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Project #2 : Round Table Class Minesweeper HMS Sir Lancelot (1/96th scratchbuild)


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3 hours ago, Dancona said:

I bet you are glad that is done now 😁

Most definitely !!! Still a few small bits to add but the worst is out of the way. It was made a lot easier thanks for @Iceman 29 's CAD drawings which he posted (maybe now he has almost finished his Blythe Star he can get on with some CAD for a main winch 😜)

 

 

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  • 2 months later...

Its been a couple of months since my last update, unfortunately i've been tied up with moving house and then i was in Western Australia (Perth) for 5 weeks so i've only just this weekend managed to find any time to spend on this.

 

I decided to try and tackle the railings on the wheelhouse deck, originally i thought i'd use some PE for this but then realised that the chance of these not being mangled when i attached the splinter matting would be slim and decided instead on using a solid screen that the matting could easily be fixed to with some plastic railings on the inside - the solid screen would then act as the back of the matting. Alas before reaching this decision i'd already attached the wheelhouse which made the whole thing very fiddly.

 

Anyway i fabricated some railings from evergreen, being plastic i figured these should be relatively easy to bend around the inside of the screen. Once these were on i then made the handrails and finally the matting from milliput, shaped with a wet brush and cocktail stick.

 

Next job is to finish the lifeboat then the dreaded winch !

 

 

IMG_2481

 

IMG_2482

 

 

 

 

 

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  • 2 weeks later...
Posted (edited)

 

I finally forced myself to sit down and work on the design for the etch sheet. As i spend most of my working day sat behind a PC screen the idea of doing the same in my leisure time wasn't that appealing so i think i've been putting this off for months. Also this is my first time doing anything like this so there was some trepidation happening too.

 

Anyway for those who have never done this before i've set out what i learned below - feel free to skip !

 

<waffle start>

Its recommended that when you do this type of thing you use a scaleable vector graphics (SVG) program. Basically these allow you to create an image that won't lose detail at higher resolutions. If you imagine a normal JPEG type file, it contains a pixelated version of your image so as you zoom in on a circlular shape the edges will gradually start to become grainy due to the pixels that make up the image. SVG programs work in a completely different way and store the image as a series of instructions which are rendered on your pc screen. For example if you draw a line the the program will not store the pixelated image but something like this:-

 

line x1=100 y1=200 x2=200 y2=300....

 

So the object you've drawn is described rather than rendered. In the above simple example there will also be other items (arguments) on the "line" command such as colour, thickness etc. Using an SVG program you can still use your mouse to create the shapes/lines you want but they are stored as code (XML if you want to get technical).

 

Obviously at some point in the PE process the image will have to be committed to acetate sheet for processing, the point of SVG is that this happens right at the end and is done by the company doing your PE who will have a much higher resolution setup so the limitations introduced by rendering into pixels are kept to a minimum.

 

There are quite a few SVG programs out there, Inkscape seems popular and is free to download/use but there are others. Unfortunately i had to do my design on a work PC which meant i couldn't actually install anything so i ended up using a browser based program called SVG-EDIT. The front end for this is a little basic and sometimes glitchy but it did the job and there are plenty of tutorials online if you want to get into the detail of the XML coding side of things. Initially i just used the front end but the more i did the more i found myself just writing the XML directly. This also enables you to do things that would be very hard using the front end alone. One example of this is making cogs, you could draw a polygon and then fix small triangles for the teeth to each flat surface but a simpler way is to draw a square whose diameter is the same as that of the cog you want then rotate this by 15 degrees (all done in the front end). You can then go into the code and copy the relevant section 5 times and just edit the angle of rotation to 30, 45, 60, 75 and 90. The copying the code preserves the centre of rotation and the result is a cog (ok the apex of the teeth are right angles but when they're 5mm across who cares !). You can see the angles in the rotate transform in the lines below....

 

   <rect fill="#000000" height="26.46" id="svg_352" stroke="#000000" stroke-width="0.1" transform="rotate(15 288.534 351.088)" width="26.46" x="275.31" y="337.86"/>
   <rect fill="#000000" height="26.46" id="svg_353" stroke="#000000" stroke-width="0.1" transform="rotate(30 288.534 351.088)" width="26.46" x="275.31" y="337.86"/>
   <rect fill="#000000" height="26.46" id="svg_354" stroke="#000000" stroke-width="0.1" transform="rotate(45 288.534 351.088)" width="26.46" x="275.31" y="337.86"/>
   <rect fill="#000000" height="26.46" id="svg_355" stroke="#000000" stroke-width="0.1" transform="rotate(60 288.534 351.088)" width="26.46" x="275.31" y="337.86"/>
   <rect fill="#000000" height="26.46" id="svg_356" stroke="#000000" stroke-width="0.1" transform="rotate(75 288.534 351.088)" width="26.46" x="275.31" y="337.86"/>
   <rect fill="#000000" height="26.46" id="svg_357" stroke="#000000" stroke-width="0.1" transform="rotate(90 288.534 351.088)" width="26.46" x="275.31" y="337.86"/>

 

Obviously once you've made one of these you can just copy/paste to create more in the front end.

