Bob,

What error did you make and what were the problems?

You got to the center of my question..... why do we need to
rebed/calk/seal every 4 years?

Is it possible do it once every 20 years if the "proper " product is
used?

In other words, it sounds as though you used 5200 in the past as a
selant and it failed. SO why did 5200 fail?

Chris

Bob,
I assume you addressed this to me. The error I made was bonding my
plywood/teak deck to my steel under deck, space frame type, support
structure assuming that the product is both an adhesive and a sealant. It
leaked and because the bond on 5200 is so tenacious the deck was severly
damaged in the process of resealing and many of the deck elements had to be
replaced. The 5200 is necessary because it is a flexible adhesive and it
will compensate to some degree for the difference in expansion rates between
the different materials. However, it does not squish as well as
polysulphide, nor is it as flexible. During application it is very easy to
leave small voids in the bond area. So my solution was to use polysulfide at
the deck margins and 5200 as the bond to the steel substructure. This has
worked very well. Please note that there are various types of polysulphide.
There is cauking material and sealants. The sealants are more flexible than
the caulking, but are not as UV resistant as the caulking. Check with the
manufacturer before use. It is also possible that your chainplates move
around more than any sealant can handle. In which case you should consider
using rubber boots. I don't have that problem as my chainplates are 3' x 5'
x 3/4" thick steel and they don't move much.
Steve

"bob" wrote in message
oups.com...
Bob,

What error did you make and what were the problems?

You got to the center of my question..... why do we need to
rebed/calk/seal every 4 years?

Is it possible do it once every 20 years if the "proper " product is
used?

In other words, it sounds as though you used 5200 in the past as a
selant and it failed. SO why did 5200 fail?

Chris

Hello Steve:

Thanks for the reply. 3'x5' chain plates? Must be a big rig?!?

I'm not looking for an argument here. Just trying to muck my way
through boatbuilding tradition. I'm sure you've found in a few
insistences that the reason it is the "best way" is because they have
always did it that way. Time marches on and so do innovations. I may
very well find myself going with a polysulfide. But.....

However, I am hoping there is something "better" than polysulfide and
5200. My big question is: why does 5200 fail? You mentioned that it
does not take a squish very well. I know that 5200 can not handle temps
over 150 well. 3Ms data says 5200 can elongate 1300% with out
failure. So the pull in a gap should not be the problem. May the
problem is in the pinch?
Why do you say that 5200 can not take a squish? Is it damaged and lose
the bond??

Have you ever heard of Silaprene or used it?

Still in search

On 28 Sep 2005 13:34:37 -0700, "bob" wrote:

Hello Steve:

Thanks for the reply. 3'x5' chain plates? Must be a big rig?!?

I'm not looking for an argument here. Just trying to muck my way
through boatbuilding tradition. I'm sure you've found in a few
insistences that the reason it is the "best way" is because they have
always did it that way. Time marches on and so do innovations. I may
very well find myself going with a polysulfide. But.....

However, I am hoping there is something "better" than polysulfide and
5200. My big question is: why does 5200 fail? You mentioned that it
does not take a squish very well. I know that 5200 can not handle temps
over 150 well. 3Ms data says 5200 can elongate 1300% with out
failure. So the pull in a gap should not be the problem. May the
problem is in the pinch?
Why do you say that 5200 can not take a squish? Is it damaged and lose
the bond??

Have you ever heard of Silaprene or used it?

Still in search

Hi,

Are you talking about bedding chainplates on the outside of a hull or
sealing where they pass through a deck?

For bedding I'd use eg 5200, mold release wax and some sort of spacers
to create a gasket, then seal the gasket and bolts holes/threads with
a sticky non setting compound.

I'd expect most problems occur where something is used to bed stuff
which is then tightened down too much initially, leaving a layer that
is too thin to take any movement and cannot be compressed further.

cheers,
Pete.

