The rabbet is an essential detail that helps form the shape of the boat. It also provides a 'stop' for adjoining planks to align to when tightening the wire 'clamps'. 

All of this along with the epoxy steps help ensure a watertight vessel. Do a search on this site for LapStitch and you'll find plenty of info.

From the title of this post it sounds like you may be interested in building a smaller scale boat to use as a cradle? If that's the case and you're not concerned with being watertight it could probably be done without the rabbet, but having just completed an Eastport Pram, it seems like it would be a bit more difficult to stitch together without it.

Perhaps others could weigh in on this subject. Good luck!

I totally agree with the above.  I built an EP last year, which the cradle is a half scale version.  The rabbets are essential to positively locating the boards so they can be secured with the stitches.  Trying to put it together without the rabbets to acts as the "stops" would be like trying to stack three marbles on top of each other.  Made from the same 1/4" plywood, the rabbet will be 1/8" deep, but only half as wide as on the EP plans.

I've been wanting to build the coffee table version, so I'm in the same boat.  He makes a great point about not having to be waterproof, but it still has to be structural and aesthetically pleasing.

Locating the rabbets on the boards is probably one of the trickiest parts of the build.  There are plenty of posts on this forum where people have put the rabbet on the top of the plank instead of the bottom.  This is because the way the boards curve to form the hull form, the ends look upside down.  It's sort of non-intuitive.  In fact, when I cut out my EP parts, I did made templates at the same time and made sure to draw the rabbets on the templates.  Quadruple-check the parts as they're laid out in the manual to make sure you're putting the rabbet on the INSIDE BOTTOM of each board.  Good luck and please post pics of your build!