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first published in autumn 2006
last updated 10/01/17

  Wespe-Class Armoured Gunboat: The Model 

Introductory Note

Work on this model began in autumn 2006 and then progress with various long interruption for personal reasons and due to diversions, such as the construction of tools and machnies described elsewhere on this Web-site. While you will find below a step-by-step description of building the model as it progresses, this is not a continuous 'blog', so watch out for the date on the beginning of paragraphs to identify new material. For ease of reference the following table allows to jump to the various sub-sections.

History
Scale
Materials
The hull and superstructures
The 30.5 cm Rk/l22 gun
Deck Furniture
Skylights, Companionways etc.



updated 08/01/2017
updated 03/2009
updated 10/2008
updated 10/2008

Scale

The scale chosen for the model is 1/160, which admittedly is somewhat unusual for a ship model. However, the reasoning behind this choice was that a large selection of N-scale railway figures is available that eventually will crew the ship. There are also space and portability consideration, which are important for someone, who has to move from time to time for professional reasons.
The model will  be a waterline model. This will allow a dioramic presentation of the finished model. Besides, the hull below the waterline is not quite so graceful. Above the waterline the hull is also more or less prismatic, with vertical bulwarks and virtually no sheer. These parameters together call for a bread-and-butter construction.
The building drawings are a combination of re-drawn Admiralty plans and scans thereof. These are printed to scale on the laser printer and the print-outs glued on top of e.g. the MDF board to serve as a guidance for cutting and sanding.

Materials

Choice of materials
I had been contemplating a variety of materials for the hull; for instance Plexiglas® layers with bulwarks made from brass foil. In the end, I choose MDF (medium-density fibre) board, which is available in thicknesses down to 1 mm from architectural model supply houses.  Other parts will be constructed from or covered with Bristol board, which is also available in various thicknesses (or rather weights per square metre).
The bulwarks etc.. will be made from Pertinax® (phenolic resin impregnated paper, FR-2), which is available in thickness's down to 0.1 mm. Bristol board and then Pertinax® are easily cut with a scalpel, a razor blade or scissors and will not crease or dent as metal foil might. I currently have no facilities for photo-etching large parts, but if I had, perhaps I would have made the bulwarks from brass still. The other advantage is that Bristol board can be readily and permanently glued using white glue. Bonds between large areas of metal foil and Plexiglas® might become detached, though the plating on the steam-tug, made from copper foil, has lasted now for nearly twenty years. Pertinax® can be glued using cyano-acrylate or epoxy-resins. The dinghy of the steam-tug had received planking made from Pertinax® and glued with cyano-acrylate glue.
While I have been shying away from thermoplastics, such as polystyrene, on account of it being suspicious to be not 'permanent' (e.g. the articles by Dana Wegner), practical experience shows that plastic models built over 35 years are still intact. So I may reconsider my position in this respect. Polystyrene, of course, has several advantageous properties.

Some thoughts on Etched Parts
Some people refer to the process of making photo-etched parts as chemical milling and that is the way I view it; a process to cut out and shape parts that are too small or otherwise to delicate to handle conveniently with other manufacturing processes. Unfortunately, the employment of this process moves much of the modelling work onto the computer, as the patterns or masks now are produced with the help of a drafting program. These masks are largely developed by scaling the contemporary drawings and drawing the respective part over it in a different layer. These parts are then composed into the actual mask. Of course, 'left' and 'right' sides have to be drawn separately, if the part is to receive surface-etched detail. A strict procedure of copying and mirroring has to be adhered to in order to achieve a perfect line-up. Much thinking has to go into the best shape of parts and some experimentation. The etching process is not so well controllable, as a machine tool, at least in the simple set-up I am using. The best thickness of interlocking slots or the drawing size to achieve cut-outs of a specific dimension and similar features have to be found by trial and errors sometimes. Literary it is often 'back to the drawing board'.
This set-up is only suitable for dip-etching. Commercial companies use foam or spray etching, which work faster and produce less undercut. I decided to work with very small 'frets' only, the size of one or two large stamps. This reduces the cost of material, if something goes wrong and the smaller size seems to make it easier to get uniform results over the whole 'fret'. I bought second hand a UV-source for exposing printed circuit board. It has a timer and hence makes the process more repeatable. The developing and etching vessels are plastic film tins, coming from the standard film rolls (don't get any new ones since I have switched to digital, of course). The brass is bought in a ready-sensitised state, so no messing about with UV-sensitive lacquer is needed. Much experimentation went into a suitable way of making the masks. Eventually a newly bought ink-jet printer produced sufficiently uniform print-outs on overhead foil, but the resulting masks are not really perfect. However, I did not want to go a commercial photo lithography company for them.

The hull and superstructures

Autumn 2006 - The basic bread-and-butter construction of the hull is shown in the pictures above.
The Barbette mainly consists of a semi-circular breastwork armour, backed by hardwood and by an open space covered with thin plate. The latter presumably to retain splintering wood in case of an impact. Since no tube of suitable dimensions for the breastwork was to hand, I made a short laminated one from Bristol board glued together with white glue. The edges were soaked in thinned white glue before being trimmed down on the lathe. The tube then was varnished with
filler for wood before the edges were sanded. Finally a half-circle was cut from the tube on the jig-saw. More wood-filler was applied before final sanding. After cutting in half it was glued into place. The inside of the barbette was lined with hard-paper to give a smooth finish.
The fore-deck has been covered in a sheet of thin Bristol board and the camber of the wooden decking built up with an additional piece of board and putty (I am using fast drying bodywork putty from car repair suppliers). The anchor pockets have also been lined with thin Bristol board, but Pertinax would have been better for this.
All surfaces that would have been iron plating, will be covered in thin sheets of Pertinax. The necessary holes for portholes and other opening will be drilled or cut before the sheets are fixed.
In this way the barbette was lined with sheets of Pertinax as was the deck-house. .










Cutting the layers on a powered fretsaw

Sanding the sides of each layer vertical on an improvised disc sander
The first layers
The barbette and pockets for the anchors cut out
Milling slots for the rubbing strakes
Improvised drum sander to work the inside of the barbette
Shaping the body on the new shop-made disc sander
Tube made from laminated Bristol board
Trimming tube on the lathe
Drilling the hawse pipe on the horizontal milling machine
Deckhouse partially clad in Pertinax

January 2017
Most of the decks were plated and this plating was covered in oil-paint that was mixed with sand and cement in order to provide a certain corrosion resistance and above all a better grip in wet conditions. A modelling plan drawn by Wolfgang Bohlayer shows wood on some decks, but evidence that since has become available shows that this was not the case. Linoleum decking apparently was never used on these boats. However, as the model will show the boat in its original appearence, the plating was reproduced by engraving fine lines into then sheets of Pertinax. All decks, including that of the barbette will covered in this way. The exception is the deck above the foc'sle that a cover in planks, presumably to reduce wear, where the anchors were worked. This planking was laid-out in a radiant pattern, which seems to have been more resistant to the gun-blast than the more common parallel layout. The planks were also reproduced by lightly engraving the plank seams. In reality these seams would have been more or less flush with the deck, depending on the temperature and humidity, but a light engraving adds some life to the appearance.



