Let's finish off the hull painting
Hi, its’s been a while since I last posted. That’s mainly because the final phases of painting the hull have turned out to be a lot more trouble than I was expecting. As outlined a few posts back, I created my own problems by trying to be smart and using some spray putty over a partially finished acrylic finish. That caused some nasty etching, and it has taken quite a few subsequent coats of paint and rubbing back with wet & dry to get the lower hull paintwork back to a finish that I’m happy with. And what was the special skill required for this?…none, just persistence!
And now that I’m back to a sound, faired surface with the colour I want on the lower hull, I’m ready to have a go at the upper hull colour. The waterline was marked in accordance with the plans, with the usual technique of a pencil taped to the top of a suitably sized block of timber. The only tricks here were to make sure that the keel was inclined at the specified angle (a 5mm block under the bow and the stern on the table) and to make sure that the boat was kept level from side-to-side while moving boat or the marking block (a spirit level across the gunwales). I was happy with the line, so it was onto masking up the existing painted surface.
I had tried a few masking tapes on my sample scrap of wood, and ended up using Tamiya 6mm yellow tape to get a good line, with other products layered to give coverage. From testing, I knew the 6mm tape gave a good clean line with no bleeding and it goes around corners better than wider tapes, so it suited the continuous curve around and under the stern. It is a little tricky in that area getting both a smooth curve and also making sure that the masked shape is evenly balanced (in plan view) on both sides of the keel.
After getting the yellow tape set in place and burnished on the edge that will have the wet paint applied, I then added a layer of green Bear Samurai tape. This is my usual tape for any painting that I’m doing…its thin, gives a good edge and can be left in place for longer than the cheaper tapes. In this case I’m only using it as a protective layer to stick the final masking product, so I didn’t need to place it too carefully. The final product is a plastic film with a masking tape built in (used for automative spray jobs), but I’d had it for about 10 years, and I didn’t want its overly tacky tape directly on my relatively fresh paintwork.
Here it is ready to go…
For the deck, I just taped it with 2” wide clear tape. The one I’m using is relatively stiff and it was happy to stick to the top edge of the gunwale and allow me to trim it to have a 2mm projection over the outside, without wanting to bend over and stick to the outside of the gunwale wall like the masking tape tended to do.
The first paint coat was done with the hull inverted so that I was spraying across the top of the edge of the masked area, rather than down into it…hoping that if I did a light first coat then it would seal against the tape rather than be forced under the edge and bleed. This was particularly important on the starboard side where the vertical rubbing rails are also being painted and the masking has to run across the middle of them…a fiddly job getting a good seal on those areas before starting.
The paint I am using for this section is named ‘Polar Blue’ and is from the Montana Gold range of rattle spray cans. This range is a little unique in that it is designed for artists and is formulated to be ’low pressure’…apparently this gives a skilled artist more control in tight areas. It caused me no end of frustration. I just could not get a consistently good finish without some level of paint spatter (not a problem with any of the other paints being used).
Here is a particularly bad example, highlighted with a very bright light at a low angle, but you get the idea…
It took many attempts and some testing on scrap to work out that I needed to use the ‘low pressure’ to my advantage. I’d been trying to ensure that I got maximum flow through the nozzle (warm can), kept the aperture clean between passes…all to no effect. It turns out that you need to go the other way…slow everything down, a light pressure on the nozzle, slow passes, build light coats to get a complete wet coating without spattering. It’s great stuff when you work it out. A simple wet & dry between coats to remove the prior spots and the job finished up nicely.
Here she is…the paint is still wet in this shot.
So, drum roll…how did it finish up? Did we get a nice edge? Is there any overspray? The mask removal is almost as stressful as the painting!
I’m pleased to say that it finished up pretty well. The wet edge between the upper and lower surfaces came out straight and was nice and crisp. The sections across the vertical rubbing rails were also good. Even the tiny-tiny bit of bleed on the fore edge of first rail in the following pic was easily removed with wet and dry.
But all was not completely well…the masking tape has reacted with the paint of the lower (grey) section. I thought that it might have been residual glue, but it isn’t. The adhesive somehow has a mild reaction to the paint and causes it to soften and leave a mark, like a watermark. Here is a good example (before the Tamiya tape had been removed)…
While that was somewhat alarming, I had seen this before and I’d already done some testing on my scrap piece and I knew that the clear matt top coats can remove this. The entire lower section of the hull was wet & dry sanded with 2000 grit to get a consistently smooth surface and colour, and that also removed most of this ‘watermark’ effect.
So the next step was to add a few coats of Dulux Duramax Clear Matt Acrylic. I like using this product, it gives a consistent matt finish even after a few coats and it looks and feels good. It also finished off the watermark repair and I’m very happy with the final result.
And the bow…
I do realise that I’ve gone overboard with trying to get everything right with this painting exercise, but this model was always meant to be a learning exercise…and that it has been. I promise we’ll be turning the hull right-side up, and get back to some more interesting build content soon.