randylervold

randylervold

moderator
I need to do some "fairing" of some fiberglass parts in addition to the usual pinhole filling. Anyone who's used SuperFil knows that it's quite thick and doesn't spread very well. I recall reading about some who have thinned it and I'm wondering what you thinned it with and how it worked overall -- whether it "wetted" any better when spreading it out thin over larger surfaces. I tried a small batch thinned with acetone and the acetone evaporated out it very fast not leaving much working time.

Of course I don't want to use any of the polyester products that would shrink and crack over time which is really too bad because stuff like 3M glazing putty spreads out so nicely.
 
I experienced batch to batch variation in the superfil I purchased to use on my airplane. One "kit" was very difficult to work with and another smeared on buttery smooth. I don't know if it was a shelf life thing or what, but one thing I found with the harder to spread stuff was that if I warmed it up some, it spread much better.

I was never happy with the physical properties of cured superfil. It didn't pass the thumbnail test. So, towards the end of my project, I simply switched to West Epoxy and micro...
 
Thinning

Hey Randy,

Two things you can do, 1) place the containers in the sun to soften the contents some. You should get the nice peanut butter consistency that way. 2) thin with denatured alcohol. This should only take a few drops. The alcohol won't cause any problems with anything.

Or, if that isn't working out, use the epoxy and microfiller as noted by Kyle.
 
filler

I like to mix west systems with chopped glass 1/32 then thin with alcohol.
this gives the area some (body strength) if it ever gets bumped. Micros
don't give much strength.

Ted
 
Randy,

I used Superfil around the base of my windshield. It ended up cracking and had to be ground away and redone last year. The batch I used was too heavy and thick for my preference, but seemed to get the job done at the time. If warmed, it did thin out. As I recall it actually would sag or run on vertical surfaces when the shop got really hot. I think that a simple West Systems/flox or micro slurry or good ole stinky Bondo is a better all around solution. I used Bondo for the repair job and it has been tough as iron. Used 3M glazing putty to fill the pinholes.

I've been watching for updates on your -3 project. I just can't shake the desire for starting a -3 myself. Curse you!! :D
 
Thanks for the comments guys, sounds like denatured alcohol is the way to go for thinning and improving wetting. I use West with micro also but it is harder to sand of course when mixed thinner due to the greater epoxy-to-micro ratio.

Bryan, aren't you worried about Bondo cracking over time? And how thick was the SuperFil that did crack on you? I've been tempted to use 3M glazing putty but so far have avoided the siren song of polyester.
 
The Bondo I used is the dark green, fiberglass reinforced, available at Wally World and Checker/Autozone/Pep Boys, polyester (insert siren song here) based death goo. It hardened up like granite within a couple of hours. Sanding is NOT it's forte', however. It's good for large scale buildup, blending and repair (which is why it's sold as an auto body repair product). The Superfil I used originally was layered on via a plastic squeegee and sanded to final profile but then hairline cracked in two places on the lower right side a few months after the paint job was done. (Of course.)

It was maybe 3/16" thick at the areas needing the most fill. I think it may have delam'd from the underlying fiberglass/carbon layup and then the shake 'n bake from the Lycosaur eventually beat it up. It was mostly cosmetic only and didn't pose a safety concern. The product is good, and perhaps I just didn't apply it well enough. Like you mention, it doesn't seem to wet out very well so adhesion could be the issue.

To sand the Bondo, I used a half-round rasp to knock down the high spots, then 80 grit after that. I finished up with glazing putty (in the tube, self drying) and high build spray primer. So far so good a year later.
 
Kitty Hair

The fiberglass reinforced stuff Brian is refering to in sold by the name of Kitty Hair.

Check at auto body supply houses, or paint stores.

Very strong stuff when compared to plain "Bondo".

A BIG word of caution here---------the hardener (MEK peroxide, I think it is)used in most of these will eat your eyeballs-----as in you wont even have enough time to wash it out.

Be careful, and follow the safety warnings.

Mike
 
Just wanted to post a follow-up. I just can't bring myself to use polyester products so I took the advice on using denatured alcohol to thin the SuperFil. Worked much better by providing more working time than acetone. It still flashes off after a while so you need to spread it where you want it and move on. It still doesn't wet out like a good glazing putty but I'm getting it to work well enough and I know I won't have any polyester related problems down the road.

Thanks for all the comments!
 
Filling Veritical surfaces.

When filling vertical surfaces, you want to add Cabosil to the filler mix. It will prevent sagging. It will also 'thin' (more like smooth out) the mixture a bit.
What I have found to be the best filler 'product' is a mixture of microbaloons and PolyFiber's AlphaPoxy. When mixed, AlphaPoxy is very thin. You can get a lot of micro into the mix. It sands very easily. I use food coloring to color each layer a different color so I can see just how much I am sanding away.

Always thin with denatured alcohol. I make my filler mix like cake icing, light and fluffy.
 
gpiney said:
When filling vertical surfaces, you want to add Cabosil to the filler mix. It will prevent sagging. It will also 'thin' (more like smooth out) the mixture a bit.
What I have found to be the best filler 'product' is a mixture of microbaloons and PolyFiber's AlphaPoxy. When mixed, AlphaPoxy is very thin. You can get a lot of micro into the mix. It sands very easily. I use food coloring to color each layer a different color so I can see just how much I am sanding away.

Always thin with denatured alcohol. I make my filler mix like cake icing, light and fluffy.
Click to expand...
I bought some cabosil but never used it. How is it different than microballoons?
 
Randy,

To make things perfectly clear, Cabosil is an additive, not a filler. It is a lot harder to sand if you made a filler out of epoxy and Cab. I would make up a batch of filler with microballons and add a couple of tablespoons of cabosil. Then thin with alcohol..
 
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