The rudder blade of my scow is made from a plywood blank intended for the rudder of an Enterprise dinghy and is about 15mm thick.

Considering how much smaller (in area) the scow rudder is, 12mm thickness is probably sufficient and this is what is shown in this drawing. There is nothing to stop you from using, say, one 6mm and one 9mm blank to give you a 15mm blade.

The rudder blade should be rounded at the front and the thickness tapered at the back - down to maybe 4mm at the trailing edge.

At the front of the rudder blade, the 'step' rests against the rudder stock and two doublers are installed to strengthen this point. The attachment for the shock cord (always a vulnerable point of a rudder blade) uses this strong area. A 12mm diameter hole is drilled through the rudder blade under the doublers to take the knot on the end of the shock cord, and a 6mm diameter hole is drilled down through the centre of the blade to lead the shock cord in.

The rudder stock cheeks are made from 9mm ply. This is quite strong enough for this size of rudder, but doesn't give much bury for the screws of the pintle/gudgeon arms, so I added 9mm doublers under the arms of these fittings to give 18mm bury.

The rudder stock spacers have total thickness 3mm greater than the thickness of the rudder blade - this gives a working clearance that allows, for example, for the epoxy coating on these parts. It is much easier to pack one side of the rudder blade with some thin material, than to deal with a tight fit! If you make the rudder thicker than 12mm, combine 6mm and 9mm ply to give you the same clearance.

I used a M12 (1/2") bolt for the rudder pivot that was sufficiently long so that most of the bolt in the cheeks and through the blade was not threaded. Whilst this meant I had to cut off the excess threaded part for neatness, it avoided having much thread trying to dig into the blade or cheeks.

For a bit of vanity, I wanted a curved tiller on my boat and this drawing shows how it was made. The end result was massively over-strong and heavy - instead of the four 9mm ply thicknesses shown, I recommend you use three laminations and make it a bit narrower if you make a similar tiller.

The drawing shows how to lay out the jig, made from a piece of 70x44 (3"x2") softwood, that will press the laminations of ply into the curved shape. Keeping the layers of ply in line with each other isn't easy. so I pinned them to each other at one end (in the 343mm straight length), before clamping them in the jig.

In case it's not obvious to you, don't pin the pieces together at both ends, or you won't be able to bend them!

I spent a long while with a plane and angle grinder changing the cross section of the tiller from a rectangle at the ruder stock to a circular section at the hand grip end. This effort was well worth it - holding the tiller is an absolute pleasure. I also fitted a short tiller extension which turned out to be a complete waste of time and just gets in the way. However I am over 100kg (220lb), so I don't have to move around the scow much to balance it - lighter sailors may need it so they can 'sit out'.

The tiller shown in the drawing has a slot that a projection of the rudder stock spacers pass through, and the tiller is secured to the rudder stock by two bolts that pass through the joint. This was also a bit of a waste of time - doing it again, I would work out some way of building the rudder stock and tiller in one piece.