Thanks to my sponsor, Renogy #renogysolar, I am now the proud owner of 4 of their 100-watt bendable panels!  The boat is pretty much built around these panels, so they had better work.  A few days ago I took one of them and put it up on the roof of our house facing straight up.  It gets a clear view of the sun except for a few hours in the morning and evening when shade from trees hits is.

I wired the panel to a bank of power resistors with a combined resistance of about 3.1 ohms and started logging data using my PowerLog 6S (a super-useful tool)  Fortunately, the weather has ranged from mostly sunny three days ago to mostly cloudy with thunderstorms today, excellent for testing the panel in a variety of conditions.  Here's a graph of voltage, current, and power from the mostly sunny day.  The panel doesn't quite reach the 100 watt rating, but keep in mind that the sun is not directly overhead even at noon, and I'm not operating the panel at its max power point (17.7 volts).

The graph below shows the energy (integral of power over time) collected over the course of the daylight hours for three days.  May 12 was mostly sunny, May 13 a little cloudier, and May 14 was a rare, stormy day here in drought-stricken California.

I'm really quite happy to see so much energy coming from theis panels.  I've been counting on basically getting a 24-hour average of 10 watts of useable power, or in other words 240 watt-hours per day from each 100-watt panel.  This is after taking into account all the various losses in the batteries, voltage regulation, etc. etc.  The data shown above didn't include these losses, but I think it's still safe to say that I'll get FAR more than 240 watt-hours per day per panel on an average, non-stormy day.

Of course I still have to worry about the panels getting sea scum on them, bird droppings, etc., or operating in the winter.  So I'm not about to propose using only one panel on the boat instead of two.  But it's comforting knowing that the panels really do pump out power as advertised.

I decided I needed a new rudder.  The one currently on the vehicle is too sloppily made and the pivot axis is not placed correctly for minimum actuation force (it should be at 25% of the chord).  So I'm making a mold for a new rudder.  Which means I first have to make the plug.  No CNC router or 3D CAD for me, just a free 2D CAD program (Solid Edge, actually pretty good) and some hand tools.  I drew up the rudder, cut out a template, and glued it to a piece of balsa:

Cut the balsa out and hand-sanded to an airfoil shape.  I'm a BIG believer that if you just take your time, you can create a near-perfect shape by just free-handing it with a sanding block.  Your eye is amazing tool for getting the right shape.  Here's the rudder after sanding:

I glued in the rudder post and put heat-shrink tubing over it to protect it for the time being.  Then I vacuum bagged on a few layers of light fiberglass:

Now in parallel I'm building new struts/keel (not sure what to call them).  The current vehicle has a single one but I'm going to two tandem struts for various reasons.  Now for an airfoil section this long, I have no desire to sand it by hand.  At least not when there are airfoil sections readily available in the form of R/C helicopter rotor blades.  So I take a wood rotor blade of the appropriate size and glue two blocks on the end.  The rectangular blocks will create ends that are easy to interface with the rest of the boat.  Keep in mind that I'm creating a plug here, not the real part.  Just as with the rudder, the real part will be composite.  Here's how the plug for the struts starts out:

And here's the rudder and strut plugs after filling all the nooks and crannies with filler.  Next comes waxing and then pulling fiberglass molds off of them: