Preparation - Pacific Crossing Notes: A Sailor's Guide to the Coconut Milk Run - page 44

Angling for Position
On a small boat it can be difficult to mount that much panel area free of obstructions. Any
obstruction of direct sunlight markedly reduces a solar panel's electrical current output.
This would drive up our rated power requirement, further compounding the problem. What
we can do is use the available area more efficiently by making the solar panels adjustable,
allowing them to follow the sun during the day.
Figure 3 looks at the effect of flexible mounting during January in the tropics and July in
the Chesapeake Bay. Let's assume we can adjust the solar panels' angle by up to 15° from a
horizontal position. Many mounting options will actually allow a bigger adjustment.
However, we're unlikely to adjust the panel's angle continuously during the day and most
mechanisms will only allow adjustment around one axis. Therefore, we'll stick with the
conservative assumption of 15°.