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Jay,
Your speaking of the laminating resins that doesn't
have the wax in it. Your data looks good to me. The powder and PVA trick was
first mentioned to me in regards to my issues with bondo taking forever and a
day to cure out, and still being some what gummy after weeks. If I put more
resin in the mix, I would have even less time to work with it, and it was still
gummy on the surface. I don't like to have to put on really thick coats,
just so I can remove the outer later with a grader. I've not worked with the wax
type resin yet. But I wonder if it is just easier to wash off baby powder or
PVA, then dissolve wax.
I coated most the outer surface of my bow
MBT with polyester resin the other day, to fill in all the bubble holes and
voids from the part never having been gel coated in the mold to begin with. Once
done and when the resin firmed up, I just brushed on the PVA in less then a
minute. Then the next day I just washed it off and sanded with no trouble.
My earlier testing runs, showed that was what I should
expect.
The infusion molding I've watched at the Aerocet
plant makes be believe there is a fair bit less labor when you consider they can
lay up all the layers in advance at a nice even pace, with out having to
wait between some layers being put up with resin. I watch one float being
infused that took less then a half an hour to infuse. It's sorta like painting
the outside of a house with a sprayer vs, a brush and roller. In that the
sprayer in quicker doing the actual painting, but there is more prep work to do
first.
The advantage I like most of all during the
fabrication process is not having to deal with all the fumes you have with hand
layup. Also there are some added expenses with the flow mat, runners,
tubing, release cloth, sealing cover, edge sealing means,
etc.
It is a little more work to make a mold for
infusion molding. Once you know how
the resin flows, and how to make the proper flanges on the edges of your molds,
I can see it as being reasonably easy to make a mold for infusion molding and
use it. You don't want to have to pull the resin more then 28 inches across a
area. So this means for longer runs you have to install more coiled runners
and/or the very open foam type runners, to allow the resin to start another 28
inch section. For many one off parts it's best to just hand lay up. If I
get a nice new capped pair of MBT's, then I might as well make the molds so they
can be infusion molded, so I can practice the art, and produce some nice tanks
for other Subdudes if they wish.
Regards,
Brent
From: Jay K. Jeffries
Sent: Thursday, August 27, 2009 9:01 AM
Subject: RE: [PSUBS-MAILIST] Gel Coat Type for
Depth Brent, The material you are trying to
negate with the powder I believe is a wax that is built into the resin that is
necessary for proper polymerization of the resin. This is usually what is
sanded off prior to applying another coat of resin/glass. If I remember
correctly from my readings, you can obtain the resin without the wax but this
resin should only be used for subsurface layers and additional layers have to be
applied within 24 hours of each other. The last coat should include the
wax material to limit air?s interaction with final hardening of the
surface. Check formal references as I am rusty on this subject and haven?t
looked at it for quite awhile. Infusion molding has a lot of
benefits but is actually much more labor intensive then other methods especially
when you look at all of the testing that has to go into developing the proper
placement of the infusion/vacuum ports and calculating the flow of the
resin. The labor is upfront in cutting and placing of materials but molds
can be turned around much faster. There is a great article in the most
recent issue Professional Boatbuilder that compares various methods of molding
GRP hulls. An infused hull is generally lighter, stronger, and uses fewer
materials with the large upfront costs spread out over a production
run. R/Jay Resepectfully, Jay K.
Jeffries Andros
Is., Bahamas Save the whales,
collect the whole set. From:
owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Brent
Hartwig
From:
ShellyDalg@aol.com Hi
Brent, I'm using "structural lay-up" resin for the first color coats with white
pigment. The final color coat will be with "marine grade" resin because of it's
anti water absorption properties. Regular gel coat is a common product for
boats but the added resistance to water absorption in the marine grade is better
when you consider the pressures these fairings are under while
submerged. I've
not tried the baby powder trick yet, and the PVA is generally a big pain in the
ass. I'm using it as a coating on the plug molds and recently on the "wing"
molds but it doesn't just "wash off" like the literature suggests. Pretty much
have to sand it to get it gone. Frank
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