Progress in constructing the hull
Engraving plating and planking
Excerpts from contemporary drawings


The barbette - The floor of the barhette is partially covered in planking, presumably to protect the armour-steel deck underneath from the damage that might occur, when the heavy shells are handled. The steel deck underneath and in front of the barbette armour-belt is slightly sloping to deflect incoming enemy-shells from the ammunition storage-rooms. Within the barbette this is filled with timber to make a level floor. The interpretation of the various items that can be seen in the contemporary drawings is not straightforward. However, one can see a hatch that gives access to the crew's quarters (where also the hand-cranks for turning the gun-carriage is located). Then there is a round hatch for hoisting up the charges from the powder-locker below and a square hatch for hoisting up the shells. From the drawings it appears that these hatches were covered in steel-gratings. There is a further hatch with a double-lid that, according to a hand-written notice on one drawing is a man-hole leading to the ante-room of the shell-locker. However, as it is not drawn in the cross-sections we do not know its height. There are also a couple of racks for shells and some other rack-like features, the purpose of which I do not know - perhaps for tools needed in handling the shells. Unfortunately, there are no photographic images that show the rear of the barbette.  Stairs leads down from the bridge into the barbette. In addition two ladders allow quick access from the deck.
The floor of the barbette, which apparently did not have any camber, was built up from two layers of Pertinax one representing the steel-plating and engraved accordingly, the second cut out and engraved to represent the wooden flooring. The construction of the various hatches is described below.

The 30.5 cm Rk/l22 gun

Lower Carriage

February 2007 -There are some fixtures for the gun that need to go into their place in the barbette early during the construction, including the races for the gun carriage and the semi-circular toothed rack that is part of the gun-training machinery. I decided to make these from steel, even though ferrous metals in model construction are frowned upon by museums. My justifications were that it is difficult to represent cast iron or steel by paint and that there hundreds of models in museums around the world that contain iron. I have used steel it in models some twenty years ago and presumably due to the lacquering shows no signs of rust.
Cutting thin disks from round stock of sizeable diameter is a pain I wanted to avoid. Against my better knowledge I picked a suitably sized steel washer as starting material. Unfortunately, the steel used does not cut very well at all and lot effort was spent to avoid chatter marks while turning and to obtain a reasonably good finish.
The various types of wheel collets available for the watchmaking lathe come into good use for working on inside and outside diameters of the disks.
I set up the hand-shaper for cutting the rack teeth, but had to throw away the first two attempts because of the poor material and because - again against better knowledge - I did not lock the traverse slide when cutting. The table was removed from the shaper and the home-made dividing head bolted on instead. For lack of a proper tool grinder (another project) I hand-ground a cutter for the rack tooth (0.1 mm at the bottom) from a rod of high-speed steel. For holding this tool-bit in the shaper, the old lantern-style tool holder from the watch lathe came very handy. The unwanted parts of the ring were cut away on the shaper using ordinary left and right hand lathe tools. Finally the necessary sections were trimmed off with a fine saw blade on the lathe's sawing table.








Roughing out the metal disk with the backing of a wooden disk

Grooving the races with a specially ground bit
Cutting out the inside of the large, backward ring
Trimming the outside of the small, forward ring
Shaper set-up for cutting the toothed rack
Cutting the toothed rack with a specially ground tool
Cutting away the unwanted part of the ring with an ordinary tool
The set-up showing the finished rack
The races and the toothed rack ready to be trimmed to correct length of arc

The gun barrel and lock

March 2007 - Again, because there will various visible areas of bare metal, the material of the original, that is steel, was chosen.  A piece of round bar was faced, centred and rough drilled for the bore. This hole served as a protective counter bore for the tailstock centre during the following turning operations. In order to get a good roughening finish the automatic feed was set up. Unfortunately the minimum feed per revolution on the watchmaking lathes is still too high to get a 'mirror' finish. One day I have to construct some sort of reduction gear. The outer part of the barrel has slight taper (1 degree included angle) and the top-slide was off-set for this operation. For rounding off the ends of the rings the LS&Co. hand tool rest came to good use. The work was finished off with fine wet-and-dry paper (remember to cover ways!) and steel wool. The bore was bored to diameter using the slide-rest and micro-boring tool. I had originally envisaged to also show the rifling, but a quick calculation told me that for a 1 mm bore and 72 rifled fields I would need a tool edge just over 0.04 mm wide ...








