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sp53
06-22-2015, 08:31 AM
So I used some of the fiberglass filler in a spot where it will not be seen unless I really look, but I have some low spots in it. The spot is down by the lower front mounts under the apron, but I need the practice. Do I put more fiberglass over the old or is there another product for that? I would ask them at the store, but they are in sales!

TomMull
06-22-2015, 04:57 PM
You can use multiple layers of whatever you are using. Most fillers have no fiberglass in them but are made from the same polyester resins that are bonded to and with fiberglass (glass fibers). The exception are the products that are clearly described as fiberglass reinforced, e.g. Angel Hair.
The fiberglass reinforced goo is impossible to smooth and requires a filler on top. If that is what you used, you have to put smooth filler over it. The secret to getting out the low spots is block sanding or "blocking".
You can find an array of fillers and sanding blocks and instructions from various body shop suppliers e.g. Eastwood, https://www.eastwood.com/autobody.html?srccode=ga200220&sitelinks=AutoBody&adpos=1t1&creative=47086892340&device=c&matchtype=p&network=g&gclid=CjwKEAjw5J6sBRDp3ty_17KZyWsSJABgp-OayV2_B2bbYxCPYsW-Uo85XP-DZlW0x1YLbcOnGf0CihoCUvjw_wcB
Tom

bobhustead
06-22-2015, 06:14 PM
An excellent top filler that is easy to work with sandpaper is called Dolphin Glaze by U-Pol Ltd. I haven't done any body in 3 years, but the bag the stuff comes in has WWW.U-POL.COM (https://www.U-POL.COM) and SALES@U-POL.COM for websites. I got it at a local auto parts store.
Bob

PatGalvin
06-23-2015, 10:28 AM
I've gone through a couple cans of the short hair fiberglass filler. It is great stuff for areas where you need high strength or moisture resistance. It goes on bare metal with a nice deep scuff with maybe 40 or 80 grit. If you want to put more on top, I highly recommend that you again scuff the surface of the hardened filler and create a "tooth" for a mechanical bond. When that filler goes down, it has some sort of shiny coating that sits on the surface and I don't think the new filler will stick to it well.

Basically, I would put down my fiberglass filler, scuff it well with a die grinder and 40 or 80 grit and get my desired shape, put down my polyester filler (bondo) to fill the deep scratches and block sand. Block sanding fiberglass filler is a huge amount of work - the stuff is just super hard. Polyester filler is a joy to block sand.

Then, if you still have scratches (which you probably will), use a glaze like the UPOL Dolphin Glaze (or any other two part polyester putty glaze) to fill the scratches and do final sanding. With that, shoot a couple coats of urethane primer, and work up from 180 to 400 grit and you are ready to seal and paint.

pat

CJD
06-23-2015, 04:26 PM
Hey Steve,

The same filler will work fine...but if you are really close, ask the paint supply for some glazing compound. The glaze is the same stuff, but comes in a thinner mix that spreads more smoothly to make finer build than the pasty body filler. Being thinner, it is also less prone to trap air when mixing, that leaves pin-holes after sanding. As always, sand with 90-100 grit before adding any filler over old filler.