Paint primer for fibreglass

[roadterror]

Hi guys,

I'm about to start the paint process of my Elan Sprint bodyshell. It's been completely stripped down to the gelcoat, raw fibreglass in certain areas, and I'd like to know what type of primers work best for the 2k paint system. I was able to buy a Germain epoxy primer (light yellowish colour, Leicher.. if I recall correctly) for my Europa some years ago. This worked very well but it's now no longer available. There's a primer used on normal steel bodied cars available but I'm not too sure about it.

Any thoughts/ recommendation? Will post pictures as I go along.

TIA.

Best Regards,
Brian Chan
David Works Garage
3012 Bedok Industrial Park E
#01-2018, 2026 & 2030
Singapore 489978
Off: 065 64451739
Fax: 065 62417730
http://www.davidworksgarage.com/

["busybobs at netzero]

I use Transtar 2K Acrylic Urethane Primer #6401EZ instead of Duponts similar product. Less money and just as good as long as you follow directions on container. Hope you using basecoat for a final finish.Its easy once you know how. Also if you are using any bondo make sure to use a sealer before you color coat otherwise the bondo WILL bleedthrough final finish and look like crap.


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[nebogipfel]

Brian, Accepted wisdom seems to be that the bare glass should be
initially sprayed with a polyester spray filler (ie body filler which
is thin enough to spray)

This was recommended by Miles Wilkins in his book on refinishing
fiberglass cars and gives you a uniform surface on which to put your
paint system of choice. I used Upol "Reface" on mine but I suspect
there are many similar products.

You need a gravity fed gun and need to be quick when applying it
because it dries very quickly and will solidify in the gun.

I strongly recommend you flat it DRY. I always advise NEVER putting
water on bare fiberglass and especially filler - In fact I can get a
bit boring about it!

You can then follow it up with the 2K primer and colour coats of your
choice ........ most people who have done a fair bit of painting have
a favourite

John

[roadterror]

Thanks John. That's what my paintshop recommends but I'm concerned about the issue of any reaction between the type of primer used and how well it bonds to a flexible surface. Fibreglass 'weave' showing up on the paint surface and poor adhesion - problems I've encountered with fibreglass and poor prep.

And yes, flat it DRY.

[Gordon Sauer]

I'm shooting for completion by Log in Oct in Ft. Worth so the prrof will be
in the pudding so to speak, but I decided to gel coat everything as originally
done to avoid any weave showing through, then use a 2 pack primer and 2 pack
topcoat bought from same manufacturer (in my case DuPont) to assure
compatibility. I'm not doing clear coat because my original color was only available as
a mix in a non-clear coat urethane and that was important to me. I've had
trouble in other paint jobs with "Bondo" stuff bleeding through and sand scratch
swelling and will end up using no Bondo on the car with the gel coat and
primer-surfacers as the fillers. I've always wet sanded up to the final coats and
properly done never seen how that's a problem. Gel coat prevents any fibers
from being exposed which some people have said concerned them about wicking.
Gordon Sauer

[rdssdi]

I used Dura Tech high build primer. Its a polyester catalyzed sanding
primer. It has a short pot time but cures hard and is easy to sand.

Bob
1969 Elan +2

["C.D.S."]

hello Brian,

I just finished painting my engine bay using a product called
'duratec' as a surfacing primer (spray filler)

Used quite a bit in boating circles, and by this company:
http://www.gunnarracing.com/index.htm

you can see the before and after of my engine bay here: http://
homepage.mac.com/c.d.s./engine_bay/



best regards


carl


On Feb 20, 18 Heisei, at 5:19 PM, Brian Chan wrote:

[nebogipfel]

--- In ***@***.***, Brian Chan <brian72@...> wrote:

how well it bonds to a flexible surface. Fibreglass 'weave' showing up
on the paint surface and poor adhesion - problems I've encountered
with fibreglass and poor prep.


Brian, The polyester spray filler is basically body filler so it will
adhere well to a properly prepared fiberglass surface - it's basically
the same material.

FWIW I can tell you the method I used:-

1.Repair the shell ready for paint and key the surface DRY with
production paper (p180 grade)

2.Apply spray filler as per instructions and again flat DRY with
production paper (p180)

3.Apply first 2K primer coats and again I flatted dry (p180) but at
this stage you could use water and p240 "wet or dry" paper
You could skip this stage but it gives you more chance of getting
everything flat and smooth

4.Final 2K primer coats flatted wet with P600-800

5.Colour coats flatted wet with p1500 and soapy water and then final
polish with an electric mop to restore the shine

Allow as much drying time as you can.

