I have a question about what kind of plywood to use. I have sifted through pile after pile of luan plywood, and have yet to find one good sheet. We do not have any decent fir plywood either. My final option is to use marine plywood, which is 90 dollars a sheet; I am building an Uncle Johns four rib pirogue. One thing in addition to the lack of quality of the luan, is whether or not I am looking at luan or not. The luan I have seen in the past was slightly dark brown on one side, and lighter colored on the other. It is labeled as luan, but I wonder whether these big box stores just label it as such; with no real knowlege of what they are selling. I am dying to get started, but I do not want to waste money needlessly. Other questions I have, is how many sheets will I need for a four rib pirogue that is fifteen feet long? How do I space the ribs? Thanks for any feedback.