No, not a group of pretentious highschoolers on a boat, It is an open to air cooling bed for wort, commonly used in the process of making sour or wild ale's.
I have been hearing about this a lot over the past few days; and am going to be tasting some of Alligash's cool ship beers this weekend. Has anyone else had many of these? I think New Belgium is working on one in the future, and Cantillon, Russian River (I think on one of their beers) and Alligash, use them. Can you name any others?
Yes, it's just a very rustic form of spontaneous fermentation, used primarily before closed vessel fermentation hit advances. Cylindroconical tanks allow for better substrate contact with the yeast due to the convection within the tank. Shorter, wider tanks do not allow as much contact due to lack of convection. As a result, cylindroconical tanks produce beers with fewer yeast by-products, all things being equal. You named the main players in the states using them, and along with Cantillon, there have been quite a few European brewers using this technique. I'll also add that Anchor's original brewery used roof-top Coolship-like vessels, and may still in a sense, but I am sure it's housed in a positive air filtered setting.
Usually a shallow pan, in which hot wort is placed in, and due to the surface area is allowed to cool fairly quickly. During the cooling process, wild yeast is allowed to inoculate the wort. This can be done for a complete fermentation, or just initially, then a secondary inoculation can take place.
These days, Coolship use is a bit more controlled, but the idea remains.
Embedding has been disabled, but here is a video documenting Allagash's first Coolship brew: Allagash Brewing's First Traditional Spontaneous Brew - YouTube
I've been thinking about converting an old stainless steel fish gutting/cleaning station/pan into a small scale Coolship, and building a little house-like structure around it with open (but screened) air ventilation. Our property backs up to both a apple/pear orchard, as well as a working farm (hay, cattle, etc.), so natural wind flow carries all many of airborne goodness through our yard.
A fanatic is one who can't change his mind and won't change the subject. - Winston Churchill
If you do your home made coolship, i would love to see pictures.
Another interesting piece of info: Cantillon's signature flavor may be more related to a house yeast strain rather than something truly wild blowing in the window.
Above their coolships are wooden beams on the ceiling which the brewers believe harbor the yeast strains that ferment their beer. Steam from the hot wort condenses on these beams, and the condensed water containing some of the "house" yeast drop back into the coolships. Over time, the yeast in the rafters has grown and developed to give Cantillon a regular source of "wild yeast" for use in their beer.