I have never known 2K primer to react with or indeed flake off filler
and therefore presumably spray filler

Poor adhesion is usually caused by inadequately keying the substrate
but 2K products generally have good adhesion properties.

On the spray filler and primer coats a "guide coat" (light dusted coat
of colour) greatly assists in seeing the highs and lows when you are
flatting

The method I used was based on Miles Wilkins repair and painting
techniques and my own instinct and experience

I am no authority on painting fiberglass (I paint tin cars) so it was
very much a voyage of discovery but I was very pleased with the result
and one year on it still looks good

John

[nebogipfel]

--- In ***@***.***, ***@***.***e:

"I've had trouble in other paint jobs with "Bondo" stuff bleeding
through and sand scratch swelling"

"I've always wet sanded up to the final coats and
properly done never seen how that's a problem."

Gordon, You may well have inadvertantly answered your own problem here.
The point against wet sanding fillers and less than perfect gel coats
is that both (particularly bondo/filler) absorb water. Unless
thoroughly dried this water is released slowly under the new paint
finish causing potentially blisters (micro and larger, and other
problems such as repairs and sanding marks showing up later.

Once wet it is very difficult to get all the water out and be
confident that things are OK

Polyester spray filler gives a uniform substrate to paint onto and
eliminates any possibility of textures from the laminate showing
through (Although areas with exposed matting should have been repaired
properly with surfacing tissue before this stage)

But please sand it DRY

John

[Gordon Sauer]

Actually my paint guy told me that in not removing all the old bondo from the
car the new one-pack at that time primer surfacer merely bridged the bondo
areas, then the hotter color coat solvents absorbed into the old bondo. It
seems two pack products avoid much of this potential but I was sure to remove old
bondo from my current +2 project and that's the reason for not going with any
bondo-type products this time. You really don't need bondo on a fiberglass
car anyway--the stuff is essential for metal cars where extra filling is needed,
and basically the spray fillers like Featherfill go on heavy enough to make
up for imperfections. I read back over Wilkins and at the time (1984) he
talked about not gelcoating due to drying issues but a line of current gelcoating
materials, so called finishing gelcoat, harden in themselves and as a polyester
base seems equivalent to Featherfill type products but you can roll them on
and work smaller areas at a time. Wilkins refers to brushing on a resin
catalyzed mix, no glass, in a few cases and this is basically the same as the
finishing gelcoat except it's easier to work and fills more consistently. In the
end is looks exactly like the final layer I took off my S3 DHC which is another
project. The typical moisture problems are usually seen as blisters in the
paint finish which I happily just avoided in the sailboat I redid. We'll see!
Gordon Sauer

[nebogipfel]

Gordon, Removing old Bondo/filler is essential you don't know what is
underneath it or how well it was applied and you certainly don't know
what it may have absorbed.

Bondo/filler is perfectly appropriate to restore the final shape on a
fiberglass repair providing that is all it is doing and is not in any
way a bodge on steel or fiberglass if used properly as a thin shape
restoring layer.

A certain amount of sinkage and shrinkage into repairs is inevitable
whatever paint system you use including 2K. This is why on critical
jobs I advocate priming twice as much of this sinkage occurs in the
first primer coats and if sufficient drying time is allowed (this is
where enthusiasm and lack of patience often ruins paint jobs) and then
the primer is flatted the problem is largely eliminated and the
subsequent coats will not shrink into repairs.

If I recall correctly Wilkins did not advocate putting resin over
repairs regardless of type because it offers little or nothing and
will almost certainly crack again.

He advocated using surfacing tissue on gel problems with a final skim
of Bondo/filler to finish FWIW I heartily agree with this method.

Although technology has given us new materials there are no magic
products and no substitute for doing things properly

As I said previously I do not claim any great expertise but have been
repairing and refinishing cars for more than 30 years having made many
mistakes and hopefully learned a bit along the way.

At the end of the day there are lots of opinions expressed on these
forums and it's amazing how often the crack resisting properties of
some paint or other are extolled which is frankly ridiculous So all I
do is offer an opinion please feel free to ignore it

John