Agreed Colin..

Worst years were during the 70's - 80's,- 10 yr old boats built in
late 60's / early 70's...

....Also in some boats built with the fire retardant resin called
"Heteron" (sp?) during late 70's.....

Agreed...much has been learned about building composites since
then....

Also agreed, apples /oranges here ... however, a crack in a fiberglass
cowl a few yrs ago caused water from melting snow to penetrate the
laminate on an aircraft here. (Stored outside) The freeze/thaw cycle
caused a delamination about the size of an adult hand. It started
around a fastener mount..This was easily spotted through the
transparent inner laminations when viewed from the inside..(once the
cowl was removed) and easily repaired...

Cheers!

Dave


On Thu, 24 Mar 2005 16:28:04 GMT, "Colin W Kingsbury"
wrote:


"Paul Tomblin" wrote in message
...
In a previous article, Dave said:
Ans , yes, I have seen many examples of this "delamination" of
composiets...

It would be easier to understand or give credence to your points if you
knew how to spell or punctuate.

....many cause factors, osmosis being the most common, poor
quality control/contamination during layup are others....

Osmosis happens to things immersed in salt water, which hopefully isn't
the case with aircraft rudders. And the "poor quality
control/contamination during layup" are why I specified that these things
would be caught in the initial inspection. Aircraft parts are subject to
a lot more quality control and tougher inspections that your boats.

Usenet grammar pedants should beware of preposition-object agreement in
their glass houses

Anyway, I suspect you are seeing cosmetic flaws in the gelcoat, not full
on structural failures.

In many older boats, osmotic blistering is going beneath the gelcoat,
sometimes several layers deep. However, I tend to agree that we are talking
apples and oranges here. The worst blistering is found on boats going back
into the 60s and 70s, and drops off with each passing year as manufacturers
understood layup better. Airbus started using composites in the early 80s,
by which time we were starting to get a decent feel for best practices in
manufacturing.

-cwk.