Some History
Centuries ago, the Native North Americans developed the perfect wilderness watercraft. Just like those of us living today, food was a major concern.
The canoes they developed were quiet, light enough to portage, and could carry a load, whether it was fish, rice, or venison.
After centuries of use, these canoes never had a keel because it was not necessary.
So, why do so many canoes have keels?
It started in the 1800's with the English immigrants. Instead of bringing the canoe in parallel with the shore, they would paddle into the beach bow first. So, the keel would absorb a lot of the abrasion so as not to wear a hole in the canvas. Sails were also popular, and a keel would help keep a sailing canoe on course.
The keel also adds weight, and, obviously, portaging a mast and sail would be impractical. So, these canoes were kept at the lake, usually used for just a few hours at a time. Because they were rarely carried, and never carried for any real distance, weight was not a concern.
Then, in the late 1940's, when Aluminum became popular, all of the canoes had keels. The only reason for the keel was to keep the aluminum from folding in the middle. It was absolutely necessary for structural integrity.
Since then, we've all grown up believing that canoes needed a keel. If that was true, the Native Americans would have used them long before the English came here.