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Completing the 4mm NER 6 wheel coach

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Anyone who has followed JCL's original post "A Guide to using the Silhouette Cameo Cutter" (http://www.rmweb.co.uk/community/index.php?/topic/79025-a-guide-to-using-the-silhouette-cameo-cutter/) will have seen my attempts at using the Silhouette to try and produce a NER 6 wheel coach. Rather than keep hijacking Jason's thread it makes more sense for me to create a thread of its own. It also starts going beyond my thread "Introduction to using Inkscape to produce cutting files" (http://www.rmweb.co.uk/community/index.php?/topic/80563-introduction-to-using-inkscape-to-produce-cutting-files/).


So a quick recap before continuing.


I have now produced 3 variations on the basic coach in order to assess the best technique:



The first attempt featured slots in the sides to allow glazing to be inserted from the top. MAde up from laminations of 10thou styrene, unfortunately it is very flimsy and as soon as partitions were added resulting in the joints shrinking distorting the sides



The second design is much stronger featuring multiple laminations with the glazing recessed:



Note how inaccurate the end fitting with the side is:



The third design follows the excellant series of articles by Geoff Kent that have recently featured in MRJ. I have to say of all the methods to date, this has been the most successful:



In Geoff's approach the side is of 20thou with an additional 20thou strengthener for the turnunder:



With Geoff's approach a false floor is fitted which contains the partitions and, in my case, crude representations of seats which acts as a drop in unit:



Here is the seating unit in place:



The roof is a simple curved piece of styrene fitted to a false roof that inserts between the coach sides:



Here is the coach assembled pending further work (or not):



My approach has been a bit trial and error, virtually making it up as I go along. Parts have not always fitted properly with the sides often being too short (I did not allow for the turnunder in the dimensions). So with the that in mind I have made the decision to redraw the artwork, in Inkscape, from scratch but with the benefit of hindsight.


This thread will therefore follow this redesign taking our knowledge of Inkscape further including a number of tips and tricks I have only just learnt about myself.


P.S. I really do not know why I insisted on using black styrene in the earlier versions. It has proved extremely messy covering everything in a black dust which you will see in some of the photos.

Edited by MikeTrice
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Having covered the basics of using Inkscape in my previously mentioned article I will assume that I do not need to go into great detail regarding certain aspects of Inkscape usage.


I have learnt, belatedly, that the end profile is probably the most important starting point as everything is worked out from there. Here the end view from a Carriage Diagram has been imported and sized within Inkscape. A rectangle has been created and the width set to 32mm (to match the carriage width) and a central line added, then both objects selected and aligned to centre them up, then grouped and positioned over the coach end profile. I should add that it would be possible to use Inkscape's guides however in this instance I am not certain they would help much.



A circle was added, constrained using the Ctrl key, and sized, positioned to match the bottom edge of the roof profile:



A horizontal line was added as a guide to approximate where the turnunder starts, and a 0.25mm thick line (representing 10thou styrene) drawn to represent the panelling overlay. The right hand edge of the 0.25 line is aligned to the green box.



Next another line is added but this time 0.5mm (representing the main carriage side) with the right hand edge butted up to the 0.25mm line:



The two lines duplicated, mirrored and aligned to the left hand edge:



The green circle added previously has been duplicated (Ctrl-D) and its colour changed to Red:



Now this part is really neat and I only discovered it a few days ago. Change to Node Edit mode and select the red circle, then click on the right hand node and note the help text that appears below:



Drag the selected node diagonally to the top left and watch what happens to the circle. It opens up to an arc:



Continue dragging the node until it is roughly in the right position to the right hand side of the roof. You can zoom in if it helps:



Repeat for the other right hand node but drag left and down then around until the left hand edge of the arc is in the right place:


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On completion our arc segment looks like this:



Now I have added a 2mm line representing the 40thou floor, again aligned against the bottom edge of the end:



Before continuing I need to determine how high the reinforcing turnunder strip goes. To do this I have drawn a horizontal line across from the side drawing attempting to allow space to fix droplights and glazing:



