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[John W E]

VOSPER MTB
An in-depth build of a GLYNN GUEST plan, for the beginner  
The June 2011 issue of MODEL BOATS magazine has with it a free plan and the build article to construct a semi scale VOSPER MOTOR TORPEDO BOAT from which a modeller with average skill should be able to produce a good working model, but to a person who is new to the hobby of model boats and its many ways of doing things, making this model from the free plans may seem a daunting task to undertake.  However, with the MODEL BOATS magazine build article and a build with a few more illustrations it may be possible for the new modeller to understand and undertake the making of this model with fewer mistakes.
As a side note Glynn Guest’s article in MODEL BOATS would be a larger piece of writing to cover all modelling skills    but as you know in magazine space is of an essence.
On with the build.
The first job at hand is to study the plan both sides and to read the build article so that one gets an idea of how the pieces fit together (fig1-2).
The first step is to transfer the required shapes from the plan to the building material.  This can be achieved by various methods - one way is to have the full plan copied - then to cut the required pieces out from the copied plan after that glue the cut out profiles to the building material.
The second method is to trace the shapes from the plan onto either the building material or onto thin cardboard, by tracing the shapes onto cardboard to make templates allows the shape to be duplicated very precisely and this was the my chosen method for this build.  
Materials
All hardware and wood for this build have been obtained from either the web or a local model shop nothing was custom made for the model by a specialist supplier      

[John W E]

Medium grade balsa wood is used to build the hull, so what is medium grade balsa?
As a rough guide place your thumb nail across the grain of the balsa wood then try pressing your nail in to the wood and if your nail sinks in easily making a deep indent, we can take it that this is soft balsa.   If your nail is hard to push into the wood and just leaves a small indentation this could be classed as medium balsa.   If there is very little or even no indentation this can be classed as hard balsa
5 sheets of medium grade balsa 900mm x100mm x6mm where obtained for the Maine frame of the hull and 5 sheets of 4mm x 480mm x 100mm for the outer skin
Tools for the job
A good sturdy craft knife is ideal for the job of cutting out as long as it has a sharp blade
Fine tooth razor saw is a good help for cutting some of the pieces out
A 12 “steel ruler is a must-have to aid in cutting out
Homemade sanding blocks of various shapes and sizes.  
For the first part  of the build the two most used sanding blocks where made from ½ ply wood 6” long x 4” wide with medium grade sand paper stuck on with double sided tape on one block the other has fine grade sand paper stuck on to it.    
A good handful of modelling pins or dressmaking pins about 100 will be ample plus a good handful of elastic bands to hold pieces in place whilst the glue dries.
Small set-square or better still an engineer’s small tri-square.
All parts for the hull framework were transferred from the plan onto the 6mm balsa with the use of cardboard templates (tip! Use a ball point pen not a felt tipped pen as the ink from the felt tipped pen will run into the grain of the wood.  Do not press too firmly with the pen when drawing the shapes out) before cutting any pieces double check all the parts are correct (figs 4-5-6).
The main deck pieces are the first to be cut out 2off port and starboard, remember don’t try and cut all the way through in one go, 2 to 3 shallow cuts to slice all the way through, and also cut on the good side of the marked line, start at about the middle and cut towards the bow - then from the middle cut to the stern.  When cutting towards the stern use a steel straight edge as a guide to run the knife blade along to keep the cut straight and square fig 7- fig 8.
When all the parts for the hull frame have been cut out, it is best to check them against the main plan to ensure they are all the right shape and size: note the slot for the prop tube and the main deck hatch have not been cut out at this stage.
The next step is to lightly sand the two edges of the main deck the chine floor pieces.  To do this the two matching pieces must be pinned/clamped together side-by-side.  The edges need to be sanded evenly.  Doing it this way will ensure that both sides are exactly the same in profile (fig 9.)
When both main deck and chine floor have been sanded, the next stage is to join the two halves of main deck together.
Glue
The modeller has a vast choice of glues to choose from but for this build the four mostly used types of glue are:
i)       ALIPHATIC this glue was used for all the wood work.   This glue is very similar to the white PVA glue but is slightly stronger when glue has set dry, has a higher resistance to water, and is normally yellow in colour.
ii)    EPOXY RESIN GLUE
This is used to bond the prop shaft and the rudder tube in place.  There are several types and makes of epoxy resin glue.  However, we need one that sets in about 30 minutes or slightly longer to give us time to adjust the fittings if needs be, most come in a two part equal mix (resin and hardener).  Care must be taken when using epoxy glues as they can cause an allergic reaction to some people.

