Screws all stripped and backing gone

[Reefgeorge]

This is one of my cockpit sole fish boxes. The two end lids are screwed into the stationary center section using piano hinges. The hinge screws are all pulling out of the center section. I started drilling out the holes ready to do the allen wrench and drill clean out followed by injecting something like S10 to be able to re dril and be done with it. What I found is that it is completely hollow behind the fiberglass and gelcoat veneer. Looks like I will need to come in from underneath the center brace with either individual holes and a backing material or cut out the entire length near the edge and bed in a length of material. What do You guys suggest?

Thanks,

George
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[Pascal]

Why not replacing the piano hinge with thru bolted low profile hinges. Thats how most floor hatches are done nowadays

[finatic]

How about filling in the entire void under the center strip. Glass in a piece of marine plywood and then use longer screws and 5200.

[Boatsb]

Cut the skin and fill with epoxy and kitty hair. Replace the skin and repaint. If there's a core of plywood replace it at the same time.

I do this on older boats all the time. It's a bit messy but easier than making new hatches in most cases.

[rustybucket]

Can you tell if it was cored? Possibly Balsa, foam or plywood cored and completely mush now?

If so, the correct fix would be to cut out the bottom of the laminate, re-fill the core with something (marine plywood, balsa, composite...etc) and re-glass the underside in.

If the core is completely soup, you could maybe just pop some big holes in the bottom remove as much material as possible and use a pourable transom type filler to fill the void. But this may be more trouble than it's worth really. It would be too easy to fix this the proper way.

[Reefgeorge]

I can't tell what was in the "core" of the structure originally. When I drilled out a couple of the screw holes some blackish mush is in the drill bit grooves. I can't tell if it dry rotted wood mush, moldy coring material or what. My longest drill bit just disappears into the holes with almost no resistance so there is nothing left in the center of the sandwich along the screw edge anyways. I might drill a hole into the underside at the center to see if I can figure out what innards are supposed to be.

[Cricket]

Been down this road many times. Open up the skin on the back. Epoxy and clamp some 1/4"-3/8" fiberglass flat stock to the backside of the lip. We like drilling and tapping the holes for machine screws instead of using sheet metal screws. If you can't get fiberglass strips teak is a good alternative to glue in but you will have to use sheet metal screws, it won't rot and is strong, glues a lot better than what some think. If there's a plywood or balsa core replace with foam, stay away from plywood, and then replace the bottom skin. I've scene aluminum strips glued in with 5200 and then tapped for machine screws but don't like the SS and aluminum dynamic.
Just amazes me how even good boat builders put some things together they know will fail.

[rustybucket]

I can't tell what was in the "core" of the structure originally. When I drilled out a couple of the screw holes some blackish mush is in the drill bit grooves. I can't tell if it dry rotted wood mush, moldy coring material or what. My longest drill bit just disappears into the holes with almost no resistance so there is nothing left in the center of the sandwich along the screw edge anyways. I might drill a hole into the underside at the center to see if I can figure out what innards are supposed to be.

My (uneducated) bet would be it was balsa or ply. Regardless there is no right or wrong coring material to use there. If you want cheap and easy go back with marine ply. Really for situations like this it's hard to beat marine ply. All the composites come at a much greater price and don't really give you much in return (other than a longer life). Some of the composites don't hold screws very well either and none of them hold screws better than good old marine ply.

-Cut/grind the bottom skin as close to the edges as possible.
-Remove the skin, Scrape/hose out the old core, clean with tri-phosphate then a solvent.
-Cut new marine ply piece to fit
- Make sure all pieces are well dried
- Use west system epoxy with an adhesive filler to coat the skin, then I'd pour some into the skin and mash the plywood on top of it. I'd use weights to weight the plywood down overnight removing any excess epoxy as it oozed out.
- glass in the bottom of the ply with fiberglass cloth or biaxial.
- sand and paint.
-reassemble everything

[Reefgeorge]

If I do replace the entire core, it would seem that I need something along the edges for the screws to bite into besides coring or the end grain of marine plywood so the teak strips or fiberglass flat stock seems reasonable. Would poured thickened epoxy like Scott suggested also hold screws well?

[Boatsb]

It sounds like rotted wood core.

The easiest fix is remove the back and replace with a non organic material. I do these all the time. replacing with a core will not hold screws. The screws need something that will hold better than foam.