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