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Re: Closed compartments




While Joe's situation of delamination at altitude is not totally unique,
it is certainly not the norm. 

The only air pockets that could expanded enough due to the pressure
differential to generate enough force to cause delamination are the
results of at least one of  three scenarios. This applies at least to the
blue foam cores that  Velocity builders and Alan uses.

1) The micro slurry used to coat the foam core prior to doing the
fiberglass layup is:
a) not mixed properly (too dry or the epoxy resin mix itself is bad), or
b) not applied properly (do not ensure even coating and filling of all
the small pockets in the foam. 
2) Poor technique in the application of the fiberglass cloth and epoxy
resin to the prepared surface.  
3) The gassing process of the curing epoxy creates a visible air bubble,
or a pocket of smaller air bubbles, that goes undetected before the
canard is finished.

Properly done, there should be no voids between the foam, which has
already been accurately described in terms of porosity, and the epoxy /
glass layup itself. All things being right in a non-vacuum bagged, hand
layed up fiberglass surface, there would normally be only a few small
bubbles, if any, that would have the ability to generate enough force to
break the bonds of the epoxy encapsulating them. They would be few and
far enough apart, however, to not cause delamination such as Joe
encountered.
  
Even the best, most experienced fiberglass people have less than
desirable results on occasion. (Eh, Alan?) Ambient conditions, such as
temperature and humidity, all play a part in the results of any glass
layup. It is experience and vigilance in inspecting post cured layups
that prevents any delamination. 

My intention here is NOT to lay blame. I AM wanting to educate and say 
that drilling holes into these "sealed compartments" in Velocitys is not
going to prevent high altitude delamination, unless someone is lucky
enough to place these holes in areas suffering from one or more of the
three situations mentioned above.  

Safe and Speedy Construction

Martin

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