If a picture is worth a thousand words, how many words is a movie worth?
As with the rest of the build, I spent a while planning exactly how the boat would be turned over. In his notes that accompany the plans, Iain Oughtred suggested that the lead keel ‘may’ be attached before turnover, but that this will ‘make the turnover more interesting’. This wonderful piece of understatement certainly rang true, and resulted in a spectacular piece of over-engineering on my part. With nearly half a ton of lead fixed to the bottom, I certainly didn’t want the turn to become too interesting, and besides, there was not enough space to let the boat roll over across the room, however strong we were feeling, so it had to happen with the boat staying in the same area.
The first thing was to build some gantries, with which I could lift the boat clear of the jig (and which also came in useful earlier when doing the keel). I also designed two big wheels to encircle the boat, both to have something to lift it by, and also to provide an easy way to turn it over. The wheels were made in sections so that the lower halves could be attached when the boat was lifted and the building jig removed. Each wheel then sat in a trough, complete with plywood rollers. The gantries and wheels were all made of 15mm spruce ply, and proved extremely satisfactory.
“If at first you don’t succeed, try, try again.
Then quit. There’s no point in being a damn fool about it.”
My original idea was to cast the keel using a section of steel and a combined crucible and mould – see this post
I managed to find a suitable offcut of steel quite cheaply, sandblasted it and painted it inside with stove paint. I then embarked on the great melt:
Sadly, the two gas burners I had were woefully inadequate and would melt no more than localised puddles of lead, so I ended up listening to the combined voices of reason and friends and called in the professionals in the form of Irons Brothers. The result was excellent and far better than I could ever have achieved. Apart from accurately cast and pre-drilled components, I also benefited from being able to have small percentage if antimony in the lead which makes it much harder – useful, I thought, considering all the grounding the boat will encounter.
One of the problems with making the lead so hard was that it simply refused to conform to the shape of the boat. Using ordinary soft lead, I imagine the keel would almost flop into shape under its own weight, but not this stuff! Once again I was in the fortunate position of having the furniture workshop to call upon, and having made some moulds, put the lead pieces in the veneer press and let rip with maximum pressure. They never stood a chance!
Hoisting the keel sections onto the boat was tricky, but nothing a borrowed engine hoist couldn’t manage. The actual lifting when up on the hull was achieved with some home-made gantries (of which more later) and some Ebay-tastic chain hoists.
After months of wasted time with aborted castings, waiting for proper castings, sourcing bronze bolts, assembling lifting gear, researching bedding compounds etc, the day finally arrived when the keel would finally be fixed in position.
I went of silicon bronze bolts, nuts and washers (at vast expense).
I opted for a polysulphide bedding compound called Arbokol 2150. It certainly looks the part, and can only hope its efficacy compensates for its nasty smell and its tendency to go everywhere whilst trying to apply it!
It made an excellent bed for the lead to sit on. After the bolts were installed I covered the heads in the keel with more Arbokol. Not sure if this is standard practice, but it made sense as an added barrier to water. If the bolts ever need taking out, this extra bedding compound should dig out easily enough.
Fairing the lead into the rest of the ‘keel’ was genuinely fun. We first used a belt sander with 80 grit paper, but soon discovered that it was actually easier to use a plane. It was truly weird to see slivers of shiny metal coming out of a plane with very little effort or, seemingly, too much blunting effect:
Interestingly, Iain Oughtred specifies ‘softwood’ for the stem and stern. My instinct was to use a hardwood, especially when I think of all the things I have bumped into in my time! However, he did expand on this, and suggested that the extra give of softwood was an advantage, and if I did smash the stem up too much, it could always be replaced. Besides, they are quite chunky, so a weight saving is probably in order. So, I went for Douglas fir.
As ever, trusty CNC came in handy. I decided on a construction where pieces were butted together with epoxy, and then the outermost 20mm or so was laminated. This means that the butt-jointed pieces are permanently sandwiched between the outer lamination and the apron (when glued to the hull) – they ain’t going nowhere!
Another catch-up post – the sheathing was actually completed a few weeks ago. Maybe it has just taken me this long to recover from the trauma in order to write about it!
