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fibreglass preparation

Posted: Mon Mar 04, 2019 9:19 pm
by Old and Slow
I need to make some repairs to the transmission tunnel on the Sabre Six, it lifts out in two pieces so is now indoors and easy to get to.
I'm not worried about the cosmetic finish, as there's carpet stuck (well, unstuck actually) on the surface.
What's the best way to clean the existing surface so that new glass will stick? I'm planning to reinforce both the underside and the outer surface.
All suggestions and contributions gratefully received, with thanks in advance.
Philip

fibreglass preparation

Posted: Mon Mar 04, 2019 9:37 pm
by AJL Electronics
A wire wheel followed by thinners or acetone to remove the adhesive, then feather the edges with a stone wheel in an angry grinder. Lay up as required. No need to do both sides as the feathering should go down to the backside.

fibreglass preparation

Posted: Mon Mar 04, 2019 9:38 pm
by ard126k
I use an angle grinder. You just need to remove the surface dirt and oil until you're down to the mat. The grinder leaves a nice rough surface, coat it with resin then lay the new mat on.
Alex.

fibreglass preparation

Posted: Tue Mar 05, 2019 10:25 am
by TrevorG
One trick that I used for many years in mending fibreglass fairings on my race bikes was to drill a few holes around the keyed area, stick tape on the backside and when the resin is laid down they act as sockets for the resin plugs. It helped making sure that vibration never played a part in separating the join, or so it seemed.

fibreglass preparation

Posted: Tue Mar 05, 2019 12:33 pm
by manny
Good day

on a similar note - i am attempting to use FG for the first time soon - will cardboard ( waxed ) be suitable as a mold? I am planning to make a cold air feed 'box'

Ta

Manny

fibreglass preparation

Posted: Tue Mar 05, 2019 12:56 pm
by scimmy_man
for a quick job use clingfilm on crdboard as a former.

fibreglass preparation

Posted: Tue Mar 05, 2019 12:56 pm
by AJL Electronics
As long as it is non porous and smooth, it will do. If the coating fails though, the cardboard will become part of the item. You can also use brown packing tape as release agent.

fibreglass preparation

Posted: Tue Mar 05, 2019 1:14 pm
by Corky
As Andy says, packing tape works. That’s what I use all the time when filling gaps, or moulding little bits here and there.

It’s not much good if you want a nice finished surface though :lol:

fibreglass preparation

Posted: Tue Mar 05, 2019 1:54 pm
by manny
AJL Electronics wrote:
Tue Mar 05, 2019 12:56 pm
As long as it is non porous and smooth, it will do. If the coating fails though, the cardboard will become part of the item. You can also use brown packing tape as release agent.
so on that premise - any sticky backed vinyl will do too?

fibreglass preparation

Posted: Tue Mar 05, 2019 2:13 pm
by AJL Electronics
manny wrote:
Tue Mar 05, 2019 1:54 pm

so on that premise - any sticky backed vinyl will do too?
Not messy celery. Try it with acetone first.

fibreglass preparation

Posted: Tue Mar 05, 2019 5:08 pm
by Old and Slow
I'm using clear plastic sheet from the front of a gift box thingy; once the resin is set I'm finding it peels away easily and leaves a super-gloss finish - far too "Cheshire" for my transmission tunnel, but it'll be hidden under the carpet anyway.
TrevorG - thanks for the "holes" tip - a good idea methinks.
Just waiting for some bits from Spalding Fasteners to fix everything in place, which raises the question - it looks like originally the tunnel uses self-tappers to screw directly into the floor (which looks to be about 3/4" thick fibreglass). Is this the standard fixing method?

fibreglass preparation

Posted: Tue Mar 05, 2019 5:12 pm
by AJL Electronics
Old and Slow wrote:
Tue Mar 05, 2019 5:08 pm
- it looks like originally the tunnel uses self-tappers to screw directly into the floor (which looks to be about 3/4" thick fibreglass). Is this the standard fixing method?
It isn't a good way. I would use Lokuts or Rivnuts. On a thin panel, Speednuts would have done.

fibreglass preparation

Posted: Tue Mar 05, 2019 5:13 pm
by AJL Electronics
Actually on a thick panel, it would not really allow Rivnuts to be used either, so go Lokuts.

fibreglass preparation

Posted: Tue Mar 05, 2019 5:20 pm
by Old and Slow
I've ordered "U"-clips for the self-tappers but they only slide over thin stuff, so now I'm a bit stuck. I'll look into some kind of Dzus quick release thingys I think.
https://www.merlinmotorsport.co.uk/s/bo ... -fasteners
Never nowt but what there's summat.

fibreglass preparation

Posted: Tue Mar 05, 2019 5:34 pm
by Sabreite
Old and Slow wrote:
Tue Mar 05, 2019 5:08 pm
- it looks like originally the tunnel uses self-tappers to screw directly into the floor (which looks to be about 3/4" thick fibreglass). Is this the standard fixing method?
If you have the original floor, it will be plywood covered in a layer of fibreglass as all Sabre Sixes, Sabre fours just had plain plywood floors. Fixing with self tappers was the original way of fixing the tunnel to the floor.

John