Yesterday for the first time I turned my canoe over, then I tried to get back in it. I have been thinking about adding a sail to my canoe and now that I know a bit about sailing, I know I need to plan on being able to right the sailing canoe and get back in it. So I took the canoe to the lake to practice self recovery (solo) with just an empty canoe.
I have a 17 foot two person plastic canoe as seen in my answers to this question it has built in flotation at both ends. With the canoe empty, just me in a life jacket and a wood paddle. It turns out will float the canoe just barely if the canoe is full of water it floats until I get in. The flotation will not support me and the canoe, I was sitting in the canoe floating by my life jacket with the canoe 2 feet under the surface. When I get out it surfaces with the sides just breaking the surface.
There is a cool video of a guy doing solo recovery at Solway Dory, but he is in a smaller lighter canoe, I think he is wearing a dry suit, and he has added side flotation. I watched that video before going to the lake to try it myself.
Real life me and my canoe (big & heavy). I can't throw it and have it land empty! (no surprise) Best I can do is turn it over slowly which results in it being half full of water when right side up. I was not able to get back in without filling it the rest of the way with water.
Later I took the canoe to shore emptied it and a couple of attempts to get back in the canoe when it did not have water in it. By this point I was tired, and could not make it happen. I know it is possible, but it is difficult, if I could not do it in warm water while a bit tired, I don't want to bet my life on it in other scenarios. In sailing class I was easy able to get in a Sunfish without difficult, but that is a very different boat.
When people take canoes white water rafting they add A LOT of flotation (image below), essentially the canoe is all flotation except room for one person. At that point you might as well get a kayak, what is the point of the canoe? All it holds is you and flotation.
So I want to add some flotation, at least enough so that I can get in over the side as long as I have enough strength to turn it back over. Optimally enough so if I am caring my normal load or if I have a sail I can get it upright and get in. I don't want to fill it with float bags. The point of a canoe is that you can put a lot in it.
How do I decide out how much flotation I need, and where it needs to be?