 

When you work on your design you also have to be aware of supporting the parts with brass "sprues" and doing half etched sections to make cutting/folding the pieces easier. Red indicates a half etch from the front and cyan from the rear.  You also have to bear in mind the limitations of the PE process, on a 0.2mm brass sheet the smallest size for a solid item is 0.25mm and the smallest gap is 0.28mm.

 

Early in the process i sent a draft to 4D so i could make sure i was on the right track and i would recommend this as they found some minor issues caused by the program that i had to take account of. Hope this brief explanation is useful to someone out there.

<waffle end>

 

 

 

 

The finished design Is shown below, i had no idea it would take as long as it did (getting on for 30 hours) and i still have to get it checked by the 4D people so there may be some final tweaking before its committed to brass.

 

Its sized to A5 and i filled all available space with a lot of spares and for the future (grating, cogs and wheels for winches mainly). The propeller blades are rough and will be filed, i tried to get them drawn but after a few hours wrestling with cubic bezier functions gave up.

 

Once its back though i should be able to really get on with finishing this.

 

svg_edit

 

More updates when i get the PE fret back !!

Edited by theskits62
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If that's your first etch artwork, I'd say very well done :clap:

It takes many, many hours, the time just disappears.  What people fail to realise is that in addition so actually drawing stuff, you have to design each component in a way that will work with the limitations of the etching, and also be able to be assembled.  20+ years of doing this and I get stuff wrong on every sheet I do.  Plus, in all that time, I'm still really only confident of line and raised detail at one sheet thickness...

 

If you are using 4D, (as I do) they will help immensely, I'll leave it to them to point out the bits you need to address.

 

I like to think in terms of life gates, steps that once taken, there is no going back.  Custom etching is a modelling life-gate..

 

Cheers

 

Steve

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46 minutes ago, Steve D said:

It takes many, many hours, the time just disappears.  What people fail to realise is that in addition so actually drawing stuff, you have to design each component in a way that will work with the limitations of the etching, and also be able to be assembled.  20+ years of doing this and I get stuff wrong on every sheet I do.  Plus, in all that time, I'm still really only confident of line and raised detail at one sheet thickness...

 

Thanks Steve, one thing that is puzzling me on this is how to deal with folds. On things like the flag box, lifebelt racks etc i've obviously half etched on the fold lines but was not sure whether i need to adjust the size to take account of the corner. In my design where 2 panels fold at 90 degrees they are butted together and the cyan/red fold line is overlaid on the join - do you find this works or do you leave a gap and put the fold line in that ? Also how wide do you make the fold lines relative to the brass thickness ?

 

My other simpler question is should the design work on folding away from the etch recess or into it, i've assumed "away" but my designs are simple enough this time for it not to matter but it would be useful to know for the future.

 

Thanks

Brett

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3 minutes ago, theskits62 said:

one thing that is puzzling me on this is how to deal with folds.

The rule I use is the width of the fold line is the thickness of the sheet, the fold allowance is half the sheet thickness so if the front of a box is 20mm (outside dimension) and the sheet thickness is 0.45 mm, the inner lines of the fold would be 19.55 mm apart

 

On the face or back question for fold lines, there is no perfect answer.  In general I will fold line in red, but sometimes in cyan if I'm folding away from detail.  Depending on the part, the fold should ideally close not open if that makes sense.  Where the edge is already half etched, rivet detail sheet etc, I place a partial cut line at the top and bottom of the fold line so I know here it goes later on.  This is not always a success, but it helps.  Many times these days I feel it is better to cut than fold, half etch a ledge and solder, not fold, folding is lazy really and less controlled. 

 

Finally, these days I frequently place alignment holes (0.5 or 0.7mm dia) in parts and use wire to assist alignment, the ends can always be cut away afterwards

 

Hope that helps, any specifics you can always DM me and I will try to help

 

Good luck with it

 

Cheers

 

Steve

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