Friday, April 6, 2018

Working on the tiller

Its autumn here, but still unusually warm for this time of year.  Like summer would normally be, not that I'm complaining, its very nice weather and just about perfect for getting out in the smaller boats,

Back in the workshop I’m taking a break from the “big” parts of boatbuilding, spending a little time making up the smaller bits and pieces that will be needed when the boat itself has been completed.  The rudder and tiller assemblies are the current project, the tiller and its pivot being more complex than in a boat where the helmsperson can sit close enough to just hold a tiller that’s directly mounted on the rudder stock, means that there is a bit of fiddly work to do here.

So I went to a local aluminium window fabrication company, had a dig through their scrap bin and found a piece of box section, 65 x 65 inside, with 3mm walls. That’s easy to cut, just use the sawbench with its usual tungsten carbide blade but take it quietly and it cuts fine. I sliced it back to a channel shape, 50mm deep, and shaped the pivot head to take it. I cut  the curve on the end with the bandsaw, the blade on that is not a carbide one, but the hardened teeth handle the aly just fine.  A hint, if you do this sort of work, make sure you clean all of the aly chips off the saw before you go back to cutting wood, having metal chips in the surface of your fine woodwork doesn’t help things much.
I drilled the shaped channel for a hinge pin so the tiller can be lifted up slightly past 90 deg, and put all that in place temporarily so I could make up a “dummy” to guide the making of the tiller.

Found a piece of hardboard in my scrap pile, and yes that scrap pile is very useful at times, and clamped it into the aly hinge piece, sat in the boat with a sharpie pen, held my hand about where I’d want it, and drew the tiller shape.

 One of the issues here is that the tiller needs to be long enough for me to sit on the side seats just aft of midships, thats where my weight needs to be going upwind.  In a fine ended, relatively narrow boat like this proper crew weight distribution is helpful to the boats performance.  I'll be in the back corner by that bulkhead that you can see there when on long downwind runs.

The tiller template cut out, I've set the height of the "grip" end of the tiller so that my forearm is level, parallel with my thigh when I'm seated. Thats a comfort thing.  It is though long enough so that if I'm standing at the tiller I'll need to hinge it up as I walk across when tacking or gybing.

I refined that a little, cut the shape out on the bandsaw, clamped it back in place and sat in the boat with my hand on it to check how it felt.
It felt fine, so fine sitting at the helm  I had trouble stopping my dreams carrying me away, could have sat there daydreaming for far too long.

Next, time to make up the real thing.  When cutting thin veneers the saw loses about half of the wood in sawdust, that’s a bit sad but there is no other way, so half an hour later that three metre piece of 130 x 25 was split, and the 70mm wide piece converted into 3mm veneers, the Leuco blade leaving a finish very much ok for glueing.

Next job, a jig.  I grabbed an offcut piece of  melamine laminated particle board, the stuff that they make cheap furniture of, drew around the outline of my tiller template, masked that with packing tape and screwed my laminating clamp blocks along the line on one face of the shape.

Much gluing, using the same homemade epoxy spreader that I use instead of a paintbrush, I applied a very thin glue mix to each face of the laminates as I laid them up.  As there were 12 layers in this, thin ones because of the relatively sharp bend, I started off with only six.  Clamped them at one  end, and worked along with the clamps, pulling them in in sequence a little at a time until they were hard against the clamping blocks.

 Half the veneers glued up, 5 more to go.

Fast forward a day, and I took the part tiller off the jig, tidied it up with a plane, put it back on and glued the rest of the layers on using the same clamping process.

The last 5 on, doing 12 in one shot is fussy work, every piece is trying to escape, all slippery with epoxy and under tension, so I've done it in two stages, the first layup having enough pieces to stop any springback when the clamps come off, then next day, after a bit of a cleanup to take any lumps of glue off, the rest get coated and clamped on.

Next day, and if you’re doing this sort of laminating do give the glue plenty of time to cure as the layers will be doing their best to pop back straight again, it came off the jig, and it was time to attack it with the bandsaw, then the spokeshave and carve it to its finished shape.
With the “blank” off the jig, the first thing was to outline the shape with a pencil, then run it through the bandsaw to rough out the shape.  This wood is Mangeou, a soft but very tough New Zealand native wood, it saws and machines well but is a stinker to use a plane or spokeshave on as the shavings tend to jam the mouth of the plane.  So it was out with the angle grinder with the 40 grit sanding disk on and some delicate work, light with the pressure and steady strokes to get it shaped. I’ve gone for a horizontal oval shaped hand piece this time rather than a round one, it fits my hand well and provides a place for the tiller extension swivel to be mounted.

Rough shaped, in place, that looks ok to me.  I've still to make up the yoke that will connect the tiller to the yoke on the rudder head, thats a job for another day.

After the angle grinder it was time for the fine and finishing work, so the Shinto Rasp (  came into action, a great tool this one, one of those I don’t know how I managed without before Duckworks supplied mine.
From there its sandpaper, working down through the grits until its time for the  varnish.

 The tiller in close to its finished state and position, the pivot pin is a piece of 20mm stainless steel tube cut from a bent lifeline stanchion salvaged from a dumpster at the marina, thats a good place for useful stuff that I can recycle. 

Hinged up, the mizzen mast is back a bit from here so the tiller is not going to get mixed up with it, but its well out of the way of any activity while anchored.
The "new"plywood in the image is the beginnings of the anchor well, and no, I'm not planning to be up on the foredeck in any rough weather so its going back here, counterweighted by a big truck starter  battery up in the forward end of the boat that will run the radio, gps, nav lights and such. 

The rudder head and blade are coming up next, the rudder head is a bit unusual in that it is similar to the one on the Saturday Night Special in that it runs down past the boat bottom to the depth of the skeg and has an end plate so there is some steering even when the rudder blade is fully raised. On the SNS, the boat is able to be driven through very shallow water at high speed with the blade lifted, and for a boat that will be rowed or sailed into estuaries and over the mudflats this will be invaluable.

Once that’s done, it will be time to mount the tiller and rudder head then make up the yokes.  I’ve a chunk of 6mm aly plate ready to cut up for that. My Swedish steel bandsaw blade with its hardened teeth will save me hours with a hacksaw. Watch this space.

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