Hairline cracks

[caslau]

Hi,After washing and polishing my 2004 elddis avante 534 i have got a hairline crack under each grab handle i was tempted to drill the ends of the cracks to prevent them travelling but would this be how to fix this problem?

 

[MichaelE]

These cracks sound like they are in the gelcoat and are only superficial so nothing to worry about, they tend appear around stress points ie grab handles and hinges.
This coating is only about 1mm thick and protects the fibreglass.The crack can be dremmelled out, refilled and sanded back, good product for this is Plastic Padding gelcoat which is white.
You then sand this back then finish off with finer grades of wet and dry to achieve the polished finish.
The drawback is that the colour match, but you can get a colour matched tin of white spray and flat it back to match in.

 

[JTQ]

First it is important to know if the "plastic" is glass reinforced plastic or ABS. The former as mentioned above can develop cracks in the surface gel-coat that are of minor concern, the later cracking is of much greater concern.
If it is ABS I would be exploring if it was practical to Sikafix a doubler patch on the panels under side in way of the cracks to both stop them and seal them. If so then as you say drill small holes to help stop the cracks travelling further before they are repaired. There are solvent based welding techniques for repairing ABS but it is an expensive route and probably not as durable as patching that will also help ease the stressing that causes the issue in aging ABS.