Saturday 13 June 2020

Carlins & Sheerclamps | Installation

Satisfied that everything fitted properly I prepared to glue the carlins and sheerclamps permanently in place.

It didn't take long to realise that applying glue to the sheerclamp before fitting it was not going to work. It is just not practical.

The sensible way to apply the thickened epoxy would be to do it with the sheerclamp already in place.

A friction fit secures the sheerclamp when it is sprung into the slot in bulkhead 2. This holds the length in the cabin firmly against the topsides, and leaves a wide gap between the piece and the topsides in the bow section.

So it would be easy to glue the length in the bow section, but the length in the cabin would have to be prised away from the side a little to allow the joint be glued.

Before starting the glue up, I decided to use temporary screws to hold the sheerclamp in place in the cabin section. I found previously when gluing the cockpit deck support cleats to the hull sides that friction held the frames in place during the dry fit, but they slipped all over the place when buttered up with thickened epoxy and I had to hurriedly fit a lot of temporary screws.

So I drilled for three temporary screws in the cabin, and started the glue up on the port sheerclamp.

First an old screwdriver was used to open a gap in the cabin section, as here.

I gathered up all the clamps I possessed, and the drill driver.

Then thickened epoxy resin was squeezed into the joint from a pastry bag dispenser. The screwdriver was removed, and clamps applied working forwards from the rear cabin wall.

This is what the port sheerclamp looked like after installation.

You need a lot of clamps to do this effectively!

Here is a temporary screw, stopping the sheerclamp from springing or sliding out of place.

I didn't have enough clamps to install both sides at once, so I left the port side to cure for 24 hours before using the same clamps to fit the starboard sheerclamp.

Here is a view of the starboard side.

Proving the truth of the adage 'you can never have too many clamps', I used twelve G cramps and 30 spring clamps. They did a great job!

I agonised about how much the sheerclamps should protrude above the topside panels.

About half an inch is needed in the cabin to allow the sheerclamp to be planed down to accept the curve of the cabin roof, and the same again forward of bulkhead 2 for a foot or so to accept the tops of the Dorade boxes. The notches in bulkhead 2 make this obvious and easy in the cabin, but what do we do at the bow?

Should the sheerclamp finish flush with the top edge of the topsides, or should the 1/2" protrusion continue all the way to the stem?

The photos in the build manual offer no help - their quality is too poor, as is often the case. And the text makes no recommendation.

Looking at other builders' blogs I seemed to find both approaches being taken, although it is hard to tell from photos alone.

In the end I decided to fit the sheerclamps to finish flush with the topsides at the stem, as here.

The curve from the bulkhead to the stem is very slight, so it should provide enough material to round over for the Dorade boxes while still looking graceful towards the bow.

The only thing I was a little worried about was whether there would be enough room below the sheerclamp to fit the bowsprit, where some of the topside has to be cut away at the stem.

Naturally, I didn't think about this until after the event when it was too late to do anything about it. However a quick look at the drawings showed the depth of the bowsprit at the stem is 2 1/2". A check with a rule showed that this would be a perfect fit!

So all was well. Here is a view from the bow of both sheerclamps installed.

The blue tape is covering a stout wire stitch which is preventing the join between the topside panels from cracking further, and you can see the gap at the front of the port sheerclamp which I will fill with an offcut.

Finally I glued in the carlins, as here.

That's it - job done!

Friday 12 June 2020

Carlins & Sheerclamps | Making & Test Fits

While the fibreglass cloth and tape were curing I retrieved the stock for the carlins and sheerclamps from the woodrack and made a plan of attack. The carlins would be easy but the sheerclamps would require a fair bit of bending into place, which made me slightly nervous.

The first task was to put a rounded edge on the parts.

I used my router and a 3/8" bearing-guided round-over cutter. I thought about setting up the router table but decided it was a lot of effort for quite a quick job. So I clamped the pieces to a temporary bench set up outside, and ran the router along the workpieces.

Here I am rounding over both bottom edges of the carlins.

And here I am rounding over the bottom edge of the sheerclamps, visible in the cabin and the forward deck.

