The Naiad Voyages

Mark Austen

2018.03.30 - Scribing the Waterline

When I put Naiad back in the water after her 2 year repair and refit I only had the vaguest notion of where the waterline was going to be. I knew that it would be higher than the original and I could see where the waterline lay on Shoal Waters but that only gave me a rough idea of where it was going to be. So I took a leaf out of Charles Stock's book and put her in the water for a season. On taking her out last November I could easily see, at least on one side, where the waterline was in reality. Now was the time to do something about that.


The first thing to do was to put small nails into the hull on the side where I could plainly see there the waterline should lie.


I did this at intervals all the way from bow to stern.


On the other side it looks like there is a defined line but as you go aft it becomes difficult to see.


As you can see here the line is not so defined.


And when you get right aft it could be just about anywhere.


Unlike on the other side where is is still easy to see.


I put in a fair few nails...


...and then nailed a flexible batten to the hull agains the nails on the waterline.


The result looked to be quite good as you can see here.


Using a sharp chisel I use the corner of the blade to score a deep mark along the top of the batten and into the hull.


From bow to stern.


The batten was removed and the mark made into a vee shape using a tri-cornered paint scraper.


It went a bit wonky in places, notably where the nail ad been put into the hull.


But by and large the result was good, especially from a distance.


To get the same line on the other side I put nails into the underside of the rubbing strake starting 3' from the bow at 12" intervals to the stern on both sides using a tape measure.


The nails were put into the chamfered edge.


You have to be a bit careful with nails like this as it is easy to catch your hand on them as you walk by.


A string was looped over the first nail on the scribed side and wound around the corresponding nail on the other side. The distance from the rubbing strake to the line was measured along the string...

...and then transferred to the other side and a nail put in the hull at the correct spot. The string was moved to the next nail on both sides and the measuring repeated until all the nails had been done.


The batten was put in place the the line scribed as before and this is the result. You can see that the line is not quite where one might have expected it to be sign the mud and slight weed growth.


The line about midships.


And aft.


Now the maroon top coat and the grey primer paint were removed down to the waterline with a sharp scraper.


On both sides.


And view of the after end.

A 80 grit sanding disk on a power sander, with one of my vacuum clearers plugged into the dust port, was used to smooth off the hull and to remove all of the shine on the white paint which is a two part polyurethane paint and very hard. Getting the shine of this is essential if the next layer is to bind properly. The vacuum was also essential as the dust is very fine and not something you really want to be inhaling.


I used a piece of 40 grit sandpaper to roughen up the surface even more on both the paint and the old CopperBot and I did this part by hand. I did just the first 3' or so to see how it looked and the above is the result after I washed the surface down with some alcohol to remove the copper dust.

About this time I ran out of energy and decided that this was a good start of the weekend tasks so stopped for the day.

Time for a cup of tea.