Hey Robin... this being my first laminate paddle i thought i'd request some advice from a veteran and had a chat to a chap who runs an watersports centre on the side of derwent, he's made everything from cedar strip canoes through to viking boats.
His advice coupled with the advice from a canoe making book would point towards the standard practise being just glue and clamp the pieces together flush, rather than using a joint.
I too thought about using a joint. The chap I chatted to said he'd only had one paddle delaminate, this being on the grip, which only had a small contact surface area- this was repaired with dowels- and is still in use.
I made two one piece paddles last week from cherry. I take a template along to the timber yard, and buy something which will allow two paddles to be cut from one plank, layed out opposite to one another. This reduces waste and keeps costs down. Although is significantly more wasteful and expensive than lamination.
My timber costs
for the laminate; £3.55 ash + £5 cedar= £8.55
One piece paddle; £36 plank cherry/2= £18
The glue I use is Epoxy resin, which is more than suitable, although if the two woods being joined have different properties (e.g. expand more when wet) this might not be suitable as its not resistance to hydrocycling. (unless varnish seals the paddle).
There are apparently new polyurethane glues which are more suitable for these problem woods, although I have yet to try these.
I often use both power sander and planer for removing the bulk of the waste, although care must be taken, as its easy to take too much off.