I used a rabbiting bit for this. It worked well but I had to make a base for the router to accommodate the large bit. In retrospect, I would probably try using a straight bit with a guide running along the strake. It would take a two or three passes but be cheaper and not require the router base modification. Enjoy the build. I took mine out for her second sail Wednesday. 

Barry

I havent done this before, but I hate large router bits and I hate routing in thin wood, so what about this?   Set up a small drill mounted drum sander like this:

https://picasaweb.google.com/114717787929554738224/BuildingWoodenBoatCLCNortheasterDory?authkey=Gv1sRgCKCBzczm_aKs2wE#5957260396616080722   

then lower the drum so it sticks up the same distance as the width of your rabbet.

Then screw a vertical board on the board (a fence) close to the drum the distance being = the thickness of the finished lap and you just push the boards vertically  thru the slot and sand off the proper amount.

A rabbetting block plane lets you do this without bringing heavy power tools near delicate wood. Keep the blade sharp and it will go easily through okoume quietly enough that family and neighbors won't complain and you won't have to wear ear protection. It also doesn't fling sawdust everywhere and you can feel the action between the wood and the blade. That last lets you notice any problems and stop before they get out of hand, instead of powering through and ruining the wood.

Have fun,

Laszlo

Thanks for the input. I ended up taking the bit by the horns and now it is done. All went smoothly. It was very dusty.

I like the idea of a rabbeting block plane with a fence, though the fence could not be very long because the edge of the strakes that is rabbeted is concave.

Laszlo, do you know of a good one like this?

Looking forward to wiring it all together soon!