IanD

Actually stick-on panels can often run cooler because they're attached to a steel roof which conducts heat away from them. Rigid panels with air underneath are only cooled by it if there's a crosswind to move the hot air out, otherwise it just sits there getting hotter -- it acts as an insulator like in double glazing, so the panels end up hotter than the roof (which is cooler). If there is shading then parallel panels can lose less output than series ones, though this does depend on the panel (internal connections, diodes etc.). With a lot of panels the best solution is to split them into groups with separate MPPT controllers, but few boats have enough panels for this.

The hot power loss I quoted was for rigid mono panels, which is what the vast majority of installations use because they're by far the cheapest per watt and the most efficient. CIGS panels -- the most common flexible ones -- are very similar (-0.36%/C).

I'm not saying that a solar hot water system is pointless, quite the opposite, you can get quite a lot of heat collected as well as power. You can now get solar panels which are also solar heaters, but they're *very* expensive and you need a closed-system with piping on top of the roof which you need to stop from freezing in winter -- if you spend the same amount of money on more plain old solar panels (and have enough space for them) and use the electricity to run an immersion heater, you'll get more heat for your money. I'm saying that the idea that cooling panels by pumping cooling water past them just to get more electrical power out *is* pretty much pointless, unless you then store the hot water -- which as it heats up, makes it less good at keeping the panels cool. The oft-repeated "fact" that solar panels lose a lot of output when they heat up is simply not true, as the numbers clearly show 😉

Not going by the number of boats I see which are absolutely not satisfying the CC requirements, and haven't done for months at a time or even longer... 😞

Temperature coefficient of panel power is typically -0.35%/C (mono PERC panels), so if a cooling system could keep them 10C cooler in direct sunlight (which is quite a lot) you'd get 3.5% more power, about 13W for a typical panel at maximum output -- which it wouldn't often be, so in reality the saving would be less than this. But then you need the power to run the water pump, which would probably eat up most or all of the extra power... 😞

The contrast between Manchester and Birmingham in how they treat/use/value their canals is massive...

I did try finding a Facebook friend who could drop one in for an hour or so, but the ones nearby don't have Bromptons and the ones who have Bromptons aren't nearby... 😞 I even looked into buying a new one and getting it delivered to TT but the earliest anyone could do it was this Friday, and Tim needed to start the locker build on Tuesday morning -- which is why cycling there wouldn't have worked, even if my legs had been up to it... 😉

I didn't mean there, I meant on the Ashton from Piccadilly up where several bridges had resident trolls when I went past... 😉

That's what I meant when I said "the CoP moves with rudder angle" -- and also with prop rpm. The difference is nothing to do with speed, it will happen when manoeuvring or cruising slowly at a few mph -- but given that your rudder has a relatively fine profile (5%?) the difference won't be as big as with mine (20%). If you want to actually measure the before-and-after difference you need three spring balances, one attached to a rope holding the stern back to something solid (thrust), one attached to a rope running sideways (steering), and one to pull the tiller sideways (steering effort) -- this is how rudders are measured. With the engine rpm constant, measure the three forces (thrust, steering, tiller) vs. rudder angle. You should find the new one gives more sideways force (steering thrust) at a given angle than the flat plate, and carries on working to bigger angles, but might also be heavier to steer -- or maybe the tiller force needed for a given steering effect is the same but you don't have to push it over so far. This would give you some actual measurements about how much better it works, as opposed to subjective "it feels better" which is always prone to expectation bias (result being what you expected). I'm hoping to try this with Ricky when my boat is built, if there's another similar hybrid boat with a flat plate rudder in the water at the same time...

In their defence, the trolls filling the bridges with clouds of fragrant smoke are usually friendly... 😉

That's not how MPPT controllers work. The cooling fins are just there to dissipate the heat from the internal switching circuits which convert the incoming panel high voltage/low current to outgoing battery low voltage/high current, this heat loss is typically about 5% of the total power in a good controller (95% efficiency). The controller adjusts the incoming voltage/current to maximise the power from the panels, hence MPPT. If the controller wants to reduce the power into the batteries it will just raise the incoming voltage higher which reduces panel power; if it goes all the way to the panel open-circuit voltage then the power drops to zero. Lower power throughput means less dissipation in the controller so the cooling fins get less hot. Alternatively if the batteries are full the controller can just shut down completely.

I tried explaining this, let's have another go... 😉 The force needed to move the rudder when the tiller is pushed over depends on where the force of the prop wash flowing over it acts, and there is a point called the CoP (Centre of Pressure) where you can take all the force as acting -- and where this is depends on how the pressure is distributed along the length of the rudder, which depends on its shape. With higher lift rudders (e.g. NACA aerofoil shapes) the CoP tends to be further back than with flat plate rudders, and even more so with Schilling rudders -- and higher lift tends to also means more force is needed to turn the rudder. So if you take a flat plate rudder of a given size which feels good to steer with and replace it with a shaped one the same size with the pivot in the same place (your plan) the result is likely to be heavier to steer (more force on the tiller needed) because the CoP will be further behind the pivot. A fully balanced rudder (which minimises the force needed) is not a good idea with tiller steering since the CoP also moves with rudder angle, and this can lead to the rudder "flipping over" (away from straight ahead) at either small or large angles depending on how the CoP moves.

I meant the amount of effort needed to move the tiller against the force of the prop wash, which I thought was called "weight" just like for steering on a car?

That path (from moorings next to bridge 208) is "interesting" in the dark when it's been raining... (good food and beer at the end of it though)

So a restaurant not a pub, then? 😉