Soft Spot Repair - Lay New Glass Or Reuse Old Glass?

[nautilus55]

Brief explanation: I have a soft spot on my port deck, about 7 feet long, that runs between the toe rail and the cabin top around my shrouds. Current plan is to cut out the glass on deck in sections, asses/replace the core where needed (without removing the chain plates) and epoxy it all back together before repainting the whole deck.

Should I reuse the old slabs of glass from the deck? Or just rebuild it with fresh glass, fairing compound etc.? I’ve seen people do it both ways…

At first glance, the new glass seems like a better option, because of the assurance of a strong chemical bond, especially where the new glass meets the old, (the ”seam”).
But, the old glass is quite solid and has a strong chemical bond as is.
The disadvantages of using the old glass is probably around the “seam” of the cut, meaning that we may end up with a weaker deck along the “seam”. However, if you grind back the layers of glass on either sided of the cut, leaving plenty of room to build it back up with glass layer by layer… what’s the difference?
I realize this is a pretty complicated question… would really appreciate any input.
Thanks!

 

[stickinthemud57]

Pictures would help, I think.

As you alluded to, one challenge will be making a solid attachment to the sound portion of the deck. I would think this will require a fair amount of overlap, (most likely on the bottom side?).

Something I am wondering is why there is a soft spot. Was it damaged and if so, what was the nature of the damage - impact, flex, something else? If not damaged, then what? Just not laid up thick enough initially?

My gut says keep the original material and strengthen it as needed, but I don't feel I know enough to say that with confidence.

 

[dmax]

Do a forum search on "deck core replacement" (or similar) - there's lots of information on how to do it and some alternatives to cutting the deck (though if you're planning on repainting, that's a good way to go). The general consensus is that re-using the old deck is not worth it - much easier to get a fair surface, get a good bond with the core and ensure it won't crack at the joints with new glass.

 

[nautilus55]

Thanks for that suggestion dmax, hadn’t considered how re using old glass could make it difficult to get a fair surface. Will do a search for deck core replacement, but am thinking laying new glass is the way to go. Cheers!

 

[capta]

We used new glass, but we were sailing nearly daily in the eastern Caribbean.
My bigger worry would be about the condition of the chain plate attachment to the (take your pick) rib, frame, stringer. Obviously, water has been getting in there for quite some time.

 

[nautilus55]

We used new glass, but we were sailing nearly daily in the eastern Caribbean.
My bigger worry would be about the condition of the chain plate attachment to the (take your pick) rib, frame, stringer. Obviously, water has been getting in there for quite some time.

Excellent point. As of now the bulkheads appear to be quite sound, but I will be doing a more thorough inspection when I pull the chainplates out to polish and inspect them. The bolt holes provide a great window into the bulkhead core.

 

[jssailem]

You might want to check out the deck rebuild completed by Andy at Boatworks Today. Good YouTube video from a few years ago.

He did a cockpit on a power boat, if my memory is correct. Should be similar to the type of issue you have.

I’ve seen and heard about leaving the top deck in place and opening up the deck from beneath. Sucking out the failed core, then vacuum sealing the epoxy to attach the new core and do the fiberglass in from the bottom.

Are you thinking about removing the mast? The stays and mast apply pressure to the hull and the deck holds the hull in place. There are forces I play that you will want to keep stable.

 

[nautilus55]

You might want to check out the deck rebuild completed by Andy at Boatworks Today. Good YouTube video from a few years ago.

He did a cockpit on a power boat, if my memory is correct. Should be similar to the type of issue you have.

I’ve seen and heard about leaving the top deck in place and opening up the deck from beneath. Sucking out the failed core, then vacuum sealing the epoxy to attach the new core and do the fiberglass in from the bottom.

Are you thinking about removing the mast? The stays and mast apply pressure to the hull and the deck holds the hull in place. There are forces I play that you will want to keep stable.

Boat Works Today is one of my references for reusing the old deck glass. As I recall, he actually did have problems with fairing after he put the old glass back on. The answer was right in front of me.
Excellent point about removing the mast. As of now my understanding is that the Deck is not part of the super structure on a Cal 39. The chainplates pass cleanly through the deck, and the bulkheads are lightly tabbed to the underside of the deck. They are tabbed to the hull with extremely heavy duty glass however, and I’m confident that by removing the top layer of glass and core, the rigging will not be significantly compromised while the boat is on the hard. Hopefully