Grob ASTIR CS User Manual

At ambient temperature the resin hardens in approximately 8 hours. The damaged area
can then
be primed, painted and polished.
b) Damage to the entire glass-foam Sandwich (Fig 2, Page 30)
Even if the interior laminate is damaged, first remove the external laminate that is not
firmly attached to the foam. Now extend the hole in the foam/top laminate by removing
material that is not firmly attached to the inner lamination. So that you can make a
repair
in the inner laminate you must now remove a ring of the supporting foam so that
you have a clear edge of the inner laminate of at least 20mm sufficient for the splice
(laminate
thickness to splice width 1 : 50 ratio) .
Prepare the
splices on the inside and outside laminations using the method described
above
in section a. For small damaged areas you can stick a thin plywood former onto
the inside surface of the
hole using Pattex. Lay-up the fabric to repair the inner
laminate, then fill the hole in the foam with a resin , microballoons and polystyrene balls
filler
mix. After the resin has hardened (approximately 8 hours at ambient temperature)
clean up the surface contour of the filler and lay-up the external laminate.
It is easy to introduce the plywood former into the inside of the structure if the repair
hole has an oblong form. If one or more thin nails are inserted into the ply former
before
it is inserted, they can be used to manipulate the ply and pull it up to the inner
surface.
Important: The ply former must be a good fit all round the edge of the hole to avoid
steps
in the laminate layer.
For larger holes and for weight reasons it is better to use a shaped foam insert rather
than the
filler mix of resin, microballoons and polystyrene balls. Prepare a piece of
foam which fits
exactly into the existing hole. Coat the inside surface with a resin and
microballoons mix to
fill the pores in the foam, then lay-up the inner laminate. Allow this
to harden. After hardening this foam with
laminate on one side can still be bent slightly
by using heaters. Now stick the foam patch into the hole with a thickened resin mix
(cotton
flock and/or microballoons). Bed in around the edges of the foam patch, and
seal the foam pores with a resin/microballoons mix then lay-up the external laminate.
6. Damage to polystyrene foam -supported GRP (fig. 3 page 30)
The repair is accomplished in the same way as for PVC foam except that as the
polystyrene has a sealed/closed surface structure, the laminate can be applied direct
with pure or
slightly thickened resin to the surface. Filling the pores is not required.
With
large damaged areas wait for the first laminate to harden before laying-up the
second
laminate. This will avoid wave formation in the repair patch .
Caution: If you apply too much heat to accelerate the hardening process, the
polystyrene will develop blisters and you must then repeat the repair.
7. Damage to solid GRP structures (fig.4 page 30)
This is a simpler repair. Prepare a clean edge in the laminate and cut a splice as
described above. Lay-up the repair laminate (largest patch first). After 2-3 hours, if the
resin has thickened,
you can filler the surface with a resin and microballoons mix. The
splice width should be a minimum of 20mm, a ratio of laminate thickness to splice
length
of approximately 1 :5 . If the splice surface is dirty or greasy, clean it with carbon
tetrachloride or acetone.
With
large damaged areas a former (plywood) must be used. Wet laminate should not
freely bridge over a gap greater than 20mm. Attach the ply former to the inside surface
29

Grob ASTIR CS Specifications

General

Brand	Grob
Model	ASTIR CS
Category	Aircrafts
Language	English