When I checked the manual I noted that it says to use a 1/4" round-over. I don't know why, because all the other round-overs on stringers and frames in the hull are 3/8". So I'm happy with that. They all match.

A check with a piece of scrap cleat material showed that the slots in bulkhead 2 were too tight for the sheerclamps, as predicted by the build manual. They were partially blocked with fillet material. So, I cleaned them out with a small Saburr carbide burr in the Dremel and a couple of sharp files. Here are the tools.

And here is the slot in the starboard side of bulkhead 2, after clean up.

There is now plenty of room for the sheerclamp to be inserted.

Now for the carlins. First I marked out the correct angle on the carlins where they sit against the rear cabin wall, using a bevel. Like this.

I then cut and test fitted the carlins by holding them in place with a small, temporary screw. Just to make sure that everything fitted properly. As here.

I then shaped the rear end of the port sheerclamp so that it would sit snugly against the rear wall of the cabin.

First I marked out and cut the angled face, making sure the sheerclamp was the right way up!

Then I marked out and shaped the curve on the end of the sheerclamp to sit up against the fillet. I used my Shinto saw rasp - it's ideal for this sort of thing. I used a filleting tool to mark out the curve.

That went well.

Then I carefully measured the length of the sheerclamp inside the hull, and measured the angle for the bevel at the bow. And cut it.

Here is the port sheerclamp  clamped in place, for its dry fit.

The observant reader will immediately notice that the bevel is perfect, but the sheerclamp is 1/2" too short … so much for careful measurement! No matter. A small piece of the offcut will fill that gap later.

I then followed the same process when making and fitting the starboard sheerclamp, except this time I cut it to the correct length. Here it is.

So far so good.

But there was some drama along the way.

Part way through fitting the port sheerclamp there was a loud bang, and a puff of dust at the bow. I thought the stock had snapped, but all seemed well so I put it out of my mind and carried on.

However, while fitting the starboard sheerclamp it became obvious what had happened.

I hadn't bothered to put a proper fillet between the topsides panels where they meet at the bow, reasoning that they will be cut away later when the bowsprit is installed and they don't need a permanent joint.

Instead I filled the outside of the join only, with a sort of tack weld. Except I didn't use fresh epoxy - I used some partly cured squeeze-out from some fillets.

Big mistake. This is what happened when that join was strained by the sheerclamps.

You can see that it didn't hold - there's a crack in the joint with the top half of the port topside panel. The bottom half of the joint is fine, where it is held together by a strong fillet inside the hull.

It doesn't matter - I will put an extra-strong wire stitch in there to hold it while gluing in the sheerclamps, and I will refresh the external epoxy joint before moving on.

But … Note To Self: Do not re-use squeezed-out epoxy! It has started to go off and it does not penetrate into or bond surfaces! It will fail under load!

OK. Lesson learned and no real harm done.

And lastly, I finally decided that the temporary screws holding the carlins in place were a waste of time and replaced them with bronze wood screws, as decreed by the build manual.

Here is one in place.

Now, any woodworker will tell you that it is heresy to drive a screw into end grain, which is exactly what we are doing here. It will not hold under load, having nothing to grip into.

But in this instance the carlins will be fastened with epoxy and once it's cured the screws will be largely irrelevant, so I guess it's OK. Once again I remind myself that we are building a boat - not a piano.

So one 1 1/2" 8 gauge silicone bronze countersunk wood screw now holds each carlin firmly in place.

My final task in this episode was to sand the forward deck and topsides to a smooth, matt finish with the edges of the fibreglass cloth feathered out and invisible. Here is what it looks like now, sanded to a P80 finish.

Next we will permanently install the sheerclamps, and after that we will add further layers of fibreglass cloth to the forward deck. It has to be really strong.

Onwards and upwards!

Forward Deck, Topsides & Rear Cabin Wall | Fibreglass

The time had come to lay down fibreglass cloth on the forward deck and to cover the seam between the hull sides and topsides with a strip of heavyweight fibreglass tape.

