Body Work and finish sanding techniques

[mark peterson]

I am doing the body work on my new Lonestar and needed some tips;
1. When sanding curved surfaces such as fenders trunks what type of sanding block to use.. I have a long 12-14 inch one for flat surfaces such as doors.
2. Should I stay away from Dual Action sanders and use hand sanding blocks. There is not a lot of heavy fill work that needs to be done on Lonestars.
3. Are there any good books out on Cobra finishing and painting fiberglass bodies?

thanks for any tips:

[Turk]

Check with your local body shop supply house.
There is a product known in the industry as "FART BLOCK".
It is dark gray, black and looks like styrafoam.
It crumbles, and it is sacrificial and will conform to the shape of the surface that is being sanded.

It disintegrates and in the process emits a rather foul smell.
Hence the name.
You'll need a bunch of it.

TURK

[mark peterson]

thanks turk, Sounds just like what i need.

[Bob Parmenter]

What Turk is referring to is "officially" called a grill brick. Restaurants use it to keep the cooking grill "clean". Alternately referred to as sh*t brick, for the same stinky reason. It is volcanic material with a high sulphur content, thus the pungent odor.

It is suitable for body work where rapid cutting is desired and will conform as used.

A DA is also useful and will do rapid cut, but takes some getting used to to keep it flat and not do edge gouging, or develope waves.

You don't want to use that long board on highly curved surfaces, you'll end up with flat spots. As suggested, become good friends with your local body shop supply jobber, they can steer you to the right tools and supplies.

Remember to protect your lungs and eyes through all your fun.

[Steve Siedlecki]

Mark, Check out this site http://autobodystore.com/
Scroll down and click on their bulletin board. Some good info pertaining to the bodywork and painting....
Good luck
Steve

[sfry]

Mark,
Another old trick is to use a short nap (new) paint roller for your contours. It is key however to use a guide coat when doing any sanding prior to painting. Try to stick to wet sanding for your final prep. It will do a better job. As for the DA: Great tool but use it for rough prep only.

Shannon

[Neal Jackson]

On curved surfaces you can often use just the edge (usually the front edge or a side edge) of a smaller hand sanding block to follow a flat sanding line. Get some sticky back DA sanding paper and center the hand block on it - fold the edges over the sides and front and back and have at it. Does take some getting used to.

[xlr8or]

Or you can go the easy way and just write a big a$$ check.
Man's got to know his limitations. I just can't ever seem to get body work quite right so I quit trying. I will do some light color sanding and touch up with an air brush but that' it. Otherwise I just end up paying the guy more to fix what I did and finish it right.

Give me a wrench but keep the sand paper away.

Scott

[427 S/O]

Mark, I wanted to learn the art of auto painting and decided to do my CJ-7,
I now have great respect for painters, the materials alone were in excess of
$600.00 (PPG), not counting the guns, one for primer, one for paint, paper, air dryer, breathers, air tools and hours and hours of labor.
It came out pretty good for novice, but I'll never do it again.
Farmed out the Cobra.

[mark peterson]

Thanks guys. I bought a flexible rubber block from a paint supply house and it seems to work good. I have painted many cars before and I also paint fiberglass reproduction fish so I am not new to breathing "fumes". The larger surfaces are a little more challenging to get right. Part of the fun of this project for me is the final result of doing the paint myself. I have all winter here in Michigan, so I will just take my time and get it right.

[ENTDOC]

Also try Eastwood,they have some new long flexable sanding blocks that should do well. chuck

[niles]

mark;
Go over to the FFR forum and do a search. They have several very good detailed articles and references and tutorials on painting and block sanding.
After 3 gals on primer ( 2.5 sanded off)and approaching a "perfect" body; my only advice is go very slow, and learn to sand "across the curved surfaces".
after about 6 or 7 blockings; you break the code. I can now sand the whole body in about 2 hrs.

gn

[mark peterson]

To Niles. Thanks - What do mean by sanding across the curved surfaces? This is my key question. Are you talking about going at a 45% angle?

[niles]

mark:

sand all surfaces; even the flat doors/hood in a cross-hatched fashion. Sand on a diagonal, then reverse and sand on the other diagonal. This keeps one from making troughs. On the curves(top on fenders) never sand front to rear(makes flats); but rather, about 45 to 60 degrees. Also sand (60 deg) from center, over the curve to side. Then go the other way, from the outside over the curve toward the center, again making that cross hatched pattern. You need you use a professional type long board; one that uses the 18x2in sand paper strips that clamp into the ends of the long board. Using the long board, never sand "inline with the board", but rather you slide the whole board at the 60 deg angle. Effectively sanding "kind of sideways(60 deg) with the long board.. Never sand straight. fore and aft with the long board. Get all you suppies at the "professinal body paint suppliers; not your auto stores. After the first sanding; get some 3M Evercoat; its a black powder that you apply to the primer. When you sand it the first time you will notice odd dark and light patches. The light is where you have sanded all the black evercoat off and it's a high spot. The dark is a low spot that has yet been sanded. After a while(several primers and sandings you will start to notice the evercoats is sanding off more uniformally; meaning your getting in flat and smooth with no lows/high spots.

Also, use for a first coat a black primer( I used one gallon PPG epoxy sealer/primer for the first two coats. Sand that once, using 100G. Then put on 2 heavy coats on sanding primer(use light colored). As you 100G that, you will notice that the surface will look like a zebra, black base coat showing thru the light primer. This will also give you a good feel for the high and low surface quality. After about 2 more gals of primer you will get it perfectly flat. You don't build up the pimer very thick, you sand most of it off. As you wet sand toward the end with 320 or 400 wet, use a hose as you sand, if you reflection looks wobbley, your not quite there. When the wet reflection looks like a mirror, your GOT IT!!.
Finish with wet 600 black paper) for the final surface before paint.

Dont forget the painter cardinal rule; the paint will not coverup anything; it only magnifies defects; get the primer better that perfect!! Just remember; patience and lots of dust!!

I keep thinking of more. for the inside curves, use foam blocks, sponges, dowels, radiator hoses, paint rollers work good, to use as sanding blocks for the sandpaper.

gn

[mark peterson]

Thanks for the explanation. After the first fender that has been how I have been doing it with the long board and the results are much better. You guys are awesome. Really helpful.

[ohekk]

That's the mantra an old body man taught me:

#1 - Get the Shape

#2 - Get it Straight - (coarser is straighter!)

#3 - Make it Smooth!

He told me the biggest mistake guys make is to make everything smooth before they get the right shape and get it straight...consequently they get really nice smooth waves!

For compound curves, use a flexible (Plastic) longbord also available at your auto paint supplier.

...and use that cross hatch technique as described above!

Shape - Straight - Smooth!