I like to do most of the work before gluing the scarf on the shaft together. This just keeps the parts easy to handle while doing the work.
It is amazing how much strength a layer of 2-ounce fiberglass will add to the wood. Between the two and with the cord around the edge the paddle blade can absorb a lot of abuse.
I regularly bounce my paddles off rocks. I want a rugged and durable edge to absorb the abuse. I have found that para-cord saturated in epoxy resin is very tough. While you can't exactly cut down a tree with these paddles, they will handle paddling in rock gardens or doing whitewater.
This is the hardest part of the process. I use a right angle grinder to do some freehand shaping and then refine the shape with hand tools. I try to make the edges of the blade nice and thin to keep the paddle light, while leaving the central section of the blade full thickness for strength.
Even though the blades of these paddles may be feathered, they are still glued on straight and square on the shaft. It helps to cut away some of the shaft on the power face of the blade before gluing on the blades, but this is not required.
Most of the paddles I make are feathered. This means the blades at each end are at an angle relative to each other. This can relieve some stress on the wrist when paddling and help cut through a headwind.
I use a jig I made for the band saw that helps cut a curved blade, but you can just mark the curves onto your blade blanks and make the cuts free hand.