Sorry this is basic, I'm building my 1st canoe. From what I have gathered they provide rigidity. When a strip of wood is bent it wants to straighten out. Is this outward force the critical function?

I'm debating on using strips of bamboo laminated at 1"-2" by .25" by 2-5' for ribs. They provide a good amount of outward pressure and are FREE.
Or buying some oak, hickory, ash, or something.
Or puting kligicell/divinicell foam core for deck and re-infocing sides with more glass.

Another thought, Do I even need ribs or deck re-inforcement? Can I get by w/ all glass with out being too heavy?