5/4 x 13″ x 12′ white oak. I have five of these that came out of one log, four of them perfectly clear and one with a small tight knot. They came off the bandsaw mill in Delaware that I was operating with my friend Phil. Air drying since 2022.
My keelson is 4″ wide by 3″ deep. I will get what I need out of two boards. I will plane them to 3/4″ then laminate them in place over the molds to assemble the keelson.
I needed to cut a straight edge into these boards that have irregular edges. I used thin tongue and groove plank as a guide for my circular saw. This plank is some kind of manufactured material, basically wood but assembled in a way that eliminates the idiosyncrasies of wood. They are perfectly straight. I checked them with a string line. 
My Makita circular saw is a superb instrument. Heavy. Long base plate. Heavy, accurate connections and hardware between the base plate and the motor, and to raise and lower the base plate. The base plate stays square to the blade at any depth No security button on the handle that you have to squeeze in order to start it. Adult use only.
With one straight edge, nearly perfect, I ripped 4-1/8 inch planks with the table saw, cut proud for final planing and fitting. 
