On Fri, 27 Feb 2004 23:10:29 -0500, "Marc Beroz"
wrote:

Rodney,
What do you suggest I use for core?
Marc

Closed cell foam or end grain balsa, if bonded properly, will isolate
places where water penetrates. You could also glass it solid, although
you would be adding weight just where you don't want it.


I think you are right about cutting out the inner skin, leaving enough
edge to feather and glass it back.

If you started with a piece of good marine plywood with no voids and
covered it in epoxy before starting, you might be able to keep it dry
as long as the rest of the boat will last.

You could also get away with solid _white_ oak for a good while. Not
red oak.

Do you know how old the boat is, and how long it took to get the
current problem? Also, do you know there is not more of the same
elsewhere?

Rodney Myrvaagnes NYC J36 Gjo/a


"Biologists think they are chemists, chemists think they are phycisists,
physicists think they are gods, and God thinks He is a mathematician." Anon

Rodney Myrvaagnes wrote:

On Fri, 27 Feb 2004 23:10:29 -0500, "Marc Beroz"
wrote:

Rodney,
What do you suggest I use for core?
Marc

Closed cell foam or end grain balsa, if bonded properly, will isolate
places where water penetrates.

I agree with the foam, but you are dead wrong about the balsa... I've
replaced the balsa core in many decks where the endgrain balsa has acted
like a sponge and totally rotted out.

Don't believe me ? For an example, take a look at:

ftp://ftp.sailnet.com/pearson/pearso...ted%20core.jpg

(sorry about the long address).

Brian Cleverly (to reply direct, replace the first "z" with an "n" in
the header address)

On Sat, 28 Feb 2004 18:24:10 -0800, Brian Cleverly
wrote:



Rodney Myrvaagnes wrote:

On Fri, 27 Feb 2004 23:10:29 -0500, "Marc Beroz"
wrote:

Rodney,
What do you suggest I use for core?
Marc

Closed cell foam or end grain balsa, if bonded properly, will isolate
places where water penetrates.

I agree with the foam, but you are dead wrong about the balsa... I've
replaced the balsa core in many decks where the endgrain balsa has acted
like a sponge and totally rotted out.

Don't believe me ? For an example, take a look at:

ftp://ftp.sailnet.com/pearson/pearso...ted%20core.jpg

Pearson used balsa in non-end-grain orientation in early boats.

I have a 24-year-old boat that has suffered numerous insults and
repairs and is still strong and just passed a survey. It is cored with
Baltek end-grain.

If the end-grain core is not bonded to the outer layers, water can
travel between, as it can with any core. It does not travel fast
across the grain inside the wood.



Rodney Myrvaagnes J36 Gjo/a


MOM CASTS TOT IN CEMENT

Most experts voice cautious optimism

Rodney, Brian and Marc,

Boy, I wish I had time to tell you all everything I've seen and done in
the last fifty plus years. But - let my start by saying that the
picture - though good - is a bad example. Just like so many things,
when it was first done, builders didn't understand how much trouble they
were starting.

Many builders used endgrain block filler like that. The only ones that
made it work use a filled area around each block the sequester them.
The companies the used block without that left a gap between the blocks
that served as a conduit for any water that got into the construction.

They builders that used bound sheet of end grain balsa did a little
better, but since those where largely laided up construction, the inner
layup usually left at small gap the the core edge that again was a good
conduit for water.

There were places in my current boat that had marine plywood for a high
stress area in a layup of balsa core. In some of those where the
bedding on deck had gone bad, the plywood was shot, though the adjacent
balsa core was saturated and delaminated it was still there. I could
have dried it out and reused it.

Closed cell foam is no answer either. I have a Whaler sailing dink out
here that was mistreated and now weighs in at 300+. I have also ben
contracted to repair laid-up foam core structures that were delaminating
because of water intrusion damage.

The only answer I have come up with that makes any sense is:

Do not trap water.

If there might be a place it can get in, make sure it has a way out. Do
your best to keep it out, but the thing that caused the problem was the
the water stayed in. Drain holes in the inner deck skin will stop the
migration of moisture in the core right there.

If you are going to rebuild a cored structure, learn all about vacuum
techniques for laminating. That is the only way that I have found to
create the solid lamination required.

Matt Colie

Rodney Myrvaagnes wrote:
On Sat, 28 Feb 2004 18:24:10 -0800, Brian Cleverly
wrote:



Rodney Myrvaagnes wrote:

On Fri, 27 Feb 2004 23:10:29 -0500, "Marc Beroz"
wrote:


Rodney,
What do you suggest I use for core?
Marc


Closed cell foam or end grain balsa, if bonded properly, will isolate
places where water penetrates.

I agree with the foam, but you are dead wrong about the balsa... I've
replaced the balsa core in many decks where the endgrain balsa has acted
like a sponge and totally rotted out.

