marine plywood to replace balsa

Hey great site, I have a 26 ft reinel that had a rotten core under the fuel tank. I have romoved all of this material because I was told that was the only way to fix it. The problem is that I am having a hard time finding balsa to replace it. I was told that using marine grade plywood in strips would be an alternative but I have not found any information to support this claim. Is this a good alternative and if so how do I go about making this repair, are the strips placed in resin as the balsa was and then covered, how wide do they need to be, how should I clen the hull before applying anything to get the resin to bond to it well. Thanks for any information

 

Thry these chaps for end grain balsa

http://www.baltek.com/products/egbc/egbc.html

 

Okume is probably the lightes plywood with a density of 0.4 or so.
But that is three times as heavy as balsa.
Then you could possibly use less glass and epoxy so the difference isn't that big.

 

Should work... assuming its pretty flat.... you will have a hard time bending it otherwise.. the key to success will be that you:
1. coat ALL surfaces of each strip with epoxy to make them waterproof - you dont want the rot again (waterproof glued wood can still rot if wet, warm with a bit of O2)
2. fill ANY gaps between the strips with an epoxy putty that is designed to work with the epoxy you use - this not only adds some strength, but stops any water from getting around that might get in there
3. if you make any holes, for fasteners for example, in this part (or any part) of the hull, first seal them with epoxy before putting the screw in, and use some bedding around the head for extra protection
4. put a layer of fiberglass in, soak it with epoxy, and then put the strips on top... don't just lay the strips ontop of a layer of epoxy.
5. roughen up the old surface first

This should help. But do note that the plywood will be heavier, and if you use a lot it could affect the balance of your boat. Also, its stiffer, so if its pounded a lot, the laminate layer might crack, or separate from the ply... but that would require some pretty extream multiple stress...

Good luck

 

Thanks for the help, I think i can figure it out from here, I pulled all the floor out of the inside and found this strage looking plastic feeling material under the floor in the back near the engine. I called the previous owner and he said that they poured seacast in for the stringers under the engine. It looks pretty good and is probably about the same density as wood is (a guess). Anyway the people that did this job tried to cover a drain hole, it leaked and that is were the water came into the floor and why it is only in a small area around the hole. They did not use the seacast in this area. they just did a poor job with the fiberglass and resin and I dont think they sealed it with anything.