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Prep for glass, what did I screw up?

S

Sig600

Well Known Member
Referencing this thread...

http://www.vansairforce.com/community/showthread.php?t=73794

I went out tonight and pulled the peel ply up, and some of the edges of the resin pulled up with the peel ply, and pulled the 410 filler that was underneath up with it. I ran a thin screw driver under it to see if it would hold and a large portion of the fiberglass pulled right off with it. So I'm going to pull up, sand down and start again.

What did I mess up in the prep of the metal/emp tips? I sanded them, blew off all the dust with compressed air, wiped them down with water and clean towels, then after the dried I gave them a good wipe down with alcohol. There were differing directions on whether to use alcohol or acetone, I went with alcohol since it didn't seem logical that the resin would adhere since acetone is used to thin the mix.

I've never worked with fiberglass, so I'm learning as I read and go.
 
Sig600 said:
Referencing this thread...

http://www.vansairforce.com/community/showthread.php?t=73794

I went out tonight and pulled the peel ply up, and some of the edges of the resin pulled up with the peel ply, and pulled the 410 filler that was underneath up with it. I ran a thin screw driver under it to see if it would hold and a large portion of the fiberglass pulled right off with it. So I'm going to pull up, sand down and start again.
Click to expand...


I suspect if you use acetone as a de-greaser/cleaner you'll have better results. I don't think alcohol will remove everything. I'm assuming that since you mentioned sanding, the surface has been rough up a little for better adhesion.
 
How coarse?

Getting 'glass to adhere to aluminum takes around 50 or 60 grit, really rough sandpaper that makes the metal really roughed up....same deal as the front, lower windshield 'glass.

220 grit or thereabouts, doesn't cut it.

Best,
 
Acetone vs Alcohol

Having been a chemist...

The alcohol is usually enough certainly I used to wash down glassware with 5 gals worth of the stuff, with things just as if not stickier than the epoxies.

Acetone is however much more aggressive and will eat through any non-thermosetting plastic. It basically just dissolves most organic molecules and even some salts. It?s hard to beat it as dissolution agent.

Your concern that it will dissolve something it shouldn't, well, it probably will a little but that?s not that bad when bonding two things together.
 
Thanks guys, I sanded everything smooth with 350 grit, after taking down the first layer with 150.

I'll go back and reattack with 80, and wipe down with acetone this time. Do you just let the stuff dry?
 
Yes, the Acetone will dry in a few seconds. Use appropriate gloves when using Acetone. As far as a peel ply I am not sure why you would use it at all for this application.

Pat
 
Sig600 said:
I'll go back and reattack with 80, and wipe down with acetone this time. Do you just let the stuff dry?
Click to expand...

Absolutely not. Any solvent wipe is done using the two-hand method. One hand holds a sloppy soaking wet paper towel, the other a new, dry paper towel. Scrub with the wet towel, then immediately wipe away all trace with the dry towel before the solvent can evaporate from the surface.

The goal is to get the bad stuff suspended in the liquid, then remove the liquid before the bad stuff can be re-deposited. If you let the solvent dry on the surface all you did was reposition the contamination. I use MEK. Acetone evaporates too fast.
 
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Sig600 (come on we're all friends you can tell us your name?)

I use West Systems epoxy and their product guide/user manual for us fibreglass newbies is excellent. I have followed their advice and so far I have had no delaminating issues.

Dan's advice above is as per the manual - never in doubt;).

Regards

Bob
www.rv-8.co.uk
 
One other thing to keep in mind, try to avoid the temptation to wipe your hand over the freshly sanded and cleaned surfaces you are about to join. Everything needs to be scrupulously clean, and any natural oils or contaminants from your skin can be enough to affect adhesion of resin to metals. Acetone is 'OK' but as Dan suggested, MEK would be a more effective option.

Clive
 
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