The reinforcing strips have now been added, again 0.5mm representing 20thou. It stops at the horizontal line and the bottom edge taken to where it meets the floor forming a rebate:



A 30thou (0.75mm) false floor and false roof have been added:



A close up showing the bottom corner and how, hopefully, the actual panels will fit:



A close up of the top corner:



A summary of the various thicknesses and component parts:



Another recent discovery which I was really please to discover is how to determine the length of a path along its full length. This will tell me how deep to make the various side panels to include the turnunder. Start by selecting the object then from the menu choose Extensions -> Visualize Path -> Measure Path ..... That will bring up the Measure Path dialogue. I changed font size to 4px:



Now click "Apply" and wait until the magic dimensions is added to the drawing:



Here I have work through the other parts measuring accordingly then changing colours and combining with the component descriptions:



I now have a good reference for further work and the basis of completing the end drawing.

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You know when there's something staring you in the face and you just don't take the hint? It didn't occur to me to use the thickness of the line to represent the thickness of the styrene (as my dad would day, Grammar school kid - no idea). This changes everything.





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I usually bodge it and see, then tweak it until it fits. For this build I thought I had better do it properly, but it does help if you already know what approach you are going to take.


Jumping ahead of myself (sorry folks, will cover in depth later) I can convert the parts "Stroke to Path" then break them apart to determine the outlines for the ends and partitions which should then be the right shape and width.

Edited by MikeTrice
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Following on from Jason's comments yesterday I will step through how to turn the cross section into the end and internal partitions. 


First step is to clone the cross section:



It helps if you can envisualise what you are trying to achieve. Here the end profile needs to fit between the 20thou sides, along the bottom of the coach and across the roof over the arc. The following image shows highlighted in green the shape we are trying to obtain. It might be useful to print out the cross section and use a pen to mark the shape out. Believe me, it is easy to get it wrong (I speak from experience!):




Start off by removing those elements we do not need:




The two 20thou panels are converted via Path -> Stroke to Path, the fill removed, the stroke set to blue and the width to 0.1mm:




Switch to node editing mode for the 20thou layer. Select the top right hand node and click on the "Break path at selected nodes" button:




Repeat for the bottom right node:




Click back on normal select mode then Path -> Break Apart. This breaks the original shape into two separate objects:




Select the left most object and delete it. If the wrong line disappears, click on the Edit -> Undo menu command to restore it back, then try again:




Repeat for the other side. You should now have a shape thus:




Rather than go through the same steps with the bottom panel, it is easier just to draw a line stretching from blue line to blue line:




Delete the now redundant floor section leaving the correct final profile. Change style colour to black and width to 0.1mm then sit back and pat yourself on the back!



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A similar process is followed for the internal partition. This needs to fit inside the 20thou sides and over the 20thou reinforcing strips, below the false roof and above the flase floor. Intended path shown here in green:



The unwanted parts are deleted, then the green section converted via Path -> Stroke to Path, the fill and stroke settings changed and the outer edges broken and deleted:



Given that the remaining lines are all straight it is actaully easier to draw new ones rather then mess around trying to convert the remaining shapes:



Remaing unwanted shapes can now be deleted:



All paths selected and changed to black stroke colour and, if necessary, 0.1mm



I could move the lower side curves up to meet the floor but to be honest it is not necessary, so I have left them as they are.


I am not confident that when fixing the turnunder reinforcing strips in place that they will be exactly at the specified hieght to I have adjusted the position of the shoulder by selecting all the required paths, switching to Edit nodes mode, selecting all the nodes around the shoulder and moving them virtically a little bit:



The result of this adjustment can be seen when compared to the original end section:


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Having got so far, we might as well finish the end and partition. Unlike some people I have not had any joy cutting right through 20thou styrene with the Silhouette, so I have to rely on just scoring the styrene then snapping out the pieces. When I used to do this prior to buying the Silhouette I would often cut a recatngle around the shape and snap to that first, then snap back to the final profile. Not surprisingly I have found this the easiest approach with the Silhouette as well.


