Sunday, 28 June 2015

Chainplates

My chainplates arrived during the week, so I set about attaching them. The mob I bought them from, classic boat supplies, were out of 1/4" countersunk bolts so I substituted 5/16" ones. Anyway, these puppies aren't going anywhere.

They go under the outer gunwale, in a slot machined specially for them. I drilled three 8mm holes through the hull on 45mm centres, and passed the bolts straight through. I even polished up the bolt heads. They're beautiful castings, and solid as a rock.

At this point in the plank there's a doubler under the hull, so it's 12mm thick rather than 6mm. To spread the load a little I machined up some 2.4mm thick bronze plates to go on the inside, so the hull is clamped between chunks of bronze and the bolts can't possibly tear through. If the load is big enough to take the chainplate out, quite a bit of hull is going with it.

Now that the detail is sorted for the gunwales, I epoxied them in place. I put a bunch of clamps on in addition to the screws to ensure there's no gaps.

Here's a photo showing a lash-up of my proposed shroud attachment. The holes in my chainplates are big enough that I think I can do away with deadeyes or blocks on the bottom, and just use the chainplate as a deadeye directly. I run a 6mm line up through a little Harken 29mm double "carbo" block, which weighs nothing and has no metal in it. I can splice the end of the shroud directly to the block. Here I've just tied it to a length of 4mm braided rope.

The other end of the 6mm line goes aft to a 100mm bronze cleat. This is probably massive overkill, but I have a bunch of these kicking around having decided to go for bigger ones in the spots I bought these ones for (halyards and mooring lines).

In any case, playing with it here it was really easy to set up and adjust the shroud tension. I imagine it will make stepping the mast quick and easy, and plan on doing exactly the same setup for the bobstay.

Saturday, 20 June 2015

Finished the decks.

Over the weekend I put the last couple of deck pieces on, at the bow on the starboard side. After gluing the front piece down, I cut a hole in it so I can access the anchor well and added a little bronze flange as a scupper for the anchor well.

This is only on the starboard side. There's nothing on the port side, so I'm a little concerned that Poseidon will notice Elena only has one eye and will sink us for bad Feng Shui. If I obsess too much about it, I've got another bit of bronze to add a scupper to the other side.

Mogget's taken residence in the anchor well, as expected.

The gunnels are held on with screws at 480mm centres. I haven't glued them down yet, as I'm waiting on chainplates, which will be sandwiched between gunnel and hull, so I need to make a slot in the gunnels to clear the chainplates. I think I'll skip the rubbing strip at the bottom of the top plank. I think it looks nice with just the gunnel, and am happy to carry fenders to protect the paint from docks etc.

I've been doing a bit of bronze work of late, turning a pin for the mast pivot and finishing out the centerboard lifting tackle. The lifting tackle consists of a sheave on a 6.35mm stainless pivot, with a couple of bronze plates and some more stainless to make a becket. I added 4mm stainless countersunk screws to the end of the pivot to locate it in the centerboard. These are thus far the only metric fasteners on the boat.

I've got a high zoot-factor Ronstan "orbit" 40mm double pulley up the front, with a dyneema lashing holding it to a nice old fashioned bronze eye. The mix of extremely traditional and extremely high-tech pleases the perv in me.

I really like this dyneema/spectre UHMW rope, by the way. Really like. I'm going to use it for all my standing rigging, so there will be no yucky wire.

Friday, 12 June 2015

Gunnels

If you've been following for any period of time you may have noticed I have a thing for Jarrah. Jarrah is a dense, rich, red west Australian timber, that's practically indestructable and looks really beautiful. I've done my transom in Jarrah, I've done my rowing thwart in Jarrah, and I'm using it in my mast. I really love the stuff, because it's quintessentially WA.

So, Gunnels. What better timber to mount your guns to than a length of lovely strong rich Jarrah. Easy! Off I went and bought some lengths, in 19x40, reasonably close to the 20x40 recommended by the erstwhile John Welsford.

Did I mention that Jarrah is tough, and dense, and strong? Oh, I already did, didn't I. Well, you can add stiff to that. I joined bits to make a 5m long length and tried bending it onto the boat. No way!

That prompted a week or so in the moaning chair

So then after I got over myself I tried with some Jarrah of slightly less heroic proportions - some 12x30 that I've bought for the mast. Easy peasy, but it looked a little wimpy.

The hardest bit was the stern, doing the upwards bend, not the inwards bend at the bow. Stiffness increases with the third power of depth, so the change from 40 to 30mm dramatically influences the stiffness. So I knocked my 19x40 down to 16x32, and tried again. Bloody hard work, but it went. Here's a photo of the first test-fit. I have to cut the bow end nicely and wait for more goop to arrive before I put it on properly.

Here's the join - knocking the length down from 19x40 to 16x32 made my join all but disappear.

I'm rather happy with that.

Sunday, 7 June 2015

Daydreaming

I'm vaguely thinking of what to do after I finish Elena. Somewhere in there is building a house for Perry and I to live in, and then once that's done I'd very much like to build a boat to seriously sail in. Elena has me all fired up on wooden boats, so I'm looking around at possible designs for a 26-30 foot cabin cruiser. Not a fast boat, but rather something we could sail around Australia in or even cross the Tasman.

Like I said, daydreaming.

A boat that ticks a whole lot of the boxes is the Herreschoff H28, a design that's stood the test of time and is much beloved by those who build and sail them.

As it's quite an old design, some of the plan details are actually available on the web. Most notably the offsets, which detail the shape of the hull in three dimensions. I've spent some time over the last couple of weeks transcribing the offsets onto the computer, converting them to metric, and then using sketchup to loft a 3D model from them. Here's a few views of my model thus far. As with Elena, I hope to use this model to try things out, like interior accommodations etc.

Edit: Here's a view of the working that I used to loft this design. I started by drawing the cross shaped former, which I put on it's own layer so I could easily turn it on and off. Then I made a moveable "frame former" on which I can draw frames. I have lines at the station points on the initial piece, and move it around to draw the various lines from the offsets. In each case I move the former so that either a horizontal or vertical surface is where I need it, and rule offsets onto that. Then I use the 3 point arc tool to connect offsets and make fair curves, effectively interpolating between the offsets. Some mucking about is needed to ensure everything is fair.

Once the specified lines are drawn, I then slide the frame former to various points and draw smooth frames, by selecting the points where the lines intersect my former, again using the 3 point arc tool to interpolate between lines.

The frame lines now give me more points so that I can interpolate more WL+n lines. I do this every 4", or 101.6mm.

Finally the really tedious bit is drawing a huge pile of triangles to sheet the hull. Once the lines are drawn, they get selected, then the properties changed to smooth the hull over them. You can see I started with a 101.6mm grid at the bow, but got sick of it about 1/3rd of the way along the hull and swapped to a 203.2mm grid.