REFLECTOR: Wing Delamination question

[Alex Balic]

Just to chime in here- since I did suggest using straight resin/no micro -
there is enough styrene monomer in the 2:1 resin to soften the foam- I had
an interesting checkerboard pattern of filler on the bottoms of my wings
where the ridges of micro (which were sanded exactly flush with the foam
before application of the triax ) were now standing above the foam areas- I
had mixed up the slurry for the bottoms a bit thin compared to the tops
which did not experience this problem- now, not saying that it was a lot,
and really not noticeable until I got to filling, then you could see it
plainly- I have had some of the 44:100 - laminating resin drip onto some
blue foam, and there was not any noticeable damage.
So, for filling the void- 
1)I would assume that there is some shell of cured epoxy on the foam already
which would protect it from any adverse reaction with the liquid resin, and
2) even if it softens, the void will still fill with resin and harden, so go
ahead and do it- the resin will not "melt" the foam like solvent.


-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Jeffrey Clough
Sent: Sunday, March 05, 2006 7:49 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Wing Delamination question

May be true...dunno.....but there was a thread a few years ago that said
that our epoxy WOULD eat/soften blue foam (IT DOES HAVE STYRENE in
it...wouldn't that cause some melt possibilities?)...therefore ONE of
the reasons to mix a slurry (and one of the reasons some advocated hard
shelling before applying fiberglass) was to avoid potential
softening/melting of the blue foam........
Jeff Clough

Richard Riley wrote:

> At 04:22 PM 3/5/2006, you wrote:
>
>> And by the way, I wouldn't use pure epoxy (no micro) since it can
>> melt the foam if for some reason the delam pulled the slurry up from
>> the foam.
>
>
> Look, I don't want to be impolite since I'm a guest here, but I can't
> let that go by.
>
> Epoxy will NOT chemically melt any of the foams used in these
> aircraft.  If you got an exotherm the heat could damage foam, but that
> has nothing to do with the old micro-slurry on the foam.
>
> There are several kinds of foam you might see.  Blue foam is
> Polystyrene.  It can be melted by a wide variety of solvents (lacquer
> thinner, styrene) and by polyester or vinylester resin - the kind of
> "fiberglass resin" used in surfboards, boats and Glasairs.  It is NOT
> attacked by epoxy.
>
> The other foams - Urethane (like Last-a-foam) is just about inert. 
> PVC foams are - chemically speaking - a hybrid of PVC and Urethane. 
> Polymethacrylimide, like Rhoacell, has great temperature range. 
> Styrene acrylonitrile (SAN) acts like cross linked PVC.  None are
> affected by either epoxy or polyester resin.
>
>
>
>
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