Fred W B
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| posted on 13/6/10 at 04:06 PM |
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Question for those with GRP moulding experience
I'm preparing (my first) mould to make a door panel and I'm undecided on how to prepare the inside corners of the return flanges (that
become the outer edges on the part) before starting to lay up.
Do I leave them sharp, or make a 4 mm radius fillet with plastacine?
Considerations -
If I leave them sharp:
The gel coat sharp edges on the part will be liable to chip. - I would give them a say 2 mm radius by sanding? Hopefully not breaking through the gel
coat.
Difficult to get mat into the corners when laying up.
3 mm panel gaps will look better with sharper panel edges?
With 4 mm radius fillet:
Takes time to make the fillet
Easier to lay-up
4 mm will become say 5 mm once sanded smooth if necessary to even the edge out?
So which is better/easier? The parts will be painted - eventually.
Cheers
Fred W B
[Edited on 13/6/10 by Fred W B]
[Edited on 13/6/10 by Fred W B]
You can do it quickly. You can do it cheap. You can do it right. – Pick any two.
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suparuss
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| posted on 13/6/10 at 04:30 PM |
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hey fred, id make the mould as close to what you want the end result to be, so try an get a 2 mm rad in the corners with plasticine. its not that hard
really if you soften it enough and use a plastic tool.
then when laying up dont try to go round a tight corner with the glass on the first couple of layers, lay up one plane at a time ending at the corner
to ensure good adhesion right into the corner, then wrap the remaining layers all the way round. that should leave little chance of getting air in
the corners which means there is no support for the gelcoat.
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Ivan
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| posted on 13/6/10 at 04:30 PM |
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Sorry - don't have an answer for you but would think a call to one of Dave Price's men at Superformance would give the answer.
Another really good guy is Keith Bright at Brightglass in Cape Town who has done and is doing lots of car bodies right through from concept to
completion.
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Fred W B
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| posted on 13/6/10 at 04:48 PM |
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Hi Guys
Russ - Thanks for response, that makes sense. I have learnt the butting into the corner trick while making the first mould.
Ivan - Now you mention it Justin (Jimmy's son) has invited me to go have a look at what they are doing, but haven't managed to schedule it
yet. I have seen Hitech/Superformance, but it was a long time ago, before I was worried about these details.
Cheers
Fred W B
[Edited on 13/6/10 by Fred W B]
You can do it quickly. You can do it cheap. You can do it right. – Pick any two.
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alistairolsen
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| posted on 15/6/10 at 09:54 AM |
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A sharp edge will be fine if you sand a very slight radius on it afterwards.
The main trick is ensuring that you back up the gelcoat correctly, you wont get CSM to follow any small radius and actually hold the gel properly and
this is what results in those unsightly chips.
Cut the matt edge straight and get it wetted right out into the corner in at least the first layer and youll save yourself some probklems. That or use
a strip of tissue to reinforce the gelcoat on the corner.
My Build Thread
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