Thursday, April 30, 2020

Windvane Update

So, just a quick post on the last couple of weeks of work. Since finishing the rudder modifications I've moved on to building a wind vane autopilot, which (if I can get it working well!) will be an absolute game changer for solo sailing on Moonshine. I have experimented with all sorts of sheet to tiller steering arrangements in the past and never had much success, so up until now my voyage length has been limited to how long I've been happy to sit at the tiller and steer for. Twenty hours or so has kind of been my limit, once it gets much longer than that my enthusiasm runs out and it stops being fun. For perspective, twenty to twenty four hours in Moonshine is the time it takes to get from Schull to Dingle, or Dingle to the Aran Islands. So in a few days it's possible to cover a good portion if the coast, but glued to the tiller apart from heaving-to in order to eat occasionally. Having a wind vane will allow me to stay at sea indefinitely and, crucially on a small boat with limited space for solar panels and batteries, won't use any electrical power.


The vane of a wind-vane autopilot needs to be as light as possible, to allow it to react to the force of the wind acting on it. My intention is to mould it in fiberglass, so I built a plug from plywood in the shape of the finished vane to make the mould from. It didn't make sense to buy a whole thing of mould release wax for one part so on my first attempt I tried using car wax. No bueno, it stuck badly, and I had to break the mould to get it off the plug. I then tried covering the plug in sellotape, which actually seems to work quite well if you're happy to have some ridges from the edges of the sellotape in the finished part.


Here's the bracket which is going to mount the auxiliary rudder to the hull. The bottom end of this bracket is the part of the system that I'm most worried about being broken by the impact of a big wave at sea. So in the picture I've glued all of the bits together, added a fillet of thickened resin and I'm reinforcing it with a LOT of layers of fiberglass cloth. 

In between the auxiliary rudder and the bracket above is going to be this contraption. The auxiliary rudder will sit inside on a pivot which allows it to be lifted out of the water when not in use, while this thing itself sits on a regular pintle and gudgeon set up like any other transom hung rudder. The mini-tiller at the top is where the cables to the wind vane will attach, and will allow it to be used as an emergency steering system if there is any issue with the main rudder.

Here's a comparison photo of the auxiliary rudder alongside Moonshine's primary rudder. The auxiliary rudder can be much smaller than the main rudder because when the windvane is in use the main rudder will be set to provide most of the weather helm, with the auxiliary rudder providing smaller steering inputs. If I got the maths right, the auxiliary rudder will be perfectly balanced around it's axis, allowing it to be turned by the comparatively weak forces coming from the wind vane.

No comments:

Post a Comment