Don't believe me ? For an example, take a look at:

ftp://ftp.sailnet.com/pearson/pearso...ted%20core.jpg


Pearson used balsa in non-end-grain orientation in early boats.

I have a 24-year-old boat that has suffered numerous insults and
repairs and is still strong and just passed a survey. It is cored with
Baltek end-grain.

If the end-grain core is not bonded to the outer layers, water can
travel between, as it can with any core. It does not travel fast
across the grain inside the wood.



Rodney Myrvaagnes J36 Gjo/a


MOM CASTS TOT IN CEMENT

Most experts voice cautious optimism

Rodney Myrvaagnes wrote:

On Sat, 28 Feb 2004 18:24:10 -0800, Brian Cleverly
wrote:



Rodney Myrvaagnes wrote:

On Fri, 27 Feb 2004 23:10:29 -0500, "Marc Beroz"
wrote:

Rodney,
What do you suggest I use for core?
Marc

Closed cell foam or end grain balsa, if bonded properly, will isolate
places where water penetrates.

I agree with the foam, but you are dead wrong about the balsa... I've
replaced the balsa core in many decks where the endgrain balsa has acted
like a sponge and totally rotted out.

Don't believe me ? For an example, take a look at:

ftp://ftp.sailnet.com/pearson/pearso...ted%20core.jpg

Pearson used balsa in non-end-grain orientation in early boats.


If you look closely, you will see that this was in fact endgrain.

I've had exactly the same situation with Cal (not early ones), and
Ericson boats.

I have a 24-year-old boat that has suffered numerous insults and
repairs and is still strong and just passed a survey. It is cored with
Baltek end-grain.

If the end-grain core is not bonded to the outer layers, water can
travel between, as it can with any core. It does not travel fast
across the grain inside the wood.


Agreed, certainly it can travel like that. It is not obvious in the
photo (I wish I had a better one) but there was clear evidence of the
blocks being bonded top and bottom, plus I had to break off numerous
polyester ridges that existed between the blocks.

However, the original poster asked your recommendations for core and you
didn't even hint that he would have to be extremely particular with the
way he installed balsa. FWIW, when I install new balsa I saturate it
with Sys 3 "Clear Coat" epoxy.

As an aside, that particular Pearson has been cut-up and buried in
landfill due to the discovery of gross amounts of delamination in the
hull layup.

Brian Cleverly (to reply direct, replace the first "z" with an "n").

Rodney Myrvaagnes J36 Gjo/a

MOM CASTS TOT IN CEMENT

Most experts voice cautious optimism

Matt,

Thanks for your comments.

I hope the original poster takes note of the steps required to correctly
install balsa core should he decide to go that way.

Brian Cleverly (to reply direct, replace the first "z" with an "n").

Matt Colie wrote:

Rodney, Brian and Marc,

Boy, I wish I had time to tell you all everything I've seen and done in
the last fifty plus years. But - let my start by saying that the
picture - though good - is a bad example. Just like so many things,
when it was first done, builders didn't understand how much trouble they
were starting.

Many builders used endgrain block filler like that. The only ones that
made it work use a filled area around each block the sequester them.
The companies the used block without that left a gap between the blocks
that served as a conduit for any water that got into the construction.

They builders that used bound sheet of end grain balsa did a little
better, but since those where largely laided up construction, the inner
layup usually left at small gap the the core edge that again was a good
conduit for water.

There were places in my current boat that had marine plywood for a high
stress area in a layup of balsa core. In some of those where the
bedding on deck had gone bad, the plywood was shot, though the adjacent
balsa core was saturated and delaminated it was still there. I could
have dried it out and reused it.

Closed cell foam is no answer either. I have a Whaler sailing dink out
here that was mistreated and now weighs in at 300+. I have also ben
contracted to repair laid-up foam core structures that were delaminating
because of water intrusion damage.

The only answer I have come up with that makes any sense is:

Do not trap water.

If there might be a place it can get in, make sure it has a way out. Do
your best to keep it out, but the thing that caused the problem was the
the water stayed in. Drain holes in the inner deck skin will stop the
migration of moisture in the core right there.

If you are going to rebuild a cored structure, learn all about vacuum
techniques for laminating. That is the only way that I have found to
create the solid lamination required.

Matt Colie

Rodney Myrvaagnes wrote:
On Sat, 28 Feb 2004 18:24:10 -0800, Brian Cleverly
wrote:



Rodney Myrvaagnes wrote:

On Fri, 27 Feb 2004 23:10:29 -0500, "Marc Beroz"
wrote:


Rodney,
What do you suggest I use for core?
Marc


Closed cell foam or end grain balsa, if bonded properly, will isolate
places where water penetrates.

I agree with the foam, but you are dead wrong about the balsa... I've
replaced the balsa core in many decks where the endgrain balsa has acted
like a sponge and totally rotted out.

