A quick search turned up a couple places in Chicago that carry Okoume and Sapele Mahogany plywood. They should have the hardwoods you will need as well. You can also mail order from one of the many reputable sources. Check prices all around, there are often significant differences
http://www.woodworld.com/plywood.htmlhttp://www.paxtonwood.com/ExoticPlywood.aspxMy .02 cents...If you want to build an heirloom with beautifully varnished woods go with the quality material. If you just want a cheap boat and will be painted there isnt anything wrong with using home-center lumber for a simple craft such as IMP. Just know it may not last like the marine lumber. Just depends on what your goals are and what you want and how you want to use the boat.
Keep us posted, I always liked the simplicity and looks of the IMP design, will be neat to follow your progress. I think we are getting enough midwesterners/great lakes regioners to have our own mini gathering sometime.
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My Zip build log...
http://www.vupilot.blogspot.comhttp://picasaweb.google.com/vupilot/Chr ... O0x7SvsQE#"Nothing screams poor craftsmanship like wrinkles in your duct tape."