Oyster 46 1981 - Whole deck core replacement

[dankilb]

Thanks once again for your input gents.
The genoa car track is, I think, mounted on an area with a plywood core, which is for sure rotten (I‘ll see exactly when I open that area up, at the moment trying to deal with one area at a time).
The area of the inner forestay is clearly delaminated and has been well compressed with a pretty big deflection in the top skin of glass. I’m going to be using closed cell foam for all no stress areas, was thinking of G10 or similar only in high stress areas like under the davits for example.

In the UK, the cost of G10 sufficient to cover all high load fittings would be prohibitive. Even making your own, the materials would add up. That’s why ply remains the prevailing solution for high stress areas. Marine ply plus drill-fill-drill should make it pretty fail safe.

 

[geem]

In the UK, the cost of G10 sufficient to cover all high load fittings would be prohibitive. Even making your own, the materials would add up. That’s why ply remains the prevailing solution for high stress areas. Marine ply plus drill-fill-drill should make it pretty fail safe.

Its not so expensive to make your own. I bought a whole role of 300g/m2 for £140. Yes the epoxy is costly but in the scale of things, its not a huge cost.
Far better than expensive marine ply

 

[Sea Change]

Slight thread hijack but what about using a piece of scrap grp?
Asking because I need to tackle my deck compression under the mast step, and where I am there are literally hundreds of abandoned grp boats. It would be pretty simple to 'recycle' a bit of grp cut from an old hull. I guess it would be advisable to grind off the gelcoat?

 

[Antonio Silva]

If it were me, I'd probably drill loads of small holes in the deck and inject epoxy into them, filling the core with it.

 

[Antonio Silva]

The core is soaked and has turned into mush, how do you expect the epoxy to cure?

 

[geem]

That's not going to work. The core is full of wet balsa. How are you going to get the moisture out and the mushy balsa? What do you think squirting epoxy in will do? If it's one inch core over the whole deck, how much weight will you add with epoxy? How do you expect the epoxy to bond to wet substrate?
You post adds nothing to the thread. It is not based on any knowledge of the subject

 

[Ceirwan]

Its unlikely anyone is making true G10 at home. Its made using high pressure & a heat set epoxy, not practical at home.

But you can make your own fibreglass (or epoxy) sheet that is as good for this purpose by creating the laminate between two Formica (or other non stick surfaces), and heavily weighing down the top sheet to compress it all.

 

[geem]

Its unlikely anyone is making true G10 at home. Its made using high pressure & a heat set epoxy, not practical at home.

But you can make your own fibreglass (or epoxy) sheet that is as good for this purpose by creating the laminate between two Formica (or other non stick surfaces), and heavily weighing down the top sheet to compress it all.

I have made plenty of grp sheet. My preferred surface is a sheet of glass or perspex. Just wax it first and layup. A metal serrated roller is excellent for pushing epoxy through the laminate. Once the desired thickness is created, cover with peel ply. If you need a lot thicker sheet. Make one larger thinner piece then laminate them together. For deck reinforcement, this method works perfectly well. I have also used this method for planing plates on outboards and backing pads for deck fittings. I much prefer it to marine ply. You can epoxy them in place and chamfer the edges. They last for ever and no rot

 

[CanePazzo]

Good morning all.
Time is ticking away and my project is trundling along, maybe a little slower than I would like but that’s s working on your own. Removed the top skin of glass where the genoa car track sits and to no surprise whatsoever, the ply underneath was completely rotten. The three areas opened up now (aft deck which has davits mounted on it, and the two parts of the side deck where the genoa car tracks are located) are now prepped for a sheet of glass to be put down and then the corecell pvc foam core. I was going to go with plywood core in the high stress areas but have just found, at my local engineering workshop, someone cutting up old fiberglass water tanks which have a wall thickness of about 10 mm. I’m thinking to use these to fabricate a form of G10 by laminating sheets of this together. Obviously removing all old gel coat, prepping the surfaces accordingly and the epoxying them together.
Any concerns regarding this thought?
On the idea of reusing the cut out top skin, there was a mixed response. If the corecell will adhere to the old glass of the bottom skin, why not the top skin as well? Either side of the cut would be ground down to the required bevel and three layers of glass laid in to create the bond between them and once all repairs are completed, then two layers of 450g biaxial laid over the whole deck.
Thoughts?

 

[geem]

Good morning all.
Time is ticking away and my project is trundling along, maybe a little slower than I would like but that’s s working on your own. Removed the top skin of glass where the genoa car track sits and to no surprise whatsoever, the ply underneath was completely rotten. The three areas opened up now (aft deck which has davits mounted on it, and the two parts of the side deck where the genoa car tracks are located) are now prepped for a sheet of glass to be put down and then the corecell pvc foam core. I was going to go with plywood core in the high stress areas but have just found, at my local engineering workshop, someone cutting up old fiberglass water tanks which have a wall thickness of about 10 mm. I’m thinking to use these to fabricate a form of G10 by laminating sheets of this together. Obviously removing all old gel coat, prepping the surfaces accordingly and the epoxying them together.
Any concerns regarding this thought?
On the idea of reusing the cut out top skin, there was a mixed response. If the corecell will adhere to the old glass of the bottom skin, why not the top skin as well? Either side of the cut would be ground down to the required bevel and three layers of glass laid in to create the bond between them and once all repairs are completed, then two layers of 450g biaxial laid over the whole deck.
Thoughts?

Far easier to use new laminate in my opinion and you guarantee no voids.