Body work: Shaping filler

My partial respray project progresses. Getting the paint and old filler off turned out to be trivial: two hours of careful (electric) sanding for the OSR wing; diagnosing and fixing the problem straight forward. The gel coat was damaged, and there was moisture in the matting. I just sanded the bad part out, and retissued as recommended in Miles Wilkins’s book. Now I have come to a job which is soul-destroying time consuming: building up a smooth surface with filler.

I have applied filler and am tring to get the shape back by sanding with wet and dry. Working evenings, I think it will take weeks of applying filler and sanding to get a smooth finish before painting. Am I doing it wrong? Is there a better way? tips?

I think it was mistake to take all the paint off - perhaps I should have only gone to the gel coat around blisters. Comment?

best regards, iain

Hi Iain

You have my sympathies!

The way you’re going will work but you might consider using 2 pack epoxy spray filler. This is compatible with body filler such as p38 and the spray filler acts as a replacement gelcoat. The advantage of this stuff is that whilst it is still wet ie just after you’ve applied it by looking along the flanks of the car you can see where the contours are faulty. It’s very easy to flat down too.

Because it’s basically the same as p38 in a spray form you can “sandwich” it between coats of filler.

Don’t use it over paint though.

John

I used a product called angel hair its a mix of filler and fiberglass mat it fills and sands to a nice smooth finish —easy to use - but I’m not sure what its called in ‘English’ :laughing: ed

Iain,

If you want a good result there is no substitute for taking your time.

Filler should be shaped using “Production paper” (usually white or yellow) which is designed to be used dry. Wet or dry paper is not really the best product to use. You can get production in very coarse grades and I would suggest doing the initial shaping with P60 or even P40. There is no need to worry about scratches because you will get rid of them in the final finishing.

NEVER flat filler wet - it soaks up water like a sponge.

You can buy long sanding boards which take self adhesive strips of production paper and they are very good for achieving flat surfaces or surfaces which curve in one plane (3M sell a good one) Otherwise use blocks of wood or traditional sanding pads to reduce the liklihood of creating wobbles.

Once you are happy with the basic shape, flatting of the final layers can be done with perhaps p180 (production paper) DRY.

Polyester spray filler as mentioned by Worzel John is good for the final finishing but you need a good gravity fed gun with a big nozzle to get it on effectively. If it’s a hot day you need to get it on the car and clean the gun pretty pronto - believe me, I know!! Again, if you use it, flat it dry.

I wouldn’t recommend glass reinforced filler for final finishing. It is designed to be used under filler. A good quality filler from someone like U-Pol followed by either a fine filler such as U-Pol “Top stop Gold” and/or spray filler would be the way to go.

Did I mention not getting filler wet :question: :smiley:

Just a final thought - don’t be tempted to use mechanical sanders - You WILL create wobbles. This work must be done by hand.

John,
Many thanks for this post. I’ve been using production paper (P60) and was concerned that it may be too coarse - it’s great for removing paint and old filler after chiselling off the top surface. As I get close to the fibreglass, I’ve switched to P180 but the surface isn’t as smooth as rubbing down with fine wet and dry.
You’ve put my mind at rest.
Mike

geezz guys how ever did you build an empire :laughing: —filler and sanding boards of decreasing fine grit paper makes as good a job -over ere --ed

Mike, You’re welcome :slight_smile:

The problem with wet or dry is that it is only really effective wet and I have a problem with putting water anywhere near polyester filler or indeed fiberglass with a less than perfectly intact gel coat - there are enough problems with moisture and Lotus bodyshells without adding to it yourself.

60 grit scratches are no problem when you are initially shaping filler because the final finishing can and should be done with much finer (perhaps p180) grit.

FWIW I advocate priming with a good 2K primer/filler preferably in two stages allowing plenty of drying/curing time. I tend to flat the first primer coats dry with p180 production and go down to much finer (at least p600) wet or dry on the final priming stage (wet of course). Once fully cured and properly flatted any preparation scratches will be gone and you are ready to put the shine back on :smiley:

Using this method the first lot of primer is used as a filler coat and when flatted dry it enables you to sort out the final blemishes.

Always use a light dusted “guide coat” of colour when flatting to show up the highs and lows - anything will do, even an old aerosol touch up.

Thanks All.

I’ve bought some P60, and am making progress now. Perhaps another skim or two and I’ll be priming.

I’m down to GRP in one or two places, but not through the gel-coat. Should I put some resin there to ensure I keep the matting covered? Prime it? or continue filling and sanding? I think the original problems with the paint were due to damage to the gel coat.

best regards, iain

Iain,
I think you need a sound surface for painting to avoid all the problems of blistering and cracks. Miles Wilkins’ book recommends finishing with a layer of surface tissue over repairs and I’m going to use that method to give a good solid, waterproof base. Fill over this and sand down the filler to get the required profile then primer/surfacer and paint.

I’ll give up after the filler stage and get a professional paint job. I’ve sprayed before but I’m not good enough to get the standard that I want. After all the hours of preparation, I don’t want to compromise.

Also, it’s a good idea to have the car left overnight in a paint oven to make sure it’s dry (I don’t have one!) and 2 pack is not very pleasant to use at home - I’ve used it before but life seems more precious as I get older.
Mike

Iain,

If the surface gel coat is undamaged you have nothing to worry about.

If there is any cracks or problems with the exposed glass I would suggest repairing it first with one or two layers of surfacing tissue.

If it is sound glass but you are through the gel-coat, either spray filler or a thin skim of normal body filler will suffice, then follow up with your chosen paint system. Adding resin will not contribute anything and would make it much more difficult to obtain a good smooth surface.

As Mike says, the general advice in Miles Wilkins’ book is sound, certainly repairing cracks and crazing with surfacing tissue (and with matting if they are bad) works well and trying to use resin to effect repairs is a waste of time.

I used a similar technique on my own shell with results that I am happy with two years on. I do differ from Wilkins somewhat in my obsession with avoiding water on filler and fiberglass.

There are no magic paints or products. To restore a fiberglass body you have to repair the actual structure of the laminate and to obtain a good final paint job it’s all in the preparation -laborious but true :wink:

I would avoid using cellulose primer on a 'glass body, modern 2k primers are so much more durable and resistant to solvent creep and shrinkage.

If necessary pay someone to put the primer on …

If you must use cellulose, leave it to dry for as long as you possibly can, otherwise you will see the final job shrink and deteriorate before your eyes.

[/quote:

I would avoid using cellulose primer on a 'glass body, modern 2k primers are so much more durable and resistant to solvent creep and shrinkage.

If necessary pay someone to put the primer on …

If you must use cellulose, leave it to dry for as long as you possibly can, otherwise you will see the final job shrink and deteriorate before your eyes.[/quote]

Bearing in mind that Iain is committed to using celly for the final coats, wouldn’t he run into problems in trying to apply it over two-pack primer? My understanding is that, although you can apply two-pack over celly, it doesn’t work the other way round.

Not at all. Cellulose colour will not be a problem over 2k primer (properly cured of course).

If you have to use celly primer I would recommend spraying it with as little solvent as you can get away with and then allow plently of flash off time between coats. The idea being to avoid loading the surface with solvent.

As I said earlier, the longer you can leave the primer before top coating the better. (particularly celly primer) I would suggest at least a week in good temperatures. There is also a school of thought that once flatted you should again leave the primer for a few days before top coating. None of these shennanigans are required of course if you are painting a steel body :slight_smile: