to complete a first class model which at 1:24th scale works out at 875mm length and 175mm beam.
If you prefer a pre-moulded hull, then the Kingston Mouldings grp version is highly recommended, and this T.I.D. also comes with an excellent plan. A little additional detail is shown on the Marine Modelling version mentioned earlier, though much of this is in the form of frame sections etc, which are obviously intended for builders who decide to go 'The Full Monty' and build a ply hull from scratch.