Re: [bolger] Epoxy & MDO
Hi Ron
Practical testing gave me the following, standard caveats apply. System 3
goop, ambient temperature approx 70 degrees.
MDO (paper face) to timber and MDO (paper face) to MDO (paper face) joints
fail in the timber. I was using good Doug.Fir as the timber side of the test
pieces. Failures occured sometimes in the Fir, sometimes in the wood layer
of the ply - looks like a pretty random result, dependant on local grain
structure etc. Insufficent tests for statistically meaningful answer,
though.
No failures occurred at the paper face.
6oz Glass cloth epoxied to the paper face could not be removed without
destroying the wood ply backing the paper. I believe removing the paper
layer to be un-necessary, at least from a bond-strength point of view. I've
taped straight to paper.
Incidentally, I find that the paper face of MDO (on the two types I've used)
absorbs an astonishing amount of resin - it really seems to wick the stuff
up more than all but end grain lumber.
The bottom of our (under construction) Micro is single-sided 1/2" MDO, paper
side in, glassed outside. Since I was glassing the bottom anyway, why not?
:)
Your idea of balancing forces by duplicating face treatments is interesting.
Isn't that usually done to keep panels from warping? Good for thin bulkheads
maybe? My gut feeling is that a small boat uses imbalanced forces creatively
to resist stress from one side more than the other - the egg-shell analogy.
What are you thinking of building?
Cheers
Derek
Practical testing gave me the following, standard caveats apply. System 3
goop, ambient temperature approx 70 degrees.
MDO (paper face) to timber and MDO (paper face) to MDO (paper face) joints
fail in the timber. I was using good Doug.Fir as the timber side of the test
pieces. Failures occured sometimes in the Fir, sometimes in the wood layer
of the ply - looks like a pretty random result, dependant on local grain
structure etc. Insufficent tests for statistically meaningful answer,
though.
No failures occurred at the paper face.
6oz Glass cloth epoxied to the paper face could not be removed without
destroying the wood ply backing the paper. I believe removing the paper
layer to be un-necessary, at least from a bond-strength point of view. I've
taped straight to paper.
Incidentally, I find that the paper face of MDO (on the two types I've used)
absorbs an astonishing amount of resin - it really seems to wick the stuff
up more than all but end grain lumber.
The bottom of our (under construction) Micro is single-sided 1/2" MDO, paper
side in, glassed outside. Since I was glassing the bottom anyway, why not?
:)
Your idea of balancing forces by duplicating face treatments is interesting.
Isn't that usually done to keep panels from warping? Good for thin bulkheads
maybe? My gut feeling is that a small boat uses imbalanced forces creatively
to resist stress from one side more than the other - the egg-shell analogy.
What are you thinking of building?
Cheers
Derek
I have done some experimentation, as have a couple of other people on
this list. Specificaly, Vince in message 9047.
I have glued fir boards to test sections and ripped them off after
the epoxy has cured. The board came apart in the wood.
I haven't tried to pull glass off the paper, but Vince has.
I've had a piece in the dishwasher for the last month, and it still
looks brand new.
I have paper on both sides. I'll glass the outside hull, the inside
chines, and the wear surfaces. And, probably anywhere water might
stand. Just to be sure. Otherwise, I'm just going to paint the paper.
No, I'm not going to try to pull the paper off at the joints. It's
stronger than the wood, and nearly impossible to get off. Unless you
grind it off. I might take some of the paper off on the outside of
the fiberglass butt joints, but that is only to make fairing the hull
a bit easier. Might not even do that.
Actualy, think of the paper as "celulose held together with phenolic
resin" and think of the wood as "celulose held together with ligum".
this list. Specificaly, Vince in message 9047.
I have glued fir boards to test sections and ripped them off after
the epoxy has cured. The board came apart in the wood.
I haven't tried to pull glass off the paper, but Vince has.
I've had a piece in the dishwasher for the last month, and it still
looks brand new.
I have paper on both sides. I'll glass the outside hull, the inside
chines, and the wear surfaces. And, probably anywhere water might
stand. Just to be sure. Otherwise, I'm just going to paint the paper.
No, I'm not going to try to pull the paper off at the joints. It's
stronger than the wood, and nearly impossible to get off. Unless you
grind it off. I might take some of the paper off on the outside of
the fiberglass butt joints, but that is only to make fairing the hull
a bit easier. Might not even do that.
Actualy, think of the paper as "celulose held together with phenolic
resin" and think of the wood as "celulose held together with ligum".
