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Iron Bark

Iron Bark
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  • Brazil and Beyond
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11 July, 2016

Planked up!

It's about six weeks since I last wrote - time is a precious commodity when building a boat on your own, especially when you are as slow as I am.  If you want to see what's happening more regularly, I try to update weekly on the Junk Rig Association Technical Forum under various headings.  The latest info can be found here.

Anyway, here is a 'photo essay' of the past few week's work.

As time went by, it became increasingly difficult to find anything to clamp to.  The bilge board cases were a useful exception to this rule!

The plywood on the bilge panels, overlapped the bottom of the boat.  It was getting a bit difficult to line the next one up, as I got further forward, so I got out the power planer and trimmed the surplus wood back.  This machine scares the wits out of me - it's so easy to cause serious damage with it, but I'm getting a little more confident with it.

I decided to fit the panels outboard of the bilge board cases separately.  After all, it was framed all round, so they would be well secured.  Shaping a partial scarph was tricky, but I've been lent a beautiful chisel which helped me get it accurate.

Most of the bilge board case is now closed in.  Underneath the piece under the clamp there is a completely enclosed space, with, presently, no access.  In theory, there is no need ever to access this space: all the plywood and cedar are heavily coated with epoxy resin, but I will probably fit a small hatch, just so that I can check that nothing untoward is going on.

Towards the bow there is too much shape to plank up with 12mm panels.  The 6mm that I used are almost full sheets - 1200 x 2500mm - and a bit of a handful.  But at least they are not particularly heavy, unlike the 12mm, which are really at my limits for lugging about.  A sheet of plywood, on edge, comes up to my shoulders, so lifting them around can be a problem.  Even the 6mm was a real pain to fit - on, off, on, off - so it was a relief to find that I could use the piece from one side as a pattern for the other.  I'm actually rather proud of this because it means the hull is symmetrical.

This was a particularly tricky sheet to fit on my own.  I used Bruno's pegs to locate it along the bottom and put a couple of clamps on the bulkheads to rest it on, until I could climb up onto a saw horse and get a couple of screws in.

Here is the first sheet of 6mm plywood fitted.  It is notched about two-thirds of the way along.  This is because as the chine flattens, the scarph would end up excessively wide where it meets the side panel.  Marcus, from the SibLim Club - a qualified boatbuilder - helped me with this part of the job.  He did in 3 hours what would probably have taken me 3 weeks - and undoubtedly did it a lot better, too.

Here I am precoating the plywood, before fitting the next sheet of plywood.  You can clearly see the inside of the sleeping cabin here. 

This is the photo of the forward end of the sleeping cabin.  I love the appearance of the kauri panelling. 

Shaping the final piece of plywood to fit at the bow.  I have bought a couple of Japanese pull saws and find them a lot easier to use than Western style.  They are so fast that I often use one instead of a jigsaw.  The one in the photo has a wonderfully flexible blade which also allows me to use it along curves, too.  When I use a jigsaw, I invariably have to plane the wood afterwards, but not with one of these hand saws.

This photo is taken with the camera lying back down on the strong back, looking up into the bow.  This will, of course, be the bottom when the boat is right side up.  I cleaned it up as well as I could, but once the boat is turned over, I shall pour epoxy thickened with high-density filler, into the very bottom of the boat to seal any voids and leave a smooth surface.  This very forward section of the bow will be empty.  Again, I shall probably fit an access hatch so that I can check that there are no issues over the years.

I had hoped to staple the two layers of 6mm ply together, but when I attempted to fit them, the twist of the bow was forcing the middle of the sheet away from the one below.  In the end, I had to screw from the middle diagonally up and down to get it flat.  The boat looks like a sieve and, very disappointingly, the screw points have gone through the coating on the inside.  Once she's turned over, it will have to be sanded and coated again.  However, there was not alternative solution and at least I'm sure the two sheets of ply are securely joined.

For once the gods smiled and the offcut from the full sheet fitted - just - the triangle left at the top.  By now I'd given up worrying about holes through the inside layer!

I am getting a lot better about using my power plane: here I'm making the scarph on the final sheet of 6 mm plywood.  The trouble with being an apprentice boatbuilder is by the time you are comfortable with a new skill, you don't need it any more!  (Although I dare say there will be one or two scarphs in the deck.)

The two final bow pieces: one precoated.  Precoating the plywood before putting the thickened epoxy on it might seem painfully pedantic, but the okoume (gaboon) plywood sometimes soaks up epoxy like blotting paper.  I'd rather waste some from drips than spend the rest of my life worrying that there are areas where there was insufficient glue to make a good bond.

And there we are: one completely closed-in hull.  I am very proud of what I have achieved and very pleased that it looks so symmetrical.  I just love that junk bow!

One of the reasons that I wanted to avoid screws was because all those holes need filling.  When the plywood is horizontal, it's not too much of an issue: you can make a fairly soft mix and force it in to the hole, but on a steep slope it's more difficult.  Too soft and it will drain out, too thick and it may not get to the bottom of the holes.  In the end I decided to use wooden pegs - trunells - and found large matches to be ideal.  As they are square in section, air can escape while you tap them in.  Dip in a thin slurry of epoxy and microfibres and stick them in the holes.  One swipe of my little saw knocks them off once the glue is cured.  I intended to recycle them, but the bits of glue still stuck on got in the way and even I can afford another box of matches!!

This is a photo as at yesterday.  You can see that all the overhanging ply has been trimmed off and I am longboarding the chines to get them sharp and fair.  Then they will be rounded over, ready for bi-axial glass tape, before the whole hull is faired.

In the meantime, the keel has been taking shape.  It consists of three layers of 50mm steel.  It is a special alloy, used for bridges and decorative steelwork, with additives to reduce corrosion.  Supposedly it is guaranteed for 50 years!  Long enough for me.  Murray Wilkinson, who owns Norsand, where I'm building SibLim, arranged to purchase the steel and then, even more obligingly, organised getting them cut to shape. 

The pieces of steel returned from being cut.  One of them has a distinct twist in the tail.

My friend Marcus wanted to make the pattern for the forward end of the keel, having very strong opinions as to how it should be shaped!  He thicknessed pine to the same depth as the steel, glued it up and then screwed the three layers together.  He then carefully shaped it all as one piece.  Once he was happy with it, it was unscrewed and handed to Kevin and Anton as a pattern.  It will also be used for me to help shape the deadwood along the bottom of the boat, to which the keel will be attached.

Anton picked up the steel and drove it around to the half round workshop where it was to be shaped.

It was tacked together and then Anton went to work shaping the bow, with Kevin checking that all the details were to his satisfaction.

Anton applied heat about a metre away from the after end of the twisted piece and cajoled it into place.  I hate working with metal, myself, but have a huge amount of admiration for people who can get big chunks of the stuff to do their bidding!

As you can see, the three pieces are now in perfect alignment.

The forward end was shaped carefully and Anton came back and marked again for a final finish.  More careful work with the grinder produced a smooth and fair leading edge.

A big hollow in the middle layer of the side had been worked over: a bit of filling with weld and a lot of grinding removed it altogether.