Wednesday, 15 July 2020

Seatback Frame | Making & Test Fit

It was now time to fit the seatback stringers and sheerclamps, so we can fit the seatback panels and tops to add some bulk to the sides of the cockpit in PocketShip.

The first thing to do is to put a bevel on the lower stringer in line with the sloping seatback supports.

The manual says to use a table saw, with the table set to cut a 72 degree bevel.

I don't have room for one, so as usual I planed the lower stringers to the required angle, like this. 



I used a marking gauge to cut a line for the correct bevel, and the block plane to make it. It didn't take long with a sharp plane iron.

Now, this part of the build requires a temporary seatback support to be made and held in place near the transom to support the upper stringers where they run out of the back of the boat.

They will remain supported by this temporary support until the transom skirt is installed, when they will be fastened to the inside face of the skirt.

This should be interesting! The first thing I did was to make a cardboard pattern for the support.

Here I am lifting the profile of the side and topside panel just in front of the transom.



I don't know what it's called but this thing is very useful for taking off curved and angled profiles.

Then I sprung the lower stringer in place on the cockpit deck to get a fair curve, and marked where the inside edge of the stringer should be when held in place by the temporary support.



A bit of tape does the job.

I then made the cardboard pattern. This is what it looked like, propped in place.



It would require something stiff and strong to hold the upper and lower stringers in place during installation.

Coincidentally, my PocketShip kit contained a 'spare' pair of seatback supports, for the support at bulkhead 8.

When I discovered this I wondered at the time if they would come in useful for the temporary supports, and they did. It's obviously an error, but a useful one!

Here is the pattern laid on top of one of the surplus supports.



Perfect! I merely needed to trim the ply to match the pattern, and I had a pair of temporary supports!

Here is the port temporary support held in place with some tape.



That took care of support at the stern, but what about support for the frame at the other end?

We are required to fit a small piece of ply called a seatback frame support on the rear cabin wall, level with the seatback top.

This is when I realised, as I had long suspected, that the big fat fillet that joins the cabin wall to the the topside panel is very much in the way of doing this!

So the only option available is to remove as much of the fillet as is necessary to be able to fit the frame support. Previous experience had taught me that a sharp chisel and a mallet are ideal for such work, and I soon chopped out a home for the support piece. As here.



The pencil lines show where the top and bottom of the frame support should fit.

And here is the troublesome seatback frame support, clamped in place for a test fit.



So far, so good! The time had come to test fit the various pieces of the seatback frame.

Here we see the upper and lower stringers held by the inboard face of the supports, and the sheerclamp at the top of the outboard face.



You can also see the cleat on the rear cabin wall which will support the forward edge of the seatback panel.

The sheerclamp is clamped in place, and the upper stringer is held firmly in place with temporary screws driven into the extra cleat material on the seatback supports.

The lower stringer is held in place on the deck with temporary screws in the middle two compartments. I tried using short screws which did not go through the deck but they did not hold, so I reluctantly had to use longer and stronger screws driven through the decking. I will just have to live with a bit more tidying up to do when I paint the underside of the deck later on in the build. At the stern I refused to drive screws through the deck in the sealed compartment where I would be unable to fill the holes, and was happy to find that the temporary support held it securely in a nice, fair curve.

I had also decided that a small cleat was required on the transom to accept the rear edge of the seatback panel. You can see a piece of Ash propped in place, not yet cut to size. The manual does not stipulate this but it's not much extra work to be sure that the seatback is properly supported at the transom.

That took care of the port side of the boat, so next I did the whole thing again on the starboard side. Like this.



So, all sorted and ready to go ahead with the installation!

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