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Normal Topic Paper for fiddley bits by Prosper/Stephen (Read 203 times)
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Paper for fiddley bits by Prosper/Stephen
Dec 28th, 2019 at 11:32pm
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Found this technique on HPA by Prosper/Stephen in his P-47 Razorback Natural Metal Jug:click Here for full thread

Tim. The drop tank has a balsa male mould, turned on a domestic electric drill. The finish can be rough. I've been making small items using what I've loosely called papier mâché for years, and perhaps this term is misleading, because if I remember from childhood, papier mâché means dunking pieces of paper in some form of paste until they're soft then plastering them on a male mould as seems fit, then letting the whole lot dry.

What I've typically done is to soak a single layer of paper, then coax it around a male mould (perhaps also pushing the mould thru a cutout in a sheet material, samelike plunge-moulding a plastic card item). When it's dry it can be prised off the mould and carefully wetted out with thin CA, then sanded and re-coated and repeat until the desired finish is obtained. This works for little airscoops or blisters.

This drop tank is the biggest item (by far IIRC) I've made this way, and differs in that I've used the cheapest, near-pulp, office paper called 'Copier Paper', and I've torn it and ripped it into strips and truly soaked it for say ten-fifteen minutes then really mashed it onto the mould, rubbing it and scratching it to make it a mess of fibre - all the while adding sloshes of water as req. The result is anything but smooth, and now the balsa mould is soaked too so it all needs a good while to 'dry out before the fire' as novelists used to put it.

Next it can be teased and prised and lifted and coaxed from the mould and it will hold its shape. Then I dose it drop by drop with thin CA and the result is a very coarse and very heavy blank, and I've found that this can be sanded even with 120 grit wet&dry (used dry only) to remove most of the material rapidly (dust extraction highly recommended). I use a naked lightbulb close by to give the glancing light you need to see how the work is progressing. Some other nationalities may prefer to use the sun, which is an option outside England. Then the work can be refined as you wish, adding CA if needed to fill dry pockets in the layers of paper mash, and even to patch little holes or craters in the surface.

It will help a lot if you then slice the balsa mould in half lengthwise. I make my moulds from a stack of sheets tacked together loosely, so splitting them down the middle is easy. Now you can plonk the refined paper shell on a half-mould and run a fine pen round the mould on the inside, to mark the  shell, then cut to that marked line, so you have a half-shell that will join its 'other half' correctly.

If that's all as clear as mud, let me know and I'll try again.

Stephen
  

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