Body Work: The tail. A prof sent this to me, figured I'd post it for the record.

Once again, thanks for the free advice, Dave. It is much appreciated.


Kurt
This is kind of technical, so I am not sure that everybody would like to read
it. I have opted to send email rather than post.
I have a body shop and we work with this stuff everyday but we don't
specialize in Porsche.
All of this assumes you want a very high quality finish and look.

1. There is a high degree of variability in quality of aftermarket fiberglass
parts. Priming and sanding on these parts is insufficient to create a look
equal to the Porsche look. I am optomistic - there may be parts with a good
enough finish, I have just never seen one. At least some fine grained body
filler will be required. Evercoat #417 or #416 is highly recommended and
easy to use. This stuff you can sand with 180 grit for shaping and filling.
Then good primer for finish sanding. Paint will fill nothing. Repeat
nothing. 320 grit scratches can be seen in paint.
2. Gel Coat is precious. Do not use coarse paper on gel coat. 220 is about
the lowest grit allowable. 320 or 400 is better but slower. Paint and primer
will catch on anything up to 1000 grit. It will probably be easier and safer
to fix the small imperfections in the fiberglass with Evercoat then sand and
prime the entire piece. The edges of primered areas are much harder to get
smooth. Do all your fine finish work on the primer. Wet/dry 400 paper is ok,
600 is better and slicker. Let your paper soak in water for 20 minutes or so
before sanding. Check your paper for cracks and chinks at the folds. Cracks
and folds are like sanding with 80 grit.
3. Do not use cheap aerosol primer. It has poor adhesion and has a tendency
to bridge over sanding marks. When paint is applied the lousy primer
reemulsifies and falls down into the scratches and you see the scratches
under the shiny paint. Good primer with hardener is expensive, but worth it.
You need a spray gun and air compressor to apply. Cheap $20 spray gun from
Harbor Freight Tools is sufficient for primer. Small air compressor will do
this job. Wear a mask, isocyanates are bad stuff. It may be illegal to spray
areas larger than 2 ft square where you live. (Texas rules) Just spray small
areas at a time. Prreview will also work.
4. Use sanding blocks. Little bits of hard foam rubber packaging material is
good for small tight areas. Hands and fingers leave grooves that are
invisible in primer, but appear in shiny paint.
5. Get a couple of cans of black spray paint. Spray splotchy mist of black
over your primer. When you sand, the black color will disappear on the high
spots and remain in the low spots. Low spots means more work.
6.You cannot believe how slick and smooth this must be. You cannot believe
how meticulous and incredibly detailed you must be. Look for pinholes and
imperfections with a magnifying glass.
7. Be prepared for multiple do overs. Apply product, minor screw up,
reapply, minor screw up, reapply etc. until right. This is normal, until you
have lots of experience.
8. Allow for thin layers of everything and lots of drying time. Lots of
sitting and waiting that is very important
9. Do not rely on your eyes for humps and bumps. Feeling little bumps and
humps is important. The cellophane wrapper off a cigarette package around
your fingers is a great aid for those inexperienced fingers.
10. Paint color will NOT match, unless you allow the paint shop to blend
color onto your adjacent parts. If you attach tale to existing lid, it will
NOT match the lid without blending and refinishing the lid. If you attach
tale to new lid and have that painted it will NOT match unless you blend onto
the quarter panels. Red is nearly impossible to match because of rapid
fading. Even two year old red is faded. Slight color differences bother some
people more than others.
12. Let the paint shop guys feel your work and take their criticism as
education. Tell them you want it right and want to learn what right feels
like. Most will appreciate this attitude. If they don't have this attitude,
then go to a more customer oriented shop. Group feels are common around
shops. Don't feel bad if you have to do it all again.
13. This will take longer than you can imagine. But 90% of your time will be
learning.
14. If you decide not to do this, make sure you ask the shop how much of this
they will do. The more you have them do, the more it costs.

15. CLEAN WITH MOLD RELEASE AGENT BEFORE DOING ANYTHING. Your hands will
leave enough oil to prevent adhesion. Tacos at lunch will make the paint peel.
This isn't rocket science and nowhere near as complicated as mechanical, but
requires lots of time and patience. Experienced prepper could do in about 6 -
8 hours, but we already have primer, paper, guns, etc. Don't expect less than
30 to 40 hours for you.
If someone brings in a piece, properly primed and prepped, all we have to do
is clean and paint. $100 or so. Big multiple contour pieces up to $250. We
did a Saleen Mustang double wing last month. We did all the prep on good
quality piece. $450. Lower quality piece would cost more or customer's lower
expectations would have cost less.

You can post this to the BBS if you think anyone else would benefit.

If you have any questions, call or email.

David


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Kurt B
1984 911 Carrera Cabriolet
75 914 1.8

That was great! I have been looking for such information for awhile. Thanks for posting.

Hi Kurt,

I can attest to everything stated above. I just added a wing to my 90 C2 and I did the prep. Fiberglass is very hard to get the holes filled in and smooth. The sanding I did was with 600 ans was very tedius.

When I thought I had it ready, my body guy ( a friend and VERY good at what he does)shot it with 2 part primer and gave it back to me and told me I had another couple of hours of smoothing and sanding to do to get it where HE would even shoot it.

Bottom line is you get back what you put in to it. I preped it myself because I'm a picky $hit and if it was wrong I had no one to blame but myself. My body guy gave me a lot of very good advice which is EXACTLY the same as what is stated above.

I am VERY happy with my results.





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Tom Sharpes
90 C2 Targa
http://members.rennlist.com/5150targa

I didn't chime in on this thread before now because I was curious to see some of the problem areas incountered with aftermarket glass wings. My wing (GT2) came fully prepped and in primer. All I had to do was clean it good and lightly wet sand once then paint. It looks great even under a magnifying glass! This wing was a little pricy, I think now I know why.