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donkeydrop
United Kingdom
77 Posts |
 Posted - 26/08/2008 : 10:48:00
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My PA has badly cracked/crazed paint mostly on the doors. I have stripped back to find that the underlying metal is anything but flat. A previous owner has spread a thin (1mm) layer of body filler over the whole panel and sanded it flat. It made a superb job but unfortunately because the body panel flexes the filler has cracked.
Can anyone suggest a course of action? Maybe a more flexible filler is available? My immediate idea is to fill just the hollows so that any flexing would occur on the bare metal areas. Alternatively I have thought of stiffening up the panel from the rear.
Any advice would be gratefully received.
John
PA 0909 |
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phil
United Kingdom
149 Posts |
Posted - 26/08/2008 : 14:07:07
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Hi John, dont know if this helps.
I was worried bout the condition of the timbers on my doors and the flexing. I got some mild steel and formed a new frame around the inside, once secured, my doors felt a lot more solid.
This also allowed me to bolt the hinge through the wood and steel frame.
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donkeydrop
United Kingdom
77 Posts |
Posted - 26/08/2008 : 15:42:38
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Thanks Phil.
It is true that the joints in my frames are not good so I have taken the opportunity to break the weak ones and reglue and strengthen them and have put some strengthening plates in - although your idea sounds better.
I think the flexing which does the damage actually occurs perpendicular to the plane of the metal - like a drum skin. The metal is quite soft - being aluminium.
John
PA0909 |
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George Eagle
United Kingdom
3240 Posts |
Posted - 26/08/2008 : 18:53:07
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Hi John
There are flexible fillers which come in two parts, you have to mix to get them to set i.e a resin and a hardener.
It is some time since I used such a product and I cannot recall the name! Halfords would be a good place to start.
George |
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David Allison
United Kingdom
665 Posts |
Posted - 27/08/2008 : 15:04:03
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Isopon P38 is a glass fibre resin based product - it will however crack if not mixed correctly.
Much better to remove the paint and improve the metal finish and avoid fillers where possible.
The pre-war method was to use lead - vast quantities I am told!
Regards David |
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rodb
New Zealand
260 Posts |
Posted - 27/08/2008 : 21:14:44
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Hello PA owner
The first thing you need to do is establish if the alloy door skin has small fine stress cracks. These do appear around the area where the skin has been hammered (and as a result work hardened) over the frame capping, we do this by thoroughly cleaning the alloy and applying a mix of a coloured dye with some meths then wipe this over the entire door skin. The dye will flow into the crack and stay there after the meths has evaporated. If there are any cracks then paint and filler will never hold over these. Use a magnifying glass to enhance the inspection.
We first noticed this (at our expense) on MGA door and boot lid skins in the 1980Ęs when the cars were just 30 years old. The only cure, a new panel.
If there are no cracks then the alloy must be etch primed first before any filler is applied. The alloy needs to be cleaned with a good metal cleaner just before its etched. Use a good quality Polyester 2 pack filler that is flexible; take care to mix the amounts correctly. Poorly mixed filler can also crack under paint. After sanding smoothe wash the filler with a good quality wax and grease remover twice using changes of clean rags. A quality polyester 2 pack primer filler is next and after blocking back the colour is then applied.
I do not know what paint brands are available in the UK but it is always best practice to use all products from the same manufacturer. I also do not know the regulations relating to using 2 pack products in a non-workshop environment. They contain isocyonate so are a health hazard. The single pack lacquer based products are also a health hazard, so good masks and skin coverings are essential.
Flexing is one reason for filler cracking, others are as stated above, parent metal cracks, filler applied over bare metal, an under-cure of the filler where a primer has been applied too soon, poor mixing ratios of filler. If moisture or humidity is present on the primer before the colour topcoats are applied then future cracking and or humidity blistering can also occur.
If you only fill the hollows rather than covering the entire panel you will end up with a series of circles visible all over the panel.
The best fix is to re-wood the doors and make new alloy door skins, no filler, but that is not that easy and can be costly.
Rod Brayshaw
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