Pete C wrote:
On 28 Sep 2005 13:34:37 -0700, "bob" wrote:

Hello Steve:

Thanks for the reply. 3'x5' chain plates? Must be a big rig?!?

I'm not looking for an argument here. Just trying to muck my way
through boatbuilding tradition. I'm sure you've found in a few
insistences that the reason it is the "best way" is because they have
always did it that way. Time marches on and so do innovations. I may
very well find myself going with a polysulfide. But.....

However, I am hoping there is something "better" than polysulfide and
5200. My big question is: why does 5200 fail? You mentioned that it
does not take a squish very well. I know that 5200 can not handle temps
over 150 well. 3Ms data says 5200 can elongate 1300% with out
failure. So the pull in a gap should not be the problem. May the
problem is in the pinch?
Why do you say that 5200 can not take a squish? Is it damaged and lose
the bond??

Have you ever heard of Silaprene or used it?

Still in search

Hi,

Are you talking about bedding chainplates on the outside of a hull or
sealing where they pass through a deck?

Excellent question.......... plates measure 1/2"x 2 1/2"x 20" and pass
through deck. Deck is cored: 1/4" glass, 3/4" end grain balsa, 1/4"
glass.

Plan on digging core out and potting with thickended epoxy. But still
confused about the next step: 5200 or ? to fill 1/4" gap between plate
and epoxy.


For bedding I'd use eg 5200, mold release wax and some sort of spacers
to create a gasket, then seal the gasket and bolts holes/threads with
a sticky non setting compound.

Hummm. I like the sound of that.
The above is for plates bolted to a hull?
So suggestions for plates through deck?

I'd expect most problems occur where something is used to bed stuff
which is then tightened down too much initially, leaving a layer that
is too thin to take any movement and cannot be compressed further.

Agreed. This is exactly what I have found with all other through deck
bolts. Big problem.

Things were alot easier when all I had to do was pour hot tar around
the hatch/deck channel. Not exactly yachat standards. But worked fine
til the next offload.

Thanks for the rply Pete,
BOb


cheers,
Pete.

On 30 Sep 2005 20:29:30 -0700, "bob" wrote:

Are you talking about bedding chainplates on the outside of a hull or
sealing where they pass through a deck?

Excellent question.......... plates measure 1/2"x 2 1/2"x 20" and pass
through deck. Deck is cored: 1/4" glass, 3/4" end grain balsa, 1/4"
glass.

Plan on digging core out and potting with thickended epoxy. But still
confused about the next step: 5200 or ? to fill 1/4" gap between plate
and epoxy.


For bedding I'd use eg 5200, mold release wax and some sort of spacers
to create a gasket, then seal the gasket and bolts holes/threads with
a sticky non setting compound.

Hummm. I like the sound of that.
The above is for plates bolted to a hull?
So suggestions for plates through deck?

Maybe something more flexible like Sikaflex 221/291 or equivalent
would be better than 5200.

For best leak proofing I'd use a 1/4" deep seam of 22l on the bottom,
then some round section 5/16" closed cell foam wound round the chain
plate combined with a generous amount of sticky butyl sealant, then
another 1/4 seam of 221 on the top.

Would be a little tricky, probably best to mask the top 1/4 of the
gap, put some foam in, do the bottom and wait for it to set, then add
more foam and non setting goo, pull the masking tape away and do the
top.

Still it would give 3 layers of sealing, even if the 221 failed in
part it would keep the other stuff in place nicely. Even if it did
need redoing in some remote place, it should be easy to cut through
the top and reuse the foam with more goo.

I'd expect most problems occur where something is used to bed stuff
which is then tightened down too much initially, leaving a layer that
is too thin to take any movement and cannot be compressed further.

Agreed. This is exactly what I have found with all other through deck
bolts. Big problem.

If making a gasket as above I'd use washers round the bolts as
spacers, then when they are removed I'd fill the hole with some non
setting sealant so it forms a nice donut round the bolt thread.

cheers,
Pete.