[bolger] Re: ply-foam adhesive
ghc <ghart-@...> wrote:
original article:http://www.egroups.com/group/bolger/?start=2876
was something like 3/8" thick. This wasn't the first one either, and
I've seen some in service. So some urethathane foams do have reasonable
strength. I believe there is some urethane used in some sailplane wing
layups, too. But beadfoam is pretty negligible in the strength
department. If it was my boat and I was trying to save bucks, I might
try some of the styrofoam (beadfoam is NOT styrofoam! Styrofoam is
extruded) that's made especially to use as part of roofs, as it has
extra compressive strength, and I presume additional tensile strength.
It would be easy to make a test panel and load it up to failure. Then
I'd know! But don't paint it a dark color if it's styrofoam or has
garden variety epoxy, at least not without another test to, say, 180F.
(Styrofoam is a trademark, I know, and Dow is going to come after me)
original article:http://www.egroups.com/group/bolger/?start=2876
> Beaded styrofoam has "zero" or certainly unknown strength (I've seenit
> made). Extruded "Dow" blue probably has some predictable properties,do
> however low and probably unpublished.
>
> "Real" core materials like PVC foams (e.g. Divincell), balsa,
> nomex/plastic/aluminum honeycomb, and maybe some foamed urethanes (?)
> have some fair shear and tensile strength. Shear resists bending, butsome
> fair tensile/compressive is also required to resist face buckling andpanel
> failure.I've helped to lay up a boat with deck core of urethane which I recall
>
> So, the core matters!
>
was something like 3/8" thick. This wasn't the first one either, and
I've seen some in service. So some urethathane foams do have reasonable
strength. I believe there is some urethane used in some sailplane wing
layups, too. But beadfoam is pretty negligible in the strength
department. If it was my boat and I was trying to save bucks, I might
try some of the styrofoam (beadfoam is NOT styrofoam! Styrofoam is
extruded) that's made especially to use as part of roofs, as it has
extra compressive strength, and I presume additional tensile strength.
It would be easy to make a test panel and load it up to failure. Then
I'd know! But don't paint it a dark color if it's styrofoam or has
garden variety epoxy, at least not without another test to, say, 180F.
(Styrofoam is a trademark, I know, and Dow is going to come after me)
Beaded styrofoam has "zero" or certainly unknown strength (I've seen it
made). Extruded "Dow" blue probably has some predictable properties,
however low and probably unpublished.
"Real" core materials like PVC foams (e.g. Divincell), balsa,
nomex/plastic/aluminum honeycomb, and maybe some foamed urethanes (?) do
have some fair shear and tensile strength. Shear resists bending, but some
fair tensile/compressive is also required to resist face buckling and panel
failure.
So, the core matters!
Gregg Carlson
At 12:28 PM 2/16/2000 -0500, you wrote:
made). Extruded "Dow" blue probably has some predictable properties,
however low and probably unpublished.
"Real" core materials like PVC foams (e.g. Divincell), balsa,
nomex/plastic/aluminum honeycomb, and maybe some foamed urethanes (?) do
have some fair shear and tensile strength. Shear resists bending, but some
fair tensile/compressive is also required to resist face buckling and panel
failure.
So, the core matters!
Gregg Carlson
At 12:28 PM 2/16/2000 -0500, you wrote:
>With plywood-foam-plywood or plywood-foam-fiberglass sandwich construction,
>given that foam has virtually zero shear strength, wouldn't one need to
>seriously tie the two outside layers together to avoid ripping the foam
>apart when the panel tries to flex? Maybe something like stringers on 8"
>centers and cross members on 24" centers? (Or vice-versa for soles &c.)
>These could be something like 1/4" ply filleted and glassed to the outer
>layers, between the pieces of foam. But: (1) how would you actually attach
>the stringers and cross members; and (2) wouldn't all this work defeat the
>purpose of using the sandwich in the first place?
>
>Patrick
>
>>> Double Eagle has the main house floor and all main roof areas made out
>>> of a 1/2inch ply-2inch foam-1/2inch ply composite. snip
>>
>>That seems hellishly stout! I would think you could drive a truck on
>>it. Almost as strong as 3" of plywood, if you're using a good grade of
>>foam.
