problems with smoothing a bumper

[ashley sw]

hi guys im having trouble smoothing out my front bumper i have used p38 filler but its cracking where the dip around the corner mould is. what could have caused this and is there any cure apart from ripping it out and using fibre glass first? this is the 3rd time it has happened. i have included a pic

 

[ashley sw]

bump

 

[Stani1029]

Are you bending the bumper? Or is it cracking by not being touched? Maybe a case of too hot/cold curing enviroment. Never had trouble with p38

 

[ashley sw]

it might have been bent slightly when i had it in my car to transport it to my uncles at the weekend. but if its cracking like that off the car then it will probably be worse when its on the car with all the flexing. i have used fibreglass first on the rear bumper and just skimming it over with p38filler now so hopefully i wont have trouble with that.

 

[r-reg-sr]

bumper cant be flexing when doin this type of art
good to do it while on the car
just hit it back down with rough grit paper and go deep then start again