Yeah, this is a "highdea" I've had. If I've had this idea then surely many, many others before me have too.

Yep; known since the industrial revolution:

Electrostatic Fluid Accelerator
en.m.wikipedia.org/wiki/Electrostatic_fluid_accelerator

"An early idea which garnered popular attention but didn't reach the prototype development was the use of EFA to produce thrust for aircraft.[6][7] The same basic principles used in a cooling application, at a larger scale, have been shown to provide sufficient thrust to provide some lift, and early experiments were encouraging.

"Ionocraft" devices, as they are popularly known, never achieved any practical use because the thrust generated was insufficient to lift much more than the (very lightweight) electrodes themselves. Including the power supply or any other significant cargo vastly exceeded the maximum achievable thrust. Today these devices can be built as science experiments. While impractical, lifters demonstrate in a dramatic fashion the simple physical principles involved in EFA."

While not practical for flight, it does read as at least plausible for sailing. And it's an interesting thought experiment at the least.
Anyone familiar with EFA?

On mobile so editing makes me want to throw my phone out this plane window...

Basically, you might have a positive charge at the leading edge of a sail, like the mast, and a negative at the trailing edge. The ionised air will flow from positive to negative.
what could go wrong?

Well, you could fall in the water and electrocute yourself.

Wouldn't work for petermac33, he'd plug it in the wrong way around and then have to call the SES to change a fuse.

I'd be pretty sure macroscienc has a prototype in the shed though.