We DID put some Maplin (..a now-closed electronics store..) solar panels on the wheelhouse roof of our N33, and they were an exact fit from front to back, and left to right, except that they covered the sliding perspex sunlight hatch.
BUT, even though the panels – put on the roof about seven or eight years ago – covered the entire wheelhouse area, they didn’t produce much current, and turned out to be a waste of time and cash. Our 4 big lead-acid batteries still slowly discharged – even during the summer – if the batteries weren’t used. The massive engine-start (and ‘house’) batteries (Varta 120 amp/hour from Barden UK, who give Nauticat Association members a great discount!) just didn’t pick up the very weak current which the massive panels produced (15 watts, perhaps ..that’s just over 1 amp, really, to supposedly charge 4 huge batts). So I took off the panels a couple of years ago.
For sailing boats with SMALL engines – and thus SMALL starter batteries – solar panels might produce enough charging current – especially in sunny Mediterranean climates; we often see solar panels on sailing boats in the harbour on Skyros island in Greece. But if you have a couple of HEAVY-DUTY starter batteries on, say, a 90hp Nauticat Lehman engine, then I don’t think that solar panels are much, or any, use. Maybe a small Rutland wind charger might be more useful.
My own experience – just as I’d read on various battery-tech websites – was that once lead-acid batteries have become discharged more than 50%, they just don’t hold much of a charge any more, and they certainly didn’t gather enough trickle-charge from our huge solar panels to keep pace with their gradual discharge when the boat wasn’t in use. So I bought four new batts (from Barden) about four years ago, and they’ve been well worth the investment ..they lose NOTHING, even when the boat hasn’t been used for about 3 months.
A small ‘house’ battery, and a SMALL ‘start’ battery, might possibly be successfully trickle-charged from solar panels in Mediterranean sunlight. But I found, Gregorio, that panels – even four big ones, two foot by about five foot! – were useless ..here in the UK. Others may have had better results!