So here are the two components produced so far:



First job is to duplicate them, mirror them vertically, then align the bottom edges over each other: 



To provide the straight edges to be used for snapping, draw a rectangle around each shape. The easiest way of sizing it is to select the shape and not its width and height:



Now select the rectangle and set its width and height to the same dimensions:



Now the rectangle and shape can be aligned horizontally and vertically giving a result as follows:



Finally I decided that I would rather extend the centre line to each outer rectangle to make snapping even easier. Group the objects and we can move on to another component.


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Might as well tackle the roof formers. These sit on top of the false roof and keep the shape of the arc roof. The shape we are after is shown in green:



Unlike the others this one is very simple, just draw a line along the top edge of the false roof, delete all unwanted parts and change colour and thickness of remaining lines to black and 0.1mm



As before the shape is mirrored and bounded by a rectangle to make snapping easier, then the whole item grouped. Job done!


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Moving on to the sides for a change here is the image I am working from. Now we all know that carriage diagrams are not produced with accuracy in mind and this one is no exception. As a result I am having to be very careful how I proceed. Unfortunately I do not have any photographs of the prototype but there are a few photos around of preserved NER carriages (none of which are mine, so I cannot upload them here) The best references are as a result of searching for NER 818 on t'internet. There appear to be some common style characteristics used in NER coaches so I have made a big assumption and included them for my sides:



Before going any further I have considered whether to use Inkscape's guides feature to help in the drawing of the sides and cannot see that it would provide any benefit over using conventional drawn lines set to the various thicknesses.


The first task is to create a new "Guides" layer and draw some horizontal lines 0.5mm wide (the bottom one is 0.7mm) aligned against the various panels. ).5mm is used as it is about the most practical minimum thickness for cutting in 10thou styrene:



Being a Full Third comprising 5 compartments by concentrating on drawing a single compartment first I am going to duplicate it later to create the other 4.Some 0.5mm vertical lines have been added and positioned accordingly. At this momenet I am concentrating on the door and window to its left. One of the prototype differences I noticed is that the bolection mouldings are actually inset from the panelling more that the door droplights, so additional blue line 0.2mm have been added butting against the green 0.5mm lines:



Various rectiangles have been added to a new Sides layer. The left window is 0.5mm, the door surround 0.5mm and the top panel 0.3mm. The window for the droplight is positioned based on photos of other NER designs not as shown on the diagram:



I started rounding the corners and decided that on examining photos the outside droplight frame was too thick so reduced it to 0.3mm and sized it accordingly. Photographic evidence suggests that the panels are not as fully rounded as the diagram shows, so I have left them slightly more rectangular:



Next I duplicated the window bolection and move the copy to the right, then selected all the rectangular objects and used Path -> Stroke To Path as has been covered before. Hiding some of the background clutter makes this more obvious:



Selecting the left most window bolection and then Path -> Break Apart, I selected the outer rectangle and deleted it:



The top door ventilator panel has been duplicated and moved horizontally left then the inner rectangle deleted. DO NOT AT THIS POINT ATTEMPT TO STRETCH IT.



The upper left hand panel has been duplicated and moved vertically down to the lower position on the waist (see next step) then duplicated and move right to form the door panel



Because we have already changed the original rectangle to a path we can no longer simply resize it, instead we have to go into Node editing mode, select the top four nodes and move them as a group to the new position:



Various objects to the left of the door and the door centre line have been duplicated, mirrored horizontally and moved to right of the dorr using the centre line to align with the original centre line. The second centre line is then deleted.



The door ventilator panel has been duplicated, moved to the right, then the original panel in the door broken apart and the inner rectangle deled.



Edited by MikeTrice
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To add the bulge where the door handle goes draw a circle overlapping the panel.



You may find, like me, that having drawn an arc earlier attempts to draw a circle or elipse results in an arc with just to roof profile shown. To resolve, delete the new arc and select the circle tool again, but have a look at the icons on the toolbar above. If one of the segment/arc buttons is selected click on the circle button as illustrated here, then redraw your circle:



The original panel and circle have been selected and Path -> Difference selected.



