Part 12 - Brassing the Hull - Making a Start ( I think it’s going to take me a long time!!)
Jock Willis’ original spec. for the Cutty Sark states “Yellow Metal Sheathing. Vessel to be sheathed from Keel to 18 ft water mark on top of paper and tar, sheathing to be smoothly put on, sheets to be 22, 24, 26 oz. metal”. The Cutty Sark was sheathed in Muntz metal, a brass alloy which replaced copper as the sheathing metal for wooden hull’s from the 1830’s and was used right up to the end of the 19th century when iron hulls and then steel was the standard. To keep true to the ship, after looking at various options, I set myself the challenge that it should be brass, so brass it will be! My decision for the model was “new” brass but with the shine toned down a bit with a matt lacquer top coat.
At the moment scale brass plates are not available from any of the normal suppliers (Miguel92gom spotted some brass plates made by Eskadra
Vintage Billing Boats Cutty Sark - Sheathing the Hull? | Ships of Scale however, I will not buy those for obvious reasons). The main thing about brass is that when new it is a pale golden yellow/green in colour and is obviously “nice and shiny”. However, many modellers will prefer a weathered appearance and the extent of the weathering will depend on many factors. Brass dulls down to a darker yellow and blackens in air unless lacquered.
In the absence of brass, copper is the default for most modellers. Amati’s etched copper plates are probably the best ones but are more suited to period ships. The gummed embossed copper tapes which are available from ZHL are much easier and faster to apply but again they are more suitable for larger scale period fighting ships (personally, I don’t like the look of the tapes). As to weathering, copper will only blacken Indoors but in the presence of moisture it will turn green due to corrosion but to produce the green verdigris on models chemicals need to be applied (some people like that look). However, at the end of the day, copper is wrong for the Cutty Sark.
I have gone into some detail in the following sections about how I decided to go about brassing the hull of my model and the other options I considered. No doubt there are (much) better ways of doing it - but this is how I went about it - warts and all.
Painting Option
At the start, I did consider just painting the hull (as suggested by Billing). The advantage of painting is that it is very quick to do but, the disadvantages are that it is not “metal” and it will always look painted. My thought was to use wood veneer strips as a second planking to mimic the plates and then overcoat with a brass metallic paint. I tested quite a number of paints and there are some that give quite good “metal-like” appearances. However, they varied quite a lot in colour/shade/metallic sheen. I found the metallic brass paints from Humbrol (no.54) and Revel (RV92) were a bit too dark and had a “glittery” appearance to them. The gold Humbrol paint (no. 16) was probably a bit closer to Muntz but had a slightly more darkish yellow tint to it (again, also a glittery finish). Some other “brass” paints were not “terrible” but I did not like the colour/finish they gave so I won't mention them here. The best paints I tested were the ALCLAD2, ALC-109 (polished brass) and ALC-108 (pale gold) <
ALCLAD2 link >. The ALCAD2 paints are designed for airbrushing and I found that they were far superior to anything else - but you do need to follow their recommended painting method to get the best finish. They give an excellent metal like finish and in my tests the pale gold was probably the closest match to Muntz - but, that's just my thoughts. However, all the paints I tested are much better suited for painting smaller parts using an airbrush which are not the best thing to use over large areas. Painting the C-S is more like painting a barn door! It requires many passes with an airbrush and it is very difficult to achieve an even finish. You can use a large nozzle size (0.5 - 1.0mm) or a mini-spray gun but they need large volumes of paint to work properly. Hand brushing is always an option but I much prefer the finish that an airbrush or a rattle-can give.
I did find a specialist “veneer” brass paint (
Metal Veneers | Luxury Metal Finishes) which is a two part paint with a very high metal particle content (they also do copper and bronze finishes). They provide the paint and activator in pots but they also supply it in custom spray cans. Once cured the coating is very hard and can be polished to a satin or bright metal finish. The caveat is that the paint has a very short life once activated so if you do not get the coating right in one shot it means buying new paint (which is very expensive), cutting back the paint surface and recoating. Isocyanate paints are also quite toxic so great care is needed to use them safely.
