[The following is an article I wrote last year for The Foghorn, the newsletter publication of the South Bay Model Shipwrights that meets in Los Altos, California]
Copper sheathing is a feature I’ve always liked on ship models. I’ve built several ship models that feature copper sheathed hulls starting with my first ever wooden ship model, Model Shipways’ pilot boat Phantom.
One question that I’ve had to deal with in all cases is how to make the nail pattern on the plates. One school of thought is to ignore the nails as they are hardly visible anyway. But, I like detail, so I think the nail pattern is important to include if it can be done well.
While the nail patterns seemed to vary greatly depending on the ship yard, the nail patterns on a given ship are regular and consistent. In the past, I’ve used pounce wheels and my technique with them has improved. I’ve even managed to work a technique to make the plates pretty consistent, but these techniques proved to be very time consuming.
My latest technique in the long quest for a good balance between expediency and accuracy is the use of a steel die to emboss the pattern onto the copper.
I’d always wanted to try pressing copper sheathing plates using a metal die, but published techniques I’ve read called for machining, for which I have little experience and no tools. Model Shipways’ Syren kit includes a description of making a die from small nails mounted in a wooden block, but the results are still not to my satisfaction.
Then I began an experiment when I discovered that a brass etching kit I purchased recently from Micromark (http://www.Micromark.com) also works on steel. What if I could chemical etch a die?
Micromark’s metal etching kit
I won’t go into great detail here, but chemical etching of metal is a multi-step process that starts with creating artwork using a computer, printing it and transferring it onto a piece of metal using light and a light-sensitive coating on the metal referred to as “Photo Resist”. When placed in a chemical bath, the unexposed areas of the photo resist allow the chemical to come in direct contact with the metal, dissolving away the material.
The artwork shown here was created on a computer, and was made for full plates at different scales.
When the metal has been in the etchant sufficient time to dissolve some of the metal, but before it’s eaten too far through it, the metal is removed from the etchant and cleaned up. The result is a steel plate that has the nail pattern embossed on its surface.
The etched steel and some embossed test pieces
The dies were cut from the metal sheet and mounted in a little jig I made for embossing copper tape. This embossing process isn’t perfect and I’ll continue to experiment with methods to improve it, but I made it work for now. Simply lay the copper face down on the die and use the butt end of a small tool’s wooden handle to rub the pattern onto the tape.
The nail pattern embossing jig for 3/16” scale
The idea of different left and right side copper plates seem to have become popularized as an accurate feature by Amati and others, but I think the distinction is unnecessary since the plates overlap top and bottom anyway, and the overlap covers up one edge row of nails.
The standard die for a plate made as part of a strip of copper tape is slightly shorter than for a full-sized plate since it represents a plate that has been overlapped by the plate next to it. Because of this, these plates also need to omit one end row of nails.
Die for copper tape at top, for individual plate at bottom.
Copper sheathing going on the hull of the yacht America
I made dies for 3/16” scale and also for 1/8” scale use. The first use of the dies was on my scratch model of the yacht America in 3/16” scale. I’m pretty happy with the results. And, while the process of making the dies took some work, the actual embossing of the plates was not difficult. It still took time to emboss each plate – more time than using a pounce wheel. But this has been the quickest way for me to get pretty accurate and consistent plates, and the amount of wasted material was very small.