Switching to node edit mode I have started tweaking the positions of the nodes:



Until after a while I get the shape I am after:



A 0.5mm circle has been added to represent where the door handle goes.



The circle duplicated and repositioned to mark where the grab handles go:




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This next section is going to appear heavy going although in practice it is faily logical. The difficulty is in trying to get screen captures that illustrate the process, so apologies in advance but let's give it a go.


First step is to create a couple of construction lines extended from the top of the sides previously drawn:





Add a rectangle to represent the edges of the side. This needs to be 25.33mm high (previously determined with our end drawing) and 128mm wide (e.g. 32 feet):



Move the rectangle and align to the extended blue line from earlier and aligned to the right hand edge of the diagram:



Create a rectangle and size it to the centre line of the door to the end of the side:



Duplicate it and move and align to left hand end:



Now this where descriptions become difficult. Assuming you have your guidelines on a different layer than the side just selecting them all and grouping them would end up transferring them all to the same layer, which is OK, but might mean you will want to re-separate them later. So what I have done is selected all the objects on the side layer and grouped them while the guide layer is locked:



Now the process is repeated for the objects on the guides:



I can now select both sets of groups on the two layers, duplicate them and move the duplicated to the left hand end:



The centre line of the left hand group is now aligned to the sizing rectangle to make it the same distance from the end as the right hand end.



Duplicate the objects again and copy near the centre 3 doors. Accuracy at this point is less important:



The guidelines layer has been turned off, the side objects selected and using the Align and distribute dialogue evenly spaced:



The same process is followed for the guide layer:



With both layers visible once more we now have a side looking like this (hopefully).


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First job is to select the extra panels that we are going to replace:



And deleting them:



Switch to Node edit mode and select the right hand nodes of both panels:



Drag them to meet the right hand guides:



Zoom in if necessary to align them correctly:



You can now either repeat the process for the other panels or just as easily delete the short ones and copy the elongated ones to replace them. Guides hidden to emphasise what we are trying to achieve.



We now need to draw the panel that goes between compartments. In this instance I copy one of the upper panels and in node edit mode adjusted it to fit the guidelines:



Duplicate and move the duplicates to their corresponding positions, again using the guidelines (not shown here).



Two additional guidelines have been created and aligned to the right hand edge of the side:



Here I duplicated one of the centre panels with a view to adjusting its width. WRONG!



In the end I had to delete the centre panel and redraw a rectangle then round the corners to suit. The top and waist panels have also been extended to the new guidelines.



The right hand panels and guidelines have been duplicated, mirrored horizontally and aligned to the left hand edge:



Hiding all other layers and changing the stroke colour to black, this is how it is looking:



I felt the top of the doors was a bit too high so I selected them all and then zoomed in to the central door:



And with the door height reduced a fraction:



And zoomed out again:



Need to add the bottom panel. After making the guides visible it was drawn by duplicating one of the top panels then stretched in node edit mode to suit, then the guides hidden again:



A closer view showing how things currently stand. Starting to look good:


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Nearly finished the sides, so might as well press on.


When the rectangle forming the main side was created it was based on the dimensions derived for the 20thou layer from the end profile. For this reason I have decided to colour it blue to match.



To create a rectangle based on the dimensions of the 10thou panelling layer, select and duplicate the blue rectangle and change its height to 25.17mm to suit the panelling layer. For the same reason I have coloured it red.



Remember those special guidelines we added extending from the end profile? Here they have been made visible and the position of the red rectangle moved to align with the red guideline.



When the bottom of the large lower panel was drawn it was done based on the diagram side view, however this did not allow for the turnunder and as a result is too high when compared to the panelling layer. Select the bottom horizontal guideline, and the lower panel, switch to node edit mode



Select the lower nodes and drag down to align with the red rectangle. In practice I found it easier to do each end separately:



The right hand end similarly treated then the guidelines hidden again. Now looking much better.



I realise that as work progresses I am spending less time giving detailed explanations of what I am doing, assuming any follower's skills are now up to the job. Please feel free to ask any questions if I have glossed over too much.


