gel coat

I ran a glider repair station for 20 years and have ground out many a crack.............never found any of them that extended into the underlining structure. I’m talking about cracks like those coming from spoiler box, a zig-zag looking crack is most likely indicating underlying structure has moved and must be ground out so as to see the structure below. You can get other opinions, in fact the Australian FAA, published an AD saying all cracks are structural and make the bird unairworthy!
Let the games begin............
JJ

On Monday, September 23, 2019 at 11:13:25 AM UTC-7, wrote:
I ran a glider repair station for 20 years and have ground out many a crack............never found any of them that extended into the underlining structure. I’m talking about cracks like those coming from spoiler box, a zig-zag looking crack is most likely indicating underlying structure has moved and must be ground out so as to see the structure below. You can get other opinions, in fact the Australian FAA, published an AD saying all cracks 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

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