But wherever one is in that single blade paddling progression, the easy crack cocaine of a double blade paddle is likely to end the motivation to progress any further. And the biggest loss and irony in that, in my opinion, is that the cocaine will actually prevent the paddler from getting the aesthetic endorphin "high" that proficient single blade boat control produces.
Glenn I sense you're poking fun here but I think the joke lands a bit flat after so many have already said they prefer a single blade in many circumstances but elect to use the double to make miles. I'm in that group as well. If anything my double-blade technique wallows because I spend nearly all my time practicing with a single blade.
But my most efficient solo is a Phoenix, and it doesn't sit-and-switch very well because it's not that efficient of a boat - it's not meant to go straight. So if I want to make miles on deep flatwater I will often use a double to get up a lake, then switch back to a single for enjoying, finesse, etc. I also find on longer trips it's nice to switch up the biomechics periodically.
Personally I don't find bent shaft paddles particularly aesthetically appealing and the few times I've tried them, they felt terrible as soon as I tried a correction stroke. But I don't lambast them as the devil's work, I recognize I'm ignorant about them and respect folks who can make good use of them - different strokes for different folks!
For the sake of the OP
@Blukanu , I use a fishing kayak paddle (an Adventure Tech model that I think is off the market) that extends from 240cm to 250cm. I sometimes wish it was longer when soloing my tandems (from the bow seat backwards). It can be feathered at any angle. I will adjust the feather, usually between 45 and 60deg depending on wind and how my wrists are feeling. In some wind directions I find a double suits, in some winds a single does better.
I also use my double as a pole in flatwater, something that can't be done with a single standing up.
Cruiser is right, Bending Branches and others make doubles specifically for canoes, but these days fishing kayaks are really popular, and they tend to be wider and sit higher off the water than other kayaks, so fishing kayak paddles can also serve for canoes and they open up a wider market of purchase options for those so inclined. I have a BB Navigator w a carbon shaft and wood blades. The wood blades are buoyant and the carbon is light, which I like, but I got the version w smaller blades that only extends to 250cm, and it's both a little short and a little underpowered for a tandem canoe. I think the fishing kayak version might be better. I also hate the way mine locks because it tends to come loose, but I think they fixed that in later models.