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Fiberglass *MAT* and Epoxy
Posted:
Fri Jun 16, 2017 4:12 amby JonnyPlus2
Hi,
I'm trying to use some F/G mat with West System epoxy. The mat does not want to hold to the shape of the panel I'm trying to patch at all. The West System Tech Support people tell me it should work, I'm wondering if anyone's had any success with it. The mat was kindly given to me by a friend so I have no idea of it's age. Thanks.
Best,
Jonny
Re: Fiberglass *MAT* and Epoxy
Posted:
Fri Jun 16, 2017 7:01 amby c42
Hi Jonny
A couple of questions.
Do you have any pictures of what you are trying to repair?
Does the epoxy "wet out" the FG mat?
Regards
John
Re: Fiberglass *MAT* and Epoxy
Posted:
Fri Jun 16, 2017 7:09 amby prezoom
How thick is the mat? If is quite thick, it is difficult to wet out and get to follow a contour. If that is the problem, try splitting the mat in half and use smaller pieces. You can also clean up with cheap white vinegar rather tban acetone.
Re: Fiberglass *MAT* and Epoxy
Posted:
Fri Jun 16, 2017 9:19 amby nmauduit
I always use "tearing veil" on top when fiberglassing (polyamid fabric that does not stick to polyester resin) to avoid excess material and saving time if you need an extra layer : when you have a short radius bend you can put a layer a vinyl and foam (caution : usually to be protected), wood block etc. to press fit to follow the shape you want.
Re: Fiberglass *MAT* and Epoxy
Posted:
Fri Jun 16, 2017 1:14 pmby JonnyPlus2
Hi,
I'm bonding the bobbin on the left rear suspension tower. No pics.
Regards,
Jonny
Re: Fiberglass *MAT* and Epoxy
Posted:
Fri Jun 16, 2017 2:04 pmby nmauduit
you may have to shape the mat dry a bit so that it conforms better to the target location, and use a shape and cuts to minimize stress which in turn produces spring effect that tends to delaminate (again, pressing into shape may be required). For bobbins the manual offers some useful hints
- Manual bonding bobbins
Re: Fiberglass *MAT* and Epoxy
Posted:
Fri Jun 16, 2017 3:05 pmby alan.barker
For bobbins it's chopped strand mat 2 ozs or 4 ozs. Also you need to separate some strands which you can wind round and round the bobbin between the layers of the chopped strand mat/roving/shredded.
Sorry if you already know, just trying to help.
Alan
Re: Fiberglass *MAT* and Epoxy
Posted:
Fri Jun 16, 2017 3:59 pmby JonnyPlus2
Hi Alan,
I think I remember seeing this in the manual but I had forgotten about it. Thanks much.
I shall peruse that section carefully.
Re: Fiberglass *MAT* and Epoxy
Posted:
Fri Jun 16, 2017 5:08 pmby JonnyPlus2
Well the section on bonding in bobbins was most illuminating. No wonder it didn't work, I was doing it all wrong.
The manual references 1 1/2 oz laminate. I am using 6 oz cloth but it is pretty thin stuff so I'm inferring that they are referring to mat. Since I am working with epoxy I will use some nice thick 18oz cloth. That should be beefy enough.
Anyway, thanks again Alan for your helpful post.
Re: Fiberglass *MAT* and Epoxy
Posted:
Fri Jun 16, 2017 5:21 pmby Esprit2
Matte contains a sizing that binds the loose fibers together. It gives the matte a stiff feeling, like a startched shirt.
Polyester resin contains solvents that quickly soften the sizing, causing the matte to go limp and easily conform to contours.
Epoxy resin contains no such solvents, and the matte remains stiff for a longer time. But given time, soaking in the epoxy, the sizing will soften and the matte will become pliable. Just don't get in a hurry and mix a 'hot' batch of epoxy... you need to allow a little time. Be patient, wet it out, let it sit for a while, then go back and work it.
