Hello:
Any thoughts on this.
Chainplates are a source of leaks and equal source of debate on how to
fix the leak.
Some people say use polysulfide because if you use 3M5200 you'll be
tearing your boat apart to rebed plates in a few years.
Others say the reasons why plates leak is because polysulfide do not
have required strength. The only way to solve plate leaks is to use
3M5200. Why? It has a much stronger bond.
Others say that 3M5200 loses its bond eventually and it too will leak.
Only this time the boat owner has a major problem removing the old
adhesive to rebed.

Here is the question....... Why would 3M5200 bond fail?

I called 3M tech people and they sent Tech Data Sheet (effective:
12/1/2004). Interesting data.
I also called Royal Adhesive and received data for Silaprene.
This is what I read.

Stainless to Stainless Overlap Sheer Strength
3M5200.........352 psi
Silaprene......488 psi

Interesting.

What about temperature. I was painting my garage last summer. Ambient
temp was 94 degrees F. I hung a thermometer on the side of the garage
in direct sun. Temp of garage wall was 150 degrees F. OUCH!

How hot do chainplates and decks get in many parts of the world during
the hot season? 130-150-180F? Just a guess. How does temperature effect
plate adhesive bond? I got more TDS stuff.

3M data: (Service temperature -40F to 190F) "Heat resistance-Due to
the decreased value in bond strength at elevated temperature, we do not
recommend use of this product above 190F."

Silaprene data: (Service temperature -60F to 250F) " Heat
resistance-No significant loss of bond strength until 300 degrees F."

Elevated Temperature Shear Strength
3M5200......................(70F 240psi)(150F 176psi)(190F 139psi)Teak
test substrate.
Silaprene.............(70F - 250F)No significant shear strength loss.

Question. Could 5200 fail because deck and plate temperatures reduce
its bond strength?

Has anybody used Silaprene?

Comparing data each company supplied says Silaprene has greater bond
strength than 5200 on stainless steel and keeps its strength at
temperatures when 5200 begins acting like butter (exaggeration).

Ideas about the deck temperatures causing 5200 failure
Should I use Silaprene to rebed my chainplates "forever?"

Bob

It sounds like you've identified the technique for removing the "permanent"
3M 5200.

Hasn't anyone tried a hot air gun and a putty knife?

Roger

http://home.earthlink.net/~derbyrm

"bob" wrote in message
oups.com...
snip
3M data: (Service temperature -40F to 190F) "Heat resistance-Due to
the decreased value in bond strength at elevated temperature, we do not
recommend use of this product above 190F."

Elevated Temperature Shear Strength
3M5200......................(70F 240psi) (150F 176psi) (190F 139psi)
Teak test substrate.

Bob,
Neither 5200 or Silaprene is a caulking material. Do not use as such. They
are flexable adhesives. I made this error and I can assure you it is an
expensive one. The use of polsulfide is the way to go and recaulk every 4
years. What problem?
Steve

"bob" wrote in message
oups.com...
Hello:
Any thoughts on this.
Chainplates are a source of leaks and equal source of debate on how to
fix the leak.
Some people say use polysulfide because if you use 3M5200 you'll be
tearing your boat apart to rebed plates in a few years.
Others say the reasons why plates leak is because polysulfide do not
have required strength. The only way to solve plate leaks is to use
3M5200. Why? It has a much stronger bond.
Others say that 3M5200 loses its bond eventually and it too will leak.
Only this time the boat owner has a major problem removing the old
adhesive to rebed.

Here is the question....... Why would 3M5200 bond fail?

I called 3M tech people and they sent Tech Data Sheet (effective:
12/1/2004). Interesting data.
I also called Royal Adhesive and received data for Silaprene.
This is what I read.

Stainless to Stainless Overlap Sheer Strength
3M5200.........352 psi
Silaprene......488 psi

Interesting.

What about temperature. I was painting my garage last summer. Ambient
temp was 94 degrees F. I hung a thermometer on the side of the garage
in direct sun. Temp of garage wall was 150 degrees F. OUCH!

How hot do chainplates and decks get in many parts of the world during
the hot season? 130-150-180F? Just a guess. How does temperature effect
plate adhesive bond? I got more TDS stuff.

3M data: (Service temperature -40F to 190F) "Heat resistance-Due to
the decreased value in bond strength at elevated temperature, we do not
recommend use of this product above 190F."

Silaprene data: (Service temperature -60F to 250F) " Heat
resistance-No significant loss of bond strength until 300 degrees F."

Elevated Temperature Shear Strength
3M5200......................(70F 240psi)(150F 176psi)(190F 139psi)Teak
test substrate.
Silaprene.............(70F - 250F)No significant shear strength loss.

Question. Could 5200 fail because deck and plate temperatures reduce
its bond strength?

Has anybody used Silaprene?

Comparing data each company supplied says Silaprene has greater bond
strength than 5200 on stainless steel and keeps its strength at
temperatures when 5200 begins acting like butter (exaggeration).

Ideas about the deck temperatures causing 5200 failure
Should I use Silaprene to rebed my chainplates "forever?"

Bob

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.