P38/P40 filler question

Bit of a newbie here...

Ive done bits of fibreglass work in the past and thats not the problem. My problem is thus...

Im repairing my active spoiler which was destoyed by many many speed bumps over the 140k mile life of my car. Ive rebuilt the shape of the notch on one side with fine mesh and fibreglass, sanded it down and got it looking neat. I just have to prep it a bit as it needs some filler here and there then i can paint it.

My question is this. I can get something like this,

Quickly repairs dents and scratches.

Features excellent adhesive properties.

Does not crack or flake, remains stable.

Sets within minutes.

Suitable for use with all metals including galvanised steel.

Supplied complete with usage and safety instructions.

But it doesn't mention fibreglass or plastic which i am useing.

Or do i need something like this,

Glass fibre compound for bridging holes and rust

Sets in 20 minutes

Bonds to metal and glass

Weatherproof

I also have some of this left in my cupbord from another project. Could i use this? Or will it not bond with the fibreglass? Says high adhesion, and bending would be good. i guess i would bend more than P38.

http://www.jdmperformance.co.uk/images/products/571733.jpg

High adhesion

Flexible

Easily sanded

Paintable

Im thinking P38 is what is best because it seems to be more fitting to my needs. but the P40 is fibreglass based and is making me think i should be useing that. but then the last one seems to fit the bill also. Or should i use something completely different?

Im maybe just being a retard and its very very simple but i dont want to buy the wrong thing, or stand looking at different things, one in each hand in the shop tomorrow not knowing what to pick looking like a div

anyone?

Any pics of what you have done so far? I would mesh and fibreglass behind the spoiler to strengthen it.Once dried rough up the outside of spoiler with 80 grit paper,then apply a coat of fibreglass. Rub that down once dry with 80 again till the repair is flat. Then apply a layer of cataloy, rub the rough down with 80 then use finer paper to a smooth finish for primer and paint. The first two are the best, make sure you mix it well so you dont get pinholes!

I'm no expert, but I've been doing some fibreglassing recently, and when I came to filling over the fibreglass I've been using P38. I found it easy to use and easy to sand down. The paint takes well to it also

Im in the middle of repairing Aldo87 supra after a slight 'off'.His do luck front bumper was in tatters, ive rebuilt it with fibreglass and p38, i have arms like popeye with rubbing all that filler!

Any pics of what you have done so far? I would mesh and fibreglass behind the spoiler to strengthen it.Once dried rough up the outside of spoiler with 80 grit paper,then apply a coat of fibreglass. Rub that down once dry with 80 again till the repair is flat. Then apply a layer of cataloy, rub the rough down with 80 then use finer paper to a smooth finish for primer and paint. The first two are the best, make sure you mix it well so you dont get pinholes!

thats prety much what ive done up untill the final finishing stage. I just dont know if P38 will crack and break as the active spoiler on my car often catches on things and bends. Ive decided to experiment with the bumper repair stuff for now. looks ok so far.

I only have 120 grit wet and dry in the house though

120 should be fine it may take a while to rub down though:D I dont think there is anything out there that is really flexable. I work in a bodyshop and we use fibreglass, cataloy or a special bumper repair stuff (cant remember the name just now). That bumper stuff is black and it is like a mixture of cataloy and fibreglass mixed together, even when it dries its still pretty solid. I think the only answer is to avoid the speed humps matey or stock up in repair stuff:d

yeah 120 is ok just time consuming as you say

The stuff im useing is black and you add hardener to it and it dries quite quick. Nice to work with and sands off quite well.

What cataloy exactly? just filler?

Yeah cataloy is the p38 filler, we also have stuff called top stop with is polyester resin which is easier to rub and leaves a better finish for paint. Think it costs a few bob a tin! Use a nice fine paper on the p38 will leave a good enough finish. Good luck with it

Any polyester based filler will be fine for fibreglass, however what concerns me about what you have done is that depending on the type of plastic, fibreglass does not usually bond to plastic, it seems to at first but as it goes through thermal changes, it looses the bond and separates.

I actually used my A pillar to mould my twin gauge pod from fibreglass.

The plastic bumper filler is the only thing i know of that will bond to the plastic.

well the fibreglass has been bonded good and stong to the plastic in the active spoiler for a good 4 or 5 days now. Its hanging in there good and propper

When i modified my 2 pod A pillar into a 3 pod it was all good.... but then my 2 pod was fibreglass to start with

Sounds like it may be OK then, just hope it doesn't let go once the hot sun has been on it, if that happens this year.