If you are closed up in your boat
due to cold, foggy, nights (hard to imagine in July, but...) a long term solution will be a diesel
of some sort. Heating
with something that uses interior
air and ideally exhausts to the outside will reduce humidity in the boat. (Propane heaters, and even running a stove
,does little since the products of combustion, which contain the moisture, remains inside the boat).
However, if it is not cold enough for a heater
, then plenty of air flow may help the problem.
Sailing is a sport, an athletic activity, not a sedentary one.
Fred Roswold-Fred & Judy, SV Wings, Mexico