carriage painting

Does anyone know how to prevent filler cracking over rivet/screw heads on stock which is wooden framed with steel panels fixed to the outside. The LMS P3's at the SVR dont seem to show signs of any of this, but a number of other vehicles Ive seen appear to have this problem of the filler always cracking and pushing up over screw heads?

Is it a case of getting plently of layers of paint on or can't it be prevented?

 

there are several factors at play in this situation......

StoneRoad

 

Make sure that the screws are tightened properly !

Bob.

 

there will always be a degree of flexing where you use filler, the only advice i can offer is to ensure that the surface you are filling, ie screw heads, is clear of any oil or grease before you start to fill so that it adheares properly even the sweat from your hand can effect the bonding, and to ensure that nothing has been left lose so that it can loosen the filler and yes its a case of fill, rub back, paint, rub back ,fill, paint untill you are happy with the surface .
if done properly filler shouldnt crack even with the movement of the coach and where you see coaches with filler falling out its because it wasnt done properly in the first place, or that the rust has eaten away whats left of the panel, ive seen this a few times on Mk1's where the filler had held but the metal behind it had rusted away

 

You will also get the problem if your vehicle is parked for long periods in direct sunlight and the filler bridges gaps between different materials. This can include different grades of steel, Steel/Aluminium, and metal/wood. The issue is the different rates of expansion/contraction. Some fillers seem to cope better than others. Of course if you can store yuor vehicle out of the sun when not in use everything will last a lot longer !

 

This is interesting advice. Are there any fillers notorious for coping badly with expansion/contraction? Equally are there any real winners?

I don't usually advocate naming names but it would be useful to know!

 

I think Isopon p38 is a good general filler, but do not put in too much hardener, as this tends to make the filler loose some of the flexibility. As mentioned good prperation is everything, also make sure you are appling the filler to sound metal. As trying to fill gaps in the metalwork is not a good idea.

 

We use P38 or the equivilent of at Tenterden , as long as its the flexible type it would cope ok and dont put it on too thickly several thin coats is better than one thick coat ensuring that you wipe down with degreaser between rubbing down and applying coats i tend to roughen up the metal surface a bit to ensure a good bond first it all helps

 

What filler would you use on wood?

 

do you think giving each screw used to fix steel panels to the side of a coach a quick flash over the grindstone would help with the issue of filler adhesion, seeing as most screws seems to be shiny zinc coated?

 

I would have thouth a grinder was a bit much. A wire brush in a drill may be a better idea.
However that said you can get angle grinderstones which are designed to remove paint, and rust, rather than metal. You can get these from industrial motor factors. I have used them for cleaning behind Mk3 brake discs, as they do not remove the perant material

 

I wouldnt use a grinder , what happens when you need to remove the screws in the future? a wire brush in a drill or a rotary wire brush that fits a grinder is best , thats what i prefer to use it scours the surface without damaging the screw heads or the sound metal , the only time i would resort to an angle grinder is if the panel is being replaced and the screws are badly corroded , in which case you have no other option ,other than to drill them out