The good new is that apart from the end panelling most of the initial hard work for the body is complete pending final preparation for cutting.

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  • 2 weeks later...

I have been trying to drum up the enthusiasm to post an update to this topic. Having got so far, it has taken longer to write it up than it has to actually do the work, and I have been getting withdrawal symptoms from actually doing some modelling. As a result I decided to change priority and finish the cutting pattern for the 20thou parts, which I could then start assembling and postpose finishing the 10thou panelling until later. It also means I can give you a break and do some posts about construction.


Anyway, back to Inkscape. Here is the side view we completed earlier. It is necessary to visualise those elements that relate to the 20thou side, so to illustrate it I have changed the line colour to cyan. Other lines will be deleted.



Here I have started deleting some of the panels but stopped from deleting the lower panels:



This is so I can zoom in on the door and trace the scribed edges of the doors:



The scribe lines are duplicated and moved into position for the other doors, then the remaining unwanted panels deleted:



Like a number of other people I do not have any joy cutting 20thou right the way through and have to effectively score and snap. To simplify snapping out the window apertures I have added diagonal cross scores:



This is repeated for the other apertures. I have also drawn a rectangle to represent the lower turnunder reinforcement. The length is adjusted to be the side length less 2 times the end thickness, e.g. 2.4mm. Why 2.4mm? Well I often find that 20thou styrene is often 0.6mm rather than the stated 0.5mm and it is easier to sand the sides to length to match the ends than sand the ends down to match the sides:



Here is one of the door vents showing again in cyan which line we want to keep:



3 lines are drawn and aligned to give an equal spacing:



These are then adjusted to be central to the vent:



Once again to aid snapping a bounding rectangle has been drawn:



The finished vent is duplicated and the rectangles butted up. Typically with the smaller parts I add a few spare:



Here the components so far have been duplicated , the previous parts likewise duplicated and everything roughly positioned:



When cutting 20thou I tend to butt the various rectangles up to each other:



Again to improve snapping an additional rectangle has been added to the end ofthe reinforcing strips:



Everything positioned to my satisfaction. I have added another rectangle to the top right to square everything up. Snapping out should now be straightforward:



The existing objects are duplicated, making sure they are not moved, and transferred to a new layer which will represent the scoring layer. The non scoring layer needs the score lines deleted:



Here you can see the various layers. Rather than just send a single drawing to the cutter multiple time, I find it easier to just duplicate the template and move to a duplicates layer:



As my pattern does not fill an A4 sheet I have drawn a rectangle in order to determine what size to cut the styrene for mounting in the machine:



We are now ready to cut. Hide the sizing rectangle, set up the machine and load the styrene on the cutting mat than Print and select the Silhouette printer.



On my machine I set the option to indicate the use of the carrier sheet.



Clicking on the Cutline Settings tab, then Modify Color to change the line colour to Black



Click on OK, then repeat when the Ready to cut dialogue appears, then cross your fingers that is cuts correctly.




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A piece of 20thou styrene cut to the previously determined size and mounted to the cutting mat. I tend to use a roller to press it onto the mat:



The carrier sheet fed into the machine:



To provide extra support whilst cutting I use a suitable book:



Not the easiest shot to take but you can just make out the cut lines on the sheet after removal from the Silhouette:



The basic rectangles snapped out:



Now individual snapping out to profile can take place, sometimes aided by a knife:



The inner partitions are doubled up to form a 40thou component. Here it has been snapped and is then glued without being separated. Be awarethat the ones that go either end of the coach are only single layer:



Snapping out the windows. I have used the knife to cut through more of the diagonal lines and then push out the remaining bits using a blunt tool. This is one I picked up at an exhibition somewhere:


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In best Geoff Kent fashion, the side is layed face down alongside a steel ruler and a craft embossing tool rubbed along beside the ruler to start forming a curve. A knife handle could be used but remove the blade first!



The side is then moved further up the ruler and the embossing tool used again rubbed along its length:



Keep going and you will end up with a nicely formed turnunder which can be checked against an end:



The turnunder reinforcement was also curved and offered up in place remembering to leave a 40th ledge at the bottom to take the floor. In reality I felt the reinforcement strip was too close to the windows so decided to remove 1mm from it. The spring clips alow fine adjustment to be made until solvent is applied to weld the two part together:



Here are the ends which like the partition are doubled up from 20thou. Burrs are cleaned off using a suitable abrasive. I find nail emery boards useful especially where they have a cource grit one side and a medium on the other:



I find marking out styrene and getting good accurate cuts rather frought of late. This is down to poor lighting and using a pencil that does not have a fine tip that does not give a very visible line. Instead I now use a 0.1mm UNI PIN Fine Line pen which creates a highly visible, thin mark. Here I am measuring the width of the floor in 40thou using an end as the measuring guide:



Before measuring the length, the end is squared up with a small engineer's square:



Again following Geoff's guidance the first end is fixed to a side using the square to ensure it is at right angles. The other side is also fixed in the same manor ensuring the end is fixed in the same orientation:



The two sides are fixed together and the floor is fixed in place and the whole put aside to cure. I should have follwoed Geoff's advice and measured the floor length against the assembled sides, but thought I knew better. Wrong, as you can see by the slight gap nearest the camera!



Before leaving to cure I should add that I fit some of the interior postions but not fix them in place. This is just to help stop the sides being pulled in by the solvent (more in the next post):



Additional partitions in place. I did notice at this point that they were slightly taller than I expected so ended up shaving 0.5mm off from the top straight edge:


Edited by MikeTrice
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Before continuing an important diversion: styrene warping. Nothing to do with Inkscape, or the Silhouette cutter, but very important none the less.


Have a look at this earlier false floor unit based on a 20thou false floor. Nice isn't it?



The problem occurs where solvent is used on one side of the styrene only. This test piece was made and photographed one day out of 30thou styrene:



Just one day later and it is starting to warp:



What I believe happens is that as the styrene/solvent cures it shrinks resulting in a pull on the side applied.


Going back to the original floor this partition is made out of 40thou styrene, but more importantly the components attached to it are symmetrically arranged and as a result does not warp.



On the end panel though components are only attached to one side and as a result it warps (it is not helped by the thinner material here:



So going back to the original photo of the interior the worst curvature is where the seating units are solvented to one side only of the false floor. Result, it warps.


This was a problem with my original coach design. Here individual laminations of 10thou just did not have enough strength to resist the warping:



Even my latest attempt is not immune. The corner joints are also subject to warping resulting in the sides pulling in:



This is not a problem for this build as I will be including an interior with partitions and a false floor.


An obvious solution is to limit when solvent is used, which I will cover in a later post. Another option I have seen advocated is the use D-Limonene which is supposed to be less agressive. This huge bottle was bought from Magnacol for the princely sum of  £7.50 + £3 postage, a test sample has been glued together and I will monitor it over the next few days.



Obviously styrene thickness will also play a part however to date problems have been experienced below 40thou. You have been warned.

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The main body joints have now had time to harden sufficiently for the various ends and sides to be sanded to remove any burrs and joints at the ends using a piece of 800 grid wet and dry on a flat surface:



Two partitions glued back to back with seat squabs crudely represented with Evergreen 4.8 x 7.9mm rectangular tube. As both sides are symmetrical solvent has been used to fix these:



A false floor of 30thou has been fitted and some of the seat/partitions fixed to the floor. To avoid warping Uhu Solvent Free All Purpose glue was used. Remember the unit needs to be removeable so do not glue the partitions to the sides and try not to get glue squeezing out from the floor to the coach body (guess who speaks from experience here!):



The two end partitions having seats on one side only have been glued with the Uhu non solvent glue NOT solvent:



Seat backs from 30thou have been cut and fitted. Again for the central partitions solvent was used for this, but for the ends Uhu:



Not a warp in site. Success at last:



I mentioned earlier managing to get some stray Uhu glue attempting to fix the interior in place permanently. I did manage to separate them but the Uhu is surprisingly strong. An alternative to using the Uhu would be to use Cyano however I found I preferred the working time of the Uhu.

Edited by MikeTrice
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