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.

Thursday, April 16, 2020

Rudder Revision






















Before and after photos of Moonshine's rudder, showing the change from totally unbalanced, typical 1950s rudder design to a partially balanced layout which should be much lighter on the helm.




The ongoing lockdown due to coronavirus means I haven't been able to do any work on Moonshine over the past few weeks. Luckily I've got a few parts from the boat here at home which have been keeping me busy, one of which is the rudder. This job has been on my to-do list since I bought the boat because she has always been uncomfortably heavy to steer, especially in any kind of breeze. This is partially due to the age of the sails, rig setup and a couple of other factors, but since the boat was designed in the 1950s things have progressed a little and modern rudder designs are at least partially balanced. This means that some of the rudder's area is located forward of it's pivot point, balancing out the hydrodynamic forces acting on it and making the boat much easier to steer. So this is what I've done with Moonshine's rudder, removing some area from the trailing edge and adding area forward of the rudder shaft.




While I've been at it, I've also much improved the airfoil profile of the rudder, adding some thickness to the chord around the middle and thinning the trailing edge to a fine point. Basically making it look more like an airplane wing and less like a brick. This will reduce drag and make the boat go faster, but more importantly will reduce the amount that the tiller will need to be turned to produce a certain amount of lift, again reducing the effort needed to steer the boat.



























I started by taking an angle grinder to the trailing edge of the rudder, cutting off the part that swept backwards and leaving a straight trailing edge. I thinned this out to a fine point, as close to a typical airfoil section as I could make it, and glued a block of laminated plywood to the leading edge with thickened resin.



























After attaching the block of plywood I reinforced all of the edges and the glued joint with fiberglass tape, and then laminated the whole thing with a couple of layers of 300gm CSM. I used resin mixed with filler to smooth out any irregularities and fair the shape into a nice airfoil section, and then gelcoated. I'm pretty happy with how it turned out, but the real test will have to wait for a windy day when I've got Moonshine back on the water.





Finished!!



Thursday, April 2, 2020

Update from Lockdown Land

So along with most of the world Ireland is now in lockdown. No leaving the house except for essential journeys to the shops or to exercise, and then only within two kilometers of your home. Which means life is rather dull at the moment! Fortunately I've got a few parts from Moonshine that I can do some work on to keep busy. First up is the mast base, which was originally painted in a mixture of blue enamel and deep rust but has now been stripped, cleaned and painted in a gloss black which will suit my planned colour scheme a lot better! Before and after: