Being stern about future directions

Sorry about this but mind is on the boat just now, in particular, the stern.

1. Rudder

As I build the stern, certain problems raise their heads.  This is where Ivan and I may disagree.  He and my mate, both engineers, believe one should have a blueprint and stick to it, that the integrity of the item is compromised by changes along the way.

I would say that that is so unless the designer is also the builder and has designed choice into it.  

That is, when it comes to it in situ – stand there in the bowels and have a good look about, feel the boat sailing in your mind, see that this needs to be 12cm this way, that needs to be under, not over that – that sort of thing. Remeasure, think for an hour, try various combinations and then decide on which one you’re going to be able to live with best.

This is so with the rudder.  I’m already locked into two sheets of 22″ x 3/4″ x whatever length ply, laminated into 1.5″ overall thickness.  For my sized boat and only 520 sq ft of sail, that’s strong enough.  If it’s not, if I lose the rudder at sea, then I steer by sails to get into shore and think again.  The rig allows steering by sails alone. I’ve done it before.

First of all, the hinges were the problem.  Stainless were hideously expensive and too weak for me – most ship’s chandlers cater for modern boats and they’re seriously mickey mouse. They’d bend.

However, I found an ironmonger who does these for gates:

Black-Hook-amp-Band-Hinges-457mm_500_3KTGO

If I have three of these, along with a pin preventer that stops the rudder jumping out, then there’s only one sash and pin constantly under water. When in harbour, remove the preventer and the rudder comes off, sitting up now lower sash on middle pin, middle sash on upper pin, out of the water. In a canal, I might even use the outboard only and not run the rudder at all, sitting it on its side beside the walkway at the stern.

Before laminating, I’ve chiselled a gap on each board for the sash and epoxied the wood, let it dry and harden and then, when the halves go together, I’ll have been careful to keep extra glue away from the routed area, i.e. the sash is only held in by the stainless bolts and can slide out when unbolted.

Eventually I’ll need to replace the lower pin and maybe even the sash.

2. Steering mechanism

There are two traditional choices – tiller and wheel. I like tiller, preferring it for its firm control but it’s going to have to be 8′ long and that’s a lot of wood to be moving around, plus, looking at it yesterday, it prevents point 3 below and has a very narrow sweep angle for the rudder.

Plus it kills off the walkway down the rear deck, plus I want my stempost high at the stern and that doesn’t allow a tiller. Damn. So it has to be the wheel, I suppose.

First thought was what about a horizontal wheel? That is, I could operate it with my leg, leaving hands free.

Then I went back a couple of centuries and looked at the whipstaff. I don’t like it acting directly on a tiller or having to use an extra servo but what if there were wings on the rudder [quite possible with a round-sterned boat] and lines led from those along to the covered cockpit, where this is in place:

whipstaff

First off – no one and I mean no one has this mechanism. So it must be c***, yes?

I can’t see how.

A Whipstaff lever
B Lever faced with lignnum vitae down low
C Lines back to rudder, through holes
D Slot in stick for knotted line to slide
E Fulcrum

The box is 8″ high, easy enough to step over and doubling as a first buffer for wash into cabin. Being just a stick, returned to upright by shockcord either side, it’s easy to step around.

The key is the gap in the stick where the line is knotted either side As the lever is pushed sideways, the knots want to climb up the stick and can – along the slot. When they reach the end, this limits the span of the lever and sweep of the rudder. Rule of thumb is 30 degrees is more than enough either side for rudders.

In linear terms – 12″ either side of centre for the lever, which happens to be the width of the companionway – 24″.

It can be operated seated or standing. It takes a sheet and shockcord tied opposite ways for rudimentary self-steering. This is a well used technique by cruisers, not mine.

But the thing I like most is that the line runs along either side of the aft deck central walkway, openly. I don’t like steering cables hidden below. I want to see my steering cables at all times, running through eyes and replaceable at a moment’s notice, without having to rummage below. To hell with aesthetics on this, I’m afraid.

Broadening this point, I strongly dislike lack of access. From the narrowing of the bow to the rounded stern, I have to be able to get into the guts of it with natural light. The number of guys I’ve seen in engine compartments and they were working half blind – sorry, no thanks.

For sailors, the motion is like this – pushing the lever starboard pulls on the port rudder cable. This moves the boat to port or upwind. I thought about reversing that but if you sail, you know that on, say, port tack, pushing away on a tiller is the natural way for a boat to go up to port. The whipstaff would work that way. My natural reaction is always to push away when wanting to head upwind, so the whipstaff is best configured that same way.

3. A nice spin-off to the stern arrangement is that, from the hatchway from my cabin, looking aft towards the rudder, there are two walls with door gaps which have closable shutters, at 43″ from each other. So, in following seas, either or both of those can be closed off.

Sitting behind the last of these is the outboard, the fuel tank and the generator [latter two in their own compartments]. Fire would have to get through that wall, then consume the rear deck and then get through a second wall before reaching the third wall which contains the hatch into the innards of the boat.

These outer two walls are strange because there are no sides to the rear deck, only railings – wind can go through this area at will. Plus water. So I envisage that area as wet.

All that gives me some time to deploy extinguishers. The walls are 2″ thick below waterline to 8″ above, 1/2″ ply above that to the roof.

2 Responses to “Being stern about future directions”

  1. Mark in Mayenne August 7, 2014 at 18:45 Permalink

    That is just an awful title

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