Brian,

Tom Gleaser built a KR2 in the 80's and had the same problem, I think it's
fairly common. Maybe you know this, but here it is.
I worked for 5 years in a R&D lab and in that time we tested Urethane foam
for structural and thermal properties. We found that with urethane [ and all
two component chemicals] :  if the foam [epoxy or what have you] did not
fully react [ due to varying amb. temperatures , mostly] the foam would
finish it's reaction later. The additional reaction produces off gases which
will form a bubble under the fiberglass. Post curing after the foam is
finished [sanded], is a good idea.  Problem is, you don't know until you
bird is parked in the summer sun for a while.

KRron

----- Original Message ----- 
From: "Brian Kraut" <brian.kr...@engalt.com>
To: "KRnet" <kr...@mylist.net>
Sent: Tuesday, April 27, 2004 8:46 PM
Subject: RE: KR> delaminations!


> You are correct that it is usually not a big problem if the glass
separates
> from the foam in some places. Most KRs I have seen have seperation in some
> places.  My only concern was cosmetic.  My last KR had a big bubble near
the
> trailing edge.  It looked O.K. on cold days, but the glass expanded when
it
> was hot and bubbled.
>
> Brian Kraut
> Engineering Alternatives, Inc.
> www.engalt.com
>
> -----Original Message-----
> From: krnet-boun...@mylist.net [mailto:krnet-boun...@mylist.net]On
> Behalf Of larry flesner
> Sent: Tuesday, April 27, 2004 9:07 AM
> To: KRnet
> Subject: RE: KR> delaminations!
>
>
> >I have thought of taking something like a thin steel ruler and putting
1/4"
> >deep grooves in the foam in a 6" X 6" grid pattern before putting on the
> >micro.  That would prevent the glass from separating from the foam and
also
> >give it a little more stiffness while adding very little weight.  Has
> anyone
> >ever tried this?  Maybe I will do some test pieces.
> >Brian Kraut
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>
> The foam will just fail with a "grid" pattern attached.  I really don't
see
> the need for anything more than sealing the foam with whatever method
> you chose and glassing it.  How many KRs have flown before us using
> that method and how many have fallen from the sky because of the
> epoxy/fiber delaminating from the foam?
>
> It's a beautiful morning out and I need to run by the hangar.  I think
I'll
> take my ol' "hard-shelled" bird up for a quick flight! :-)
>
> Larry Flesner
>
>
>
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>
>
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