I learned a lot about laying down fibreglass cloth when covering the inside of the bottom hull panels. A paper pattern is the key. In this instance the challenge was very much simpler, with there being just one panel of cloth on the forward deck.

First I layed the cloth out on a broad, flat surface. Here we have three picnic tables side by side.

A wall paper brush is ideal for smoothing out the cloth. My rough hands just snag on the weave.

Next I layed the paper pattern on the cloth, and weighted it down so the pattern and the cloth can't move. In this case the weights are stuffed chicken door stops, which did a great job on the hull panels. They were pleased to be recalled for service.

Next we take a marker pen and a ruler, and mark out the outline of the panel around the pattern with closely spaced dots. I didn't have enough paper to include the overlaps in the pattern, so I just measured them out with the rule on each side, as here.

Then I cut the cloth with a sharp pair of scissors, cutting just inside the marks. In this way we get an accurately cut panel even if the cloth deforms while being cut. If you follow the marks, you cut the correct shape!

Here it is being cut out.

The panel is then laid out on the forward deck and smoothed into place with the brush, like this.

Finally the cloth is wetted out with clear epoxy resin. I used a disposable foam roller, and a laminating brush to poke the corners into place, as here.

Work outwards with the roller from the centre of the panel, and up the overlaps onto the topsides and the bulkhead. That way the cloth doesn't move out of position.

Here is the wetted out panel on the forward deck.

The next task is to cover the seam between the topsides and side panels with very strong fibreglass tape, to strengthen the join.

Again, the lengths of tape are fixed in place by wetting out with clear resin applied with a roller.

Here is the tape in the cabin, on the port side.

And here is the tape in the cockpit, on the port side. While I was at it I coated the inside of what will become the seatbacks with resin.

The final task was to apply tape over the fillet between the rear cabin wall and the cockpit deck, as in this photo.

That's it with the fibreglass for now! Next up is installing the sheerclamps, which promises to be something of a challenge.

Wednesday 3 June 2020

Rear Cabin Wall, Seatback Supports & Topsides | Fillets

When the tack welds were fully cured I pulled all the stitches and prepared to apply fillets to the joints.

Now, any readers of earlier posts here will know that epoxy fillets are my nemesis and I can never summon up any measure of enthusiasm for working on them. Other than for finishing them and moving on to something more satisfying.

But based on my previous experience I now have a method and an armoury for tackling the dreaded epoxy resin fillet. This is how it goes:

Use blue tape to mark out fillets on flat surfaces

No amount of freehand work will yield a neat finish on a very slightly curved surface, such as the topside to side panel joint.

It will just look like a child has been playing with mud pies. Use blue tape to get neat edges, and lots of it.

Don't expect the first application to leave a smooth finish

The wood flour fillet mixture has to be quite thick for it to stick to the surface of the hull, and hoping for a miracle during application isn't going to have a happy ending.

The epoxy will cure with a rough and spiky surface, like cast concrete, and that is just the way it is.

A thinner mixture is much easier to work with, but it sags and falls off vertical surfaces and that is not the way to go.

Use industrial abrasive finishers to dress the rough fillet

These include carbide burrs and abrasive wheels used in a corded or cordless drill to rapidly remove the rough surface and achieve a good profile.

I call this dressing the fillet.

Sand dressed fillets to a good surface

A dressed fillet can be sanded to a reasonably good surface, either by hand or with a finishing sander. Use a P80 grit.

Apply a coat of fillet mix as a fairing compound

Apply a coat of thinnish wood flour fillet mixture to the fillet, effectively as a fairing compound, and let it cure completely.

Sand to a good finish

It is possible to achieve a good, smooth surface to the fillet by sanding, again either by hand or with a finishing sander and using a P80 grit.

This will be good enough for the application of fibreglass cloth, and after two or three coats of clear resin have been applied to the cloth and sanded the fillet will be invisible.

But if a truly smooth surface is required for e.g. a paint finish, then apply some fairing compound made from glass micro balloons (use the phenol variety below the water line) and sand by hand to as fine a finish as you wish. I have finished fillets to a P220 grit for paint in this way, and they look great.