[John W E]

more pics

[John W E]

iii)    CYANOACRYLATE OR SUPER GLUE
Yet again there are many makes and types of this glue but experience has shown the ones that are sold in model shops for the modeller work the best for us    
In this build super glue is used to bond different materials, such as plastic to wood and cardboard also your fingers to the model SO BE VEARY CARFULL WHEN USING THIS GLUE IT WILL BOND YOUR SIKN IN SECONDS AND THE FUMES CAN IRRITATE THE EYES PLUS HARMFUL WHEN INHALED SO DO BE WARNED ABOUT THIS HEALTH HAZARD
iv)   LIQUID POLY
This glue is used to bond plastic parts of the build such as the gun bandstand.
Once again lots of companies produce this type of glue, but I have found that the HUMBROL one works the best for me on styrene card.
Let’s get back to the building of the model    
The two halves of the main deck were laid on a flat surface and lined up, a strip of cellotape is applied along the length of the joint from bow to stern - this is so it forms a hinge joint in the two halves of the deck.  The deck is then hinged open and glue applied to the two mating faces.  The hinged joint is now closed and the excess glue is squeezed out.  This also pulls the two halves of the deck together and the deck is then placed on a flat surface (extra cellotape may need to be applied across the deck to help prevent the deck from pulling open).
It would be advisable to place something such as a piece of polythene/grease proofed paper or similar on your working surface to prevent the deck from being stuck to the surface.
Weights are then applied on the top to keep the deck flat whilst the glue dries.
The same method as above is used to glue the chine floor together - they are then set aside until the glue has fully dried (fig. 10)  
As the glue is drying we can move on and begin to assemble the keel and appropriate pieces.  
As the keel was cut out in one piece we require the hole for the prop tube to be put in and this is first done by offering the keel to the plan and very carefully marking off the position of the prop tube angle plus the positions of the supporting cheeks either side of the keel.  When this has been done we can cut the main keel where the prop tube goes through. (fig.11)  before reassembling the keel with the side cheeks it may be best to make a strong back-up for the supporting of the keel and this will also keep the keel level whilst it’s being glued.  The strong back was made from a square bit of timber approx 6 inches long and about an inch square and is covered completely with cellotape to prevent the keel from sticking to it. The keel is then glued and assembled then clamped onto the strong back (fig.12) ensure that the keel is the right length and also the hole for the prop tube is the right size before the glue has set.  
Assembly of the keel to the chine floor
First a light sanding to remove all overspill of glue on the keel and the chine floor and then mark out the location for the hole in the chine floor for the motor.  We first draw a centre line down the middle of the chine floor using the stern as a datum - we can work out various lengths along the boat.  After cutting out the hole for the motor in the chine floor we next have to locate and glue the keel into place along with the bottom tapered ribs, (use a small setsquare to keep the ribs square with the floor and  keel ) (fig 13)  

[John W E]

MOTOR, PROP TUBE, AND COUPLIING  
When selecting the prop tube for the model a standard M4 X 228mm propeller tube with bronze bush bearings was chosen along with a standard DYCO coupling - these are ‘off the shelf’ from the local model shop.  When trying to obtain a solid coupling as referred to in the model boats build article, the ones that were available needed to be altered to fit the prop shaft.  Whilst this is not a difficult task, it was felt to be outside the build for beginners expertise parameters for this particular model build (all materials to be standard and off the average model shop shelf).
The prop tube size refers to the length of the tube but it will be noted that the shaft is longer (approx 267mm in length)  it will have a 4 mm thread on one end of the shaft the other will be plain.  The propeller fits on the threaded end of the shaft with a lock nut and washer to secure the prop on.  
The plain end of shaft is where the coupling is located.
The DYCO coupling is in three parts; two brass inserts and a flexible plastic centre body - one brass insert will need the 4 mm hole in it to match the prop shaft diameter and the other brass insert will match the motor shaft 3.2 mm.  You will also need a small Alan key to fit the locking grub screws in the inserts.
MOTOR
The motor in this build came from the spare box on my work bench and at the time I thought was about the right RPM (17000) for this model but it was discovered to be of a lot lower RPM so a Graupner speed 500 has been ordered to replace it.  The new motor has a RPM of 17600 which will be ample.  
Back to the build
To work out the motor angle, we need to temporarily fit the prop tube in to the keel at the correct position and angle.  You may have to open up the hole in the keel with a round file a little but do not make the fit of the tube too slack - a nice push fit is what we want.  Next we have to make an alignment jig to help with setting up the motor, the easiest method is to temporarily remove the plastic insert from the coupling and replace it with a neat fitting piece of solid tube of the same length as the plastic insert.  This when fitted between the motor and shaft will hold the motor rigid and at the same angle as the prop shaft.  At this stage you will see the motor mount is different in this build compared to the one in the MODEL BOATS article. Again this was done NOT as a better way of fitting the motor but to keep it in the parameters of off the shelf build for the beginner.  A standard motor mount supplied with the motor is used but this time the motor is mounted upside down.  The motor was held in place with the use of a small piece of bluetack placed between the top of the keel and motor. The motor mount was squared up and the angle of the mount marked onto two pieces of cardboard - this was then cut out to make templates.  These were offered up next to the motor to ensure that the angle is right, when happy ¼ plywood was used to make the two mount supports, ¼ square Obechi is then glued to the inside of the top angled edge of the ply wood.  This is then glued to the chine floor in the right place (figs14-18) at this stage you may wish to follow the MODEL BOATS article and glue the prop tube in place, but for ease of skinning the hull and sanding, I removed the prop tube and motor until later in the build.
The next step is to fit and glue the transom in place, use a set square to help keep the transom square and vertical to the chine floor (fig.19) when the glue has dried move on to fit the forward bulkhead and stem post (fig. 20) move onto the next stage of fitting the deck only when the glue has fully dried on the last two stages.  Apply a small bead of glue to the top edge the transom and the forward bulkhead plus stem post and with the deck sitting on a flat sturdy surface, line the edge of the transom up with the top inner edge of the stern of the deck.  At this stage ensure the stem post lines up with the centre of the bow on the underside of the deck - when the two parts are correctly aligned, temporarily pin and apply some weights on top to hold the structure in place until the glue has set  (fig. 21).  At this stage it was found there was a slight flex in the deck,  so two additional supports were added to hold up the deck (arrow is pointing at them in photo).  As the model is built out of mainly balsawood and if untreated balsawood comes into contact with water - it is a bit like a sponge - it soaks the water up and expands splitting joints and so forth, so it is best to seal all the areas with sand and sealer now as we cannot access these parts of the hull when it is skinned, a total of 3 coats were applied to the bottom of the chine floor and underside of the deck.
The step on the main deck is next to be constructed and this is made from 4 pieces of 6mm balsawood, the shape and size is transferred from the plan onto the material and then cut out - but it is left 2mm oversize on the outside edge do not cut out the torpedo scallops at this stage these 4 pieces are glued and pinned into place at the bow (fig. 22).  If you have the use of a small set of clamps it will be helpful.  When all the glue has dried recheck all joints for any gaps or splits and if there are any fill them in with glue.  
Next we have to sand the angles on the edges of the main deck and the chine to match that of the stern and the mid bulkhead, this is achieved with the use of a long sanding block, sand a little bit at a time and check often with a straight edge along the hull and across the sides to ensure that you are not sanding hollows into the hull sides.

[John W E]

more pics

[John W E]

Skinning the hull                  
The sides of the hull are the first to be skinned with 4mm balsawood Commence at the stern of the boat first gluing and pinning the sections into place alternating from side to side.  You will find that this will stop distorting the hull (also take note in which way the grain runs on the skin - it should run top to bottom or from the deck to chine) (fig. 23).  When the side skins have been completed and the glue has dried - sand the bottom so that the edge which is glued to the chine is flush with the chine and also has the same angle as the hull bottom, (tip mark the centre line along the length of the keel - this is a visual aid so that not too much materials are removed when sanding the keel) - use a long wide sanding board (fig. 24).
Skinning the bottom of the hull
The bottom skin joints are offset to the side joints by half the width of a plank.  This is to improve the hull strength, we start at the stern of the hull and glue the first plank half its width forward of the stern and again alternate from side to side (see the arrows in fig. 25) When planking towards the bow, we may find it easier to reduce the width of the planks to help with the bow angle.  If the prop shaft has been removed for ease of skinning, it helps to put a reference mark on the skin at the point where the prop shaft hole is.    
Sanding and filling the hull skin  
For filling small gaps in the hull it was found the soft fillers such as polycel or plastic wood worked well but I found that a plastic filler called white putty did the job just as good as the rest and sanded very easily. When sanding the hull skin use the largest sanding block you can to prevent sanding hollows either side of the glue joints as the glue hardens the area surrounding the joint.
Big hint: when sanding the hull work on a clean bench free from all off cuts and mess as when I had finished sanding and turned the hull over there was a big score mark in the deck from a screw that had been left on the bench after I had removed the motor HUUUUUMMMM   

[John W E]

Smelly Sticky stuff and tissue  
Sealing the hull
As in all walks of life there are many ways of doing things and it is the same for sealing the hull, my first idea was to use a two part finishing epoxy such as Z-POXY but after a long think and a good supply of caffeine the down side of this method for the beginner became apparent (it’s sometimes difficult to achieve a good even finish and you must have the resin mix perfect - if it all goes wrong you may end up destroying the hull to remove the epoxy)  so we will put that idea on hold for a new day.
So let us stay with the method used in the model boats magazine article.
First off we apply three coats of sand and sealer rubbed down between coats.  
The tissue used is of a medium grade - it was found best to cut it into 4 panels one for each side and the other two for the hull underside, start on one side by applying dope to the hull side.  Attach one short edge of the tissue with a small amount of dope to ‘tack’ it down at the stern (just at one point here, allowing the dope and the small area of tissue to dry).  When the dope is dry - stretch the remaining tissue panel towards the bow remembering to smooth out any wrinkles working towards the bow we apply ‘neat’ dope with a brush. Keep doing this until the whole of the side area you are working on has been treated. This was done on the two sides first and when the tissue and dope had dried, the top deck edge of tissue was trimmed level with the deck.   The small overlap at the chine was trimmed evenly.
The bottom panels were applied using the same method beginning at the stern and working towards the bow.  When the dope had all dried out 3 other coats of dope were applied on the top and a very light sanding between each coat of dope to help produce a smooth finish. The sealing of the deck is done using the same method    I did try spreading the dope with an old plastic credit card - but speed is of the essence here – before the dope dries out.   I would advise strongly a lot of practice being put in, before attempting this method of applying the dope with the credit card spreader.   See fig 26 and 27. The next important thing to do is make a stand for the boat to sit on and hold it steady when we do the rest of the work .the stand was made from 12mm plywood the bottom hull profile is marked onto cardboard and when the correct shape is achieved through trial and error this is then transferred to the plywood then we fit some soft foam for the hull to sit on
At this stage the access hatch was market out on the deck, and using a new sharp blade in the knife and a steel strait edge the hatch was cut out it is best to cut the short section across the grain of the deck first the cut the long sections last using the steel strait edge to stop the blade running off (fig.28)

[John W E]

