Say you want to drive the moisture out of gelcoat. I've used a heat
gun to do it and was surprised at how much water came out.
So, what would a high power microwave unit do? Water absorbs the
microwaves much better than the polyester so it would get hot and come
out. This would avoid the months of waiting for a hull to dry if you
are repairing blisters (a real scam as blisters are not a real
problem).

Probably would work well, but I know of no way to do this safely. You would be irradiating the world.
Steve

"Frogwatch" wrote in message ...
Say you want to drive the moisture out of gelcoat. I've used a heat
gun to do it and was surprised at how much water came out.
So, what would a high power microwave unit do? Water absorbs the
microwaves much better than the polyester so it would get hot and come
out. This would avoid the months of waiting for a hull to dry if you
are repairing blisters (a real scam as blisters are not a real
problem).

On Wed, 24 Mar 2010 20:20:45 -0700 (PDT), Frogwatch
wrote:

Say you want to drive the moisture out of gelcoat. I've used a heat
gun to do it and was surprised at how much water came out.
So, what would a high power microwave unit do? Water absorbs the
microwaves much better than the polyester so it would get hot and come
out. This would avoid the months of waiting for a hull to dry if you
are repairing blisters (a real scam as blisters are not a real
problem).


Some years ago I read, in one of the boating magazines, about a guy
that had invented an innovative method of drying a hull. He removed
the door from a micro-wave oven and bypassed the "door-open" safety
switch. Placed the oven face down on the deck and turned on the power.

I never read anything more about the method and have visions of him
heating the saturated deck core to the point that steam was generated
and the resultant upheaval.

Water when heated turns to steam and I can assure you that the steam
will come out :-)

Cheers,

Bruce

On Mar 25, 7:58*am, wrote:
On Wed, 24 Mar 2010 20:20:45 -0700 (PDT), Frogwatch

wrote:
Say you want to drive the moisture out of gelcoat. *I've used a heat
gun to do it and was surprised at how much water came out.
So, what would a high power microwave unit do? *Water absorbs the
microwaves much better than the polyester so it would get hot and come
out. *This would avoid the months of waiting for a hull to dry if you
are repairing blisters (a real scam as blisters are not a real
problem).

"some" blisters are not a problem.

Who said anything about being safe? Seriously, you could put an
absorber on the far side to stop the waves or even a metal plate (thin
foil) to reflect em back to be more efficient.

In article ,
says...

On Wed, 24 Mar 2010 20:20:45 -0700 (PDT), Frogwatch
wrote:

Say you want to drive the moisture out of gelcoat. I've used a heat
gun to do it and was surprised at how much water came out.
So, what would a high power microwave unit do? Water absorbs the
microwaves much better than the polyester so it would get hot and come
out. This would avoid the months of waiting for a hull to dry if you
are repairing blisters (a real scam as blisters are not a real
problem).


Some years ago I read, in one of the boating magazines, about a guy
that had invented an innovative method of drying a hull. He removed
the door from a micro-wave oven and bypassed the "door-open" safety
switch. Placed the oven face down on the deck and turned on the power.

I never read anything more about the method and have visions of him
heating the saturated deck core to the point that steam was generated
and the resultant upheaval.

Water when heated turns to steam and I can assure you that the steam
will come out :-)

Cheers,

Bruce

Won't vacuum boil out water vapor?

Scotty

--
For a great time, go here first... http://tinyurl.com/ygqxs5v

Bruce writes:

On Wed, 24 Mar 2010 20:20:45 -0700 (PDT), Frogwatch
wrote:

Say you want to drive the moisture out of gelcoat. I've used a heat
gun to do it and was surprised at how much water came out.
So, what would a high power microwave unit do? Water absorbs the
microwaves much better than the polyester so it would get hot and come
out. This would avoid the months of waiting for a hull to dry if you
are repairing blisters (a real scam as blisters are not a real
problem).

Some years ago I read, in one of the boating magazines, about a guy
that had invented an innovative method of drying a hull. He removed
the door from a micro-wave oven and bypassed the "door-open" safety
switch. Placed the oven face down on the deck and turned on the power.

Innovative and dangerous.

I never read anything more about the method and have visions of him
heating the saturated deck core to the point that steam was generated
and the resultant upheaval.

Water when heated turns to steam and I can assure you that the steam
will come out :-)

Heat the laminate + water quick enough and you create blisters. This is
one of the quality assurance tests of printed circuit boards. Too much
moisture (which is much, much less than found in any boat laminate) or
poor laminating quality (still much better than you hand layup boat
laminate) will cause blisters. OK, that test involves much higher
temperatures than what you are likely to subject your laminates to.

Bear in mind that high temperatures degrade laminates.

Why not try the kind of equipment used to dry out buildings that
got drenched one way or another? It may not be as innovative but
also much less likely to damage your boat or indeed yourself.

/Martin

On Thu, 25 Mar 2010 11:04:49 -0400, I am Tosk
wrote:

In article ,
says...

On Wed, 24 Mar 2010 20:20:45 -0700 (PDT), Frogwatch
wrote:

Say you want to drive the moisture out of gelcoat. I've used a heat
gun to do it and was surprised at how much water came out.
So, what would a high power microwave unit do? Water absorbs the
microwaves much better than the polyester so it would get hot and come
out. This would avoid the months of waiting for a hull to dry if you
are repairing blisters (a real scam as blisters are not a real
problem).


Some years ago I read, in one of the boating magazines, about a guy
that had invented an innovative method of drying a hull. He removed
the door from a micro-wave oven and bypassed the "door-open" safety
switch. Placed the oven face down on the deck and turned on the power.

