Moisture Meters Not Reliable!
 

http://www.yachtsurvey.com/moisture_meters.htm

Moisture Meters Not Reliable!
 

Bwahahahahahaaa thats what happens when you sail a sponge wrapped in
plastic.

When will you people ever learn?

Joe

Moisture Meters Not Reliable!
 

Interesting reading. Thanks Bob.

"Bob Crantz" wrote

http://www.yachtsurvey.com/moisture_meters.htm

Moisture Meters Not Reliable!
 

Bob Crantz wrote:
http://www.yachtsurvey.com/moisture_meters.htm




Ah yes, David Pascoe, purveyor of misinformation about
engines & hater of cored laminates.

This seems to be one his less whacko essays, but on the
whole I am dubious about much of what Pascoe claims.

The best way to find how much water is in the laminate would
be to cut it open & look directly, as Matt Colie suggests.
Since fiberglass can be repaired to be stronger than new, if
you *really* wanted to know, this would be the obvious course.

Another way would be to put the boat into a giant microwave
oven.

Most people don't want to know that badly, so one wonders
why they claim to attach so much importance to trapped
moisture in their hulls.

Fresh Breezes- Doug King

Moisture Meters Not Reliable!
 

Most people don't want to know that badly, so one wonders
why they claim to attach so much importance to trapped
moisture in their hulls.


Dave wrote:
Dunno about hulls generally, but my understanding is that in the case of
decks it gets pretty expensive to do the repair if you let them get spongy
all over.

Sure, but are readings in the deck liable to be false from
the boat being recently hauled? That was the *big* *issue*
Pascoe was raving about.

Also, delamination and/or rotting wood core in the deck is
detectable without using a moisture meter... actually, cores
can get delaminated from things other than water saturation.

DSK

Moisture Meters Not Reliable!
 

actually, cores
can get delaminated from things other than water saturation.


DSK


Ohhhhhh the nightmares!!!!!!!!!!!!!!!
How can you stand for it?

Joe

Moisture Meters Not Reliable!
 

Also, delamination and/or rotting wood core in the deck is
detectable without using a moisture meter... actually, cores
can get delaminated from things other than water saturation.



Dave wrote:
If it's just delaminated without being moist, you're looking at a much less
serious problem, methinks.

Why? Delamination is delamination, big reduction of
structural integrity.

If it is due to moisture, then it could be a bigger job to
fix because the you would want to fix whatever let the water
get in, as well as perhaps rebuilding the edges of the cored
area.


... So how ya gonna tell whether the delamination's
due to moisture without using the meter?

When you cut it open to re-laminate it, you'll easily be
able to tell.

The only difference is that if the core is wood, & rotten,
then it will need to be replaced. Foam might be OK to
re-laminate in place.

DSK

Moisture Meters Not Reliable!
 

actually, cores
can get delaminated from things other than water saturation.



Joe wrote:
Ohhhhhh the nightmares!!!!!!!!!!!!!!!
How can you stand for it?


???

They build airplanes out of it too Joe.

I would rather have a boat that is light & strong & sails
well; cored composite laminates are an excellent way to
achieve this. All you have to do is learn what's good &
what's bad, and look carefully enough to spot the difference.

DSK

Moisture Meters Not Reliable!
 

Nah, just one side of it. Can be done in small sections if
easier that way.


Dave wrote:
The one time I tackled such a problem, it was the deck of an Islander with a
plywood core. The deck was made up of 3/4" plywood sandwiched between deck
and overhead. I wouldn't have wanted to replace less than half of the entire
area at once, because the plywood was the major source of support of the
deck. Smaller pieces would have weakened it.

Also, if there is any water in the ply, it will wick along
the grain into other (eventually all) areas. You made the
right call.

But plywood isn't really a "core" in the structural sense of
the term, it's more like the main part... a better term
would be fiberglass coated plywood... which can be great
stuff, it's just heavy.

If the fiberglass skins were strong enough to take the deck
loading without buckling, then you could replace the plywood
in small sections & not worry about it. The bond between
F-glass skins would be the important thing, not the
continuity or rigidity of the plywood.

I recently worked over some bad spots on the tugboat's deck,
and replaced balsa core with filled resin slurry, then put
the original deck surface back on, then fiberglassed over
it. I don't know what sort of load the deck was designed
for, probably doesn't need as much strength as a sailboat
deck. But it seems plenty strong, at least as solid as the
rest of it.

Fresh Breezes- Doug King

Moisture Meters Not Reliable!
 

The work is not that hard if you do it yourself. But if
you have to hire someone--ouch!

"Dave" wrote

DSK said:

Most people don't want to know that badly, so one wonders
why they claim to attach so much importance to trapped
moisture in their hulls.

Dunno about hulls generally, but my understanding is that in the case of
decks it gets pretty expensive to do the repair if you let them get spongy
all over.