The Naiad Voyages

Mark Austen

2021.05.11 - Rudder Sink Weight I

The plan for the rudder sink weight has become just a little bit more complicated than I expected. I have some steel bar that I can use to make the two weights but this has number of problems that make using steel bar impractical. The first is that the size of the required bar, even in two parts, is too big. The second is that the rudder blade is not flat but curved and thick steel bar is difficult to bend to conform to the curvature. The third is that steel bar on the blade is going to make the rudder less effective due to turbulence. The fourth is that steel rusts and even with a protective coating rust is going to form. The fifth is that chunky great steel bars on the blade is bound to snag when sailing. All in all, steel bar was discarded as a means for weighting the blade.

Instead I decided to use some lead. After all, I have plenty of it. This is where it started getting complicated. The lead would have to be melted and cast into a suitable shape. That being the case it seemed to be reasonable to make that shape as hydrodynamic as possible. To cast lead you need to have a suitable mould and although you can use wood, it chars easily and if the lead is too hot, it burns.

That leaves proper casting sand which is easy to get hold of and for melting the lead I can either use the forge or the gas stove. An empty tin can will do for a heating pot but I'll need something to make the correct shape. I decided that the weight should be round and domed. Think of a round disc that has one surface shaped so that the edges are thinner than the centre.

The only thing that I have that is even close to being suitable is the cast iron lid to a small dutch oven that I have, but it is marred by having a handle.

So,I shall try to use a piece of plywood. 

Somehow.

It's difficult to explain how I intend to do this, but will be much easier to show it is use. I'll photograph the process and we shall see what happens.

The weights will be bolted to the blade necessitating two holes in the blade and these will be drilled over-size, filled with epoxy and the epoxy drilled to the correct size so that the edges of the wood of the blade are not exposed to water.

Should be a nice project.

But I think you see what I mean by "getting complicated".