Plywood for core

[Ocean Girl]

And more pics

[Ocean Girl]

Last one, profile of lid.

Thanks for all the great advice.

[jkindredpdx]

I've used stitch and glue plywood when building canoe and kayak hulls. The problem with resin over wood, is that the water gets in through holes or cracks caused by expansion and contraction of the wood. Once in, the moisture gets trapped inside. So, I lean toward sealing with resin only on one side and leaving one side (the bottom of the lid) unsealed so it can breath and dry out. Another option would be to oil solid wood boards joined for lids rather than fiberglass.

[minaret]

Originally Posted by RainDog

Indeed the hatch is in good shape and fits very well except for the core saturation. Ocean Girl will upload a picture, but I think I will take Minarets advice and use Coosa. Once i remove the bottom skin and get it really well cleaned my plan was as follows. Let me know if my plan is bad:

- grind/sand edges of existing fiberglass to taper edges
- Clean with acetone
- Lay down a bed of slightly thickended epoxy
- Put the coosa core in. let epoxy cure.
- Fill an gaps around the edges with tickened expoxy. Let it cure.
- Glass over the core with 2 layers of 1708
- Primer, paint

Pretty good. A few points-

No taper will be required. Grind for prep but since you will be glassing to the inside of the flange, you do not need to taper as you would for a repair. Leave your glass long and green trim it flush for no grinding afterwards, but this can only be done in poly. Using epoxy for this is probably a mistake. If the original inner skin was truly 1/4", your new one must be as well or the hatch will no longer sit flush. A 1708 is about a 1/16", less if you glass well. This means that you need more glass thickness than necessary for strength. Much of the original layup was probably poly and Matt. It will be faster and much cheaper in poly. Alternatively you could do a thinner layup and rely on weatherstrip on the coaming edge to make up the difference, but this will load your hinges.

Use a notched trowel to apply your filler (I use poly CoreBond, which stays flexible and will not crack unlike epoxy). You should also drill 1/4" holes in your core in a 4-6" grid pattern before bonding. This will allow an avenue for squeezeout. There should be no gaps, and you should be able to fillet for glass at the same time. I always apply a sealer coat of resin to the core before bonding as well. Often the underside of a factory poly hatch is finished with brushed on Gelcoat as the exterior is obviously the molded side and they don't go to the trouble of finishing the inside, ie fairing, primer, and paint. If you do it in poly, you can glass it, check fit, and then brush on a coat of gel with no other work required. You cannot do this with epoxy. Of course, if the inside of your current hatch is finished (a rarity), you will have to finish to match.

[nimblemotors]

This looks like a pretty straightforward repair, I wouldn't overthink or overspend it.
Just cut out the inner glass sheet (like already done, leave area at the edge) to get all the rot out, and get some non-rotting material the same thickness as the ply, and glue it in and glue the bottom you cut out back on,
and your are done.

Polyester resin would work (if doesn't melt your core material), epoxy too, 5200, gorilla glue, doesn't matter much really. coosa-shmoosa, I'd just get some corkboard or even 'fatigue' stand-on foam rubber mats.

I'd replace the area where the hinges go with solid material, maybe here you want some epoxy (as it doesn't shrink) but just drill oversize holes and fill them with the epoxy, like any cored holes are done.

You are gonna see the cut lines, could really fill and paint if you want.
It is a locker cover, not furniture, or a transom.
You could get all crafty and turn it into a big project... Inlay your boat name in the wood veneer...
Just my $0.02

[ElGatoGordo]

I'd use ACX, and like said above I wouldn't coat but rather paint the inside. But I'm lazy and don't care what the inside of my locker looks like :-)

[Richard5]

Being a perfectionist and taking pride in my work I agree with Minaret.

That said, I am surprised at the lot of you. ACX? This race to the bottom hasn't yet found the bottom. Allow me...take those big honking nails you salvaged back in the boat yard and stretch a piece of old sail cloth across the opening. Stab those nails through the sail cloth and cast off wood scrapes to be used as cleats top and bottom and bend those nails to clinch them below the deck. The first person to complain about the ill fitted seat is next in line for the MOB drill.

[bletso]

Actually I have a little experience at this. It all sounds a bit foreboding at the outset, but it is just time. Yes, the selection of materials is always a question. For me, it was just trying to figure out what the original guy did and then making a best guess.

Stbd aft cockpit | Sailing Vessel Vigah
Hatches | Sailing Vessel Vigah

[ElGatoGordo]

Originally Posted by Richard5

Being a perfectionist and taking pride in my work I agree with Minaret.

That said, I am surprised at the lot of you. ACX? This race to the bottom hasn't yet found the bottom. Allow me...take those big honking nails you salvaged back in the boat yard and stretch a piece of old sail cloth across the opening. Stab those nails through the sail cloth and cast off wood scrapes to be used as cleats top and bottom and bend those nails to clinch them below the deck. The first person to complain about the ill fitted seat is next in line for the MOB drill.

Slightly aloof this morning? Or was it early in life you became better than us mere mortals? Lol
What a joke of a post, thanks for the helpful info (insert roll-eyes emoticon here)

[minaret]

Originally Posted by Richard5

Being a perfectionist and taking pride in my work I agree with Minaret.

That said, I am surprised at the lot of you. ACX? This race to the bottom hasn't yet found the bottom. Allow me...take those big honking nails you salvaged back in the boat yard and stretch a piece of old sail cloth across the opening. Stab those nails through the sail cloth and cast off wood scrapes to be used as cleats top and bottom and bend those nails to clinch them below the deck. The first person to complain about the ill fitted seat is next in line for the MOB drill.

Race to the bottom is right. I often wonder why I bother explaining how to do it right, when very few here seem to be concerned with that. Much more concern over doing it quick and cheap. I think the $500 a month set needs their own forum so they will leave us regular boaters alone with their whining about time and money expended. It may not be furniture to you, but to me it's a yacht, and that should be finished finer than any lump of wood sitting in someone's living room. If you can't see the advantage in taking the time to build something that will truly last, I can't be bothered to try to convince you otherwise...

[minaret]

Originally Posted by Ocean Girl

More pics

Look carefully at this pic. If that's 3/4" core, the inner skin is more like 1/8" than a 1/4". Not surprising. Most peoples "1/4" is not even close by eyeball.

[RainDog]

Originally Posted by ElGatoGordo

I'd use ACX, and like said above I wouldn't coat but rather paint the inside. But I'm lazy and don't care what the inside of my locker looks like :-)

The original point of this thread was to try to understand what difference it would make to the end result of the project if it was done in different grades of ply. I never got any responses along those lines here, but did find the info on woodenboat forum: What type of plywood do you use for boatbuilding?? [Archive] - The WoodenBoat Forum

[jkindredpdx]

If you check out Wooden Boat Magazine archives, Richard Jagels The University of Maine - Office of Human Resources - Dr. Richard Jagels answers any question about wood and and boats that you can imagine.

My understanding is that Marine ply is required below the waterline where it will be continuously submerged. Waterproof/outdoor ply is ok for stuff above the waterline... I think both have waterproof glue and the difference is in the species of woods and voids... IMO though, no matter what type you use, I wouldn't seal both sides with glass/resin. As for species, I think Okoume is a preferred veneer for rot resistance. I believe Koa is good also.