So … that's a long winded way of saying that I'm not going to bore the reader with a long catalogue of photos of the interminable and tedious making of fillets.

If you have a look at earlier posts you will see all of the above activities in action. Instead, here are some selected highlights to show you what I mean.

This is a fillet on the forward deck being dressed with a carbide burr and a small but powerful corded drill.

And here are the forward deck fillets after sanding, fairing, and final sanding by hand and the finishing sander.

These fillets will be covered with fibreglass cloth sometime soon.

Here is the taped out starboard topside join in the cockpit, ready for fillets to be applied.

And here is the fillet between the rear cabin wall and the cockpit deck, being dressed with a Spiraband abrasive wheel and a cordless drill.

And this is the same fillet, after fairing and sanding with the finishing sander. It's now ready for the application of heavy duty fibreglass tape.

And last but not least, a reward for the boatbuilder after two days of purgatory, sanding fillets ...


Tuesday 2 June 2020

Rear Cabin Wall, Seatback Supports & Topsides | Installation

With the cockpit deck installed I could move on to the upper hull assembly, which was very exciting!

I wired in the seatback supports and the rear cabin wall, having lifted the angle for the wall from the drawings.

In this picture we see the angle of the cabin wall being checked with a bevel, and the supports held upright by spring clamps.

I first installed the cabin wall with just three wires along the bottom, to make sure that it fitted correctly.

When satisfied I put in stitches to the deck at six inch intervals - six in each side and one in the middle.

I quickly found that a really sharp 3mm bit is required to drill holes for the wires. I started off with a dull bit which tore out the plywood under the deck where it had been coated with epoxy and was too hard to drill through easily. A new bit quickly solved the problem.

Here is a view of the stitches from inside the cabin.

I managed to get a really nice edge-to-edge join on both panels, and it was a good stiff fit.

Next I wired in the topsides panels.

This is the wire stitching toolkit. A supply of premade stitches and a selection of pliers ...

… and a drill with sharp 3mm bits, and a sharp bradawl to mark out the holes for accurate drilling.

You will note that the bit in the drill chuck is extra long. It will drill holes up to 80mm deep, and I got it specifically to drill the holes in the forward deck area where we have to drill at 45 degrees through the sides and sheerclamps and up through the deck to take the very long stitches required to secure the topsides at the bow.

The port topsides panel went in easily enough. Here it is viewed from the bow.

And here is the starboard panel going in.

Here is a view of both sides from the bow.

And another view from starboard, looking forwards.

In just a few hours PocketShip had changed dramatically! As so often with this build, weeks and even months go by without any visible change and then overnight ... hey presto! It really is a boat after all!

Next came tack welding of the topsides and the seatback supports.

The supports at frame 6 were riding a little high off the deck and needed to be pulled down tight against it before tack welds were applied. The build manual suggests using a hot glue gun for temporary positioning of components, so I tried that.

All went well until I applied the tack welds. The epoxy softened the glue and it let go, and the supports sprang up from the deck again. Oh no!

I quickly needed some means of pulling the topsides together at frame 6, but I don't have any clamps long enough to span the hull. But I do have some steel sash cramps which can be bolted together to make them really, really long.

So I rapidly measured the breadth of the hull and assembled a pair of sash cramps accordingly, and deployed them. As follows.

That worked just fine, and is what I should have done in the first place. Hot glue - whatever next?!

I tack welded the topsides and side panels together at the same time, carefully avoiding the joint with the rear cabin wall in case it needed to be tuned.

Accordingly, with the topsides in place and welds cured I made a quick test fit of the seat backs. This is what I found.

You can immediately see a gap at the bottom of the seatback, caused by the cabin wall being at too acute an angle.

It was clear that the wall needs to sit on top of the deck, and not meet it edge-to-edge as I had first thought. This would move the bottom of the wall back half an inch or so.

So I pulled the stitches and rewired the wall in the correct position. All was well.

I then tack welded the cabin wall in place, and poured a glass of something cold to celebrate.

Next up, it's fillets … whoopee!