Make a fender mold


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AndrewL92
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Ciao a tutti,
avrei bisogno di qualche consiglio per realizzare uno stampo per un parabordo. Il parafango è in fibra di vetro e vorrei realizzarlo in fibra di carbonio.
I miei dubbi riguardano i bordi che vanno verso l'interno e quindi creano angoli negativi che impediscono la creazione di un unico stampo.
Poiché questi bordi si trovano su quasi tutti i lati del paraurti, quale pensi sia il modo giusto di procedere?

Grazie mille


Warren (Staff)
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You will likely need a split mould to mould those inner return lips to avoid mechanical locking.  If you inspect the GRP one carefully you may still see traces of the flash lines which will tell you how they split the GRP mould.   Don't rely on that totally but it will be a good starting point. 

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
AndrewL92
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Thanks for the reply.
I know that from a photo it is not easy to understand but do you think it will be okay if I divide the mold in this way?
Or do you suggest me to proceed differently, making more parts or dividing it differently?


Hanaldo
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AndrewL92 - 9/24/2020 1:43:40 PM
Thanks for the reply.
I know that from a photo it is not easy to understand but do you think it will be okay if I divide the mold in this way?
Or do you suggest me to proceed differently, making more parts or dividing it differently?


Doing it this way will result in super obvious flash lines on the finished part, right in the middle of the cosmetic areas.

Much better to put your barriers on a radius where you can. For fenders, you generally do the main 'face' of the guard as one piece, and then each of the mounting flanges where it returns on itself can be split along the radius. So for these guards, you will likely end up with at least a 3, potentially a 4 piece mould.

Warren (Staff)
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As Hanaldo said.  It also makes demoulding easier as you can demould each flange/edge then the part should pop out quite easily as its just a large flat surface. 

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
AndrewL92
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I tried to create the mold following your advice.
I made a first mold for the main fender area and then a mold for each of the mounting flanges.
This is the result.





There are small flaws, but they are all in the non-visible areas.
Since it is one of my first molds, I wanted to know if you think it can be used to proceed with the infusion.

In case how do you think it is best to proceed?
I believe that with such a mold the only thing to do to proceed with the infusion is to finish the rear part of the mold and then cover it with the release agent and then pack it all.

Thank you so much for any advice and I apologize for my English.
Hanaldo
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No reason why you can't use it, some of those flange shapes are going to make things challenging for you but it's certainly usable. 

You either need to seal the flanges with something before bolting them together, or you will need to envelope bag the entire thing. Envelope bagging I find quite unreliable for infusion due to the propensity for leaks, especially on larger complex moulds like this, so I try to avoid it. for sealing the flanges, the easiest and most reliable way I've found is to use an RTV silicone gasket maker (do NOT use an adhesive caulking silicone, these will bond your flanges together regardless of release agent). The downside is this is a bit difficult to clean up after the infusion, so it becomes a bit of a pain to reuse the moulds. Another way I do it is to run a 'bead' of gelcoat all around the flanges, and then bolt the flanges together before the gelcoat cures. This is significantly easier to clean up, but doesn't seal as reliably as the silicone gasket. Using either method, don't forget to seal up your bolt holes as well.
beliblisk
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Hanaldo - 11/19/2020 12:05:18 AM
No reason why you can't use it, some of those flange shapes are going to make things challenging for you but it's certainly usable. 

You either need to seal the flanges with something before bolting them together, or you will need to envelope bag the entire thing. Envelope bagging I find quite unreliable for infusion due to the propensity for leaks, especially on larger complex moulds like this, so I try to avoid it. for sealing the flanges, the easiest and most reliable way I've found is to use an RTV silicone gasket maker (do NOT use an adhesive caulking silicone, these will bond your flanges together regardless of release agent). The downside is this is a bit difficult to clean up after the infusion, so it becomes a bit of a pain to reuse the moulds. Another way I do it is to run a 'bead' of gelcoat all around the flanges, and then bolt the flanges together before the gelcoat cures. This is significantly easier to clean up, but doesn't seal as reliably as the silicone gasket. Using either method, don't forget to seal up your bolt holes as well.

Regarding the sealing mould parts.

Would you say that gum tape in 2mm recess integrated in the flange works better than gelcoat method?

I used RVT silicon befor but as mentioned its a pain to clean so for next multi part tool i was planning to go gum tape route.

thanks a lot

Edited 2 Months Ago by beliblisk
Hanaldo
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beliblisk - 11/19/2020 7:25:04 PM
Hanaldo - 11/19/2020 12:05:18 AM
No reason why you can't use it, some of those flange shapes are going to make things challenging for you but it's certainly usable. 

You either need to seal the flanges with something before bolting them together, or you will need to envelope bag the entire thing. Envelope bagging I find quite unreliable for infusion due to the propensity for leaks, especially on larger complex moulds like this, so I try to avoid it. for sealing the flanges, the easiest and most reliable way I've found is to use an RTV silicone gasket maker (do NOT use an adhesive caulking silicone, these will bond your flanges together regardless of release agent). The downside is this is a bit difficult to clean up after the infusion, so it becomes a bit of a pain to reuse the moulds. Another way I do it is to run a 'bead' of gelcoat all around the flanges, and then bolt the flanges together before the gelcoat cures. This is significantly easier to clean up, but doesn't seal as reliably as the silicone gasket. Using either method, don't forget to seal up your bolt holes as well.

Regarding the sealing mould parts.

Would you say that gum tape in 2mm recess integrated in the flange works better than gelcoat method?

I used RVT silicon befor but as mentioned its a pain to clean so for next multi part tool i was planning to go gum tape route.

thanks a lot

Tried it, but didn't find it very reliable. The tape tends to compress quite easily, and it often ends up that in some areas it doesn't contact the opposite flange properly and doesn't seal. It also still makes a hell of a mess, its just as hard to clean up as the silicone.

beliblisk
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Hanaldo - 11/19/2020 9:02:24 PM
beliblisk - 11/19/2020 7:25:04 PM
Hanaldo - 11/19/2020 12:05:18 AM
No reason why you can't use it, some of those flange shapes are going to make things challenging for you but it's certainly usable. 

You either need to seal the flanges with something before bolting them together, or you will need to envelope bag the entire thing. Envelope bagging I find quite unreliable for infusion due to the propensity for leaks, especially on larger complex moulds like this, so I try to avoid it. for sealing the flanges, the easiest and most reliable way I've found is to use an RTV silicone gasket maker (do NOT use an adhesive caulking silicone, these will bond your flanges together regardless of release agent). The downside is this is a bit difficult to clean up after the infusion, so it becomes a bit of a pain to reuse the moulds. Another way I do it is to run a 'bead' of gelcoat all around the flanges, and then bolt the flanges together before the gelcoat cures. This is significantly easier to clean up, but doesn't seal as reliably as the silicone gasket. Using either method, don't forget to seal up your bolt holes as well.

Regarding the sealing mould parts.

Would you say that gum tape in 2mm recess integrated in the flange works better than gelcoat method?

I used RVT silicon befor but as mentioned its a pain to clean so for next multi part tool i was planning to go gum tape route.

thanks a lot

Tried it, but didn't find it very reliable. The tape tends to compress quite easily, and it often ends up that in some areas it doesn't contact the opposite flange properly and doesn't seal. It also still makes a hell of a mess, its just as hard to clean up as the silicone.

So we actually have to choose lesser evil in this case and dummy vacuum befor actually laying any of the materials.

I used gasket type rvt on custumers tools (quality wasnt the best) and i actually pulled gelcoat off the flange when demoulding...... but it held vacuum perfectlySmile

Still on the look out for better solution.

GO

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