Races and rack provisionally in their place inside the barbette

Facing and centring a piece of steel rod for the gun barrel
Rough drilling of the gun barrel
Turning the barrel using the automatic fine feed
Taper-turning with off-set slide rest
Rounding the 'rings' using a hand turning rest
Boring the barrel using a micro boring tool
Set-up showing for milling the seat for the lock

For drilling holes for the trunnions and milling the seat of the lock the diving head was set up on the slide-rest. I could have done this operation on the milling machine, but on the lathe the dividing head is centred automatically. The outer end of the barrel was supported by the arm with an appropriate centre fitted. The resulting shape from the milling operation looks like a keyhole, but something like a mushroom shape with sharp edges is required. This was achieved by hand filing. For the next operation the set-up had to be transferred to the mill anyway: milling the seats for the square trunnions. The trunnions merge in a concave curve with the barrel. The trunnions were turned up on the lathe as disk with two round stubs protruding from either end. In the dividing head on the mill the disk was milled square to the size of the seat (or rather the other way round). These parts then were soft-soldered to the barrel. Back on the mill the concave curves of the square part of the trunnion were milled using a miniature ball-head cutter, rotating the barrel in the dividing head.
Aiming a gun in these days was a rather primitive affair, using just simple sights. The sights (two of them on either side of the barrel) consisted essentially of a round bar with a sliding rod to give the elevation. The beads (mounted near the trunnions) were observed through a ring of inverted U-shape on top of the rod. The bar was screwed into a notch in the barrel. Now, drilling into a round at a tangent is nearly impossible without deflection and breaking the drill (0.3 mm!). Therefore, I ground flat a broken drill bit to make a make-shift micro-mill and sunk a start hole. This was finished with an ordinary drill.




Close-up of the milling operation in the dividing head with support

Working drawing and files used to finish the lock seat
Milling the square part of the trunnions
Milling the seat for the trunnions
Trying the trunnion
Milling the concave transition between trunnion and barrel
Milling the seat for the sights Drilling the seats for the sights
Round-
milling  the lock piece
Cutting off the finished lock piece

The next thing to be tackled was the lock piece. This 'wedge' has a rather complex shape with a flat front, but a round back and various recesses and cut-out. I decided it would be best to undertake most of the machining operations while it is still attached to some (round) material that can be easily hold in a collet. The round back was milled on the mill's rotary table after the various coaxial holes had been drilled and the flat sides milled, all in the same set-up. For machining the other recesses the piece had to transferred to the diving head on the mill. The large ring was also turned up and two holes drilled into it for seating the circular rack that forms part of the elevating gear.
The most time consuming part turned out to be the cover piece for the lock, which in the prototype was fastened by five hexagonal head bolts. It holds the moving and locking screws in their place. It took me four tries before I produced a half-way satisfactory piece. Soldering the microscopic bolts (0.4 mm head diameter) in place got me quite a few grey hairs. Finally a fake locking screw was turned up and the moving screw, which moves the lock in and out, was faked from a couple of drilled-together 0.1 mm copper wires, covered in a thin layer of solder to make them look like steel.
The various parts of the lock were assembled using lacquer and cyanoacrylate glue.



Milling square and hexagonal bolts

Facing the locking screw in special protective brass collet
The (almost) finished gun barrel with its lock
Part view of the drawings for the photo-etched upper carriage frames Surface etched frames for the upper carriage Filler and covering pieces laid out for soldering Assembled side pieces and ties laid out


The upper carriage

Throughout 2008 - Much time has been spent on re-drawing the carriage as templates for etched parts. After the etching process has been more or less 'mastered', surface etched parts of sufficient quality were produced.

