hull reinforcement

[blaze_125]

I'm fairly new to boating, I don't know the slang and proper words of most things I'll be talking about here, so bare with me and educate me when needed.

I was planning to revamp my boat and make it all pretty again. At first I wanted to simply slap a new sheet of plywood on the current floor and build from there but my plans quickly got shattered. The reinforcements that sit under the current floor are rotten and pratically falling appart.

The current floor seems to be layered like this.

Fiberglass mat
Wood
Wooden reinforcement/filler foam
fiberglass hull

I'll be removing the first 3 layers and be left with an empty hull.
I got some 2X4 that have been sitting in the basement for over a year so it's safe to say they are dry. Can I cover them with fiberglass resin and use that to replace the reinforcements? When I say reinforcement bars, I'm talking about the wood thingy that runs from the back to the front of the boat.

Once the new reinforcements are installed... what do I use for foam? Will regular insulation foam in a can do the job?
http://www.homedepot.ca/wcsstore/HomeDepotCanada/images/catalog/44de1dd8-4beb-429e-a2a1-5bcc11290a57_4.jpg

I'm on a tight budget, but I still want to make sure I don't sink first time I take her back to the lake.

[blaze_125]

after some reading around here, I beleive the "reinforcements" I'm talking about are really called "stringers".

[blaze_125]

For the ones who care... this is the baby I'm fixing up.
The exterior is pretty much perfect... aside from a small hole in the shell(which probably led to the rotten floors) and the transom.
I may need to create a new thread for the transom, or maybe I'll just add to this one.

[blaze_125]

So here are the pictures of my problems...

First pictures you can see the rotten stringers
And the other pictures are of the transom.

I have no idea how to change the rotten wood in the transom because it's got that pit right in front of it.