>
>
>
>------------------------------------------------------------------------
>GET A NEXTCARD VISA, in 30 seconds! Get rates as low as 2.9%
>Intro or 9.9% Fixed APR and no hidden fees. Apply NOW!
>http://click.egroups.com/1/932/5/_/3457/_/950721894/
>
>-- Easily schedule meetings and events using the group calendar!
>--http://www.egroups.com/cal?listname=bolger&m=1
>
>
>
With plywood-foam-plywood or plywood-foam-fiberglass sandwich construction,
given that foam has virtually zero shear strength, wouldn't one need to
seriously tie the two outside layers together to avoid ripping the foam
apart when the panel tries to flex? Maybe something like stringers on 8"
centers and cross members on 24" centers? (Or vice-versa for soles &c.)
These could be something like 1/4" ply filleted and glassed to the outer
layers, between the pieces of foam. But: (1) how would you actually attach
the stringers and cross members; and (2) wouldn't all this work defeat the
purpose of using the sandwich in the first place?
Patrick
given that foam has virtually zero shear strength, wouldn't one need to
seriously tie the two outside layers together to avoid ripping the foam
apart when the panel tries to flex? Maybe something like stringers on 8"
centers and cross members on 24" centers? (Or vice-versa for soles &c.)
These could be something like 1/4" ply filleted and glassed to the outer
layers, between the pieces of foam. But: (1) how would you actually attach
the stringers and cross members; and (2) wouldn't all this work defeat the
purpose of using the sandwich in the first place?
Patrick
>> Double Eagle has the main house floor and all main roof areas made out
>> of a 1/2inch ply-2inch foam-1/2inch ply composite. snip
>
>That seems hellishly stout! I would think you could drive a truck on
>it. Almost as strong as 3" of plywood, if you're using a good grade of
>foam.
"fritz koschmann" <fritzdf-@...> wrote:
original article:http://www.egroups.com/group/bolger/?start=2842
it. Almost as strong as 3" of plywood, if you're using a good grade of
foam.
Sorry I don't have any great advice on adhesives. I know there are some
cheaper grades of epoxy out there which should still be stronger than
foam, but I don't know about their water resistance. I wonder if the
foam is somewhat porous if you could use Weldwood or something? Would
have to be well clamped, of course.
original article:http://www.egroups.com/group/bolger/?start=2842
> Double Eagle has the main house floor and all main roof areas made outThat seems hellishly stout! I would think you could drive a truck on
> of a 1/2inch ply-2inch foam-1/2inch ply composite. snip
it. Almost as strong as 3" of plywood, if you're using a good grade of
foam.
Sorry I don't have any great advice on adhesives. I know there are some
cheaper grades of epoxy out there which should still be stronger than
foam, but I don't know about their water resistance. I wonder if the
foam is somewhat porous if you could use Weldwood or something? Would
have to be well clamped, of course.
Double Eagle has the main house floor and all main roof areas made out
of a 1/2inch ply-2inch foam-1/2inch ply composite. So far I have used a
lot of epoxy on the first and most of the second hull. I still have the
floor between the two hulls and the main roof, plus the roof on the
second hull to do. Having used much more epoxy up to this point than I
thought I would I have been mulling over alternative adhesives
especially for these large laminations. The PL Premium maybe is too
thick? Has anyone had any experience with paste epoxy glues? Perhaps
the best method is the one I have used so far epoxy resin plus silica
but I would like to explore alternatives. Cost is an important factor
but also ease of mixing, spreading etc.
Fritz Koschmann
of a 1/2inch ply-2inch foam-1/2inch ply composite. So far I have used a
lot of epoxy on the first and most of the second hull. I still have the
floor between the two hulls and the main roof, plus the roof on the
second hull to do. Having used much more epoxy up to this point than I
thought I would I have been mulling over alternative adhesives
especially for these large laminations. The PL Premium maybe is too
thick? Has anyone had any experience with paste epoxy glues? Perhaps
the best method is the one I have used so far epoxy resin plus silica
but I would like to explore alternatives. Cost is an important factor
but also ease of mixing, spreading etc.
Fritz Koschmann