The formula is more complex

we get weak joints from the factory when the stresses go from paddle blade to nearest hand not to center joint.

fewer grams mean higher profits

EUREKA ! take the paddle shaft(s) over to MACHINE SHOP. Ask how much for 2 aluminum tubes 0f say 5" to SLIP fit into CF or Al shafts already attached to your blades. If you have the $$, bring your mail order hardwood dowel for an ID 5" fit.

Chop a hole into dowel for the stock spring/button latch. Gflex and screw into dowel. Epox the dowel end grains, prophylactic bothe dowel ends, Gflex ID 5" tube and dowel then fit together

PRESTO ! MAX JOINT !

PRIMO !

? works or breaks where 5" ends ? the Gflex goes a long long way here.

Hi Gene,
Any join in a shaft is a weak point regardless of engineering. (assuming usable engineering) If you want a stronger paddle shaft, use a one-piece paddle.
As a repair of a broken paddle, what you describe would work to make a working paddle. It likely would still break when putting full body weight on it in you method of self rescue.

I've tried out a few two-piece paddles and most are fine for use, no looseness in the joint unless it's a cheapie paddle/shovel. I know about those loose joints, my old cheapie two-piece has a lot of slop in the joint. I use it as a single blade paddle as a spare on deck. Yep, you can paddle a kayak with a single blade paddle. Very effectively.

There's an engineering concept that runs "Strong, light, cheap, pick two." What you describe would be strong, cheap/inexpensve but not light. If you want strong and light, it will cost more.
If you can successfully get 'strong, light and cheap' working, go for it.

Mike Savage
South West Cork