Using veneer strips and paint was tempting because it would simplify things but veneer strips are thicker (0.5~0.6mm) than using foil and if it all went horribly wrong I could have easily ruined the hull beyond recovery.
Brass Metal Sheet - Shim Stock
My first attempts at making my own plates did not work out because I could only find brass shim metal in 100mm wide sheet rolls. I had a lot of issues cutting it neatly and consistently mainly because brass is harder than copper and it has a tendency to curl up when it is cut in strips. Brass has some spring in it so flattening it out again without leaving marks is almost impossible. I tried a few types of hand cutters/scissors but, to some extent or other, they suffered from turning the edges over, curling and creasing the metal or were not able to keep to a good cut line. Carefully scoring the brass with a cutting blade and then bending it up and down against a flat edge worked to some extent but it was very difficult to do, very slow and …. repeat for 2000+ identical plates = good luck with that! I decided the time needed to make all the plates from sheet brass would be better spent doing other things.
Nail Pattern
People who have made their own copper plates have also embossed the nail pattern into them by using a jig (pins in a block) and a press. However, brass is quite hard to mechanically emboss and etching the patterns into the surface is the best way to do it but unless you have access to decent photomask equipment and know what you are doing, it is not something to do yourself unless you really want to learn how to do it. I did find a custom etch service that gave me a “ballpark” figure to make some sheets of brass plates (similar to the ones that Amati does in copper) but the full price turned out to be far too expensive so I quickly ruled that option out.
In reality, when you see the hull from any distance away it is almost impossible to see the nail heads (or the plate overlap) because the tacks that were used on the C-S were actually quite small. The image that I took on my visit shows the plates and tacks, the plates are between 0.8 and 1mm thick and the tack heads are 10mm in diameter and 1mm proud. Scaled to the model, the heads would be ~0.12mm in diameter but, more importantly, they would only be ~0.01mm proud of the surface - that’s about 1/8- 1/10th the width of a hair - microscopic! In fact the resolution of the human eye is only 0.1mm at 25 cm so properly scaled it would be impossible to see the nail pattern and overlap pattern when viewing it from more than a metre away. You can also see how the plates are overlapped along and down the hull (the image is oriented with the bow to the left). For the observant, the plates look very coppery in colour so I did some fact finding and discovered that the brass they used in the restoration was a cheaper alloy which has become oxidised giving the reddish tinge.
Not having the nail pattern on the plates greatly simplifies things and it is actually the correct thing to do from a scale factor - so that was my decision!
Plate Size and Positioning - Brass Reel
To get around the brass sheet problem I scoured the internet and eventually found a supplier of 0.1 mm x 5 mm brass foil. 0.1mm was the thinnest foil they do at 5 mm, they also had 8mm but I thought that was too wide. The scaled plate size for the model is about 16 mm x 5 mm . I decided to go for slightly longer plates at 18 mm x 5 mm to allow 1 mm overlap at the ends and I was able to buy a 50 m reel which meant that I could cut the plates from the strip very easily with some sharp cutters.
To cover the hull, the plating strakes need to more-or-less follow a straight line from bow to stern taking into account the complex curves (as shown in Cambell’s plans). In effect the plates run parallel to the water line.
On the model there are approx. 17-18 strakes of plates at the bow and stern but at the centre of the hull the girth expands to about 24-25 strakes. To accommodate the middle section of the hull without leaving gaps or needing wedges and/or stealers I marked off the hull at the top of the sheathing (which is just above the waterline) and used my waterline marker to draw a series of strake lines along the hull to act as a rough guide. The hull needs about 2000 plates to cover it (I think!). On the ship the plates are overlapped so that starting at the bow, the next plate overlaps and the strake below overlaps the top strake (as in the image). I could have tried to butt the plates together which would have given a smoother finish but I decided to overlap the plates that way l could adjust the overlap to follow the strake lines without leaving gaps and it is actually the correct way but, it does leave a slight step.
