8 replies to this topic

[venkman]

Hello,

Anybody have any ideas or know of products to make these look good again. Most of arches have bubbles on them ,maybe 1-2mm. A couple have holes splitting and some a bit large, whats suitable to repair them, I know fibreglass products but is it mesh or just a resin??

Thanks  20250810_191752.jpg   26.33K   2 downloads  20250810_191731.jpg   28.26K   2 downloads

[weef]

If you know fibreglass you will have a good idea that to successfully repair the micro blistering shown in the pictures can be difficult.

The techniques require the parts to be heated to expel moisture several times during the process and 2K is the best painting process, with all the complications that has for the home repairer.

It maybe best to replace rather than repair in this instance unless you have access to professional equipment.

[venkman]

If you know fibreglass you will have a good idea that to successfully repair the micro blistering shown in the pictures can be difficult.
The techniques require the parts to be heated to expel moisture several times during the process and 2K is the best painting process, with all the complications that has for the home repairer.
It maybe best to replace rather than repair in this instance unless you have access to professional equipment.

Ah OK. I thought maybe you just wet and dry then spray over.

[Ethel]

It wouldn't really cost you anything to try.

 

You could also take a mould off it so you'll never be short of a replacement.

[bluedragon]

Fiberglass is a glass mesh coated with polyester resin. If you have a tear or large crack, the best way to repair is to lay new mesh over the gap and coat it with resin. Easier probably to just search the internet on fiberglass repair for detailed instructions.

 

For small holes there are some putty-like products you can use, but for a crack that goes all the way through I think it's better to use glass mat and resin to prevent future cracking.

 

As for the blistering, IMHO there are two most likely causes:

 

1) poor paint prep or

2) constant exposure to moisture (most common cause - long term use of a car cover outdoors in damp climates, made worse if the cover doesn't breathe well.)

 

Paint will blister if exposed to constant moisture long-term - that's why we are warned not to leave damp car covers on for long periods of time without letting them dry off regularly, and why there are special marine-rated paints for the immersed sections of boat hulls. Even top quality automotive paint will blister if left damp for months and months.

 

It is unlikely the fiberglass is holding moisture within, encapsulated in polyester or even epoxy resin as it is. Stripping the paint and primer down to the bare fiberglass surface or gelcoat will be enough. Then use a good quality epoxy primer to help resist future moisture penetration (it still won't be immune though) and it should last as long as the paint on the rest of the car.

 

Dave

Edited by bluedragon, 15 August 2025 - 07:31 AM.

[bpirie1000]

Always wear a mask when sanding fiberglass or gel coating with chemicals....... or you will not be around to enjoy the hard work...

[venkman]

Thanks for the advice people, I'll have a experiment over the weekend

[bangermadness08]

Don’t mean to hop on a thread, but over winter my arches are looking tired and could do with a sand and re paint. What sand paper would you recommend for sanding back and re spraying?

[Ethel]

Depends on whether it's paint or gel coat. It's no different to steel really. The resin is the same as filler. If it is gel coat, you'll likely want something a bit coarser to get a good key to prime & paint. & Be wary of too much speed is using a power sander because heat won't dissipate as easily as over metal.