Thanks to all who responded, several via direct e-mail.
It took a combination of several suggestions, and a bit of understanding of physics (or geometry) to get it taken apart.
I've had the "collar tool" all along but didn't realize that's what it's for! Thank goodness I'm a hoarder, and didn't throw it away after all these years (?10y) since I bought the paddle. (it didn't come with instruction, which I think it would have been useful, as the "tool" needs to be used on the fattest part of the collar. Not to mention I couldn't figure out why this "thing" came with the paddle to begin with)
Still, it took some soaking before the "tool" finally worked!
I will try putting some lubricants to the thread. Will see if it prevents repeat of the same.
I'm slightly baffled why only just the carbon shaft had the problem, repeatedly. The other one (fiberglass) never had any issue of getting stuck. I wash BOTH of them after every paddle...
: April, if you haven't got the paddle separated by now, I think the
: obvious solution is soak the paddle in fresh water and maybe hot
: water. Most likely salt is causing it. Paddle gets wet, salt
: water infiltrates, dries in the joint as you paddle and locks it
: up. You can put a plastic bag over the joint area with elastic
: bands or tape and fill the bag with water over the joint if you
: don't have a better way of soaking it. Good luck.
The Connyak BBS