Hi all,

I am currently moulding a bumper and want to ensure I keep things as genuine as possible.

I have a ridge/lip on the top of the bumper and some tabs behind it but am wondering on possible ways to replicate this as part of my split mould.
The ridge is 4mm thick as per pic below and runs along the top of the bumper as per the picture.



I am planning on building the flange for the mould as per this pic: black = bumper, red = flange, green = mould, blue = 2nd part of mould


questions:
a) how would I replicate the ridge using a split mould? Is my diagram the optimal way of achieving the ridge? I don't want to lose the mounting taps behind the top of the bumper as a steel reinforcement bar is located there.
b) how would I get fibreglass into such a small channel when reproducing the part when I did the lay up?
I did think that I would have to gelcoat the blue split mould and then fibreglass some material into the space then squeeze the fibreglass together as it was curing but I am worried that there will be voids between the two lay ups which I want to avoid.

Any help would be appreciated as this bumper is giving me some challenges and ideally I'd like to build a mould which will allow for one session lay up instead of bonding in additional parts.

Thanks
Dave

If you use a lightweight CSM like 80/100gsm or 225gsm at the heaviest then you won't have an issue getting it into the groove. I've worked with much tighter grooves than that and not had any problems with voids. Once you have filled that groove and are satisfied there are no voids, let it completely cure before continuing with the rest of the layup. This will guarantee that you don't push any air back into the groove during the rest of the layup.