Iain doesn’t actually mention sheathing in the plans or notes, except to say that the ballast keel may be laid on a double layer of 10oz glass. However I know from my communications with him that sheathing is a good idea if the boat is made of okoume ply instead of a denser and more durable species. I instinctively prefer the idea anyway – I have seen plenty of marine ply self-destruct when exposed to the elements, so I find the idea of a great thick epoxy layer very reassuring. And this is really the intention of this kind if sheathing: the glass is there mainly to provide a robust method of holding a thicker layer of epoxy in place than would otherwise be possible. From what I gather, if all you want is more stiffness and/or strength, you would be better off adding more plywood rather than glass. (There is a very interesting chapter entitled “Believe it or not, wood is best” in Dave Gerr’s excellent book “The Nature of Boats“.)
Initially therefore had no real idea of what cloth to use. I got a steer from Robert Ayliffe (of Norwalk Island Sharpies) via Iain, who suggested 400gsm biaxial. The two problems with this were that a) I couldn’t find any, and b) I was concerned that it sounded a tad heavy. I also agonised over whether to follow Reuel Parker’s writings and use xynole. It is not available in the UK, and I could not discover whether the available alternatives were as good – or indeed if he is still a xynole fan. In the end I stuck with the safe and popular option of glass, and went for the next lightest cloth to 400gsm that I could find, which was 320gsm biaxial.
The way I laid it was as follows:
- Starting a generous 5 inches to one side of the centreline, on the bottom, the first width was draped over the opposite chine.
- This was trimmed approximately to the waterline (plus a bit more each end to make sure the chine was still generously spanned).
- A second width started a few inches inside the chine, on the bottom, and draped over the chine down to the sheer.
- This was trimmed to the sheer.
- Both these overlapping layers were wetted out at once, with peel ply on the 10 inch width that will eventually be occupied by the keel.
- This first side then received two further epoxy coats plus a microballoon/epoxy coat, each applied just as the previous layer gelled.
- After the first side had completely set and the peel ply was removed from the keel zone, the whole process was repeated on the other side (though without peel ply this time).
The idea was to make sure that the keel area ended up with two layers of glass, as well as the chines (which were already taped, so now have a total of 3 layers). As a bonus, the topsides will actually have a double layer below the waterline, but most of this second layer was really only there to make sure the chines had their double layer.
Procrastination is my sin.
It brings me naught but sorrow.
I know that I should stop it.
In fact, I will — tomorrow.
Dear oh dear – I must apologise once again to both my readers for having taken so long to update things here. Though progress has been dogged by real life repeatedly barging in, there is in fact quite a bit of progress to report. The trouble is, once you put off writing these updates, the harder it is to get round to doing them.
The first decision after attaching the bottom was how to treat the chines. I had nothing much to go on, but could immediately see that they were a part of the boat that needed protection. The intention always was to sheathe the hull, but it was also clear that the chines were in danger of being a) too sharp to lay glass around and b) of such soft material (okoume) to make the sheathing vulnerable to cracking in the case of even minor impacts.
I therefore decided to rout away about 12mm x 12mm from the corner and replace it with epoxy thickened with high density filler. In the event I ran out of high density filler about half way back, but the standard colloidal silica made a perfectly hard substitute.
When hardened, this was then rounded over with a radius of around 10mm – 12mm. Because the angle of the chine averages about 113°, I could not find a router cutter to do this, so reverted to the real old school technology of a scratch stock
The next step was to cover the chines with glass tape. I am very conscious that Haiku needs to be built lightly, so there was no question of having a really heavy build-up of glass-epoxy, but with the chines I wanted as many layers as possible, and initially at least this tape to span, secure and reinforce the hardened edges. The way I would subsequently sheathe the rest of the hull would mean that the chines would get another two layers of 320g glass. Because of this further glassing to follow, I used peel ply for the taping operation.
While working on the chines, I also took the opportunity to rout out and replace with thickened epoxy these edges of the centreboard cases just below the pivot points. The idea is to provide waterproof areas into which I can rout some recesses, which in turn will accommodate UHMWPE guide strips to keep the centreboards snug while raising and lowering them. For anyone new to UHMWPE, it is an amazing plastic – just a form of polythene so quite cheap, but exceptionally wear resistant and very low friction.