Attaching the Plates
In order to attach the plates to the hull I had to do a few experiments to see what worked best. Degreasing the brass with a suitable solvent such as acetone or rubbing alcohol is essential before applying any adhesive. I did not clean the surface with fine emery paper because the brass I bought was very clean but, if the brass is very dirty or heavily oxidised this may be necessary.
For the adhesives I tested a few of the common ones on some scrap to see which worked the best; CA, epoxy and contact,
CA
Generally I am not a fan of CA and avoid it. It is very messy to use and you have limited time to position parts. It is OK for small parts but is not very good for large pieces because the fast setting time does not allow for making fine adjustments. It does stick the brass down (as well as fingers!) but I found that it was also very easy to “ping” the brass off again without much force. Getting the CA on the surface and edges of the plates is inevitable and it needs to be cleaned off using a CA debonding solution. CA also has a problem of being quite brittle and from experience even well stuck metal parts gradually can become unstuck because of thermal cycling and humidity.
Epoxy
2-Part epoxy works better than CA but again it is a very messy adhesive to use and the pieces need to be held in place with masking tape (or something) while the glue sets up (and hope that nothing moves). You also have the choice of using the quick or long set epoxy. Like CA, excess adhesive squashes out from under the strip onto the edges and also smears on top of the brass. If it is not cleaned off before the glue cures, removing any excess hardened glue from the edges and face of the brass is a nightmare. The brass-wood bond is however more durable than the CA.
Contact
Contact adhesive works but you need to coat both the wood and the metal, let the glue air dry and then carefully apply the brass. Again, contact glue is very messy to use, it is high in volatiles and it is difficult to get an even coat on both the metal and the wood without excess. The grab is quite strong so if you get the positioning wrong it is very difficult to reposition parts.
Generally all the liquid glues are very difficult to apply thinly and evenly. Excess adhesive gets onto the edges and face of the metal which is then difficult to remove without marking the surface.
After my tests with all the liquid adhesives I was not happy with using any of them - small parts fine, just not very “user friendly” for large areas.
Bonding Tape
Using double sided bonding tape (similar to using the embossed adhesive copper tapes that some people use e.g. the ones available from ZHL Model) was my next consideration.
There are many types and brands of tape available but the best ones form extremely strong bonds to a variety of materials. I tested a number of types and found that 3M 9448a or 9495MP both worked very well. The 9448 is a tissue based carrier and the 9495 uses a PET film. Both are very thin tapes and are resistant to heat, chemicals and moisture. The tape bond reaches its maximum strength after 72 hrs but it is possible to reposition the plates by carefully warming it with a hair dryer. You can also use 3M 94 primer which improves the bonding but the plates are not supporting any load and just need to “stick” to the hull so I decided this was not necessary - in fact the plates are so well stuck if you try to lift them they will actually pull the wood away with it!
To make the plates I applied the tape to a length of the brass strip (about 1m at a time). I found the best way to do this was to place the brass in a narrow piece of C-channel and use that as a guide to unroll the tape down onto the brass.
To ensure a good bond I ran a cork roller over the tape to firmly bond it and then cut the strip into 18mm tiles with some sharp flush cutters. The rinse and repeat cycle was rather tedious to say the least but I eventually ended up with a box of plates - I’ll probably need more but there is only so much fun that can be had at any one time! The only issue I found was that the tape is a tiny bit wider than the strip so there was a small overlap at the edge but it was easy enough to just run a scalpel blade along the edge to trim any excess off as I came to lay the plate.
To get started I placed some masking tape along the top marked line and then carefully positioned each plate following the line with 1mm end overlap adjusting as I went. I brick tiled as I came down the hull. To ensure good bonding after laying a section, I ran a hair drier over the plates to warm them up slightly and then ran my cork roller over them to make sure they were well and truly stuck down. After I had put a couple of strakes on I checked and adjusted the next line to make sure the spacing would be more-or-less even as I worked down the hull.
About 200 plates down, only another 1800+ to go!
I’ll post an up-date when I have worked my way down to the keel on this side but at the rate I am going I am estimating it’s going to take me most of Feb’ to finish the sheathing.