Don't believe me ? For an example, take a look at:

ftp://ftp.sailnet.com/pearson/pearso...ted%20core.jpg


Pearson used balsa in non-end-grain orientation in early boats.

I have a 24-year-old boat that has suffered numerous insults and
repairs and is still strong and just passed a survey. It is cored with
Baltek end-grain.

If the end-grain core is not bonded to the outer layers, water can
travel between, as it can with any core. It does not travel fast
across the grain inside the wood.



Rodney Myrvaagnes J36 Gjo/a


MOM CASTS TOT IN CEMENT

Most experts voice cautious optimism

http://www.transomrepair.com/


I used this stuff to fix the tansom on my boat.

And its waterproof.


On Fri, 27 Feb 2004 23:07:39 -0500, "Marc Beroz"
wrote:

Thanks for your comments. I've responded to some of your points below.

Here's what I understand of your situation: 2 layers of fiberglass,
1/2 to 3/4 inch of mush in between them for diameter of approx. 2
sqft. and you have access to this mush through a small (6in.max)hole
in the middle once you removed the cowl.

That's correct. The core is 1/2" plywood.

The "right" way to fix this would be to rip off the top fiberglass
skin and expose all of the rotten plywood, then replace the core
material and apply a new fiberglass skin, then re gelcoat the whole
thing recreating the antislip patern on the deck somewhere during the
process.

I figured if I removed a fiberglass skin, it would be the inner one since I
have good access & I wouldn't have to deal with the non-skid. This leads me
to another question if I go this route. In one area the mush core has been
removed all the way to the edge of the deck. To replace this core, how close
to the hull/deck joint should I cut the fiberglass skin? If I cut too close
to where the deck meets the hull, I won't have enough space to grind out a
bevel & then reglass the skin back into place. On the other hand, the
further out from the hull I stay with my cut, the harder it will be to get a
good bond between the new core I install & the inner fiberglass skin that I
did not cut out along the edge of the hull. (I'm having a hard time
describing this.) I've been mulling this over for awhile & been been
thinking I'd cut the deck's lower fiberglass skin about 2.5 inches away
from the hull. Any thoughts?


I suspect that this may not be the best solution for you for whatever
reason. A 22 ft sailboat with a cabin trunk does not have a very
large fordeck,and does not have a large unsupported area.

The only reason I was looking for an alternative is that I want to minimize
down time. I was looking to make the quickest repair without sacrificing
safety. I thought that if I made a foam repair & that failed, I could always
do the traditional repair at some point in the future.


So lets look at the the desired outcome before we go straight to
fixes. You want to replace the core with as little effort as possible
and still have a safe boat. The core simply seperates the two layers
of f/g to make for a stiffer panel section. To do this, the core
needs to be VERY WELL bonded to both top and bottom skins.
If your deck feels stiff with the mush inside, it's probably fairly
well build (or at lease the top layer is fairly thick).

Using 2 part polyurathane foam is an accepted practice in boat
building, especially by power boat builders. They tend to use 2 part
P/U foam to do everything from filling holes and deadair space to
bonding (non structual- eg: fish wells) items to the boat. This stuff
sticks to anything and is just as dense as cheap end-grain balsa core
- which is used in most boat decks built post 1975ish.

I would suggest that you go ahead and try the 2 part P/U foam but with
these precautions: get ALL of the rotten wood out, throughly clean the
area between the skins with acetone (3+ times)

I assume you get the acetone in there by shooting it in with a syringe &
then allowing it to evaporate out?

, mix very small batches
of foam and let it expand and dry before applying the next batch(this
stuff expands so much that it WILL push the 2 layers of f/g apart if
it is trapped.

I've looked at the foam products & have wondered how I could get 2 part foam
back far enough between the skins. Is there any way to spray it rather than
pour it? Or are you thinking that I close off the cowl hole in the inner
skin and then pour 2 part foam in from above the deck. I don't have
experience with 2 part foam. Is it real viscous prior to setting up or will
it flow? What if I used 1 part spray foam?

once all of the foam is in, router out (or cut
manually) about 3/4 of an inch back from the opening where you filled
and replace with thickened epoxy. Give yourself enough room so that
the screws that keep the cowl on bite into the epoxy rather than the
foam.

Agree

IMPORTANT things to remember:
1. Get all of the "soft" wood out

I can get all the soft stuff out that I can move with a 1/16 inch diameter
piece of wire but that won't be as good as having good access to the problem
area with a skin removed.

2. clean throughly with acetone
3. mix small batches
4. let each batch cure before applying next batch(make sure you get it
into all of the corners
5. seal all edges with epoxy (just like wood, the foam will absorb
water, so keep it dry at all cost
6. Spend more of your time on the water


The more I consider the obstacles, the more I think I may just have to bite
the bullet & get to work cutting glass. I'd be interested in what you think.
Thanks, Marc