Tony Dalton describes to Model Boats his building and conversion of a KM Bismarck model into an R/C.
Here's the Dragon 1:700 scale kit of the famous German battleship KM Bismarck, Photo 1. After reading some favourable articles about the kit I decided to attempt to build it with as much detail as possible, but also converted to radio control.
The kit comprises 11 moulded frames containing 248 detailed plastic parts with a brass photo etched sheet containing a further 33 parts, a sheet of decals and a multi-folded sheet of instructions, Photo 2. It should be said that it will be only around 15 inches long when completed, so 'r/c and running gear miniaturisation' are the watchwords.
Following some investigation I discovered that a wood deck and some further photo etched parts were available from White Ensign Models (WEM), these being duly purchased and the photo etched sheet comes complete with three double sided pages of very detailed instructions.
Step 2: Radio Control Installation
The initial task was to find suitable r/c items that were not only small, but also light. A very small servo was located that weighed only 1.6gms together with a small electronic speed controller (ESC). Details of these are listed at the end of this article.
Step 3: ESC and Receiver Modifications
This was purchased in kit form, since I did not intend to use the plastic box supplied as I was convinced that it would not fit into the hull of the model and on receipt I was proved right. The printed circuit board (pcb) was trial fitted into the hull and did not require any further modifications. All that was needed was for me to assemble and solder the components to the printed circuit board in accordance with the supplied instructions. The device was then tested and found to work satisfactorily.
Step 4: Reducing the Receiver Size
Looking at the receiver it was evident that it was too large to fit inside the model, so the plastic housing and connector were removed, reducing the unit in size and weight. The servo and esc would later be wired directly to the receiver board, thus saving some weight on plugs and sockets.
Step 5: The Propulsion System
The plastic propeller shaft stubs (port and starboard) were drilled through their centres in order to allow a 1/16 inch diameter brass running tube to be inserted. The centre tube is cast as part of the hull, which is supplied in two halves, this requiring a small slot to be cut down the centreline of each half shaft stub. The two halves of the hull were then glued together and a 1/16 inch drill run down the slot, opening it out to accept the centre running tube. The propeller shafts were made from 0.9mm diameter brass rod, each threaded at one end M1.0. The propellers, as supplied with the kit were each drilled and tapped M1.0 to match the shafts and then screwed on and bonded into position. The A frames were each very carefully drilled out to accept a short length of 1/16 inch brass tube for shaft bearings.
The twin rudders were each drilled and tapped 16BA and two small shafts made from 0.8mm brass rod with a 16BA thread cut at each end. The rudder post tubes were made from 1.5mm copper tube and two small tiller arms fabricated from brass sheet. The three flexible couplings were made from short lengths of silicone tubing with brass bushes inserted and glued in at each end. All these parts can be seen in Photos 3 and 4, just prior to their assembly into the hull.
Step 6: Hull Layout and Displacement
In order to determine how buoyant the hull would be with all the radio gear installed, the upper hull moulding was glued in position on top of the assembled lower section. This then allowed the complete hull to be placed in a bowl of water (the test tank!) and the radio equipment (battery, radio, esc, rudder servo and three motors) placed in it, Photo 5. The hull was amazingly stable and floated level about the waterline. So, a bit tight on weight, but good enough!
Step 7: Stand Modifications
Having carried out the initial assembly of the hull I decided it was time to assemble the stand to protect the hull during the process of assembly. Having done this, the hull was placed on the stand to find that it was not very secure as it did not fit as snugly as one would have expected. So the stand was modified by adding some additional support pieces to the end sections that would follow the shape of the hull up its sides, Photo 6, and this solved the problem.
Step 8: Final Hull Layout and Wiring
Having assembled and glued the hull together, I noticed that the sides had to be sprung out in order that the deck would seat into it correctly. So, some full-width bulkheads were made to correct this problem and they also support a small platform within the hull to which the rudder servo and power switch were mounted. There are also some small dividers added in order to retain the esc and receiver in their correct positions. Two small printed circuit boards were made; one to assist in combining the wires and decoupling of the three motors and the connection to the esc; the second was used to interconnect the battery and power switch wiring.
Step 9: Painting the Lower Hull
The propshafts were removed from the hull together with the twin rudders. The upper half of the hull above the waterline was masked off, allowing the lower section to be painted red together with the rudder blades. The three plastic propellers were painted bronze, then everything was allowed to thoroughly dry prior to re-assembly.
The individual r/c assemblies were tested before they were wired together and fitted into the hull together with the propeller shafts and rudders, Photos 7 and 8, all followed by functional testing of the complete system. So far, so good!
Step 10: Deck Assembly
In order to gain as much access to the r/c gear within the hull, I decided to increase the size of the cutout in the deck. To do this, the two halves of the deck were joined together using masking tape. Then, the lowest level of the main superstructure was placed over the main weather deck and marked around its base to show the area that would be covered by this base part. The next step was to mark the increased size of the cutouts, such that they still remained within the perimeter of the superstructure. As always, double, double check before cutting!
