HI Vermonster. While you could use oak, I think you'll find that it's much too heavy for your purposes. Oak is generally used to make trim and/or pieces that need to be steamed and bent. In fact, red oak and can be steamed and tied into a know, if done correctly. However, generally speaking, most tin boat guys tend to go with high quality, NON PRESSURE TREATED, exterior grade plywood such as Aurauco brand available at most Lowes/HD. You could use marine grade, if you can find it and don't mid the expense. The only thing that makes it "marine" grade is that it is void free and uses high quality glue between the plys. MDO ( not MDF) is also a good material and is used to make professional exterior signs.
After laminating the appropriate number of pieces of plywood together to get the desired thickness, you'll then need to seal/waterproof it. There are a couple methods most folks use. The first is to use a high quality, wax-free polyester resin and fiberglass mat to fully encapsulate the plywood. The other is to use 2-parts, spreadable epoxy to seal the wood. It is a bit more pricey, but it tends to be less work, lower fumes and you can use any leftover epoxy for all kinds of cool stuff. You will need to paint it after it dries to give it UV protection. Once treated, using either of these methods, the wood should outlast you. If you don't have the time, money, or inclination to do either method above you can also use several coats of Spar Urethane and/or several coats of high quality, exterior grade paint like porch paint, or Rustoleum Professional Oil based enamel, also available at Lowes/HD. These methods will by no means waterproof the wood like f'glass and epoxy, but you should still be able to get several good seasons worth of use out of them. Be sure you attach them to the hull using either aluminum replacement rivets and/or stainless steel hardware dipped in 3M 5200 marine caulk. You can get everything you need at Lowes/HD including angle and stock aluminum, except for the f'glass and epoxy supplies. However, you should be able to get epoxy from any West Marine boating store. That's really about it. The rest is up to your budget and imagination. Good luck. Holler if you get stuck.