Glass Fibre Repairs - experience anyone?

[poison]

Hi I've bought some s/h side skirts off a mate and they need some minor
repairs, I've done a bit of glass work on canoes and surfboards but there is
an area where the Gel Coat has crazed from being hit on a kerb. Anyone have
any ideas on the best way to fix this? If I just paint over it the paint will
also craze after a while if the body kit flexes.

I could chip and sand it back, but if I use body filler it will just break off
after a time if there is any movement. If I use glass and resin to fill it
back up it's hard to sand back to a nice flat finish. A friend suggested
flowcoat (a brush on Gel Coat that is sort of auto levelling, maybe not god on
curved surfaces?) and then sand that flat. Flow coat is a polyester product
and I imagine the side skirts are too as epoxy is expensive and an overkill
(but who knows as they were made in Japan).

Any helpful thoughts would be appreciated.

Cheers

Gazza
"PO1SON"

[John Wakely]

Hi Gazza,

You will need to dig the gel coat out and sand back to the laminate to check
if the resin has craked right through. When fibreglass suffers a big impact ,
the resin can break , but the glass fibres will hang together , giving an
effect similar to a cracked hardboiled egg shell. If you just fill over this
it will be a weak point and will probably crack again. What you need to do is
to gind the cracked area away, feather the edges out , then put a backing
against the hole ( some form of plastic sheet so the resin won't stick , and
build up the laminate again. When it is cured turn it over and grind back into
the laminate you have just done to get a clean , solid surface, feather out
the edges again , and then lay up another layer of laminate on the ground out
area. Now you should have a good sound laminate but with excess thickness on
the front and rear. Just rip into it with a 100mm disc grinder with a sanding
disc ( about 60 grit ) until it is back to the original shape and thickness,
Inside probably doesn't matter too much .You should now have a sound laminate
the correct shape but just needing preparing for paint . Spread a thin layer
of Bog (any polester base type will do ) or make your own by mixing resin and
Talcum powder . Sand to shape when cured , skim with body putty , prime then
paint . Sounds like a mission but it is really easy. Don't wear out your arm
use the disc sander ( $20 ones work really well )


Regards

John Wakely

[John Wakely]

Hi Gazza,

You will need to dig the gel coat out and sand back to the laminate to check
if the resin has craked right through. When fibreglass suffers a big impact ,
the resin can break , but the glass fibres will hang together , giving an
effect similar to a cracked hardboiled egg shell. If you just fill over this
it will be a weak point and will probably crack again. What you need to do is
to gind the cracked area away, feather the edges out , then put a backing
against the hole ( some form of plastic sheet so the resin won't stick , and
build up the laminate again. When it is cured turn it over and grind back into
the laminate you have just done to get a clean , solid surface, feather out
the edges again , and then lay up another layer of laminate on the ground out
area. Now you should have a good sound laminate but with excess thickness on
the front and rear. Just rip into it with a 100mm disc grinder with a sanding
disc ( about 60 grit ) until it is back to the original shape and thickness,
Inside probably doesn't matter too much .You should now have a sound laminate
the correct shape but just needing preparing for paint . Spread a thin layer
of Bog (any polester base type will do ) or make your own by mixing resin and
Talcum powder . Sand to shape when cured , skim with body putty , prime then
paint . Sounds like a mission but it is really easy. Don't wear out your arm
use the disc sander ( $20 ones work really well )


Regards

John Wakely

[poison]

Hi John

Great thanks, I've done a little glass work but was not sure where to start or
how far to go, so you that's great you answered all my questions. I'll have to
do a bit of building up on the back around any repair as it's really thin
stuff, much thinner than any NZ made body kits I've seen. I just hope it's
poly and not Epoxy so my resin will stick.

What a great resource this list is. So once again. Thanks.

Gazza
"PO1SON"

[John Wakely]

Hi Gazza ,

Glad to be able to help . Don't worry about the thickness . I used to do a lot
of radio model aircraft flying and designed and built them myself , most with
fibreglass fuselages etc. As a consequence I became very practised in repair.
Some of these would have a thickness of less than a millimetre , but the
method still holds . Try to use cloth ( more thin layers than a few thick ones
is better and easier ) rather than chopped strand mat as it gives a better
glass to resin ratio and is much stronger and able to withstand flexing . If
the skirt is an epoxy moulding , use the same system only in epoxy , but you
will then have to use cloth as the chopped strand mat has a binder that
dissolves in polyester resin , but not in epoxy, so it doesn't go all soft and
floppy and conform to the shape . Good luck .

Regards

John Wakely

[John Wakely]

Hi Gazza ,

Glad to be able to help . Don't worry about the thickness . I used to do a lot
of radio model aircraft flying and designed and built them myself , most with
fibreglass fuselages etc. As a consequence I became very practised in repair.
Some of these would have a thickness of less than a millimetre , but the
method still holds . Try to use cloth ( more thin layers than a few thick ones
is better and easier ) rather than chopped strand mat as it gives a better
glass to resin ratio and is much stronger and able to withstand flexing . If
the skirt is an epoxy moulding , use the same system only in epoxy , but you
will then have to use cloth as the chopped strand mat has a binder that
dissolves in polyester resin , but not in epoxy, so it doesn't go all soft and
floppy and conform to the shape . Good luck .

Regards

John Wakely

[poison]

Hi John

Thanks for that, the mouldings are from chopped strand so it must be poly.
Good advice about using mat rather than chop, I never knew about the
resin/glass ratio.

Cheers

Gazza

Original Message -----
From: John Wakely
To: MX5List
Sent: Saturday, May 28, 2005 7:48 PM
Subject: Re: Glass Fibre Repairs - experience anyone?


Hi Gazza ,

Glad to be able to help . Don't worry about the thickness . I used to do a
lot of radio model aircraft flying and designed and built them myself , most
with fibreglass fuselages etc. As a consequence I became very practised in
repair. Some of these would have a thickness of less than a millimetre , but
the method still holds . Try to use cloth ( more thin layers than a few thick
ones is better and easier ) rather than chopped strand mat as it gives a
better glass to resin ratio and is much stronger and able to withstand flexing
. If the skirt is an epoxy moulding , use the same system only in epoxy , but
you will then have to use cloth as the chopped strand mat has a binder that
dissolves in polyester resin , but not in epoxy, so it doesn't go all soft and
floppy and conform to the shape . Good luck .

Regards

John Wakely