From my experience in my CD-22 and other boats, there is nothing (other than refrigeration air conditioning) that will cool you in a boat cabin better than an electric fan, especially blowing right in your face and on your upper torso.
I have three 6" diameter two speed fans in my CD-22 that are mounted on clamps so that they can be moved around to meet various needs when helming, sleeping, eating, and cooking. Very flexible. They also de-fog and de-ice the windows in the winter.
One is mounted above the forward starboard window where it cools the helmsman, de-fogs the starboard front window, and can be pointed toward the galley or the dinette.
The second is mounted above the forward port window, where it takes care of the window, cools the passenger, and cools the dinette or anyone sleeping in the convertible berth at night.
The Third is back in the starboard rear corner of the cabin above the galley where it cools the cook, de-fogs the door window, and can be used to help distribute the heat from my Force 10 Cozy Cabin propane heater in the winter.
All three have cords long enough to allow them to be moved around several feet from their home position as well. I should also mention that they all have an oscillating direction function that can be turned on or off.
I also have the bigger 3 speed portable FanTastic Fan, but it is more suited for a larger boat like my Sea Ray with more flat places to set it, and would be much harder to use and move around in a smaller boat like a C-Dory.
The power draw of these fans is minimal, just a few (0.5-2.0) amps at 12 volts, and a good battery system can run them for hours.
Their cooling effect will be less in humid climates (Northern California summer humidity runs from 15% to maybe 25% in the daytime), but they still work OK when the moisture in the air is greater.
Short of adding a generator and a full-blown AC unit, they seem to be the simplest and most effective choice I know of, both in terms of cost and function.
Joe. :teeth :thup