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Hanaldo
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Hey all, Was hoping for some feedback on a part I'm building at the moment, little bit unsure how to go about it. It's a roof panel for a Lotus Exige Sport 240, which I have been repairing and modifying over the last week. My issue is that the roof has a scoop in it, which is used to supply air to the supercharger at the back of the car. This scoop unfortunately gives me an undercut on the front, and I'm not sure if I can get away with doing the mould in one piece, or if I'm gonna have to do a split mould. I sort of think I might be able to get it out from the back, but I'm not sure. What do you think: This is the front of the roof: 
This is the back:  Now the back I can flange around that undercut and that's fine, but it does have a rolled edge that I will need to copy, and I'm worried that this is what will stop me from releasing the mould from the back:
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Hanaldo
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brainfart
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> but it does have a rolled edge that I will need to copy
Why? Can you do it without that round edge? Or modify that front part so the undercut is gone?
If you want to make a split mould, I'd try to make a large one for pretty much the whole roof and have one or two small detachable mould parts in the back and/or front which can be removed. Split line on that round edge.
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Hanaldo
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That rolled edge is a sealing face, there is a rubber seal that sits between the roof scoop and the scoop on the rear body. I COULD do it without that rolled edge, but I would prefer to keep the factory fitment. Unfortunately I can't see any way of changing the shape of the front to get rid of the undercut. The customer isn't keen on extending the scoop, and I have just built the lip underneath so that the roof meets the windscreen. I would prefer to do it in one piece if I can because Im doing infusion, and split moulds can be a pain when it comes to sealing properly. I normally envelope bag the whole thing, but on such a large panel that obviously raises the cost of the consumables. Where do you think would be the best place to make the split line, if I needed to do it that way?
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brainfart
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On the rounded edge, parallel to it, so that this second mould gives that edge its shape.
Sounds really dumb, a split mould to produce 1cm of the part, but better than having a long split line across the big flat area.
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brainfart
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Hanaldo
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Group: Forum Members
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Gotchya. That was one way I thought of doing it, the other was to do the split line on the front edge, following the edge of the scoop. So essentially doing the lip as a separate piece, eliminating that undercut. I would then have a split line along the lip edge though, which wouldn't be too hard to sand off but obviously more work than if it were on the back edge. So do you think that doing it along the back edge will allow me to release the part? I was still a bit worried that the undercut at the front would lock me in enough to not allow release, even if I didn't have that rolled edge at the back. Shouldn't be an issue?
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brainfart
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I don't know if the front will bind when you try to rotate the part out of the mould by lifting the back upwards. Hard to tell from the pictures. Depends on how far that lip goes into the scoop on the front? If in doubt make another split line in the front of the mould, like the one I suggested in the back. Then again the original makers of this roof had a way to get it out of their mould, otherwise you wouldn't have it now to play around 
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Hanaldo
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Group: Forum Members
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The lip will only go as far as you can see in that picture, as I will block the front of the scoop off when I make the mould. So what you see in the picture is where the mould will be formed. Having hacked up and reconstructed the inside of the roof to give more head clearance, I got the chance to understand how Lotus originally made the roof, and it's quite clear it was done in 3 pieces. There was an inner skin and an outer skin, and then the scoop was bonded on separately and moulded in before painting. I even uncovered the filler when I sanded away the corners of the scoop to build that lip. The whole thing is very thick and very heavy, and I've gotta say I'm not very impressed with it for what is an OEM piece.
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brainfart
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If you post more pictures of the front we can argue and nitpick about the best split line locations for making this mold ridiculously complicated. > I've gotta say I'm not very impressed with it for what is an OEM piece.
It's good enough, made them some money.
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