An open goal here – surely there is some ‘bottom’ joke to put in to liven up the blog? However, I think I’m too wrapped up in boat-building to think of one.
The bottom went on in two layers but, as with the sides, each layer was scarphed into a single piece before fitting. Probably not strictly necessary with the type of joints I am doing, but I offset them between the layers.
All glued up. Again, mostly done with temporary screws, but with some clamping assistance. I had planned to vacuum bag it on, but I would have been using a sheet of polythene on the top only, relying on the first layer of ply to complete the vacuum. Unfortunately, a test showed that the ply is too porous to establish a decent vacuum, so to make it work I would have needed to seal the first layer from underneath – either with epoxy or polythene. The prospect of grovelling under the hull to do either did not appeal.
The second layer seemed to take gallons of glue. We coated both surfaces with unthickened epoxy first, then applied a generous amount of thickened to the installed layer. I thought it looked like too much glue at one point, but it proved to be just right – we had just enough squeeze-out (at the edges and the predrilled screwholes) to give confidence of a good join, but no more.
There was an article on the BBC website the other day about whether a bottom can constitute a work of art – well, I think I have proved the point! (Sorry – couldn’t resist it in the end.)
Here is a shot of the forward apron during the dry run. When cutting the sides to shape, I had relied on Rhino (the CAD software I use) to convert the 3D part to a 2D shape, and then added an extra 50mm all round – or so I thought. Because the ply is somewhat tortured each end, I couldn’t treat the side as a developable surface and simply ask Rhino to unroll it – instead I had to use its ‘smash’ command. This is not a command I normally use, so you might have thought I would read the instructions. Perhaps if I had, I would have seen that this does not automatically result in a correct shape in all directions. In this case I lost the curvature at each end, so far from ending up with 50mm spare, I ended up with absolutely nothing at all! It was sheer dumb luck that it was not too short.
The second side followed without incident, though as with the first we had to get it very accurately placed to avoid running out of ply each end.
“Optimist: Someone who figures that taking a step backward after taking a step forward is not a disaster, it’s a cha-cha.”
With all the bulkheads and assemblies on the building jig, it was time for the chine logs and sheer clamps.
Here, wide boards of Douglas fir are being scarphed on the CNC. I have used a 1 in 12 angle as I did with the plywood. In addition there is a very shallow groove for a spline to stop the pieces slipping during glue-up. The wide boards were then ripped to width before gluing because I can’t get 30 foot lengths through our saw!
Chine logs in. In section these end up as a rhombus with 40mm sides. The plans say you ‘may’ make them up as two thinner layers. I’m extremely glad I did, even using Douglas fir. Who wants a fight to the death with a piece of wood? It’s certainly not how I’m used to working. Heaven knows what it would be like if using mahogany. This picture shows the first layer of the chine logs glued in.
Here, the first of the sheer clamps is installed. In contrast to the chine logs, these are installed whole. Being only 25mm thick, this is not unreasonable and indeed the bending forces were not too bad – though again, I would not have fancied it with a stiff hardwood. However, we did find that to make them land successfully at stem and stern, a good deal of twist had to be applied – more than you could do without mechanical assistance (in the form of a clamp attached to the end to act as a lever).
DISASTER! Everything clamped up fine, and I spent about an hour admiring our handiwork and thinking about next steps, before locking up and going home. Everything was OK when I left, but coming in next morning I was greeted with this sight – the sheer clamp had broken in two places. Somehow it had just given up the struggle in the small hours.
It has got me slightly worried that there is something wrong with the Douglas fir I bought, but testing samples of it to destruction – not very scientifically, I admit – suggests it is just as strong as I would expect. Maybe it was all to do with the twist rather than the bend.
It has been well said of Barnaby Scott by those who enjoy his close acquaintance that if there is one quality more than another that distinguishes him, it is his ability to keep the lip stiff and upper and make the best of things. Though crushed to earth, as the expression is, he rises again – not absolutely in mid-season form, perhaps, but perkier than you would expect and with an eye alert for silver linings. (With apologies to Wodehouse, P.G.)
There being not much else for it, we pressed on and removed the offending item before fitting both new ones as double layers like the chines. They now seem solid as a rock and no hint of further trouble.