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.

Seatback Blocking | Stanchion Holes

The seatback blocking was all installed, levelled and flattened. The next step was to make sure the stern blocking was ready for the boom gallows stanchions, which are 25mm stainless steel and will require very strong support blocks.

First, we have to bore a 25mm hole through the blocking at the stern of the boat. The exact position of this hole is not obvious in the build manual or the drawings, so I decided where it would go myself.

I marked in the centre of the hole 11.5cm from the transom skirt. This looks about right.

I used my UJK drill guide to bore perfectly perpendicular holes. I purchased this last year with just this sort of task in mind.

It is very difficult to drill a perfectly vertical hole by hand, and it is impossible to make large holes in this way.

But with a really good drill guide it is achievable.

First I set up the drill guide on the port seatback, fitted with a 25mm Forstner bit. Here it is.

I did the set up without the drill fitted, so that it was easier to manoeuvre. The base plate is secured to the blocking with a woodscrew, to hold it in place.

And here it is in place on the starboard side, with the drill fitted.

I used a level across the base plate to make sure it was level, like this.

Boring the holes was straightforward, but I think I will try the small corded Bosch drill next time.

This cordless DeWalt drill is very big and makes the drill guide top heavy and a bit hard to handle.

My small Bosch cordless drill isn't powerful enough for this, but I think its corded counterpart would be. We will have a test run at some point.

Anyway, I successfully drilled both holes port and starboard. They are very clean cut and perfectly perpendicular.

Here is the hole in the port seatback.

Very nice!

The next task is to install some sort of block on the floor of the seatback locker to receive the bottom end of the stanchion. That looked like it might be quite 'challenging'!

Seatbacks | Test Fitting

It was time to do a proper test fit of the seatbacks, to make sure they were ready to install when required.

First, now that the locker openings had been cut out, I made a quick fit to check that they look OK. They did.

Next I marked out where the temporary screws would be required to hold the seatbacks in place, and drilled all the holes.

I used 3.5mm screws, which are the right size for use on the relatively skinny stringers. I assembled a box of screws with plywood washers, and got out the drill driver.

Here is the starboard seatback, screwed in place.

I didn't use screws along the bottom edge. The screws driven into the seatback support frames hold the bottom in place very nicely, and a heavy weight closes any small gaps.

I'm happy with that.

The port seatback was a good fit too, as here.

Looking good!

Seatback Lockers | Gluing Flanges & Cutting Out

I would soon be fitting the seatbacks so needed to have them ready. Not much work was required and it was an easy background task.

First I glued the locker opening flanges in place, simply weighting them down on the bench, as here.

When cured I cleaned them up and cut out the locker openings. I used a Japanese keyhole saw which I purchased for making holes for inspection ports and portholes. Here it is in use.

Cleaning up the edges was quick and easy using a saw rasp and a Spiraband abrasive wheel in the drill, like this.

Finally, the edges were finished off in the vice.

That's it! All ready for a test fitting.

Upper Breast Hook | Installation

The upper breast hook needed some slight trimming to obtain a good fit, but it was pretty much good to go as it was. 

When happy that it was ready to install I drilled screw holes in the sheerclamp, with a deep bored countersink so I could plug the holes later. This was not for aesthetic reasons, but because I thought I would need to round over the edge at some stage and did not want to hit a screw head with the router bit.

I used a router to bore the holes, with a drill and countersink bit to cut holes for plugs at the same time. Here is the bit.

And here is one of the holes which it bored.

You can see how it has bored a deep countersink to accept a wooden plug.

Next I clamped the breast hook in place so I could mark where the pilot holes would be. Like this.

The breast hook must be very closely aligned to the sheerclamp, which means that the pilot holes for the screws must be very accurately marked and drilled.

Previous experience told me that using the bradawl would not be suitable. The slender point cannot be accurately centred in the screw holes.

Nor did I wish to place a screw in each hole and tap it with a hammer. This would dislodge the breasthook, even if only slightly, and the pilot holes would be in the wrong place.

I recalled that I had seen the solution to this problem on television some time ago, and Googled it to see if it was available. It was! It's called a Marxman and this is what it looks like.

You put the nozzle in the hole, and lightly press the base. It squirts a dry jet of fluorescent pigment through the screw hole and onto the surface to be drilled, exactly marking it out!

A quick trip to the local hardware store, and problem solved.

Pilot holes were drilled and the breast hook was test fitted, as here.

I have only one screwdriver which exactly fits the countersunk bronze wood screws which I am using. Here it is.

This tool once belonged to my grandfather. It is date stamped 1939, so it's been around a long while! It is also stamped with the 'broad arrow' mark of British ordnance, which means that it was Crown property and most likely used in military service. I always wonder about its history when I use it.

Happy with the fit I glued and screwed the upper breast hook in place and left it to cure, as here.

The forward deck looks a lot more neat and tidy now!

Seatback Blocking | Fitting & Levelling

With the transom skirt permanently installed and the upper stringers now fixed in place, it was time to install the blocking in the seatback tops. The blocking will receive hardware fittings later in the build.

The pieces of blocking had long since cured and had been made ready for shaping. It remained to bevel them to fit tightly between the sheerclamp and the upper stringer in each seatback.

To achieve this I made a cardboard pattern for the top face of each piece of blocking. Here are the patterns for the two pieces which will carry spinnaker sheet blocks on the starboard side, either side of the seatback frame support at bulkhead 7.

There is a distinct curve to the inside and outside edges of these pieces. It is very slight but it has to be taken into account when shaping the blocking. If they were fitted with straight edges the stringers would be deformed.

The angles are taken off the sheerclamp and upper stringer with a bevel gauge, and marked up on the blocking. The bevels are then made on the sides of the blocking pieces using a variety of tools. Wood rasps and saw rasps were especially useful.