February 2009 - The side pieces have been assembled. A filler was sawn from 0.8 mm brass sheet and the etched covers soldered on. Then 'rivetted angle-irons', from etched parts were soldered on. These will connected by tie-plates. The frame is also strengthend by horizontal ties. These are composites from several etched parts in order to show the rivetting. The horizontal ties were soldered to the side pieces, while the bulkhead-like ties were glued in because it would have been to difficult and risky to bring the heat for soldering at the right places. The covers for the trunnion-bearings were bent from an etched part and soldered together.
The upper carriage was further kitted-out with wheels, the gears etc.  The front and rear rollers were turned from steel to give them a real 'steel' appearance. On the prototype the rear rollers sit in excentric bearings that allows them to be brought into to contact with the rails on the lower carriage: when being fired the upper carriage slides back on these rails, the rollers allow it to roll back into the firing position.
Assembled carriage from the rear
Assmbled carriage from the front
Carriage with the barrel in place. Note the trunnion bearings cover (not yet trimmed to lenght)
Added the rollers plus the sockets aft for the lever that is used to turn the excentric bearings of the rear rollers

March 2009 - The gears were cut from brass stock in the milling machine with the help of direct dividing head and different division plates. The shape of the teeth is not exactly correct, because I used a disc-shaped burr as cutting tool. However, at this module (0.06), where the teeths are merely pitched 0.1 mm apart, this is hardly noticeable. The gear wheels are parted off from the stock on the lathe. The gear segment that will be attached to the barrel was produced in the same manner.


Cutting the gears for the gun elevating mechanism using different division plates
Cut-off wheels before further machining
to be continued ...

Deck Furniture

Bollards

May 2007 - The ships was fitted with four pairs of bollards of square cross section; two at the rear and two on the raised quarterdeck. Luckily a good rather close-up photograph of the real specimen is available (see main page). The bollards are milled from round brass stock. Round stock was chosen as a starting point rather than e.g. flat stock, because it can be held easily in the lathe for turning a spigot on which, by which the part can be held for further machining. Otherwise it would be difficult to mount such small a part on the miller for machining five sides. The spigot is also a convenient reference for machining and for fastening on the model eventually. From the lathe the raw part is transferred to the dividing head mounted on the milling machine. After each pass with the tool, the part is turned by 90º or 180º depending on requirements. Thus a square and symmetric part is produced. For a final machining step the part is transferred back to the lathe and the dome shaped head formed using a very fine file on a roller-filing rest. The job is completed by rounding off the corners using a not-too-hard rubber-bonded abrasive wheel (CRATEX) in the mini-drill. Remaining machining burrs are removed by offering the part to wire brush wheel.



Turning the raw bollard

Mounting the raw bollard in the dividing head on the milling machine
Milling operations: first squaring, then producing the waist
Rounding off the cap
The roller filing rest
Finished bollards and part of working drawing
Drilling the holes for the bases

September 2008 - The base for the double bollards were intended to be a surface etched parts, but I was not happy with the results. So I decided to make them from solid brass. Solid brass was easier to handle for machining than brass sheet. Nevertheless the envisaged machining operations prompted me to make a couple of gadgets, fixtures, for the mill and the lathe.
Milling around the edges or on top of flat material always presents work-holding problems. Worse, if several identical parts have to be produced. Hence I divined a work-holding block with several clamps and stops running in a T-slot. Similarly holding small parts for cutting off on the circular saw is tricky and best done on the lathe with a special saw table clamped to the top-slide. This saw table allows parts to be safely clamped down for cutting.
The three parts of each bollards were soft-soldered together.







