Repair of Quadrant Cover Question

[Ward H]

I'm ready to repair the quadrant cover on my C30. The core of 1/4" plywood is rotten and the cover sags when you stand on it when at the helm.
The bottom of the cover is just a skim coat of fiberglass and gelcoat. I'm guessing the strength comes from the top coat of fiberglass and plywood.

My question is what do I replace the plywood with:
1. Plywood. I have non marine but would I need marine grade?
2. Balsa, which I have
3. G-10, which I have

I was thinking that the G-10 epoxied to the top layer of fiberglass would be the strongest and not I would not need replace the bottom skin. Weight isn't an issue.

Here are a couple of photos of the 16" x 20" cover.

 

[kappykaplan]

My boatyard the rotten plywood in the cockpit sole with a solid foam core. Makes things a little quieter when running the iron jenny.

 

[Ken Cross]

It seems like a pretty large area for 1/4 inch plywood. does it have center supports?

Ken

 

[Ward H]

It seems like a pretty large area for 1/4 inch plywood. does it have center supports?

No center supports or stiffening ridges. One of the reasons I was considering G-10 over plywood and balsa was I thought it would be stiffer.

 

[Scott T-Bird]

I think the G-10 is a good plan.

 

[kloudie1]

or a foam like Airex or devinycell (sp)
https://www.greatlakesskipper.com/t...cjARbHe5RgAA5wrAom8sWmgENfzJ_BzBoC3bgQAvD_BwE

 

[victorhoisington]

So my H28 had a similar problem. I built a new custom cover made from teak and birch paneling with a stainless cover for the emergency tiller access.

I'm an amateur wood worker so, things I learned, even though the entire cover (all sides) was covered with epoxy, I should have allowed more room for expansion and the back needed more support where it hung over the transom. However, overall it came out nicely and was much sturdier than the original and certainly nice to look at.
Just an idea

 

[Bob S]

This I believe is somewhat common. On my C30 MKIII I scrapped out all the rot and let it sit over the winter to dry out thoroughly. I didn't want to remove all the wood core because I didn't want to ruin the integrity of the top side diamond gelcoat. I filled the voids with a thickened epoxy - Progressive Wet/Dry 700.
https://www.epoxyusa.com/Wet_Dry_700_epoxy_putty_p/te05.htm
I don't remember it being this expensive when I bought it 8 or 9 years ago but it has lasted, the gallon goes a long way. I've repaired my keel with it and over this past winter used it to fillet the inside corners of a custom battery box. I still have a third of it left. Yours doesn't look too bad.
Make sure you seal it from the topside. Any hairline cracks or drilled holes not cored per Maine's instructions will leak water back into it. I don't think the water migrated in from the underside.
Good luck, it never ends!!!