Starting the planking

With the keel, transom and stem pretty much done, it’s time to move onto working out how the planking will work. This isn’t an easy job – each plank is a different width and shape, and all that has to be worked out early on.

Stage one was making little blocks the same width as the plank landings will be (that’s the overlapping section between each plank where the nails go). We did a rough calculation about how wide each plank should be for a start. But the plank widths vary – that’s because you need a narrower plank where the hull curves sharply, and wider planks where the curve is gentler. So the spacing of the planks starts off wider near the keel, and narrows further up. Plus we needed to allow for the optical illusion of the rubbing strakes at the sheer which will make the planks look narrower than they are. We tacked the blocks onto the centre mould to mark where the plank landings would be.

Once we had got it looking right at the centre section, we used a vanishing point board to work out the plank spacings at different sections on the boat.

Then it was just a matter of tacking battens on at each landing point. And for the first time we can see the actual outline of the boat. Pretty nice. Although we need to make some adjustments at the stem where the battens need to concertina up a little.

Nailing the battens on near the keel took a bit of effort…

Drilling the prop shaft hole

This has been just a little tricky! We have had to drill a hole, about 30mm diameter and 600mm long, right through the keel, to take the propeller shaft from inside the boat to the stern.

We thought long and hard about how to do it, and eventually came up with a three part plan. This video gives an idea of how we went about it.

The first thing was to drill a 10mm pilot hole. We welded a standard HSS drill bit onto a meter long length of rod, and fixed up a wooden jig to hold the drill in place. The supports would ensure it stayed roughly in line, but we couldn’t guarantee that the drill bit wouldn’t wander off course a little. We did a couple of test drills, and found that it came out about 3mm off where we intended. Not bad.

Then we fabricated another drill bit. This time it was two meters long, with a couple of cutting blades welded in the middle to make a bit that would drill a hole about 20mm diameter. We fed the end of the drill through the pilot hole, and adjusted its position so that it was in place. There was enough slack in the pilot hole to allow us to shift it to correct the inaccuracy in the pilot hole. Drilling was slow progress, mostly we think due to the problem of clearing waste material from the cutting blades.

Then we fabricated a third drill bit, same design as the second, but with cutting blades the right diameter to take the stern tube. This went through much more easily, and the stern tube fitted like a glove.

Nuts and bolts

Not a massive amount of visible progress,  but that doesn’t mean we haven’t been busy. The keel assembly is to be bolted together, but you can’t get the nuts and bolts we need off the shelf in B&Q. So we have had to buy bronze rod, cut it to length, and tap threads on to match.

Elsewhere we have used silicon bronze screws, and in a couple of places we have had to drill large diameter holes, and use a bit of threaded bar as a diy nut.

The transom is now cut to size, and screwed to the giant knee we made up. That’s not going anywhere in a hurry.

With all the keel parts shaped, it’s time to bolt them together, with everything braced to a ridge plank to keep it in one place. And it’s really satisfying seeing how tight the fit between the keel parts is.

That messy paint is aluminium primer – all the parts have already been painted with wood preservative, but we are also painting primer in the parts that will be hidden from view.

We’ve also had our resident boatbuilding guru Nigel Gray back in, this time giving us tips on the black art of cutting the groove in the stem where the planks will slot in. Anything you want to know about the difference between the bearding line and the rabbet line, you’re in the right place. Just ask Mick here, he was taking it all in…

The spine nearing completion

The central spine on Cygnet is nearly done. We’ve got the stem shaped roughly, the keel and hog are cut, there’s just the transom to finish off. We’d made it too small at first, so Martin has cut and glued an extra plank onto the top. Now we just need to cut it to shape.

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But that’s not as easy as it seems. Even though the plans have got a shape for the transom which we can copy, we’ve needed to allow it to be up to half an inch bigger all round so that when we fit the planks we can bevel them in to fit nicely. 

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Then we can temporarily clamp it in place to see if it fits and lines up with the other moulds. Plus we’ve decided to make the knee a bit beefier – that’s the piece that John is holding in place here. 

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So we cut an extra piece to make it larger, just need to join the two together now. 

Next job, picking up the engine – after checking that it runs properly first. More on that to come…

The stem starting to take shape

This is a really nice bit of the project – shaping massive chunks of oak into the components for the stem and keel. We’re using the bandsaw to transfer the shapes from the plywood templates for each part onto the pieces of oak plank. Can’t imagine what it must have been like doing this entirely with hand tools – maybe that’s one for the future, doing a boat build using only eighteenth century technology!