As an extra (super-detailing) wood deck had been purchased from WEM, the moulded anchor chains had to be removed from the plastic deck, but a super-neat job was not necessary as the wood deck would cover it all anyway. Next the two halves of the deck were glued together, making sure they were accurately aligned as the next stage was to fit the complete deck to the hull.
Now, the additional internal bulkheads made their worth clear, as the deck fitted perfectly. Once the deck is glued into position, it is not possible to gain access to the rudder tiller arms, so before going past the point of no return, a final check on the rudder function was made before gluing the deck into position, masking tape holding everything in position until the glue set, Photo 9.
Step 11: Final Hull Painting
With the deck now glued in position, any excess adhesive was trimmed away from the hull sides/deck joint, then the deck cutouts were masked over as was the lower half of the previously painted hull. The top half of the was then painted grey. Once dry, the masking was replaced to allow painting of the black boot topping. All this is standard model painting stuff.
Step 12: Wood Deck Overlay
This is self-adhesive, so needed to be carefully removed from the backing sheet and any cutouts for the moulded deck fittings were also pushed out before it was carefully placed on the plastic deck and firmly pressed into position. I was amazed at the accuracy of the cutouts and how perfectly the wood overlay fitted to the main deck.
Step 13: Superstructure
I decided to build all the small parts for the superstructure first, starting with the big guns. These had some additional photo etched parts added to the turret range finders and at 1:700 scale the parts are extremely small. I am not sure that it was worth doing as they are certainly not very noticeable, Photo 10.
Next came the different deck levels of superstructure, some of which had wood decking to be fitted and all had photo etched parts to be added in the form of railings, catapult tracks etc. Photos 11, 12, and 13 give some indication as to the amount of additional detail work involved when using the photo etched parts, but they do make a distinct visual difference and improvement to the basic kit.
Step 15: Lighting
In for a penny, in for a pound, and some working navigation and illuminated interior lights seemed a good idea. Surface mount LED's did the job nicely and those chosen only measured 1.5 x 0.75mm. Photo 14 shows an example with its very fine connecting wires.
The corners of the bridge housing (by the bridge wings) were drilled to accept the two supply wires using a 0.3mm diameter drill. The two wires from each LED (port and starboard) passed through these holes and the LED’s body was then bonded to the front face of the cabin.
A small printed circuit board was constructed to which the LED wires were terminated. The board also contained the supply series resistors and the LED's that provided the internal lighting.
The after navigation light was mounted on the rear face of the second mast. The supply wires from the LED passed through the block on the mast and then were used as mast guide wires by passing diagonally down to the base on each side of the rear hangar and out through the bottom to a terminating printed circuit board. Photos 15 and 16 show LED’s mounted on the superstructure and second mast.
Step 17: Aircraft and Cranes
There are two Araldo Seaplanes, Photo 17, and one of each is mounted on the port and starboard sides of the catapult gantry system.
There are also two cranes mounted either side of the superstructure and these would normally be bonded into position on the main deck. However, as the superstructure is required to be removable in order to gain access to the r/c system, the cranes were modified to allow them to swing out and away from the superstructure by fitting a short 12BA threaded rod in the base of each crane and then tapping the main deck to match, Photo 18.
Step 19: Final Assembly
Having put together all the individual units, including the different levels of the superstructure, it was time to start fitting and finally gluing them all together. The lowest deck level of the superstructure was drilled to allow the wires for the navigation lights to pass through and be terminated to two small printed circuit boards. These were joined together and a plug lead added for connection to the battery within the hull, Photo 19.
Each deck level was then added to the base section, gradually building up the main superstructure including the funnel assembly, lifeboats, launches, the aircraft, guns, searchlights and masts. Photo 20 shows the completed superstructure and Photo 21 shows the main deck with all its guns in place. A stand for the superstructure was made so that it could be safely displayed separately from the hull at exhibitions, allowing a view of the internal control system.
Photo 22 is of the completed model and sea trials took place at the St. Albans & District MES Exhibition in September 2012, Photos 23 and 24. The model performed extremely well and cruised around the small artificial pond without any problems. Yes, it is barely 15 inches long, but nevertheless it looks and has the 'majesty' of a battleship on the water.
Building a working r/c model like this at 1:700 scale is not for the faint hearted as some of the parts are very small and prone to slip out of your hands and tweezers, particularly when it comes to cutting and folding the etched brass parts. So yes, there is a fair bit of scrabbling around under the workbench looking for the missing part that has flown goodness knows where! Mind you, I am glad that there were some spare parts supplied with the WEM optional photo etched sheet! The model was a challenge, but isn't that what our hobby is all about?