Take a look at the link below. There is a nice picture done a few months ago by Kurt Maurer, showing a hollow shaft for a paddle using 8 strips with a "v" cut into the edge of each. The process can use a standard table saw with standard blade, set at a 45 degree angle. Just put a notch in the center of one edge of the strip, then assemble 8 of them, with the un-notched top of one strip fitting into the notched bottom of the next. You'll have some corner of the strip hanging out, but that gets sanded off later. For an oval shaft, use two strips which are slightly wider than the rest.

http://www.kayakforum.com/cgi-bin/Building/index.cgi?review=156788

The illustration below is from a post by Shawn Baker

read it at: http://www.kayakforum.com/cgi-bin/Building/Archive50.pl?review=58405

You can get more on building paddles on Shawn's website: http://www.geocities.com/shawnkayak/
there is a link to paddle building on the left side at the bottom of his homepage.

For more specific info on the birdsmouth technique, go directly to his page: http://www.geocities.com/shawnkayak/paddle/birdshaft.html

Hope this helps.

PGJ