Boat floor repair - Fletcher / Speedboat

[D12ty]

Hi all, after a bit of general advice, I have a Fletcher GTO which I've recently adopted and am giving it a once over before joining the waterways! I have taken up the carpet due to it being soaked and found the ply on top was sodden so removed it, fortunately in one lump which will make for a perfect template when I lay a new sheet down.
under the initial sheet of Ply I found more plywood which was also soaked so requires replacement also. From reading other threads I believe I am best to cut along the edge 1/2" inch from the sides and lay another piece of ply down which I will template from cardboard.
Can anyone share any further repair methods and recommendations including what thickness of ply to use? I have attached some pic below to give you a visual of what I'm up against

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[seaangler23]

I think it was an arrowhead I replaced the floor in years ago, make sure you use decent marine ply and soak everything in epoxy or it won't last, I'd say 10 or 12mm ply. I broke the floor back out it doing jumps but I was young and probably did a crap job

 

[D12ty]

Thankyou, is it normal to have 2 sheets of ply on the floor? I didn't previously have a hatch for the middle of the boat(not sure of official name) should I have one?

 

[oldsaltoz]

Two sheets of ply would indicate a rushed repair, too much trouble to remove the old failed deck.

 

[oldsaltoz]

Looks like you have your work cut out on this one. First thing will be to dry her out and get her undercover if possible. Cut a hole in the ply and have a good look around below the deck for any cables that may be damaged with cutting the sheet out. Make sure the cut is angled so the old floor will lift out without binding. Have a look at the compartments to make sure they have limber holes or not, this is a common failure area if the holes have not been properly treated. I insert a bit on conduit plastic and fix it with epoxy resin and micro balloons with a few strands of glass. If the compartments are not accessable being below deck. Consider filling them with swimming pool sticks, cheap and closed cell so will not soak up moisture and will keep her floating if holed. Check all ribs and stiffeners for damage or rot, another common failure. Marine ply is very expensive and the market has some pretty awfull imitations, looks good but poor quality under the cover sheets. Poliester resin will not stick well to old poliester, so use an Epoxy based resin with stitched glass made for use with an epoxy resin only. Grab yourself a concrete grinding disc with 40 grit rating, it will make short work of any glass removal and give you good control, not to mention you will still have it at the end of the project. They have a slight dish in them with a flexible backing and last very well. Normally a light brown colour. Fits a standard angle 100mm grinder.

That should keep you going for now.

Good luck and fair winds.