Fitting of the prop tube
If you have remembered to mark the position on the hull for the prop tube it is a simple task of opening the hole up gradually with a small set of drills then files (fig 29-30) test fit the tube into the hull and when happy with the fit and position mark on the prop tube with a pencil where it exits the hull so that when we replace the tube with glue on it, the tube will be refitted to the same correct position, then we abrade with sandpaper  the section of tube which is going to be bonded into the hull
Temporarily seal the end of the tube to prevent any glue entering inside and this is achieved by covering the end with cellotape (fig. 31) next we need to mix the epoxy glue, slow setting is best for this job as it gives us time to make any small adjustments which may be required when fitting the tube in place.  We apply the glue mix in to the hole in the hull with a small spatula or a tea /coffee stirrer from your local fast food take away, as we insert the tube into the hole rotate the tube 360° to spread the glue in the hole as the tube is fitted (fig. 32).  Just before the glue has set and it is rubbery, check the alignment of the tube then cut off any overspill  with a sharp knife (fig 33-34) then set the hull aside for the glue to fully dry.

[John W E]

and more pics

[John W E]

Fitting of rudder
The rudder is in three main parts, rudder blade and shaft, rudder tube with a rubber O ring then brass washer then the lock nut, and lastly the tiller arm (fig. 35).
The position for the rudder is transferred from the plan to the hull and marked, then with a small diameter drill a pilot hole is drilled, the hole is then opened up to the correct size using a round file.  If one uses a drill of the same diameter as the rudder tube you run the risk of splitting the hull (figs 36-37).  Tip use a set square to keep the drill square and vertical to the hull, when assembling the rudder tube the rubber O ring fits between the flange on the tube and the hull and is not adequate on its own to seal the tube to the hull,  so the same method as fitting the prop tube in the hull was adopted with the rudder tub by using epoxy resin to seal the tube in - then before the glue has set the washer and lock nut is fitted to the tube on the inside of the hull and just nipped up just over hand tight.  When the glue has set, we then fit the rudder blade into the tube applying a little grease to the shaft before fitting, temporally secure the tiller arm to the top of the rudder shaft making sure the arm is at 90° to the rudder blade
Torpedo cut-outs  
These where marked off on the deck and then with the aid of a suitable diameter plastic tube wrapped in sand paper the half round scallops are sanded to size and shape (fig A1/A2)  

[John W E]

Suppressing the motor and Refitting  
Today’s radio has advanced a long way from days gone by in that the new 2.4 sets are a lot less prone to outside electrical interference from the motors which drive the model or any onboard electrically driven devices so is it necessary?  Well if you are going to use 27/40 MHz radios transmitters - yes it will be a good thing to do and so this is one way of suppressing the motor

You will require:
Three 100nF (0.1uF) ceramic capacitors,
Three small pieces of insulation, to cover the exposed parts of the capacitors legs  
One 25 watt electric soldering iron,
Flux, to clean the area to be soldered
Solder,
File /sand paper, this is to clean the motor casing before applying the flux (fig 38)
Step 1
Hold the motor so that the back of the motor is facing you, the two electrical power terminals need to be at 9 O’clock and 3 O’clock then you clean the casing at 12 O’clock with a file or sandpaper and apply a small dab of flux.
Step 2
With the hot soldering iron apply heat to the fluxed area on the motor casing and apply the solder so that you tin the area (to ‘tin’ is to apply a thin layer of solder) then clean /flux after that tin the two electrical power terminals on the motor.
Step 3  
Now for the CAPACITORS, the capacitors that we are going to use are known as ceramic none polarized in other words it makes no difference which leg of the capacitor is soldered to the motor casing therefore we solder one leg of the capacitor to the casing and the other leg to the electrical terminal at 9 O’clock the second capacitor is soldered from the casing to 3 O’clock the third capacitor is soldered between 3 and 9        O’clock.  Now that we have the soldering iron hot we may as well solder the power supply cables to the motor terminals (fig 39-40).
The motor is refitted back into the model and reconnected to the prop shaft with the coupling and now we can test run the motor.  If you have an amp meter it will be of great help in this next step of the build to determine how good or bad the motor is aligned to the prop shaft, if there are any tight spots in the drive line it will be picked up here. The amp meter is connected between the battery and the motor on the positive side (fit sketch in here of amp meter motor) if we test the motor with the amp meter when it is in a free state (nothing connected to the drive output shaft) there should be a reading on the amp meter of about 0.75 amps to 1.25 amps depending on the motor we have.  If we reconnect the coupling and shaft now take note of the reading on the amp meter (we are looking for a reading that is the same as or about 0.25 amps higher than the free state running of the motor).  The closer we are to this, the better the drive shaft alignment is, if the reading on the meter is high say 2 amps we must look for the problem by rechecking the motor alignment (fig. 41).

