Friday, 24 July 2020

Boom Gallows Tube Support Blocks | Making & Test Fit

The bottom end of the boom gallows tubing would rest on the locker floor inside the seatbacks, and would require strong support blocks of some kind.

I decided to experiment by making a test block, and see what happened.

The first task was to find suitable timber for the blocks.

I had some Ash left over from my first boatbuilding project, but it is a rough sawn board and needs a lot of work to make it useable.

I did however have a big piece of Kauri which I had been saving for years, thinking it would be good for making strong fittings for a boat!

It is - or rather was - a chopping board for the kitchen. Here it is.

As I said, it is made of Kauri which is a giant member of the pine family endemic to New Zealand.

It is very slow growing and has a very tight grain. It is knot free and easy to work. No surprise that it was logged to near extinction in the last century.

Kauri is legally protected and I would be amazed if you could find any now, but some years ago things were still being made of reclaimed boards or salvaged logs, and I'm guessing my chopping board is such an article.

This is its makers mark.

It was made in 1976, so it's well seasoned!

It is also ideal for making some tube support blocks.

First I made a cardboard pattern, like this.

To get the correct curve to fit over the fillet on the hull I found a plastic pot in my cupboard with exactly the right diameter. This is it.

There is always something in my cupboard which provides an exact profile for any curved edge!

Then I cut off a chunk of Kauri and shaped it into a test piece. Here it is.

And here it is in place on the locker floor.

 This looked like it would work, so I went ahead and made a pair of support blocks for installation. Here they are on the bench.

They fitted nicely but it was immediately obvious that they did not have sufficient depth to provide a steady support for the tubing.

I therefore doubled the depth of the blocks by 'laminating' another chunk of Kauri on top of them. It worked really well!

Here is the resulting support block test fitted on the port side.

The piece of dowel shows where the stainless steel tubing will fit. There is plenty of depth in this block to provide solid support for it.

And here is the other block on the starboard side.

These two-part fittings are held together with screws at this stage, but satisfied that this was the solution I took them apart and laminated them permanently with thickened epoxy.

Here they are glued up and curing.

The next challenge will be to drill a deep and perpendicular 25mm hole in their upper face using the pillar drill.

But for now I was pleased with progress.

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