fiberglass mesh in foam wings

[Fletcher, Richard]

Hi Ed, 
 
    What I usually do is to lightly sand the foam to create a shallow recess
that the mesh will fit into. That is the way my big Extra wings are done
using CF mat material. These are the strongest wings I have ever owned, 5
full seasons and still going strong. No flexing whatsoever.
 
 

Thanks, Rich 

 

-----Original Message-----
From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org] On
Behalf Of Ed Alt
Sent: Tuesday, December 21, 2004 7:39 AM
To: discussion at nsrca.org
Subject: fiberglass mesh in foam wings


I'm getting ready to sheet a pair of Temptation wings and have questions
about using the fiberglass screen mesh reinforcement strips they call for.
First, how necessary is it to even use any?  I can see where it obviously
adds strength and stiffness in those sections directly under the mesh, but
at the same time, it will also create a raised-up section of sheeting
directly adjacent to the mesh strip.  It seems possible that there would be
no bonding of sheeting to foam for about 1/4" to 1/2" wide all along those
seems, at least not if a thin layer of epoxy is used.  It also seems that at
the point where the sheeting does begin to bond with the foam again, it
would be subject to shearing forces that might tend to pop the foam beads
out over time due to bending loads on the panel.  Maybe not? I have no
experience with this method, so it's all speculation.  It seems that a
fairly heavy application of epoxy would be needed to bond foam to mesh, mesh
to sheeting.  Is it possible that the same or better strength result could
be accomplished with a slightly heavier wood selection and still be as light
or lighter than adding mesh and extra glue?
 
Asuming the mesh is really necessary:  The 2nd question is about the
adhesive to use if the mesh is used.  I normally use either Pro Bond or
Elmers polyurethane glue, which does a terrific job of bonding several bead
layers deep into the core.  I think it probably stiffens the structure alot
as a result.  However, it's not clear to me if this would be a good adhesive
with the mesh applied.  In theory, it would do a good job of filling that
gap I'm worried about along the mesh edges.  Has anyone tried this and are
you happy with the results?
 
The last question is about how far to run the aft reinforcement strip.  Do
you really need to run it all the way to the tip?  At some point, you really
get diminishing returns as you get further out in the panel. Sorry for so
many questions!
 
Ed

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