Cut-in waterlines are a truly useful tool. Their primary purpose is to permanently scribe the waterline of a yacht into the topsides, that way it can not be erased or lost. Aside from this purpose, it also serves a few other wonderful services as well.
The most famous is the ability it affords you to paint your bottom without masking off the top. The bristles will simply fall into the groove and stop there. This allows you to simply paint up to the cut in waterline with ease and care without accidentally getting bottom paint on your topsides.
Taping off your waterline might not sound like a big ordeal, but when you are painting in a tidal grid, time is a very important item and one that is very limited.
As the tide is going out, you will begin scrubbing and scraping, then you have to chip off any loose paint, followed by fairing in any rough edges. This is a lot of work and adding one more step of taping off the waterline is not usually appreciated.
Having a cut in waterline allows you to simply start painting after the bottom is clean. The edge is there and unmistakable.
The second advantage of a cut in waterline is it makes it easy to see where your waterline is supposed to be, even if you raised the bottom paint as your cruising home becomes overweight. The cut in line will never move, and you can gauge how over loaded you are by how far under the water the line is.
The last and probably least thought of advantage of this scribed line on your hull is the ability to record and protect your waterline information, no matter what your yacht goes through.
We are repainting our topsides, and the bottom edge of the topside paint will go all the way down into the bottom paint area. The worker wanted to know how far into the bottom paint to sand, and the answer was easy to give and hard to forget: “Down to the cut in waterline”.
Now I could leave the country while the boat was sanded without worrying about where the worker was sanding. Best of all, when we repaint the bottom, I know how far above the cut in waterline to raise the boot stripe.
Having a cut in waterline boasts many advantages, ones that are typically only thought of as the moment they are needed arises. If you have one, enjoy it, and if you don’t have one but do have spare time to kill, consider adding it to your cruising yacht.