Michiel wrote:
central part of the deck (not all of it) is balsa cored and one side
of this is saturated with water. All of it has some delamination.


Bad stuff, delamination.

I drilled some holes from the inside and found that the port side is
wet and some of the balsa is dark and the starboard side is mostly
dry.

So as much as half the deck is still sound, you're saying?

... The water may have come in at holes for deck hardware and some
cracks in the gelcoat, one of them spiderweb shaped.

Yep. Very common problem.

... As an extra piece
of information, the mast rests on a higher area of the deck which
seems to have a thicker core (probably not balsa) which is dry.


I would hope that the area between the mast step and the
compression post (the pillar inside holding up the spot the
mast sits on) would be solid. If it's any kind of core, even
plywood, it's going to compress over time.


I want to stop the water from getting in and I'm also concerned that
the delamination will cause the gelcoat to flex more and thus crack
more. It's been on my mind and I've thought of the following options:

1 - leave it be. put deck hardware back on sealing carefully with
polysulfide or 3M 4200. Perhaps drill a large number of holes in the
inner skin so the balsa can dry out.


That's not fixing it, that's ignoring it and hoping it will
go away.

You could do this, but at some point things are going to
start breaking.

2 - cut out inner skin, scrape out old balsa core and glue down new
balsa or plastic core and then cover this with polyester and
fiberglass.


Yep. This is fixing the problem. It's also a lot more work
than it seems like, hence the advice from another post to
throw the boat away and start over.

3 - cut out inner skin, scape out old core and add multiple layers of
fiberglass and polyester, building up until the deck is nice and
stiff.


Not as good an idea, it will still be a lot of work and will
make the deck very heavy & not as strong. You could laminate
in a grid network to get the stiffness & strength formerly
provided by the core, but that would still be a little bit
heavier and bulkier.


I'm strongly leaning toward option 3, but also considering 1.

Let me know what you think, please!


I think you should have checked for this before buying the
boat. It's fixable... but getting there is going to suck.
Working upside down on fiberglass is one of the biggest PITA
jobs I've ever tried, almost as bad as being a roofer's
assistant. If you do it, don't skimp on prep work.

Fresh Breezes- Doug King

I just got a Jamestown Distributors catalogue supplement in which they
have both balsa core material and plastic core material. I always
wondered why OEM builders do not use synthetic cores and the prices
will tell you. Balsa is $27.00 for 1/2" 24"X48" while the plastic of
the same size is $53. Go with plastic if you are doing it yourself.

So as much as half the deck is still sound, you're saying?


Michiel wrote:
Of the part of the deck that is cored, half is wet now.

Good enough, but just drying the wet part isn't going to be
enough. It's going to need to be dried & rebonded, you might
as well replace it.

... . There is some flex in a couple of
spots (maybe 3/16"), but not so bad it can't be used now. I can stand
on it just fine and I'm not the lightest. My concerns are leakage into
the interior, gelcoat cracking from the flexing and having the water
in the core can't be good.


Exactly. The former owner should have been concerned!

Fortunately, not the entire deck is cored.

The problem is not that the deck is cored, nor is it
unfortunate. Properly engineered cored fiberglass structures
are great, they're stiff & stronger & lighter than anything
comparable. The problem is that many owners of cored boats
don't take care of them & keep the cores from delaminating
and/or rotting.

To say that you wish your boat had no core is to say that
you wish it was heavier & weaker than it is (or was originally).




I would hope that the area between the mast step and the
compression post (the pillar inside holding up the spot the
mast sits on) would be solid. If it's any kind of core, even
plywood, it's going to compress over time.


There's a wooden core about 2" thick. The deck seems solid there. In
the interior photo's you can see the two posts that hold it up.


So, there's a wooden beam in beteen the fiberglass skins,
like say a 2x4?




Well, I think this is going to be my next project.

Thanks for your input!

You're welcome. BTW the advice to cut off the top & replace
the core without having to work upside down is good, if you
can put the boat inside or at least under a roof.

I also saw that you asked about using hardware stroe
polyester resin. I would not try this, since polyester's
bonding strength is much less than epoxy's. If the cost is
*that* much of an issue, then I suggest you try a different
approach, such as cutting away all the core from underneath
and building a plywood sub grid, and bonding it into place
with a lesser amount of epoxy. It will be heavier & less
elegant inside but strong enough and less expensive.

Fresh Breezes- Doug King