Drilling set-up
Milling the beading
Sawing off surplus material
Parting off the individual bases
Milling a bevel
Parts of double bollards
Work holding for soldering
Bollards, chain stoppers and spill

Chain-stoppers

May 2007 - One pair of chain stoppers is located immediately behind the hawse pipes as usual. A second pair is placed above the chain locker, which is located immediately in from of the armoured barbette. The bodies of the stoppers are rather complex castings, calling for some complex machining operations in model reproduction. The same basic technique as for the bollards was used. Given the complex shape, however, machining is not possible in one set-up. for certain operations the axis of the spigot has to be perpendicular to the milling machine, while for others, such as drilling it has to be parallel. For the latter and for milling the various slots, I choose to transfer the dividing head to the lathe. This has the advantage that its centre line is at the centre of the lathe spindle.
The slots were milled using a micro-tool made from a broken carbide drill, the end of which was ground flat. This results in a non-ideal clearance of 0º, while the cutting angle and side rake are that of the original drill bit. However, not much metal is removed so that this doesn't really matter here.



Milling the profile of the chain stopper

Milling the slots on the lathe
Milling bits and product
Squaring the part on the upright collet holder
Close-up
Round-milling on the rotary table

One set of stoppers was milled from brass, while for the other one I used PMMA (PLEXIGLAS®, PERSPEX), the main reason being that I ran out of brass stock. However, genuine PLEXIGLAS®, is pleasant material to machine and easy on the tools. It holds sharp edges and it easier to see what you are doing than on the shiny brass. Acrylic paints seem to key-in well - basically its the same molecule, of course. On the downside one may note that small and thin parts are rather brittle. Using diamond-cut carbide tools gives a nice smooth finish, but normal CV- or HSS-tools can also be used, of course.
While for the bollards and the front pair of stoppers the spigot could be on the geometric centre of the part, making it easy to measure while machining, for the after stoppers I had to place the spigot to the centre of the pipe down to the locker, so that the concentric rounded edges could be milled. The pictures show this operation.

October 2008 - The stoppers have now completed with etched brass releasing levers, etc. The fore stoppers were also soldered to surface etched base plates.


Undercutting using a micro saw bit Stoppers compared against a 5 Euro-Cent coin Drilling the hole for the release lever
Finished after stopper
Etched fret with stopper base plates (bottom left) and levers (bottom right)
Finished fore and after stoppers (right column)

Anchor capstan

August 2007 - One component that always has puzzled me somewhat as to their manufacture in a model has been the sprocket on capstans. While the geometry on horizontal windlasses is quite simple, with suitable depressions for the chain links around the circumference, the sprocket on a capstan is a complex affair. In any case the capstan head cannot be manufactured in one piece. So I broke it down into three pieces: the spill head, the sprocket and the base drum with the pawls. The whole capstan has more pieces including four guiding rollers and a finger to pull the chain off the sprocket. The cast base on the prototype will be reproduced as a surface-etched part.
The sprocket started out as a 2.5 mm brass rod taken into the dividing and into five notches were milled to produce something like a five-pointed star (these sprockets typically have five or six arms). The notches for the horizontal links were cut on the lathe with a forming tool. The sprocket then was faced and drilled to fit onto the capstan stem. The next step is cutting it off. This produces some burrs that need to be taken off. Luckily I have collected over the years almost every type of work-holding device that was ever made for the watchmakers lathe. Here the insert jewel chucks came handy to hold the 2.2 mm by 0.6 mm sprocket for facing-off.



Milling the sprocket, 1st step

Milling the sprocket, 2nd step Cutting with a forming tool
Drilling the sprocket
Facing-off the sprocket in a jewel chuck
Capstan head ready for cutting off

The capstan head is a simple turning job. The curved surfaces are pre-cut with appropriate lathe tools and then finished with very fine files. Incidentally, the implement shown on the appropriate picture is a rare miniature micrometer, also coming from the watchmakers toolbox and very handy for measuring narrow recesses and the likes. They came in sets of three, the other two are a depth-micrometer and one for measuring the width of notches respectively.
Finally, the three parts are soft-soldered together.

September 2008 - Again the guiding rollers are a simple turning job. The shapes were produced with a free-turning graver and by rotary milling in the dividing head. In the meantime various etched parts had been produced, including the base plate made up of two different superimposed parts and minuscule pawls. Also a chain separator from 0.3 mm copper wire rolled flat was produced. The various parts were soldered together.

