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Acid Etching - Acid Etching

R/C Submarine modelers

Postby John » Fri Apr 25, 2003 8:23 am

I am considering acid etching the deck of my scratch VIId in order to get the required detail.

Research on railway modellers and electronic PCB sites would indicate that there are 2 possibilities:-
a> proprietary iron-on PCB sheets on copper
b> UV expose brass sheet using photoetch chemicals from maplins (UK version of radio Shack)

Both methodologies sound straightforward but I would value practical advice.

a> Thickness of sheet? Brass or Copper? How much depth can I expect to be able to etch? Could I etch straight through?
b> Should I apply the etched sheet to the fibreglass plug to create a pattern in the mould or should I apply the sheet to the finished model.

Sorry to be always asking questions. Maybe when I finish this I will be able to contribute more.

John Horsfall SC 2960
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Postby TMSmalley » Tue Apr 29, 2003 11:36 am

Or better yet - you could do a story for the SCR!

Somewhere I have an article I saved off the net - the site is now down - if you are interested I will email it to you.

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Postby JWLaRue » Tue Apr 29, 2003 9:51 pm

Well....since I do offer for sale photo-etched Type VIIC decks (and some other items as well), perhaps some of these answers based on my experience may help:

a) Thickness of sheet?

This depends on the scale of the model you are building. In general, the thicker the piece, the more resistant it will be to those pesky dings that are inevitable with an operating model. For my 1/48th scale decks, I suggest that a thickness of 0.015" be used. For the 1/32nd scale decks, go for at least 0.018 - 0.020".

Part of this is that you want to try to keep the extra weight above the waterline to a minimum.

There is a trade-off however. See question 'c'.

b) Brass or Copper?

Given a choice between those two: brass. This because brass is slightly less malleable. But my preferred choice is actually stainless steel. It is much more resistant to dings!

c) How much depth can I expect to be able to etch?

With a single negative (meaning you are only etching from one side) you can go all the way through the metal piece. However, the etching process does not produce a 'straight' cut down through the metal. You get an undercut...and the deeper you etch, the more undercut you get.

One way to minimize the undercut problem is to create two negatives...one for the top and one for the bottom. Any place that you want to have the etching process go all the way through the metal, the negatives would have identical lines.

If the line exists only on one negative, you end up with a half-etched line. This is how items such as hatch outlines are done.

So a good rule of thumb is etch to half the depth of the metal.

d)Could I etch straight through?

See previous answer.

e) Should I apply the etched sheet to the fibreglass plug to create a pattern in the mould or should I apply the sheet to the finished model.

Only if you plan on cutting all those deck slots by hand....and that would appear to contradict the purpose of going the route of photo-etched parts! :D

-hope this is useful. Please feel free to ask more questions and I'll be glad to try to help.

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