> By wet t-shirt, do you mean placing the fermenter in a tub of water,
> draping the t-shirt over the fermenter and into the water?

Yep. I had come across an article in an old Winemaking Magazine
after reading your post. The technique can lower temperatures
dramatically but it's limited by the dewpoint which I take it
is set by the relative humidity.

It seems that the closer you get to 100% humidity the nearer
you are to a 0 degree temp drop. If you have, and I'm making
these numbers up, something like 90 F ambient temp and 30%
humidity you can get up to a 30 deg F temp drop. There was
a chart published with the article but there must be forumlas
out there somewhere.

There's also the possibility of getting an old fridge and
setting your carboy inside. If your only making 23l or so
at a time that may do it but like Tom says I don't think you
need to worry about the temperature of reds all that much.

Don