BucketEars - Fill the cracks and holes
When building quick, you end up with a bunch of little cracks here and there that need to be filled, like maybe a corner didn't come together properly. Also the plywood will have voids and cracks in various places. Don't worry, this is normal, and here are many techniques for filling and sealing those cracks.
One of the easiest fillers that you can use is mix up Titebond II glue with fine sawdust, such as what is in your belt sander catch bag. You can also use wheat flour (bread flour), other powders, or combinations of powders.
Mix TB2 with the powder to make something that looks like peanutbutter.
You can use epoxy or other glues instead, but I prefer TB2 because it is non-toxic.
One other common trick is to put regular sawdust in your blender and chop it up. Please don't email this picture to my wife.
Get your helper and start filling in all those little holes.
For screw holes, you can glue a toothpick in the hole first, then fill over the top.
The face (big flat part) of plywood is naturally very impervious to water. The edges are a different story, they sometimes can act like a soda straw and will suck water into the wood.
The edges of plywood really need to be sealed up, and this is a good start at doing that. You use the filler then sand it after cured to make it smooth. Later you can epoxy and fiberglass the chines.
I should have been more picky at the store and gotten a better sheet of plywood. This one had a couple of large chunks missing, and I used fillter to fill up the missing wood.
On the inside of all the corners, you need to seal the corners. This is really easy to do with PL-200, see next picture.
The way you do it, is to squeeze a bead in the corners and then use your fingers or a popsicle stick to smooth the glue into the corner better. Go ahead and seal every corner on the inside of your boat.
This is what PL-200 looks like. It is a carpenter's glue, is about $2 per bottle. When applied, it feels like thick peanut butter, and when it is cured, it stays a bit rubbery.
PL makes a lot of different blends of their glues, this is the one I prefer. It does not bubble up like some of their other blends.