Stems

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!

20150309_111507

Blocks glued together to form half the stem, ready for shaping

20150309_111516

Outer shape machined on, plus locator holes for gluing the two mirrored halves together

20150309_112231

Two halves temporarily together to test fit

20150309_125429

20150309_124354

Laminating jigs for gluing on curved laminations (one stem, one stern)

 

20150309_160943

Laminating

20150310_145941

Final machining of half stem

Sheathing

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:

  1. Starting a generous 5 inches to one side of the centreline, on the bottom, the first width was draped over the opposite chine.
  2. This was trimmed approximately to the waterline (plus a bit more each end to make sure the chine was still generously spanned).
  3. A second width started a few inches inside the chine, on the bottom, and draped over the chine down to the sheer.
  4. This was trimmed to the sheer.
  5. 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.
  6. This first side then received two further epoxy coats plus a microballoon/epoxy coat, each applied just as the previous layer gelled.
  7. 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.

20141212_140548

First width, not yet trimmed to waterline

20141212_143938

Second width being laid

20150109_124221

Frist side wetted out – peel ply is just visible in keel area which must eventually receive a second layer

20150109_124208

For subsequent coats we put polythene on the floor – doh!

Chines

Procrastination is my sin.
It brings me naught but sorrow.
I know that I should stop it.
In fact, I will — tomorrow.
–Gloria Pitzer

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.

20141204_173758I 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.20141204_173812


20141208_143040When 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


20141208_161849The 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.
20141208_162405

20141208_162414


20141208_103119While 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.