Here are the two pieces of spinnaker blocking test fitted on the port seatback.

I had no idea where the spinnaker blocks would end up being fitted, so I asked for ideas on the PocketShip forum.

The labels show where two builders told me to put it. One said 26 inches from the cabin wall, and the other said 55 inches from the stern. You can see that there is a big difference!

I guess the simple answer is that it doesn't matter too much where it goes ... and it will be some time yet before we have to worry about that.

When I had obtained a good fit on all the pieces of blocking I glued them in place, held with temporary screws.

I fitted them with about 5mm raised above the seatback, to allow for flattening and levelling.

Here the port spinnaker blocking is being levelled off.

I am using planes and chisels to rough them out at this stage.

This is the blocking at the stern on the starboard side being levelled and flattened out.

I am using a Japanese  saw rasp to flatten out the blocking, and the orbital sander to finish it off with P80 grit.

Here are the spinnaker blocking pieces on the port side, levelled and finished.

And here they are on the starboard side.

You can see the holes where temporary screws held them in place during installation.

It is very important that the rearmost piece of blocking at the stern is absolutely flat, both across the seat back and fore and aft.

This is because it will be bored to receive the 25mm steel tube for the boom gallows, and a stanchion support fitting will be fitted on top of the seatback to hold the tube in place.

Each tube must be perfectly perpendicular to the seatback, and in line with its counterpart on the opposite side of the boat.

So I spent a lot of time fussing here, to make sure it was as flat as I could make it.

The result was this.

The bubble in the level is exactly in the middle, as it should be. Hooray!

Finally, as a last check that everything was as good as it could be, I laid my longest level across the boat at the stern. Like this.

To my great satisfaction (not to mention relief), the bubble was again right where it should be. In the middle of the glass!

What a result!

Wednesday 15 July 2020

Transom Skirt | Installation

The time had come to install the transom skirt - another milestone event! Once the skirt is permanently in place I can complete the seatbacks.

This was a straightforward exercise. I taped the joints inside and out to minimise any mess.

First I mixed up a small quantity of thickened epoxy glue and coated the faces of the transom skirt support blocks, and the ends of the upper stringers and transom cleats.

Then I fastened the transom skirt in place with temporary screws, and mixed up a batch of fillet mixture with wood flour.

I used a pastry bag to dispense the fillet mix, filling the open join between the skirt and the transom. It took a lot of mix to fill it - two doses from my measuring cups, which is over 150mll.

This is what the installed skirt looks like from astern.

And here is the view from inside the boat.

There was very little squeeze out from the inside joint - it is a very good join and fit.

I will leave everything to cure fully, and then sand and shape the external fillet.

We are really moving along nicely now!

Seatback Frame | Transom Cleat Installation

I mentioned in a previous post that I decided to fit cleats on the transom to receive the rear edge of the seatback panels.

Just relying on a skinny epoxy fillet joint here would not be satisfactory.

I made the cleats from some scrap Ash left over from the floorboards. They were quite fiddly and time consuming, each edge being bevelled, but it was worth it to know the panels will have a secure landing.

Here is the starboard cleat glued and clamped in place.

And this is the port cleat, similarly secured.

I will clean them up nicely when they are cured.

Seatback Panels | Marking Up

I would soon need to glue the seatback locker flanges to the panels, and cut the openings.

I wanted to make sure they were in the right place, but there are no dimensions to follow. As usual!

So I decided where to locate the opening by eyeballing various options until it looked right. I settled on a position where the flanges are 6cm from the seatback support and 6cm from the bottom edge of the panel.

I had already marked in the location of the cleats, supports and stringers on each panel to help me do this, and then I marked in the openings.

Here I am holding the locker flange in place with a heavy weight on the port panel while I pencil in the opening.

That's that done!

Transom Skirt | Test Fit

I had never really believed that fitting the transom skirt would be as easy as the build manual suggests.

In the manual the skirt is simply bent into place and fastened to the transom skirt support blocks with temporary screws.

There is no recommendation on how to achieve this without eight hands or several helpers, and a large dose of luck.

One try at bending it 'freestyle' confirmed my suspicions, and I moved straight on to my contingency plan of fitting temporary support blocks to hold the skirt in place when fitting it.

I fitted three wedges (port, centre, starboard) with bevelled tops to match the slope of the transom skirt.

A test fit went without any difficulties. Here is a view from inside the boat.

The edge-to-edge fit with the top of the transom is not perfect, but is certainly adequate for a strong filleted joint.

Here is the port support wedge, with a sliver of daylight visible through the joint.

One advantage of having the upper stringer temporarily held in place is that it can be tuned before final fixing.

Here I have shimmed it to get its alignment with the sheerclamp as good as it can be.

Here is the test-fitted skirt viewed from astern.

I was pretty pleased with this result, but closer inspection the following day showed that the fit could be made just a little better, so I removed the skirt and refitted it.

You probably can't tell the difference in this photo, but this is the improved fit seen from inside the boat.

As mentioned, I was able to get a good fit for the upper stringer by tuning it a little, as this view of a level across the port seatback shows.

The bubble is smack in the middle - result!

Seatback Frame | Cabin Wall Sister Cleats

In a previous post I mentioned that the seatback support cleats on the rear cabin wall were not substantial enough, and would need to be sistered.

It was a straightforward task. I made each sister cleat in two parts, partly because I had some short lengths of scrap cleat material and partly because I would not have to scrap a whole cleat if I messed up a bevel.

Here is the starboard sister cleat in place.

And here is the port sister cleat.

Now we have a really strong and wide ledge for the seatback panels to land on. Much better!