Hi Carsten: Re corrosion, the bronze keel cooler is bolted through a fiberglass tank lid – you need some form of isolation in whatever you do. Tank liquid is deionized water with antifreeze added to the required temperature. Note that if you do not need cold weather protection leaving the antifreeze out is more efficient. A tank of about 20 gallons/80 liters is sufficient to handle our freezers and fridge with the boat hauled out. Shape should favor surface area over depth, but in the end depends on your structural system and space between framing. Good luck.
Posted by Steve Dashew (December 18, 2010)