Historically canoes never had keels. It was only when European boat builders started copying native American boats did keels come into common use. Contrary to popular opinion, the keel adds little or nothing to either the stability or tracking ability of a canoe. Stability is more a function of the bottom shape. A very round bottom, like that of a Chestnut Cruiser, will give you a “tippy” boat. A broad flat bottom, like that of a Chestnut Ogilvy, will give you a stable, stand-up boat. Most designs fall somewhere in the middle.
Tracking ability, the tendency of a canoe to travel in a straight line, is also a function of the hull length and shape. Longer boats tend to track better. As above, the rounder the boat bottom, generally the better the tracking. Boats with little or no rocker* also tend to track better, as more of the boat length is in the water. That said, I recently encountered a Bob’s Special, with a 2″ deep keel, and I couldn’t help but think that would help with the boats tracking, particularly if the boat was lightly loaded.
What the keel does do, especially on a canvas covered canoe is, along with the brass stem bands, provide bottom protection. They also, almost always leak. Drilling holes through your carefully sealed outer canvas and screwing a keel to the bottom of your canoe, no matter what bedding compound you use, is simply asking for water to come in. My solution is to add a Kevlar® or fiberglass keel plate in place of the keel. I attache this directly to the aircraft fabric which is already encapsulated with an epoxy filler/primer. With Kevlar® this is like having a steel plate down the bottom of your canoe. If you’re planning on using your canoe in white water this is a must have. Although fiberglass is not as strong, it is much less expensive and easily repairable. For a cottage or recreational canoe this is an excellent option.
* Rocker: viewed from the side of the canoe, rocker is the amount of curve in the hull, much like the curve of a banana. A straight keeled canoe, with no rocker, is meant for covering long distances in a straight line. The full length of the hull is in the water, so it tracks well and has good speed. As the rocker increases, so does the ease of turning, at the cost of tracking. Native American birch bark canoes were often characterized by extreme rocker.