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Steve Broad
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I would like to make a one piece mould (less work) of the front of my Elan so I can make a one piece flip front. The bonnet will be fitted and blended in prior to making the mould. I can't see any locks. The mould should flex around the wheel arch lips. Can anyone see any problems?
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oekmont
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Yes, the problem I see, is that the mould should flex around the lips of the wheel arches. A mould as flexible as that will result in inaccurate parts.
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MarkMK
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I think that Steve meant to say that the pattern/plug will flex around the wheel arch area in order to allow it to come out of the resultant mould. It's hard to judge from the picture, but it looks like the only potential locking area might be the return edges on the arches, if you plan to incorporate some?
On such a large part the only concerns I can really see are all the detailed contours at the front section and getting a good release, especially on a new mould. It's possible that you might get some breakage on the pattern or the mould surface getting it out. Not certain if you plan to make the final part in GRP or carbon, or by what method but building in, at least, one parting line might help you get a decent part first time even if it involves a bit of work to tidy-up the join
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Steve Broad
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The mould would only need to flex slightly to get is past the arch lips. The plan would be to add a support bar between the wing bottoms once bagged.
Part to be made of 4 layers of 210gsm prepreg carbon with 5mm Nomex core.
Gettting the mould off without damage is a valid point. Also getting the finished clip out of the one piece mould could also prove tricky. OK, so I make a multi-part mould. Next, how many parts and where to put the joins? One joint straight down the middle would be simplest but would this be sufficient?
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oekmont
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I have made quite a few carbon sandwich car bodys. You can believe me, when i tell you, that a mold, that can be flexed 2-3cm by hand will not stay in shape during the bagging process. This is a minor problem, if the part ýou are doing will be flexi too. But you will have a hard time, bending a 5mm part back in place.
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MarkMK
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If you're making a mould suitable for pre-preg, then I'm guessing that it'll need to be reasonably sturdy and able to withstand the required cure temperatures anyway, so a bit of flex in the finished part looks necessary to de-mould, but hopefully that'll be there around the side sections. I think I'd likely consider putting the parting line laterally along the forward-most tip of the nose. This way you'll be able to focus on releasing the more intricate bumper area in one section and it'll present a relatively straightforward angle of release. This will then, hopefully, allow you to flex the panel a bit more when getting out the top panel and side wheel arch sections. I don't think that splitting it down the centre will offer you much in terms of making things easier.
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Steve Broad
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+x
If you're making a mould suitable for pre-preg, then I'm guessing that it'll need to be reasonably sturdy and able to withstand the required cure temperatures anyway, so a bit of flex in the finished part looks necessary to de-mould, but hopefully that'll be there around the side sections. I think I'd likely consider putting the parting line laterally along the forward-most tip of the nose. This way you'll be able to focus on releasing the more intricate bumper area in one section and it'll present a relatively straightforward angle of release. This will then, hopefully, allow you to flex the panel a bit more when getting out the top panel and side wheel arch sections. I don't think that splitting it down the centre will offer you much in terms of making things easier. Good point. Making the joint along the front of the bumper also makes tidying it up afterwards a lot easier.
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Steve Broad
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+xI have made quite a few carbon sandwich car bodys. You can believe me, when i tell you, that a mold, that can be flexed 2-3cm by hand will not stay in shape during the bagging process. This is a minor problem, if the part ýou are doing will be flexi too. But you will have a hard time, bending a 5mm part back in place. Thanks for that. Could I get away with a 3mm core? I am also considering making the part using infusion instead of prepreg as I have the equipment, resin and cloth. Which method did you use?
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oekmont
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I use infusion for the big parts, as the material get's quite expensive. I don't know how stiff you want your part to be, but 3mm sandwich is usually enough for body panels. I followed your project on lotuselan.net (I am a elan fan). you are planning a flip front? No offense, but I think that this might be a little beyond your current skill level. To get this looking nicely and working good, you will need to do some serious rework on the bonnet and the car (an inward edge around the back of the bonnet for example). I would recommend to redo the front in cf sandwich, cut of the original section out and glue both parts together. Personally, I would do it with resin infusion, with soric lrc 3mm as a core. But split mould infusion is a difficult task. Prepreg will be a lot easier for people with less experience. I would make a three or four piece mould (front, sides and maybe top, depending on the original bonnet cut off)
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Warren (Staff)
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I would agree that by the time you have added flanges and stiffened the mould sufficiently then you would need a multi-part mould to get a release.
You will struggle to make a dimensionally accurate or a part that easily lines up if you keep the mould or part too thin..
Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
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