Two steps forward, one step back

“Optimist: Someone who figures that taking a step backward after taking a step forward is not a disaster, it’s a cha-cha.”
–Robert Brault

With all the bulkheads and assemblies on the building jig, it was time for the chine logs and sheer clamps.

20141105_150803Here, 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!


20141107_124027An assembled joint with spline visible


20141107_124120First handling of those crazy long whippy things


20141111_180147Chine 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.


20141112_171227Here, 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).


20141112_171142As in the rest of the assembly my approach has been to clamp – not too tight, to avoid glue starvation – and then hold in place with screws. However, all the screws come back out afterwards.


rupture4DISASTER! 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.


rupture2It 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.

The Great Leap Forward

I now feel bad having titled this post as I have – a flippant reference to one of the most disastrous and cruellest mistakes in human history may not be in the best possible taste! What I was trying to convey was that though all the work so far has been rather slow and without any obviously impressive results, I now suddenly have something that could be mistaken for an upside-down boat.

In my eagerness to get something put together, I made the aft half of the building jig first and assembled only the components for this section. These were the centreboard cases, bridge deck components, cockpit sides and all the associated bulkheads. Together these make a completely rigid standalone structure and constitute a significant part of the boat’s internal structure in terms of work. Because the building jig consists of a wide box section made on the CNC machine, I had the confidence that bolting on the forward section without being able to eye along it would still be accurate. I was then able to mount all the remaining bulkheads and the aprons. It was amazing how quick they were, compared with the components that had to fit together in advance. The final picture shows most of this complete, though bulkhead 2 was elsewhere temporarily.

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Aprons

The first all-solid components are the aprons – fore and aft. Thank God I didn’t have to make them by hand!

Douglas fir for fore and aft aprons

Douglas fir for fore and aft aprons

Clamping up blanks

Clamping up blanks

Clamping up machined sections

Clamping up machined sections

Everything has been shaped by the CNC – the chine logs and shear clamps, and well as the planking, should all land perfectly on these surface (notice ‘should’ rather than ‘will’!)

Clamps

How many times have I read that you can’t have too many clamps? Even with all the clamps from a furniture workshop, accumulated over 25 years, I could see that I would need rather more – if nothing else to avoid clamp wars!

Enter some rather splendid offerings by Urko. These are the best value clamps I have ever come across – sturdy steel construction, never slip along the bar, easy to use one-handed, weight just right, none of that horrible screwdriver grip handle nonsense – I could go on. 50 of these beauties at a very good price from Tilgear should come in very handy.

 

Building Jig

This is the first of a number of posts to bring me back up to date, as quite a lot has happened in the last month or so.

Not wanting to do anything quite ‘by the book’, my building jig is not altogether conventional and was not even built in one go, but it is essentially along the same lines as normal. As with the rest of the build, it was first planned on the computer:

buildingjig_screencapHere it is being planned with all the assemblies that will ultimately go on it


buildingjigAnd here it is on its own, ready to be exploded and programmed for cutting out on the CNC.


20141021_122622Machining the 18mm MDF that the jig is made from. I pondered this for ages, because it uses a shocking amount of material, but because we mostly use MDF for jigs, moulds, templates etc, most of this can be re-used once the boat has been finished – it is only screwed together.


20141021_122608A few finished components. The grooves you can see are locations for the uprights – a lot more accurate than relying on me let loose with a tape measure!


20141023_164218Half the building jig, with assemblies starting to go on (but that’s for next time…)

Note the adjustable feet, which were used in conjunction with a laser level to set everything up. The actual weight though is held by wooden feet screwed to the floor after eveything is levelled.