Assembled capstan head
Shaping the head of the rollers by rotary milling
Set-up for shaping the rollers using the geared dividing head
Etched fret with capstan base plate (top left) and pawl (bottom centre) Finished Capstan (bottom left)

Skylights, Companionways etc.

September/October 2008 - The basic structure of the skylights etc. consists of strips of Pertinax that are cemented together with cyanoacrylate glue. More intricate parts are etched from brass. In the past I have constructed the skylights around a piece of Plexiglas milled to the right shape. It was not possible here, as the skylights will have to painted to represent wood, while the bars will brass colour. It would have not been possible to mask the Plexiglas for the spray painting.
Hence, the frame of the engine room skylight consists of a an etched brass part, folded up and soldered together. On the inside grooves had been etched in that serve to locate the bars to made from thin copper wire. The lower frame was constructed from Pertinax. The wooden gratings on both sides of the lower frame are again etched parts. Once this structure was complete, a square block of the size of the footprint of the skylight was milled from a piece of Plexiglas. In the next step the roof-shaped faces were milled on. To this end, a small insert vice was set to the appropriate angle of 40° in a larger vice bolted to the mill table. The fixed jaw of the insert vice pointed upward and the side of the block to be milled rested against it. This ensured that all four inclined faces would have the same angle and would start from the same height with respect to the reference (bottom) face of the block. A very smooth surface with little tool marks can be achieved on Plexiglas. The final polishing of the surfaces was done using CRATEX-type drum polishers followed by a felt drum loaded with polishing paste. All in the same vice setting to ensure a flat surface. I was lucky the Plexiglas 'house' fitted like a plug into the skylight frame.
The prototype construction of the boiler room skylight is not completely clear from the drawings, so that I had to 'fudge' it a bit. First the central piece that supports the chimney was shaped from a piece of Plexiglas. The PROXXON drilling machine was abused as a milling machine to this end: a diamond-cut milling bit was taken up into a collet and the height of the machine set so that the bit reached just below the table. Now the Plexiglas part was passed free-hand along the mill. The form to be cut out was printed on a piece of paper that was stuck to the Plexiglas. It was tested against the shape of the etched grilles in order ensure a snug fit. The box around the skylight was constructed again from Pertinax.

Etched parts for the skylights.
Shaping the central part for the boiler room skylight
The completed boiler-room
skylight

Unglazed framework for the engine room skylight
Squaring up a Plexiglas block for the skylight
Milling the sloping faces
Polishing the sloping faces Finished Plexiglas 'glazing' block
Glazed engine room skylight

March 2015 - The skylight above the officers' quarter in the back of the boat was constructed again around a little block of Plexiglas that was milled to shape and then polished. The panelling was constructed from various layers of 0.4 mm thick Pertinax. For sanding the edges square the then newly constructed micro-grinding machine and edge-sander came handy. On the prototype the upper part of the skylight could be lifted off and the coamings of the hatch had half-round trimmings around. For this something half-round of 0.4 mm diameter was required. Short length of half-round wire was produced from lengths of 0.4 mm diameter copper wire that were stuck onto a piece of aluminium that was milled flat in situ to ensure an even thickness of the half-rounds. I am not absolutely happy with the result, but one has to consider that the skylight has a footprint of only 7 mm by 8 mm.


Offficers' mess skylight Milling Plexiglas block for the officers' mess skylight
Milling half-round copper wires
Grinding 45° bevels to half-round wires Squaring up parts on the micro-grinder
The completed skylight
Milling and drilling operations on a hatch
Various hatches

January 2016 -
Constructing the man-hole cover in the barbette gave the opportunity to test the just finished micro-milling machine. The item was milled from a small block of Plexiglas. The machine was also used as a co-ordinate drilling machine for getting the holes in the rack in one line and evenly spaced.

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