Found two gliders during refinish where age-related gelcoat cracks
had gone into the structure. One required local repairs only, the
other a complete replacement of inner 4 metres of top wing skin
glassfibre (outer layer). The gelcoat cracks on that were
incredible.

Localised gelcoat cracks found some to be overload/accident
damage related (pushed in during belly landing eg). Others
radiatong cracks from airbrake box corners and the like.

Most major manufacturers have published service bulletins that
are a great help.

Eric


At 03:31 24 September 2019, 2G wrote:
On Monday, September 23, 2019 at 11:13:25 AM UTC-7,

wr=
ote:
I ran a glider repair station for 20 years and have ground out
many a
cra=
ck............never found any of them that extended into the
underlining
st=
ructure. I=E2=80=99m talking about cracks like those coming
from spoiler
bo=
x, a zig-zag looking crack is most likely indicating underlying
structure
h=
as moved and must be ground out so as to see the structure
below. You can
g=
et other opinions, in fact the Australian FAA, published an AD
saying all
c=
racks are structural and make the bird unairworthy!
Let the games begin............
JJ

That makes sense as gel coat is a coating on top of the structural
fibers.
=
Crazing looks horrible, but the structure is fine.

Tom