[John W E]

fig 41

[John W E]

Rudder servo          
There is no position shown on the main plan for locating either the rudder servo or the main battery, so a dry run fitting of these two items is necessary to obtain their best position.  It was found that keeping the two aligned on the centre line of the hull to give better stability to the hull. Also keeping the rudder servo in line with the rudder post a closed loop steering arrangement can be used (fig 42).
The servo supports are made from ¼ ply with ¼ square Obechi glued to the top edge and bottom outer edge. These are then fitted to the servo and the whole unit is glued into place in the hull (fig 43-45).
For the next part of the rudder installation, we require the transmitter and receiver with power packs which are going to be used in this model.  We need to plug the rudder servo into the appropriate channel in the receiver.  Next; set the stick (which is controlling the rudder) on the transmitter to the middle position and set the trim for that channel to the central point. Now switch on the receiver and then the transmitter - this will centralise the rudder servo.  Fit the rudder horn on the servo ensuring that the two arms are at 90° to the servo body also ensure that the arms are parallel to the rudder tiller arm (fig. 46).  We must now connect the servo arm to the rudder tiller arm - this can be achieved in a number of ways and if you have a look at the illustrations in figs 47 to 53 this will give you some ideas.  The first illustration in fig 47/49 is not very good as it has a tendency to jump out of the holes in the arms.  The connecting rod in fig 49 /50 is much better as the ends are bent in a “z” shape and this prevents the rod from jumping out of the holes in the arms. In fig 51/52 this method for connecting the two arms together is a lot better, as we use plastic end pieces called clevis’ these can be adjusted in length which makes setting up a lot easier  (fig 53/54).  Once the rudder and servo are connected together do a test to see if there is full movement of rudder and servo.

[John W E]

and more pics

[John W E]

some more pics

[John W E]

Wheelhouse and Bridge
Add a strip of balsawood to form a shelf for the main hatch to sit on - this is made from scrap wood and is glued to the front end of the hatch opening under the deck (fig55/56).
The wheelhouse floor is the next part to make; it was found that making a cardboard template for the floor from the plan simplified the marking off of the floor angular shape (fig57/ 58). Two floor pieces are cut out from 6mm thick balsa sheet one has a 6mm section cut out from the middle section (fig 59/60) we now need to make the bulkhead (wall) which separates the wheelhouse from the bridge.  However, there is no front or back view drawing of the wheel house to help us, so we have two options - one is to make a drawing and template or go the trial and error route by cutting cardboard shapes out then trying for size and fit.
If we look at the photos’ from (fig 61to 65) this will help understand how we transfer sizes from the side view plan and from the top view plan onto the card template and then onto the balsa wood bulkhead.  You will see that there is 6mm removed from the bottom of the bulkhead and this allows for the floor thickness.  We now need to make a cardboard template of the inside longitudinal bulkhead shape of the wheelhouse which is shown in (fig 66).  This is then transferred to 6mm balsawood.  
The next step is to cut these parts out and then sand them (fig 67).
The wheelhouse bulkhead is glued to the wheelhouse floor. The subfloor is then glued on top of the main floor, followed by the wheelhouse inside central longitudinal bulkhead. This assembly is allowed to dry and is then sanded to blend all the edges (fig 68/69).  The next step is to skin the outside of the wheelhouse in either thin ply 0.8 or cardboard - the choice is yours.  For the build 0.8mm ply was used (fig70-75) and when completed seal the super structure with sand and sealer.
The next step is to make the window frames; these were done by drawing them out on card from a cereal box, cutting them out and then applying them to the wheelhouse in the correct position. Seal them with sand and sealer (fig76-78).
The wind deflector around the top edge of the bridge can be made by cutting 2x6mm plastic strips into 6mm lengths and then gluing them to the top edge of the bridge which is then covered with a strip of plastic (fig 79/80).

