Serious epoxy problems
Frogwatch
problems that cause me to doubt that this building method can work for
my N. FL conditions.
I built her with System 3 resin using the slow hardener due to the
heat here. I used the metering pumps o get correct ratios and
followed the builders directions.
All went well for the first two years but then got a separation of
epoxied wood at the transom. This had been glued by first painting
the wood with epoxy followed by a thin layer of epoxy/fiber paste and
serious clamping. I pried the two layers apart last year and re-
filled with epoxy thinking the problem solved (NOT).
Yesterday, I found the biax separating from the stringers, a long
piece that had been clamped to the gunwales and glued separating and
other places where the epoxy simply had not adhered to the wood. I
will be able to use her for the next couple weeks (scallop season) but
this will require some major surgery.
Under N. FL humidity and rain, it is nearly impossible to keep her dry
and I suspect that swelling of the wood due to absorption of water is
the big problem.
I plan to remove all the rest of the expensive paint i put over the
original epoxy primer because it simply did not adhere anyway. Then
will grind out the bad areas dry everything and try to re-glass the
bad areas after using a heat gun to dry them.
I would hesitate to use epoxy/glass over wood for another project here
in N. FL conditions.
Paul Oman
doesn't sound right to me. Note that wood expands and contracts with
moisture - epoxy and other things with temperature.
Might also be an amine blush issue between the different coats of
epoxy. Also, most epoxies are brittle and cannot handle movement without
the reinforcement of fiberglass cloth. There are flexible epoxies to use
when painting...
Epoxy primer is just solvent thinned epoxy. If you covered your hull
with epoxy during building then it was already primed.
If you used a 2 part LPU coating you certainly needed an epoxy primer,
but your epoxy blushed, that would explain a few things.
Email me privately and I will get you a sample of our Basic No Blush
epoxy for you to evaulate.
So what did the MAS epoxy folks say?????
paul oman
in...@epoxyproducts.com
progressive epoxy polymers inc
www.epoxyproducts.com/marine.html
Frogwatch
> progressive epoxy polymers incwww.epoxyproducts.com/marine.html
This is worse. The biax glass actually cracked over the stringers and
the 8 oz glass cracked over the gunwales. These are not high stress
areas but the stringers where it cracked does have a 1" radius of
curvature. Note, these cracks and delams are in areas covered by
glass. These are not normal use stress cracks but the epoxy
separating from the wood and the glass actually cracking afterward.
The epoxy primer is a 2 part material thinned with Isopropyle alchohol
to protect the epoxy from UV. It works well and I will use it as my
finish coat from now on.
All of the areas appear to be areas where the epoxy simply did not
adhere to the wood well allowing the epoxied glass to flex and crack.
My issue now is how to fix the delams. Do I simply inject epoxy and
drive screws to hold them till it sets or do I leave said screws in
place. I worry future epoxy by itself will also fail.
In areas where the layers of biax separated from the stringers, do I
somehow make the biax layers adhere to said stringers or do I grind
away the old biax and replace it with fresh stuff.
Paul Oman
is strictly a surface bond so if you had lots of sanding dust, etc. on
the surface that would impact the bonding.
Adding/thinning with Iso alcohol does nothing to address the UV issue.
You cannot add uv blockers to thermoset resin systems like epoxy.
Thinning/solvent adding to epoxy will mess up the epoxy properties. If
applied too thick you get solvent entrapment in the epoxy making it sort
of rubbery. Best is probably a thin coat of solvent thinned epoxy on the
raw wood then 'straight' epoxy with the glassing. Then enamel or water
based paint on top...
paul oman/progressive epoxy
Lew Hodgett
"Frogwatch" wrote:
> The epoxy primer is a 2 part material thinned with Isopropyle
> alchohol
to protect the epoxy from UV.
Wrong alcohol. you need denatured not isopropyl which contains water.
You also must limit alcohol to less than 5%.
As far as the glass is concerned, 8 OZ is little more than sealing
tape.
At a minimum, you need a couple of layers of 17 OZ, double bias glass.
Leaving wood unglassed is asking for trouble which you seem to have
found.
Time to break out your right angle sander/grinder with some 24 grit
and take everything back to bare wood, then reglass making sure you
seal all wood with glass.
If that is more work than it's worth, probably time for a new boat.
Have fun.
Lew
Frogwatch
Never take advice from people who do not read.
Just wait a frekin' minute!
It just sounds like you didn't prepare the wood properly. I use a
sawblade turned on it's side and scrape negative gashes into the wood to
produce a more mechanical bond than chemical. Also, you may have had
other problems with the laminating process, sometimes with Epoxy, more
is not necessarily better..
Frogwatch
I intend to something similar when I re-glass the bad areas.
JustWait
299e26...@p28g2000vbn.googlegroups.com>, dbo...@mindspring.com
says...
Hey Froggie, Scotty here from that other group;) I think I remember back
when you were doing this, did you encapsulate the wood in Epoxy? I have
always been against that, moisture gets in, but can't get out. I suggest
regular paint as a sealer, just for the record...
Ed Huntress
"JustWait" <justwaitaf...@gmail.com> wrote in message
news:MPG.252a962...@eternal-september.org...
FWIW, Paul Oman nailed the major issues that look like a possible failure
route here. First, how long did you wait between painting on the original
coat of epoxy and applying the paste? If it was too long, amine blush is a
possible culprit. Depending on the mix, 12 - 15 hours can be too long. 24
hours is more likely the max. After that, you have to remove the amine blush
with soap and water, and you will get NO chemical bond, in any case. You'll
have to roughen the surface of the prime layer and depend on the mechanical
bond.
Second, "serious clamping" can be a mistake with epoxy. If it's squeezed out
to a layer thinner than roughly 0.003", strength falls off quickly. Below
0.002", it can all but disappear. Unlike resorcinol or some other adhesives,
you shouldn't clamp epoxy more than it takes to hold everything in place.
That applies especially to amine-cure epoxies. Clamping wood more than a
minimum will leave some percentage of the bonded area with a too-thin layer,
which can be a starting point for peel or cleavage failure.
As Paul also said, brittleness and low peel strength of most epoxies,
combined with swelling and shrinking of the wood, can lead to failure. Peel
strength usually isn't much of an issue when epoxy is used to bond wood, but
it's an inherent weakness of the adhesive -- again, especially with
amine-cure epoxies. It's most likely to show up at place where end grain is
exposed. Slowing down the absorption rate by coating with epoxy and fabric
is the best solution for that, because it will allow the creep rate of the
epoxy to partially catch up to the wood expansion, but it's not perfect.
--
Ed Huntress
Bob
> First, how long did you wait between painting on the original
> coat of epoxy and applying the paste? If it was too long, amine blush is a
> possible culprit.
Excellent !
> Second, "serious clamping" can be a mistake with epoxy. If it's squeezed out
> to a layer thinner than roughly 0.003", strength falls off quickly. Below
> 0.002", it can all but disappear. Unlike resorcinol or some other adhesives,
> you shouldn't clamp epoxy more than it takes to hold everything in place.--
This would be my guess. got to have somthing left to make the bond.
Ive seen similar effects when people sqeeze every last bit of calk/
sealant/adhesive out of a joint when bedding hardware.
Another consderatin is wood type used. the bond problmes increases
with more dense/increased mosture content/oily woods.
was it teak or white oak or douglas fir?
bob
> Ed Huntress- Hide quoted text -