Polyurethane glue expands
Gorilla Glue and other polyurethane glues are strong, durable and waterproof, and the excess trims away fairly easily, but remember that the glue expands as it sets. This is great if you are using clamps or weights-- the glue expands to fill small voids between the two joined surfaces, and the clamps/weights keep the pieces from being forced apart. Without pressure, you're likely to end up with a too-thick (and therefore weak)layer of glue between the hull and the centerboard flap, and the thickness of the glue layer is likely to be uneven. One way to apply pressure in this case be to turn the hull upside-down -- you glue down the flaps, cover them with a strip of waxed paper, then lay down a flexible wood batten, topped by weights -- bricks, cans, or whatever you can find to apply even pressure along the batten. The waxed paper prevents the excess glue squeeze-out from bonding the batten to the hull.The only certain advice I can offer is this: when you use polyurethane glue, be sure to wear gloves. Wherever the glue touches your skin you'll get a dark stain that won't wash off, and takes days to wear off. I repair and refinish antique furniture and I speak from experience.