I have expressed opinions that might be interpreted on both sides of this issue:
My most recent experience indicates It's probably a good idea to seal the wood, in and out, before covering.
You're not going to keep all the water out. I had water get under the covering of a flying boat, and it made the un-sealed ply skin of the hull all gooshy and moldy. That was real high on my "BAD" list.
try to slow down the water from soaking in. take the wing off and let it dry out when it's being stored.
Radios in baggies are as likely to hold water in as out, so I strap my radio/batteries to a perch in the middle of the fuselage. The water has to get deep before there is any standing water on the circuitry. Mount the receiver somewhat aft, also.
If a plane flips over, it floats nose-down. mount the radio so it will be out of the water regardless. If you flip the plane, it will float nose-down on the wing. Everything that will be under water should be sealed, but take out the tank, batteries, and all the foam and get it dry anyway.
I love my 4-cycle OS, but the bearings got a lot of water in them and rusted. It happened to my friend's ENYA, too. In examining the 4-C arrangement, this is not likely to work itself out easily. OIL your bearings after every flying session. Corrosion-X is a GOOD product to protect the bearing and electronics. Available at FBOs, Marine suppliers, and from
www.corriosionx.com