Or... mix a little acetone or ketone into the epoxy. The solvents will attack the sizing, then being volatile, will evaporate. They may cause the epoxy to take longer to cure, but it will still cure. Try a test piece before committing a batch to your project.
Regards,
Tim Engel
Re: Fiberglass *MAT* and Epoxy
Posted:
Fri Jun 16, 2017 6:53 pmby JonnyPlus2
Hi Tim,
I knew what the problem was I just didn't know what the *cure* was.
Thanks for this, I will give it a test shot tonight.
A very kind gentleman in Atlanta is going to send me a 10 sq ft "sample" of his company's 1/4" needled mat. Although it *is* thick there is no sizing in it to mess things up. I'm hoping that it will not be too thick once I've added the epoxy. That however is for later, tonight I'll test your method.
Re: Fiberglass *MAT* and Epoxy
Posted:
Sat Jun 17, 2017 9:35 amby alan.barker
JonnyPlus2 wrote:Well the section on bonding in bobbins was most illuminating. No wonder it didn't work, I was doing it all wrong.
The manual references 1 1/2 oz laminate. I am using 6 oz cloth but it is pretty thin stuff so I'm inferring that they are referring to mat. Since I am working with epoxy I will use some nice thick 18oz cloth. That should be beefy enough.
Anyway, thanks again Alan for your helpful post.
How i understand things you have Tissue ( very thin for finishing)
Chopped Strand Matt/roving/shredded ( falls apart easy eg. 11/2 ozs, 2ozs, 4ozs etc.)
Woven Mat (woven and choice of weights/thickness)
Alan
Re: Fiberglass *MAT* and Epoxy
Posted:
Sat Jun 17, 2017 9:40 amby alan.barker
alan.barker wrote:JonnyPlus2 wrote:Well the section on bonding in bobbins was most illuminating. No wonder it didn't work, I was doing it all wrong.
The manual references 1 1/2 oz laminate. I am using 6 oz cloth but it is pretty thin stuff so I'm inferring that they are referring to mat. Since I am working with epoxy I will use some nice thick 18oz cloth. That should be beefy enough.
Anyway, thanks again Alan for your helpful post.
How i understand things you have Tissue ( very thin for finishing)
Chopped Strand Matt/roving/shredded ( falls apart easy eg. 11/2 ozs, 2ozs, 4ozs etc.)
Woven Mat (woven and choice of weights/thickness)
For the Bobbin and everywhere on a Lotus use only Chopped Strand Mat/roving/shredded (except for finishing before paint with Tissue.
Alan
Re: Fiberglass *MAT* and Epoxy
Posted:
Sat Jun 17, 2017 11:44 amby JonnyPlus2
Hi Alan,
I think that what I have is 6oz cloth which is about twice as thick as a dress shirt. I will experiment with mat this a.m. My son is bringing some 18oz cloth from the Big City tomorrow which I shall play with.
I'm keen on cloth as it gives an inherently stronger repair as there is less resin in it.
Thanks for your help and support, I'm having fun learning.
Re: Fiberglass *MAT* and Epoxy
Posted:
Sat Jun 17, 2017 12:24 pmby alan.barker
Imho you are better with Chopped Strand Mat/roving/shredded as used by Lotus to make the cars.
With the Chopped Strand Mat the first piece is the smallest then the following slightly bigger and so on.
This way the stress is spread over a larger area. This stops stress cracks caused by stress being in one concentrated line.
Have a close look at the other Bobbins on the car and how they were laminated by Lotus.
Or buy the book written by Miles Wilkins about grp.
The only place i know where you always get stress cracks on a +2 are next to the Headlamp in the square corners (body).
Imho this was an oversight by Lotus and they should have made corners with a big radius or laminated a rope underneath to spread the stress.
When i need grp materials i always go to a boat yard or chandlery for top quality products.
Well anyway good luck and don't forget to wear rubber gloves to stop hairy fingers
Alan