[John W E]

more pics

[John W E]

pics a plenty

[John W E]

plenty a pics

[John W E]

Engine room hatch cover
The engine room hatch cover was made in one piece from 2mm thick lite ply which has been sealed with sand and sealer and 2 coats of dope applied on top.  When dry it was sanded with fine sandpaper and the mock hatches are then outlined with 1.5 x2mm plastic strip which is glued on with super glue (fig81/82).
Torpedo tubes
After a long look through the bits box for a suitable tube to make the torpedo tubes I drew a blank.   I was looking for something like a sweets container plastic smarties tube; I’ve eaten too many sweets already!!!!!!
The answer was to use round electrical plastic conduit pipe of 20mm O/D this was cut to length, then one end was plugged with balsawood which was glued in and sanded to a dome shape to represent the torpedo tube door (fig 83-88).  The next stage is to mark and cut the front angle on the tube - this can be done with a saw or as in this build a sanding block (fig89-90).  The support bands that go around the outside of the tube are the next thing to make and fit.  These are made from 1.5x3mm wide plastic strip glued in place with super glue. Tip here keep all the joints of the support bands on the bottom of the tube.

Next the tube stands are made and to start we need plastic card 1.5mm thick and a circle cutter.
Mark off the width of the stand onto the card and then mark the height of the stand. Cut this section out.
In the centre cut a hole the same size as the diameter of the torpedo tube (fig 91) - cut the hole in half this will give you two parts of the stand (fig92) do this 3 times and it will give enough vertical supports for the two stands.
The side supports are next to make and for these we use the same thickness plastic card 1.5mm and for this part of the build use a paper hole punch to punch out all the holes.  Have a look at (fig 93-94) the method used to make the side supports is self-explanatory.  The compressed air firing chambers are made from several pieces of tubing which are cut to fit inside one another to produce the rough shape. Plastic filler is added to the outside and left to harden off, the final shape is then produced with use of a file and sand paper (fig95.96)

[John W E]

    fig 78 (referred to further up in the build)

[John W E]

figs 83 onwards...

[John W E]

pics a

[John W E]

Gun bandstand
The Gun bandstand is the small piece of floor the gun operator stands on when firing the gun. In this model it is made from 1.5 plastic card.    Draw a circle of 90mm diameter then inside that circle draw another smaller circle of 70mm diameter. Draw a small circle again of 26mm diameter inside the other circles - we need to divide the circles up into 8 equal segments and we do this by drawing lines equally spaced through from the outer edge to the centre - this is to draw what looks like a wagon wheel (fig97).  With a circle cutter, cut out the circles starting at the outside (fig 98) - you will need to cut out two of the smaller inner circles.
The next stage is to make the floor braces (a bit like the spokes in a wheel) these are made from wooden tea /coffee stirrers.  Cut and glue 8 pieces in place using super glue (fig 99.100) then add the laths which the gunner stands on.  They are made from 1.5 x4mm plastic card glued on top of the floor braces.  If we use a compass to mark the different diameters onto the braces, it helps to keep them inline and true to the centre (fig 101).
The next thing to make and fit to the stand is the outer wall.  This again is made from 1.5 x 14mm plastic card.  We turn the stand over, then make and fit vertical supports around the outer edge these are made from plastic card - when these are dry, glue the outer wall in place (fig102/103/104).
The gun support.  
The gun support was made from an old paint brush handle as the taper on the handle only needed a little bit of alteration to match the one on the plan (fig 105\106\107).  
The gun is next to be constructed, and was made from old copper wire, plastic card, plastic tubing and balsawood.  Start by cutting the rectangular base from 2mm thick plastic, then glue on top the two long boxes made from balsawood covered in plastic card (fig108).
Next the gun barrels are made from thick copper wire with two half circles of copper wire soldered to the ends of the barrels to form the shoulder rests.    The barrels are then inserted all the way through the middle of the long boxes. Cover 2/3 of the exposed barrels with small diameter plastic tube or insulation from electrical wire (fig109).
The gun shield supports are next to be made along with the shield from 1.5 plastic card (fig110/111/112).