I never read anything more about the method and have visions of him
heating the saturated deck core to the point that steam was generated
and the resultant upheaval.

Water when heated turns to steam and I can assure you that the steam
will come out :-)

Cheers,

Bruce

Won't vacuum boil out water vapor?

Scotty

Well, yes I suppose that you are correct in that a decrease in
pressure results in water vaporizing at a lower temperature, however
suspect that the evaporated vapor has far less energy then water vapor
that is produced by heating. At least it is difficult to put a pot of
water out in the sun and power a steam engine with it :-)

I suspect that the O.P. was trying to devise a method to laminate
layers and get a chemical bond between layers. In practice no one who
works in the trade seems to consider this a problem. The worry about
laminating epoxy structures is always amine blush and cleaning it
prior to laminating the next layer.

There are epoxies that do not produce blush but I have never seen them
used in actual practice. I suspect it is a matter of cost.

It would be interesting to see some testing of laminated structures
produced by continuous laminating, I.e., not letting the epoxy set up
between layers, and the same structure produced by waiting until each
lamination hardened and then sanding with coarse paper before applying
the next layer.

Cheers,

Bruce

On Thu, 25 Mar 2010 21:50:05 +0100, (Martin
Schöön) wrote:

Bruce writes:

On Wed, 24 Mar 2010 20:20:45 -0700 (PDT), Frogwatch
wrote:

Say you want to drive the moisture out of gelcoat. I've used a heat
gun to do it and was surprised at how much water came out.
So, what would a high power microwave unit do? Water absorbs the
microwaves much better than the polyester so it would get hot and come
out. This would avoid the months of waiting for a hull to dry if you
are repairing blisters (a real scam as blisters are not a real
problem).

Some years ago I read, in one of the boating magazines, about a guy
that had invented an innovative method of drying a hull. He removed
the door from a micro-wave oven and bypassed the "door-open" safety
switch. Placed the oven face down on the deck and turned on the power.

Innovative and dangerous.

I never read anything more about the method and have visions of him
heating the saturated deck core to the point that steam was generated
and the resultant upheaval.

Water when heated turns to steam and I can assure you that the steam
will come out :-)

Heat the laminate + water quick enough and you create blisters. This is
one of the quality assurance tests of printed circuit boards. Too much
moisture (which is much, much less than found in any boat laminate) or
poor laminating quality (still much better than you hand layup boat
laminate) will cause blisters. OK, that test involves much higher
temperatures than what you are likely to subject your laminates to.

Bear in mind that high temperatures degrade laminates.

Why not try the kind of equipment used to dry out buildings that
got drenched one way or another? It may not be as innovative but
also much less likely to damage your boat or indeed yourself.

/Martin


I recently read an article in one of the boating magazines - Practical
Boat Owner - that discussed osmosis repairs. They noted that while the
old method was to tent the hull and install infrared or plain old
electric heaters to dry the hull. This was, of curse, in English
weather. The article went on to say that this is no longer done
because in practice it was not effective as they stated that the real
problem in osmoses is poorly cured resins which absorb water.

Whether this is the final word in osmosis treatment I don't know
however I did recently did a fairly extensive treatment of osmosis on
a 40 ft. sail boat, built in 1971. We ground out all the blisters,
pressure washed with water two times letting the surfaces dry between
washes, washed with acetone, and filled the blisters with chopped mat
and polyester resin. Sanded smooth and then rolled two coats of epoxy
on the entire underwater portion of the hull.

Some time later the boat was surveyed and the Surveyor took moisture
readings every foot and the moisture content was nearly constant from
the top to the bottom of the hull, and fell well within the "good"
portion of the meter dial.

Whether this is a valid test I'm not sure but it certainly cured the
blisters :-)

Cheers,

Bruce

Frogwatch wrote:
Say you want to drive the moisture out of gelcoat. I've used a heat
gun to do it and was surprised at how much water came out.
So, what would a high power microwave unit do? Water absorbs the
microwaves much better than the polyester so it would get hot and come
out. This would avoid the months of waiting for a hull to dry if you
are repairing blisters (a real scam as blisters are not a real
problem).

A few years ago there was a system developed in Europe that used a
combination of heat and vacuum to dry out laminates.

I see it is now available in the USA.

Take a look at:

http://www.hotvac.com/testimonial/default.aspx

Brian C

I do not think Microwave heating to eliminate moisture in fiberglass is practical. The oven in a microwave unit is a reflective
cavity. You would have to have a reflective chamber the size of the boat and a several megawatts of RF to be effective. There
would be dead spots and spots of excessive heating, just like in a microwave oven. Even if you would do this, you would still have
to provide a means of absorbing the moisture generated in the chamber's air. (Basic gas laws and equilibrium apply) There are more
practical ways of achieving this. It is important to understand the problem in order to find a solution. No construction material
lasts forever. They each have their disadvantages and advantages and a finite life. The failure mode of all fiber based plastics
are UV driven disintegration and osmosis. Osmosis is the wicking effect all fibers have when exposed to a liquid, which causes
hydraulic delamination at the weakest bond. Although FG is not waterproof, it is not readily permeable either and there is your
dilemma. Once moisture has invaded the material, it is next to impossible to get it all out.Even though fiberglass boat
construction has been around since the 50's, there are not many boats still around that old. The cost of FG hull maintenance is
only exceeded by wood. All other materials have a better TCO (total cost of ownership). I'm sure that statement will generate some
flames, but it is observable and self evident,
Steve.