If by swamp cooler, you mean a constantly wet T-shirt over a bucket (preferably) or a carboy...then, yes : ) More cooling in high humidity environments: use a fan and/or ice also.
I used to use a large rubermaid container filled with water (what I call a swamp cooler). I used frozen 2 liter bottles to keep the water cool. I would usually change the bottles in the morning before work and at night before bed. In the middle of summer I might have to change them when I got home from work. This method kept the temp about 4 or 5 deg below ambient temp.
I received the Cool Brewing fermentation cooler as a Christmas gift, and I love it. It's basically just a big-ass soft cooler made big enough for your primary fermenter. I keep a few half-gallon plastic jugs of ice in the freezer and swap them out every 12 hours or so. After fermentation calms down in a few days, I'll stop replacing the ice and let it ramp up to room temp to finish out. This works out great for me in warmer weather. I've been able to keep the temp at 65-67F with a room temp of 74F (according to the stick-on thermometer strip on the fermenters vs. my A/C thermostat reading) on most ales. However, my last fermentation was a big active RIS, and I was only able to keep it down to 70F until it calmed down a bit. https://www.cool-brewing.com/
I've used a very large tupperware tub filled halfway with cold water with great success. This is probably around 10-15 gal of water outside the fermenter. I use a frozen 2 liter or two. For 5 degrees, I'd have 4 on the ready. I swap them every 10-12 hours. They need about a full day to refreeze. If properly tended I can keep temps at about 62F (ambient) in a 68F basement.
def the way to go i throw a tshirt over my bucket, then put the bucket in a rubbermaid tub slightly bigger. fill with about 4 inches of water and rotate three 16 oz bottles of ice 2x a day. keeps it about 7 degrees cooler than ambient temp.
I recently had a similar issue .. ( Live in Houston ) My carboy was around 73 degrees in the coolest part of the house .. I simply wrapped a full size towel around the carboy and stuffed 4 frozen gel packs inside the towel ( evenly spaced ) ... it worked amazingly well. I bought 4 more and kept 4 frozen so they were ready when the others had warmed up. Lowered the Carboy temp to around 68 constantly for 7 days until the airlock stopped.
Something I posted before: My homebrewing area (utility room in my half basement) is a bit too warm now (ambient about 72-73°F). My preference is to ferment my Wit beers around 70°F (although 72°F would be OK). So, since fermentation is an exothermic reaction (it produces heat) I need to ‘manage’ the fermentation temperature. Right now I am able to do that by simply placing my bucket on the basement floor; the basement floor operates like a heat sink drawing the ‘excess’ heat away. I will just use the ‘floor method’ unless the fermentation temperature exceeds 72°F. If that occurs I will place my fermenter in a shallow Rubbermaid pan (about 5 inches tall) and put water in the pan. The presence of water increases the heat sink effect by cooling a couple more degrees. If I should need even more cooling I will place a towel (or a T-shirt) around the bucket for evaporative cooling. If even more cooling is needed I add a fan to the mix. If even more cooling is required I add some ice to the water; refreezable blue ice blocks. Cheers!
I've used the wet cloth method. Fill basin with several inches of water. Place fermenter inside with wet towel wrapped and strapped. Direct fan toward top of the towel to maximize cooling. Can definitely get several degrees drop out of it. It's not my goto method anymore (cold cellar floor or temp controlled freezer, depending on how cold I want to make it), but it works.
How are you guys measuring temperature? I have the LC thermometer strips on the side, but when submersed in a cold liquid I tend to doubt its accuracy (not that it's extremely accurate in the first place). Are you dropping a thermometer into the fermenter each time? This would be ideal but I'd hate to be opening the thing constantly.
I had my Johnson Controller taped to the outside of the Ferm bucket above the water line, but I was skeptical about it's accuracy. When I took a gravity sample, the temp was reading around 50. So I just stuck my mash/boil thermometer in the swamp cooler water and kind of guessed that the difference was along the lines of where I wanted to be.
