Posted by hopalongsail (hopalongsail@…>)
I agree with Benjamin re blisters. After spending scores of hours on
the Web researching the subject, I found no certainty on the cause
or cure. All of it is theoretical, although it is hard to determine
that because the folks in the blister repair business speak with
with great assurance.
That is not surprising since blister repairs are a big ticket
revenue item for many boat yards.
But, as one surveyor reports, a bad blister repair job can make the
situation worse.
Re moisture meters, they are not infallible. You can get false high
readings based on many non-moisture matters, such as what is behind
the hull (water tanks, metal), additives in paint or gel coat and so
forth. They also need to be properly calibrated. And with balsa
hulls, the readings are likely to be higher than fiberglass hulls
since wood nearly always reads higher than fiberglass.
That said, seepage of moisture into a poorly made solid fiberglass
hull or cored hull can lead to such things as delamination. TPI has
made cored hulls for decades and has a reputation for good work.
Making them properly takes more skill and money than making a solid
fiberglass hull. But they are stronger and lighter and provide
better insulation.
Posted by Dave_Benjamin (dave_benjamin@…>)
Re moisture meters, they are not infallible. You can get false high
readings based on many non-moisture matters, such as what is behind
the hull (water tanks, metal), additives in paint or gel coat and
so
forth. They also need to be properly calibrated. And with balsa
hulls, the readings are likely to be higher than fiberglass hulls
since wood nearly always reads higher than fiberglass.
Also time of day can make a difference. We were investigating some
spots on a boat early in the morning. There was indication of
moisture damage to the deck which had us concerned. We tapped the
area out with a plastic hammer and it sounded solid yet the moisture
meter was screaming “damp.” We moved on to other parts of the
inspection. Later in the day when the sun had been up for a while we
rechecked the same area of deck and it was fine.
The surveyor needs to know what he’s doing. Sadly many don’t.
Sometimes the only way to really tell is to drill a small hole and
inspect the core material that adheres to the drill bit. Then the
hole can be filled with epoxy and topped with some gel-coat.
Also I think epoxy barrier coats are overrated. If they are applied
when the boat is brand new (read prior to launch) that’s one thing
but if it’s an older boat remember that the barrier coat works both
way. All moisture in the hull will be sealed in. So let’s say you
haul out for the summer in Mexico where’s that moisture going to go?
Makes me wonder if prolonged exposure to heat while on the hard might
cause some problems.
Posted by katorpus (katorpus@…>)
There is a simple reason why boats in the Gulf experience more
blistering than those in the Great Lakes and the Northeast…they
tend to spend ALL of their time in the water.
If a boat is hauled and on the hard for 1/2 the year (or
more)…every year…then it’s GONNA dry out (naturally). It doesn’t
matter WHAT the weather is like outside, there’s no PRESSURE driving
the moisture inward. 6 months “wetting”…six months “drying”…do
the math. Even if there were NO recovery going on during this
period, it would (obviously) take twice as long for blisters to
appear in the first place.
I’m not gonna get into whether (or not) the warmer waters in the
Gulf contribute to water intrusion. It’s a given that our
slime/barnacle problem is worse down here (zebra mussels not
withstanding). Our water temperature in Corpus Christi reached a low
of maybe 59 this past winter…and that wasn’t for long. It was back
up to 81 in April.
A blister repair job need not be horrendously expensive. A weekly
steam cleaning during the haulout helps a LOT (drives out the gunk,
heats up the hull to drive out water)
I agree re: moisture meters. Take 10 different meters from 10
different manufacturers, you are gonna get a wide spread of
readings. The key to reading the moisture meter is RELATIVITY.
What does it show for the area which you KNOW isn’t wet (say…6"
below the toe rail, maybe?)…what does it show below the water
line?.. My rudder was “off the scale”…guess what?..drilled a
hole in it up high and another down low and water POURED out of it.
Use the SAME meter throughout your “drying time”…note the reading
(marked on the hull) in various areas as you go along. If you
suspect that it is wet, it probably is. It’ll show improvement first
near the water line. It may NEVER show improvement way down low
(gravity, you know?). If you want to speed up the process of
discovery, drill some holes in the cored area way down low and see
what comes out (into the core, NOT clear thru the hull…do this
from outside). Be sure and patch them PROPERLY afterwards). If the
balsa fluff-stuff that comes out with the bit is wet, then the core
is wet in that area. You can reasonably surmise that similar
readings in other areas will result in similar discovery when
drilled.
Posted by Frank Minelli (myslo@…>)
Right on the money, kator. When I had that problem, with my 33, and put the meter to it,. it read 100% below the water line, with deccrasing value as I went above it (all over the hull)
The ¨test holes in some places actually produced water flow for several seconds.katorpus <katorpus@…> wrote:
There is a simple reason why boats in the Gulf experience more blistering than those in the Great Lakes and the Northeast…they tend to spend ALL of their time in the water. If a boat is hauled and on the hard for 1/2 the year (or more)…every year…then it’s GONNA dry out (naturally). It doesn’t matter WHAT the weather is like outside, there’s no PRESSURE driving the moisture inward. 6 months “wetting”…six months “drying”…do the math. Even if there were NO recovery going on during this period, it would (obviously) take twice as long for blisters to appear in the first place.I’m not gonna get into whether (or not) the warmer waters in the Gulf contribute to water intrusion. It’s a given that our slime/barnacle problem is worse down here (zebra mussels not withstanding). Our water temperature in Corpus Christi
reached a low of maybe 59 this past winter…and that wasn’t for long. It was back up to 81 in April.A blister repair job need not be horrendously expensive. A weekly steam cleaning during the haulout helps a LOT (drives out the gunk, heats up the hull to drive out water)I agree re: moisture meters. Take 10 different meters from 10 different manufacturers, you are gonna get a wide spread of readings. The key to reading the moisture meter is RELATIVITY. What does it show for the area which you KNOW isn’t wet (say…6" below the toe rail, maybe?)…what does it show below the water line?.. My rudder was “off the scale”…guess what?..drilled a hole in it up high and another down low and water POURED out of it.Use the SAME meter throughout your “drying time”…note the reading (marked on the hull) in various areas as you go along. If you suspect that it is wet, it probably is. It’ll show improvement
first near the water line. It may NEVER show improvement way down low (gravity, you know?). If you want to speed up the process of discovery, drill some holes in the cored area way down low and see what comes out (into the core, NOT clear thru the hull…do this from outside). Be sure and patch them PROPERLY afterwards). If the balsa fluff-stuff that comes out with the bit is wet, then the core is wet in that area. You can reasonably surmise that similar readings in other areas will result in similar discovery when drilled.