[PSUBS-MAILIST] Fiberglass
Alan James via Personal_Submersibles
personal_submersibles at psubs.org
Mon May 4 17:38:30 EDT 2015
Hank,I mean when the fiberglass has cured & just the surface is tacky.It is meant to be like this to form a chemical bond with the next layer.If you wait for the surface to dry (in time) then the next layer doesn't adhere as well.I used clear cast polyester resin in art works, & you had to add paraphin wax inliquid form to stop the surface becomming tacky.There are two general types of polyester resin used for repair. Laminating or Bonding resin which cure to a tacky surface and Fiberglass or Marine Finish resin which cures to a non-tacky surface.Laminating resin (Evercoat # 100560, 100561) is used for initial coats on wood or for multiple applications with fiberglass cloth or mat. This resin is air-inhibited which means it will cure to a tacky finish and does not require sanding between coats. This is desirable in laminating because the layers adhere to each other better. This product should not be used as a final coat unless measures are taken to seal out the air during the curing process.Marine and Fiberglass resin (Evercoat # 100553, 100552, 100554, 100517, 100518, 105499, 105498, 105500, and 105501) is non air-inhibited or waxed resin. It is for the final coat. This resin cures with a hard non-tacky surface. When the catalyzed resin is applied as a final coat to the laminate coats of resin, the wax rises to the top, sealing off the air and allows the resin to cure to a hard finish, which can then be sanded, painted or gel coated.NOTE: Cannot be used with aluminum, redwood and/or close-grained woods like oak or cedar. Do not use with Styrofoam.Alan
From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Sent: Tuesday, May 5, 2015 9:14 AM
Subject: Re: [PSUBS-MAILIST] Fiberglass
Alan,
Tacky means weak hardener ratio or poor mix. Tricky stuff!
Hank--------------------------------------------
On Mon, 5/4/15, Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
Subject: Re: [PSUBS-MAILIST] Fiberglass
To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
Received: Monday, May 4, 2015, 5:11 PM
Hi
Alan,
Interesting comment
about the polyester being designed for one shot. The
polyester resin I used is from 3M and the instructions say
that it you restart the job on a cured layer you should sand
it lightly first - so that's what I did, since it took
about a month to get the desired number of layers on. It
didn't seem to have any bonding issues with layers
applied on cured material. This particular 3M polyester
cures fully in 2 hours, and didn't feel tacky after
that, so perhaps this is brand specific.
Good point about the sections
helping make the mirror versions of the MBTs. I made
templates out of thin particle board to cut out the foam
sections, and by flipping the templates was able to make
mirror image tanks.
Best,
Alec
On Mon, May 4, 2015 at 4:33
PM, Alan James via Personal_Submersibles <personal_submersibles at psubs.org>
wrote:
Hi
Scott,some great ideas
from Alec there.I like his
idea of using sandwiches of thinner sheets of
polystyrene.You should be
able to trace a shape on one sheet, cut it out,
thencopy around it on to
the corresponding sheet of the mirror imageballast tank, to get two tanks that are
identical.When I did mine
I marked the hull with a felt pen as to where
theballast tank was going
to fit against it. I covered this area with
plasticfood wrap. I then
draped glass mat over it & epoxied about 3
layers over this. Polyester resin will
disolve the plastic food wrap. This approach may be a
problemon vertical walls & there
may be a similar appoach that works better.You need to embed this shape in to the polystyrene
section by wire brushingout the
polystyrene untill it's a good fit. Because of shrinkage
of the fiberglass& warping it
won't nessecarily be a perfect match & may require
additional work.Once you have the
polystyrene shape done you cover it with fiberglass & go
overthe area you formed against the
hull.I used epoxy because it can go
straight on to the polystyrene (test it first)
&you can spend a month slowly
building it up, whereas polyester resin is
designedto be laminated in one shot. It
is air inhibited & remains tacky on the outersurface unless it has a wax additive.I once made a 1/4 size ambulance out of
polystyrene using mainly achain saw.
Great fun but one hell of a mess.Alan
From: Alec
Smyth via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal
Submersibles General Discussion <personal_submersibles at psubs.org>
Sent: Tuesday, May 5,
2015 3:33 AM
Subject: Re:
[PSUBS-MAILIST] Fiberglass
Hi Scott,
Coincidentally your timing is really
good, because I just finished four rather complex-shaped
MBTs for the new sub. Since my sub is a one-off rather than
a series production item, I used the method of glassing foam
plugs that are then dissolved, rather than making molds. To
summarize:
- The plugs
are a sandwich of many layers of pink home insulation foam
from HomeDepot. When I did Snoopy's saddle tanks I cut
out the sections with a hot wire, but this time I realized
my jig saw does the job in about a tenth the time. Step one
is to cut a whole bunch of sections and glue them together.
