We are really excited with the progress on our stanchions and what we have learnt means we have redesigned our aft solar “arch” yet again (I’ve lost count, this might be the 10,000th version).
Stanchions and Gates
This was our first stanchion base. The carbon fibre tube is 250mm long with an external diameter of 26mm. The 20mm of FR4 was drilled with a 27mm bit, then the original stanchion base through the deck with a 32mm bit. Before fitting the stanchion base tube we drilled a hole in it so that there would be a chemical and mechanical bond between the epoxy in the tube and around it. We capped off under the deck and then used thickened epoxy to fill the hole, bed down the FR4 and fill the whole of this tube.
The actual stanchion is 800mm long with external diameter of 30mm and internal of 27mm. It drops onto the base. We will be filling this tube with thickened epoxy (except where the stanchion base is). The stanchion tube will be removable although we will have a through bolt to secure it onto the base.
We have now fitted two more stanchion bases which are the ones for the gate on the port-side. These need braces which we have been working on.
This shows the two stanchions for the port side gate. The braces have been temporarily zip tied in place.
The gate braces are 1100mm with external diameter of 18mm and internal diameter of 15mm. At the bottom these will slide onto a permanently fixed gate brace base which is 250mm with 14mm external diameter.
You can see the beginnings of the FR4 shape that the gate brace base will be epoxied into.
This is the ready to fit base. We will epoxy the FR4 into place and then extend the hole through the deck, cap it underneath and then epoxy the base tube into it.
Originally we had planned to drill the stanchion for the brace to go through it. I’m concerned about this weakening the stanchion so as a first test we will shorten the brace and then lash it to the stanchion. We do want the stanchions to be removable but it doesn’t have to be very quick or something that is done frequently. We could even cover the line used for the lashing with epoxy as it could still be cut off and replaced.
Both the stanchion and brace will be filled with thickened epoxy for extra strength.
Aft Solar panel “arch”
I have now started modelling the aft solar in 3D (using FreeCAD). Again we are building this from Carbon-fibre tubes as below.
Again we are using the nesting feature of the tubes to fit the arch securely to the deck. However the bases are longer (650mm) and larger diameter (34mm), also they drop through the deck onto a “shelf” we have built in the lazarette locker where they will be bonded into place (and filled with thickened epoxy and have an FR4 surround epoxied to the deck).
The corner “stanchions” that go onto these stronger bases are 1200mm long and 38mm diameter. They will have diagonal braces both forward and across the boat.
Attached to the corner stanchions (fixings not shown yet in the model) are more 1200mm uprights. We have this two stage upright for a couple of reasons. First, we cannot physically get the corner “stanchions” far enough apart for two solar panels between them (215watt 24 volt Victron panels that are 1580mm long and 808mm wide). So these are positioned 110mm wider on each side (slightly wider than the bulwark at this point which is not ideal – we will need to be very careful coming along side high quays/locks – but the stern is much narrower at this point than most of the boat length). Secondly. to allow us to tune the height (to clear wind vane self steering) before epoxying the joints permanently).
The outer tubes (which will be the next size up in diameter) will have a longer tube (same diameter as the corner stanchions) inserted in them that is free to rotate (this tube filled with thickened epoxy). The arm for two solar panels (filled with thickened epoxy) will be attached to this inner tube (we are going to make joints from triangular plates of FR4 bolted and filled with thickened epoxy). The plates will encapsulate between 100 and 200mm of the tubes to spread the load of this joint.
The result of this is that each pair of solar panels on an arm can be swung round 180 degrees (just clearing the stays) so that the panels are above the aft cabin (and mizzen boom).
Having the 4 panels side by side over the aft cabin would still mean one would be mostly sticking out on each side. This is why we have another way of moving the panels. Each panel can be freed to pivot around the swing arm. That means the outer panel on each side can be swung into a storage mode underneath it’s inner panel.
We can put the outer panels into storage mode when all the panels are behind the boat for our normal sailing configuration of two panels behind the boat with a total width only slightly greater than the width of the stern and 430 watts.
However, we have a more compact mode that we will use during storms (to reduce the risk of waves hitting the panels) or when in tight marinas/docks. This will have the panels swung over the aft cabin with the outer ones stored underneath so that we only have two panels width which is less than the width of the boat for almost all their length. Obviously we cannot use the mizzen in this configuration. However, we will be able to use a Hydrovane (if we can stretch the budget or a Hebridean if not) wind vane self steering in any of the solar configurations. We will also be able to use the side decks with enough height under the panels in any of the configurations.
One side benefit is that we can very easily let panels hang down vertically for easier cleaning.
Addressing the flexibility concern
As soon as a design allows for movement flexibility and strength are key concerns. We have 3 types of movement:
- The corner uprights can be lifted off their bases (mainly to get them out of the way of cranes/travel hoists). However the fit is snug and there are through bolts and cross braces (also removable).
- The two solar panel arms (each with two solar panels) can swing around the vertical axle so that the panels are either behind the boat or above the aft cabin.
- The solar panels themselves can pivot around their arm so that the outer panel can be stored under the inner one.
We are addressing this in a number of ways. First, remember that the model does not show any of the braces, or joints. Second, every tube will be filled with thickened epoxy to avoid compression failure. Beyond that we have solutions for each panel position.
Sailing goalpost.
When the panels are behind the boat (either two wide with two stored under or four wide) we will lock them solid into place with a hinged “goal post”. A goal with a top bar connected to the boat via two uprights that are attached to the stern by hinges will be pulled up and under the panels. Locking brackets under the panels will be positioned about 3/4 of the length away from the boat. The goal post will be pulled up by lines attached high up on the outer corner uprights. Once the goal post is up and locked into the panels the panels will be unable to pivot around the arms and the arms will be unable to swing around their upright axle.
The goal post will only tie in the central panels and the solar arms.
Outer panels when anchored
We will use simple props to hold up the outer panels when at anchor (not designed to be strong enough for sailing or bad weather when these panels will be stored under the inner panels).
Panels over the aft cabin
We will use simple props combined with tie downs to secure all corners of all the panels when they are above the aft cabin for a storm at sea or when in a tight marina/dock.
Surviving a hurricane
We would not expect any of these options to survive a hurricane. So if we end up anchored/moored when a hurricane is expected then we can remove all the panels and tie them down flat on the aft cabin behind the shelter of the wheelhouse (they are too larger to fit through any of the hatches into the cabin).
Remembering the constraints
While it is easy to criticise our choices remember that we have had to work around some significant constraints:
- Budget. We have to be able to do this ourselves on a low budget.
- Our stern is very narrow by modern standards (approx 1.6m at the outside of the bulwark).
- We have a mizzen mast. Currently the boom sticks out over the push pit to level with the very end of the stern. We are going to have to shorten the boom by abut 450mm.
- We need wind vane self steering to reduce energy consumption on passages (and anyway we think they are an important safety feature, especially if they can be used as an emergency rudder).
- We need a lot of solar capacity as we aim to be as close to fossil fuel free as we can manage (we know we will need to use diesel heating in winter in colder climates).
Summary
We are very excited with this new design. A key advantage is that we can build it before the mizzen mast goes up (because we have decided to take the plunge and shorten the boom) and before fitting the wind vane self steering (because the height is adjustable). Also we have significantly simplified the joints we need to make and the calculations by using vertical uprights and right angle joints (plus the braces). This is also the first design that really addresses the “reefing” options and the ability to lock the panels in position.
Hope you like it 🙂
Sustainable Sailing 
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