Shaping The SCAMP Sailboat Rudder

I found that shaping the rudder was intimidating and more complex than the centreboard. This is the process I came up with.

rudder materialrudder material

The rudder blank before any markings. I had prepared a template of the cross section at the widest point. I had taped the plan on the window and traced the outline on light cardboard. I glued this to plywood and cut it on the bandsaw.

I had also marked on the template at half inch intervals, the amount of material I would be cutting down.

The template shows the profile and the full thickness of the rudder. I put a clear mark on the template where the half thickness point is. On the leading edge this was at the pointiest part and on the trailing edge it was on the middle of the flat end section.


marked up

I marked on the rudder a centerline and the depth of cut across the width and roughly where I expected the shallowest cut to end up. I also marked where I expected the leading, trailing and bottom edges to be. This gave me an idea of what the lower part of the rudder would look like and how the transitions would occur.

I also marked the the half point around the thickness of the blank using a felt marker.


shaping scamp rudder

Using a wood rasp I started cutting the leading edge slightly below the pivoting area at the top of the rudder.

I had cut my template in two where my marks showed no depth of cut. Or rather, it is just a fraction of a mm.


shaping

This process took a lot of time. I checked against my profile frequently and marked what needed to be cut with a pencil. At first I only cut about 6 inches wide until my template fit perfectly. The template is the full thickness of the board.


extending cut

Having an accurate profile, I put some pencil marks on it so I would not cut into it and went on to extend the cut downwards and upwards. I stopped shaping at about 8 inches from the bottom.

At the top I stopped shaping just before the curved line transferred from the plan. I will leave this part till I've made the top of the rudder assembly and decide how to finish shaping it.


rudder trailing edge

I followed the same procedure for the trailing edge. I made an accurate first cut across from where I had started on the leading edge of the Scamp rudder.

It took longer than the other side because there is more material to remove. I tried using a belt sander but it took so much material off so quickly that I was afraid to cut too much off, so I went back to the rasp.


rudder shaping

I also extended this line to about 8 inches from the bottom. Since the rudder blade curves quite a lot on the trailing edge, it is a bit harder to cut evenly. I still have to adjust the cut in the lower end.

I've been cutting slowly, checking as I go. The plywood lines are very useful but not completely accurate and I had a spot where there was a slight distortion even though the template showed accurate cutting. I think I had a spot of maybe higher glue or epoxy. It was only a fraction of a mm but still shows as a wavy line.


rudder shaping

I used my random orbital sander with a coarse paper to cut the lower part of the rudder and blend the leading edge and the trailing edge.


Scamp rudder

At this point the rudder is roughed in. The shape needs to be fine tuned and improved but it is getting close. I'll use the sander with a finer paper to do this.

I'm not claiming my shape is the best most accurate shape. I think the process is sound and can be used to make an accurate board. It's not difficult to shape the leading and trailing edges but the lower blending area take a bit of care.

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emails: Christine

This web site reflects my personal ideas and doesn't represent anyone else's point of view. I record the process I have followed and the result. I am not saying that it is the right or best way.