A little light metal work

Hey, I’m excited. I’ve had two like and one comment to the blog. Thanks for the like patmcf and the like and comments from saxisgood. Saxisgood is one of the most loyal of the readers¹ and can be relied on to make comments. Thanks for you both – please keep it up. ²

Anyway, this has excited me so much that I’ve just had to burst into print but a few days after my last post.

In the last couple of days I’ve given up woodwork, gluing, filling , fairing etc³and have fallen back on an old favourite – metalwork.

And it concerns the centre board⁴ pivot.

The centre board is set in a slot in the bottom of the boat and is held loosely in the boat by a rod passing through a hole in the board. This rod is glued across the slot so that, as the board is pivoted about this rod, more (or less) of the board sticks out of the bottom of the boat. Now any self respecting engineer would know that this is guaranteed to make the board wobble. A better mechanical solution would be to have the rod stuck to the board and to pivot it by having a bearing surface at each end, running in bearings glued to the boat. But no, sail boats don’t follow this logic. The rod is fixed and the bearing surface is the hole in the centre board. It’s a very short bearing surface (25mm max) so is quite highly loaded and the board wobbles . Having a stainless steel rod passing through a wooden centre board won’t last long, so two stainless steel trunnions have to be glued into the centreboard.

The piece on the left is one “trunnion”

Here’s where the metal work comes in. I had to hand a piece of 3 mm stainless steel. Cutting these pieces out posed a problem. A hacksaw would take too long, the angle grinder would probably do it but would also take some time and make a lot of sparks. How about the jig saw – I had used one several years go to cut up two Triumph Herald rust buckets to make one slightly less rusty car which my son drove around for a year or so- so I knew they could cut thin metal – how about this stuff. I found some “special” blades for stainless steel, held the sheet firmly with a couple of G gramps, spread oil liberally along the cut line and, with the jig saw to as slow a cut sped as possible, got to work.

The noise was appalling, smoke and oil went everywhere but the special blade did the job – it took about 10 minutes to cut each shape. Then the corners had to rounded off and the burrs removed using the angle grinder and that was it.

All I have to do now is glue them in place and cover the board with glass fibre cloth ………

Wish me luck for next week.

Notes

1. Now at the grand total of 3 in any one day – so much for making a living with this!
2. The making comments, that is.
3. Only temporarily, you understand.
4. Just in case you don’t know what a centreboard is, it’s a large flat (or aerofoil) board that replaces a fixed keel in a proper yacht. Keels (and centre boards) stick out below the boat to provide some lateral grip in the water so that by clever resolution of forces at different angles lets the boat sail at an angle towards the wind, and it does it without the benefit of software – isn’t that clever?