--- In bolger@y..., "Ron Magen" <quohog@w...> wrote:
> My question are, for you people with REAL-TIME experience -
>
> 1)do you sand off the phenolic impregnation at the site of your
> cloth/epoxy attachment at seams, chine's, & fillets?
>
> 2) do you use the one-sided MDO for hulls where the exterior is
> completely glasses so there is no film barrier between the
epoxy
> and the wood substrate?
>
> For the 'open minded' part; I would like to hear specific answers,
> rather than my own impression from 'reading between the lines' of
> already posted messages and building experiences.
>
> Regards and thanks in advance,
> Ron Magen
> Backyard Boatshop
People,
Of late, there has been a lot of discussion, some of it quite heated,
about who's epoxy, and how used, is the "best".
To my mind that's like walking into a bar and saying, "The BEST Bourbon
{or Rum for us sailors} is . . . " No mater what you say, there's going
to be a bar fight.
Learn all you can about YOUR favored materials, experiment and KEEP
RECORDS, have an open mind to OBSERVE, and proceed.
In the 'Learning' vein I ask for feed-back on the following proposed
course.
I'm in the process of determining my next 'build'; deciding between a
couple of designs. What I am fairly certain of is that I would like to
use MDO for the hull and deck. I WILL be 'glassing the exterior of the
hull - albeit the per ounce weight may be rather low. {I'm a 'belt and
suspenders' kind of guy - so NO DISCUSSION on this point}
Having experience with woodworking & finishing, painting & framing {as
in ART, not WALL}, and photography & print mounting, I know what ever
you do to one side of a {relative thin}structure you should do to the
other side. This is to achieve a balance of forces. A lot of the recent
discussion about epoxy 'encapsulation', oil-based Alkyd vs. water-based
Acrylic paint, moisture content of wood vs. 'breathable' finishes, seems
to skip over this salient point . . . which actually links them all
together.
MDO - with a permanently attached 'film' on BOTH SIDES should
'neutralize the opposing forces as well as prevent delimitation (as long
as the edges, cut and otherwise, are given proper attention} That's the
theory.
My question are, for you people with REAL-TIME experience -
1)do you sand off the phenolic impregnation at the site of your
cloth/epoxy attachment at seams, chine's, & fillets?
2) do you use the one-sided MDO for hulls where the exterior is
completely glasses so there is no film barrier between the epoxy
and the wood substrate?
For the 'open minded' part; I would like to hear specific answers,
rather than my own impression from 'reading between the lines' of
already posted messages and building experiences.
Regards and thanks in advance,
Ron Magen
Backyard Boatshop
Of late, there has been a lot of discussion, some of it quite heated,
about who's epoxy, and how used, is the "best".
To my mind that's like walking into a bar and saying, "The BEST Bourbon
{or Rum for us sailors} is . . . " No mater what you say, there's going
to be a bar fight.
Learn all you can about YOUR favored materials, experiment and KEEP
RECORDS, have an open mind to OBSERVE, and proceed.
In the 'Learning' vein I ask for feed-back on the following proposed
course.
I'm in the process of determining my next 'build'; deciding between a
couple of designs. What I am fairly certain of is that I would like to
use MDO for the hull and deck. I WILL be 'glassing the exterior of the
hull - albeit the per ounce weight may be rather low. {I'm a 'belt and
suspenders' kind of guy - so NO DISCUSSION on this point}
Having experience with woodworking & finishing, painting & framing {as
in ART, not WALL}, and photography & print mounting, I know what ever
you do to one side of a {relative thin}structure you should do to the
other side. This is to achieve a balance of forces. A lot of the recent
discussion about epoxy 'encapsulation', oil-based Alkyd vs. water-based
Acrylic paint, moisture content of wood vs. 'breathable' finishes, seems
to skip over this salient point . . . which actually links them all
together.
MDO - with a permanently attached 'film' on BOTH SIDES should
'neutralize the opposing forces as well as prevent delimitation (as long
as the edges, cut and otherwise, are given proper attention} That's the
theory.
My question are, for you people with REAL-TIME experience -
1)do you sand off the phenolic impregnation at the site of your
cloth/epoxy attachment at seams, chine's, & fillets?
2) do you use the one-sided MDO for hulls where the exterior is
completely glasses so there is no film barrier between the epoxy
and the wood substrate?
For the 'open minded' part; I would like to hear specific answers,
rather than my own impression from 'reading between the lines' of
already posted messages and building experiences.
Regards and thanks in advance,
Ron Magen
Backyard Boatshop