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Martin running a test on the bandsaw

One thing we weren’t sure about was how tight a curve the bandsaw can cut, so we did a test on a bit of scrap wood. Each part will have to fit together really tightly like a super-accurate home-made jigsaw puzzle in three dimensions, so it’s a fiddly job.

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Stem parts nearly finished

The of course the bandsaw blade snapped, so that put an end to the evening.

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Jerry John and Martin trying to work out whose fault it was…

Caption competition? Log on to this blog to tell us what you think was being said here…

Next time – cutting out the transom maybe?

Shaping the stem

We’re finally making actual bits of the actual boat, which makes a nice change from building ourselves a workshop which seems to have been taking weeks!

Work has started on the spine of the boat, from the stem and apron at the front, down the keel to the transom. These parts will all be made out of massive planks of oak that have been slowly seasoning in the main workshop.

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Norman and Poppy marking out the shape with carpet tacks

It starts with laying carpet tacks on the outline of each part on the full-size plans, then pressing a thin piece of plywood onto it. This is then cut out to make a template.

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John and Dave cutting the oak

Then we laid the templates on top of the oak to get the best fit and waste as little wood as possible. It’s a good plan to try to get the grain of the wood to follow any curves in the templates. And no, John hadn’t cut through all that oak with a handsaw, we used a handheld circular saw to get through most of it, it just couldn’t cut deep enough to get through the plank in one go.

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Rough cut stem parts with their templates

Next job, get the parts planed down to the right thickness and start cutting them out accurately.

What do we do about an engine?

 

Cygnet will be a traditional wooden motor launch, whose main job will be ferrying passengers and crew out to the Frederick Henry Swan once she is finished and on a fore-and-aft mooring on the Tyne.

And because she’s a proper boat, there won’t be an outboard engine, but an inboard one. This means that we need to think carefully about how we build this into our construction plans. Unlike an outboard, which you can sling on the transom at the end, an inboard engine is an integral part of the design.

This is a possible engine that we already have. Actually we have two of them, both in a condition that you can see Phil is delighted with!

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Phil worrying about the state of the engine

It’s a Stuart Turner P55M, which is a two-stroke twin cylinder petrol engine of 1930s design. It’s about 8HP, running at 1650rpm. But as you can see, it’s in really poor condition, is seized solid and would take a lot of work to restore. Plus, at 8HP it’s more powerful than we need for Cygnet.

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Restoration project?

An engine of that power needs a large propeller of around 12″ diameter, and there isn’t enough space in the existing design for one that big. So should we look for an alternative engine, and if so, what? Whatever we do, we need to move fast, because we can’t proceed very far with the build without knowing what engine will be installed.

Whatever engine we choose will drive a propellor via a prop shaft – and we will need some other bits and pieces to support the prop shaft and keep water out of the boat.

We will probably get these bits – stern gear, it’s called, from a firm called T. Norris who specialise in this sort of kit. They want to know what fitting the gearbox has – that’s something to check out when we decide on which engine to use.

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Stern gland from the coble Irene Patricia

Working backwards from the engine, the prop shaft will pass through something called a stern gland – it’s a bronze casing that contains grease-covered bits of rope that act as a bearing and seal the water out. That’s the theory. The prop shaft disappears into the wedge – see the previous post for details about that – and emerges via another bearing. The propeller fits on the end.

Another question – do we mount the engine directly onto the inside of the hull, probably resting of a couple of chunky bits of oak? Or do we fit some flexible engine mounts?

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Solid engine mounts on Irene Patricia

And how do we drill a hole, big enough for a 3/4″ prop shaft, into the wedge? That’s a seriously long hole, and it needs to be very accurately drilled. Our boatbuilding guru Nigel Gray already has some tips on drilling long accurate holes – more of that later.

 

Early Days

Jerry,
Good article, I’ve taken the liberty of moving your pictures up the article from the bottom and into the text. While the system is a bit clunky compared to FaceBook or Twitter it allows one to do a bit more than posting selfies!
After you have placed a picture, illustration or drawing you can move it about or resize it.
TBE

transom

Jerry,
Just a note on the bit about the transom – we do have a shape for it from the plans, it’s just that cutting it out is a job that we haven’t got round to yet – so it’s not quite right to say that we can’t work it out until later in the process.
Blog looks good with the pictures spread out through the story though.
M

M,
Oh but I think that’s exactly why we shouldn’t be cutting it to shape now. I recall Nigel G saying that it should be left until later…..
This sort of discussion is one of the reasons why a blog is so useful – wouldn’t you say?
J

Hi,
If you are sure of the method you are going to use to fit it to the sternpost go ahead. Remember that the bevel will have to be taken into account. I.e. the after or outboard face is the true shape. Also, you will need to decide if it will have horns to protect the plank ends.
Good luck!
N