Proceed with caution if buying from the big box stores. I'm prototyping a new design using the cheap stuff. Here's an excerpt from my build log:While reading this post, please keep in mind my comments are based on the assumption the hull will have a natural wood finish. If you decide to paint it, some of the comments below may not be applicable.
Here's two images showing a side-by-side comparison. 4mm Okoume is on the left. 5.2mm Exterior grade on the right.
Now you might be thinking: "hey wait a minute...the exterior grade looks like some nice even layers. And you'd be right. However, they also laminate a .5mm skin layer to each side.
And that's where the problems begins. It's hard to find a full sheet with no cracks in it as shown. Also, if you sand on it, be very gentle otherwise it easily disappears and you can see the underlying layers.
I wish I had a large drum sander so I could sand off the paper-thin exterior face plies to see how the wood quality is underneath. But maybe it's best not to look behind the curtain.
The Exterior Grade ply has 2 different colors on each side. Which is another challenge to overcome.
One side has a nice mahogany color... resembling Okoume. The other is almost white in color with some interesting grain lines running in it. The dark horizontal lines are not cracks.
If the color was consistent on both sides of the sheet like Okoume, then it wouldn't matter which side you started working with because they are the same.