Posted for "Ron Laughlin" <ronlaughlin@hotmail.com>:


I'm looking advice on ways to improve on my body working techniques. I've been using micro / epoxy exclusively. It works well for me while doing the rough fill and shaping work. Where I struggle with it is in trying to get those last tiny bubble holes and slight surface imperfections filled and sanded smooth enough for primer. Micro just doesn't seem to work very well for me with the final detail work. I'm considering trying some of that polyester based "spot" putty that body shops use for final surface prep. I'm worried that I might have unequal shrinkage between it and the micro that could show through the paint a few years later. Has anyone experienced that problem? Also, I've never used Superfill. Would that product be a better choice for final surface prep? TIA

Ron Laughlin
Legacy 156


[Superfil is great stuff, but you have to be gentle with that final sanding, as fully cured it's much softer than the epoxy/micro filler you'll mix yourself.  I like to use it to take the last minor "wavies" out of the micro... it works great for that. Something else to consider is that microspheres come in a couple different grades, and I'm pretty sure the stuff that Lancair sells by the bag is the garden-variety, lower grade of that product.  I only say that because mixtures made with it tend to drag quite a bit and can wind up a bit grainy unless mixed just a bit on the moist side.  There is a higher grade of microspheres called Q-cell that costs about twice the price of plain old micro, but it seems to make a smoother mix.  I understand that the difference is that ordinary micro tends to have a lot of broken spheres in it, making it a bit coarse.  Q-cell is apparently processed a bit differently and so retains a much higher percentage of unbroken baloons as a result.  Anyway, to help keep things smooth you can apply a little heat with a blow dryer while you're working the micro, that tends to make it a bit easier to deal with as well. Someone here also recommended using peel-ply over larger micro fill jobs, smoothed with a Thalco squeegee... I've also had excellent results using that little trick... thanks to whoever it was that suggested it.

I don't think anyone recommends using polyester-based spot putties over epoxy structures as it doesn't adhere very well... I've used gobs of bondo all over the projects I've worked on as temporary attachments in places where you simply can't get a clamp, and in every instance removing the bondo has taken little more than a few sharp blows to knock it loose.  It also shrinks at a different rate than epoxy-based products so it can cause you fits long after the body work is completed.  The final filling of those last few pinholes can usually be accomplished with glazing putty, typically a lacquer product, just don't clean the surface with thinner or acetone after using it... it will just go away.

I am by no means an expert in this field, but these are some things that I've picked up along the way that have served me pretty well.  I wish that Joe Penaz was a subscriber, as I'm sure he would have plenty to say about all this.  (Joe's body-work/finishing series in the Lancair Network News is also a great source of data.... that stuff was published back in 94/95 if memory serves and is still dead on.)   Another person whose abilities and knowledge in this area far exceeds my own is Brad Simmons... perhaps he'll jump in here and share what works for him with the rest of us... he does some great work, so I'd pay close attention to what he has to say.  I hope this all helps.

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