What filler to use on Polyester body

Guys, Can anyone recommend a filler for my Body Shell, a post on a replica forum suggested PCL polyprimer , "The PCL primer can be sanded wet or dry though, it does not absorb water or moisture of any kind. I usually sand it dry, but for the final sanding before paint its best to wet sand with 320. This primer uses the same MEKP catalyst to cure as fiberglass resin (mix about 1 teaspoon per quart for a 3 hour cure), it can be speed cured with heat if you're in a hurry without any problems.
The PCL Poly primer does not absorb water, it uses a catalyst, so I figured it would seal out moisture,I went searching for the product above to see if it was available in NZ , still not sure if its available here, but I did find these posts that I thought were interesting to say the least. Comments like this "I don't use Poly as it sucks up moisture like a sponge, not good on glass bodies and even worse on steel."
This now leaves me confused as I once painted a car and 5yrs later all the bondo started to blister and you could see everywhere it had been applied on a steel car, and it was wet sanded, and my Countach polyester shell will need some filling here and there, and I really don't need a repeat of the last car, any thoughts on what these guys are saying.
Spray on bondo pros and cons - THE H.A.M.B.
I am hoping someone from NZ, can reply with what is available and works in the NZ market.
Regards
Graeme
 
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I have had good luck with Clausen's SPF1 Sandy Filler primer. 3 different cars, all over 5 years old now and no problems.
 
Spray on "Bondo" of polyester resin chemistry is a great way to straighten a car with minor surface waves or distortions over a wide area of the body. Obviously if there is just localized damage regular filler would be the way to go. I use it on fiberglass (most fiberglass bodies are made using polyester resins), like the fact it is 2K, is very high build, cures quickly and easy sanding. Many who use such types seal it before color coat with an epoxy primer to prevent die back or "soaking up". I cannot comment on that part as I have never personally noticed this was an issue although I do not paint that often and have little experience with the new water base paint systems.

The brand I use is "Fiberglass Evercoat" product name is "Feather Fill".

(You may have acknowledged this) I would guess the reason your filler blistered off a steel bodied car is that during wet sanding, water got under the bondo and rusted the metal. A fiberglass body cannot have the same type failure even if water goes through the filler.
 
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I totally agree with Rob. Featherfill G2 is a good 2K filler. Any seal coat for paint works, but I do prefer the epoxy primer.
 
Thanks guys for the answers, as far as the steel car, I ground off some of the bondo places expecting to find rust but there was nothing, the weird thing was that where ever the bondo was years later the paint just flaked and fell off, the car was painted in dulon, maybe I just choose the wrong brand of bondo, my late father in law used to run his own panel shop, and all I remember was his warning that once you grind down to bare steel don't touch the panel, as the grease from your skin will cause problems later. I believe the modern way is to grind it bare and then seal with a epoxy based paint and then bondo it.Can anyone in the trade confirm this, I believe the pcl product uses MEK to harden it much like the fiberglass polyester resin, but after much searching I find it not available in NZ
Thanks guys
 
look at this site, we use standox since 30 years, some is okay, most it total okay, they have a perfekt spray-bondo from polyester and also verry high filling primer/filler combinations, fast drying, easy sanding, also good ep filler for isaolation from bad-paints like thermopaint´s,....
and yes, both is right, hand grease demages much, but after proper cleaning no problem anymore, and technik today on old cars, scratch or sand deep to panels and make a good building up the new colour, best results and real longtimesave
 

Randy V

Moderator-Admin
Staff member
Admin
Lifetime Supporter
My car is getting:

Filler - Rage Gold
Primer - FeatherFill
 
Same here!

Same here too!

I have been around the trade most of my life. Although been decades since I was in the trade. Our company, amoung other things develops associated paint shop products, am in shops a few times a month.

Currently I see no primer before bondo, it's direct to freshly ground steel. No pro would let the steel surface get oil, grease or water on it before filler. Water did not damage your bondo, unless the bondo had some sort of quality or mix issue. Very most likely it was water corrosion under the bondo, even if there was no obvious corrosion visible once removed. Fiberglass will not have the water corrosion problem although you will still want to keep oils off it.
 
Graeme,
Here are some good videos on fiberglass repair. The first is a series of repair how tos.

https://www.youtube.com/watch?v=i9hfpOCnzEs&list=TLrMkgo21sLIBjDx0BiqQKKvUKPagMzAII

https://www.youtube.com/watch?v=Zka0i0SOGd8&list=TLrMkgo21sLIBjDx0BiqQKKvUKPagMzAII

Here is his channel.
https://www.youtube.com/channel/UC0kDqq-pSzdqFUk3oTaHBuA

For automobile stuff, fiberglass and steel checkout this guys channel. If you can't find it here, ?????
https://www.youtube.com/channel/UCH7RpXjPcKNSw5Shb4WCIGA

Lots of good stuff on Utube.
Here is another good channel.

https://www.youtube.com/channel/UCzA2PE7vg9R_ebLiBSjCxEw

Do a search for fiberglass repair /paonting.

I have seen and heard that if you sand blast auto metal you have to prime right away. You have stripped off the anti corrosion from the factory. Then do the bondo repair. "Bondo" is just a trade name for body filler. Agree with everything stated above. Just have to be careful with primers as some will shrink during curing. That may take weeks on some of them. Don't apply heavy coats. Will trap the solvents underneath. Get and read the spec sheets with whichever primer you use. Observe the mixing guidelines(some need to sit 15-30 mins. before application) and flash times between coats.

Bill
 

Peter Delaney

GT40s Supporter
Graeme, for what its worth, I used a complete system from Spies Hecker (a DuPont company) on my GT40, and am just about done on my 71 Corvette.

Guidance came from the guy helping me with the Vette - he has been doing restos for over 15 years & has developed the following "Golden Rules" for fibreglass finishing :

- Never use "Bondo" or "bog" fillers ! Any defects deeper than 1mm should be filled with chopped strand mat & resin.
- Use Spies Hecker "Raderal" polyester spray filler all over (heavy coat with a putty gun)
- Block back dry with 240grit
- Use Spies Hecker "Vario" primer
- Block back to 320grit (minimum)
- Use Spies Hecker base coat & clear

Let me know if you need more details

Kind Regards,

Peter Delaney
 
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