If I weren't so tight-fisted, the ideal solution here
would be to mill a single block of foam using CNC equipment,
but I get by with what I have on hand if it'll save
money - and a milling job would probably take quite a lot of
it.
- The glued
sections are only a rough draft of the final form. Next you
have to shape them until the steps between sections are gone
and everything is nice and smooth. I use three tools to go
from the draft to the final product, in this
order:1) A plain old wood saw2) A
Stanley Surform shaver, with flat and or rounded blade
fitted depending on the surface. This thing is absolutely
essential and I use it for 99% of the job. See http://www.stanleytools.com/default.asp?CATEGORY=SURFORM+TOOLS+AND+BLADES&TYPE=PRODUCT&PARTNUMBER=21-296&SDesc=Surform%26%23174%3B+Plane+Type+%96+Regular+Cut+Blade3)
Sand paper
I'm
afraid I have no scientific answer to ensuring symmetry. I
just put the plugs side by side and do a bunch walking in
circles, taking measurements, and using a level. The plugs
won't come out identical, but close enough to be
functional. This part is more sculpture than
science.
- Next, paint
the plugs with several coats of water-based paint. This is
to prevent the resin from dissolving them. Water-based
because if not you run the risk of the paint dissolving the
foam.
- Now apply
layer after layer of wetted fiberglass cloth. I don't
mean all in one sitting, I mean iteratively for about a
month. There are two main considerations then, cloth and
resin.
I can't
give you a specific recipe for cloth or the cost for cloth,
because I used a combination of material I already had on
hand and new stuff. I have purchased from http://www.fibreglast.com
in the past, but this time found lower prices on eBay for
what turned out to be perfectly good material. Mostly I used
6.5 oz (quite light) cloth so that it would drape better,
but that depends on the shape of your tanks. For instance,
on the inside face that goes against the hull, you can get
away with much heavier material since its a gentle curve in
just one plane, and the same goes for any flat surfaces. But
if you have compound curves or tight curves its way more
challenging to drape cloth without forming air bubbles. I
make the walls that go against the hull thinner, since they
aren't going to be banging against things like the outer
or upper faces will. On average I probably put down ten to
fifteen layers of cloth. The pros use vacuum bagging to
prevent bubbles. With my caveman fiberglass skills I just
try to avoid them in the first place by selecting
better-draping cloth, and when I get a bubble I remove it
with a flap wheel before putting down the next layer. In the
middle of my layup I put down several layers of Kevlar. This
material is trickier to work with than fiberglass, it
can't be sanded and once cured you can only really go
through it with carbide tools. The idea is to increase
survivability by making the MBTs puncture resistant. If I
hit a rock or a dock I still expect the resin might crack,
but it should be quite hard to put a hole in the Kevlar. You
might think this hard layer should go on the outside, but I
put it mid-schedule so I could sand imperfections out of the
fiberglass layers above it.
This job (new sub, not Snoopy's
tanks) took ten gallons of resin. Everyone will tell you
epoxy is stronger than polyester resin. However, epoxy is
$76 per gallon vs. $34 for polyester, and Snoopy's
polyester tanks have held up perfectly well for years. So,
for me, this is a case of cheaper-is-sufficient and I went
with polyester.
-
Iteratively sand and fix imperfections with a fairing
compound. I used West Marine's #410 fairing filler (http://www.westmarine.com/buy/west-system---410-microlight-filler--P004_120_004_016).
You can do this with Bondo as well, but #410 is easier to
sand.
- Dissolve the
plugs. When I made Snoopy's saddle tanks the pink foam
dissolved instantly with gasoline. This time, despite being
the same brand foam it was somehow gasoline resistant, but
acetone did the job.
Best,
Alec
On
Mon, May 4, 2015 at 9:22 AM, via Personal_Submersibles <personal_submersibles at psubs.org>
wrote:
Alec,
I was curious if you could go into details about the
making of your saddle tanks?
*Where did you get the foam and fiberglass and what
types did you use
*How did you shape the foam to ensure symmetry
*Was there any difficulty or anything you would do
differently
Thanks,
Scott Waters
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