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350TSS · 23-04-2019, 05:53 AM

I spent a few hours yesterday considering why my first few attempts at CF moulding had not been a total rip roaring success. The following is pure conjecture but I think I may have uncovered the root cause. Time and alteration of technique will tell.
The failures, apart from a few minor surface imperfections in the gel coat, have been where the epoxy resin and the first layer of CF has failed to closely adhere to the gel coat leaving a cloudy, milky looking air bubble, the gel coat is therefore unsupported and very weak. The first and subsequent layers of CF have not followed the contour of the mould.
I have been using 2 grades of CF mat, the very fine fibred expensive and very difficult to work with loosely woven and very shiny type and the cheaper “black stuff” which is much more tightly woven, easy to cut as it maintains its weave pattern but is quite stiff while laminating and extremely difficult to make conform to complex contours in a mould. To date my technique has been to first put down a layer of epoxy resin followed by one lamination of the expensive stuff followed immediately by another layer of resin and then by the black stuff. Using a roller on the expensive stuff is problematic as it can snag the weave and distort it. Consequently I have been using the roller, to the extent possible given the contours of the mould, after and between subsequent laminations of the black stuff.
I am pretty sure the separation between the gel coat and the first layer of CF is not for want of stippling but rather because the adherence to the gel coat is weaker than to the second layer of CF, the black stuff. This despite being thoroughly wetted with epoxy resin is too stiff to take the sharper contours and drags the first layer away from the mould.
I think I have two possible alterations to technique that could resolve the issue
1. Only use the expensive CF mat on complex moulds
2. Allow the first lamination to set before applying any subsequent laminations of the black stuff and accept that in complex moulds there will be a degree of separation and loss of strength where I do so.
I share this for anyone mad enough to contemplate having a go at making their own CF parts.
Despite the problems of the past few days I really do now feel optimistic and energised to complete this project, progress is happening and whilst there are a number of difficult issues to solve (successfully bonding the two halves of the petrol tank together for one), they do not seem to be overwhelming in complexity or number.

23-04-2019, 05:53 AM	#909
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,419	I spent a few hours yesterday considering why my first few attempts at CF moulding had not been a total rip roaring success. The following is pure conjecture but I think I may have uncovered the root cause. Time and alteration of technique will tell. The failures, apart from a few minor surface imperfections in the gel coat, have been where the epoxy resin and the first layer of CF has failed to closely adhere to the gel coat leaving a cloudy, milky looking air bubble, the gel coat is therefore unsupported and very weak. The first and subsequent layers of CF have not followed the contour of the mould. I have been using 2 grades of CF mat, the very fine fibred expensive and very difficult to work with loosely woven and very shiny type and the cheaper “black stuff” which is much more tightly woven, easy to cut as it maintains its weave pattern but is quite stiff while laminating and extremely difficult to make conform to complex contours in a mould. To date my technique has been to first put down a layer of epoxy resin followed by one lamination of the expensive stuff followed immediately by another layer of resin and then by the black stuff. Using a roller on the expensive stuff is problematic as it can snag the weave and distort it. Consequently I have been using the roller, to the extent possible given the contours of the mould, after and between subsequent laminations of the black stuff. I am pretty sure the separation between the gel coat and the first layer of CF is not for want of stippling but rather because the adherence to the gel coat is weaker than to the second layer of CF, the black stuff. This despite being thoroughly wetted with epoxy resin is too stiff to take the sharper contours and drags the first layer away from the mould. I think I have two possible alterations to technique that could resolve the issue 1. Only use the expensive CF mat on complex moulds 2. Allow the first lamination to set before applying any subsequent laminations of the black stuff and accept that in complex moulds there will be a degree of separation and loss of strength where I do so. I share this for anyone mad enough to contemplate having a go at making their own CF parts. Despite the problems of the past few days I really do now feel optimistic and energised to complete this project, progress is happening and whilst there are a number of difficult issues to solve (successfully bonding the two halves of the petrol tank together for one), they do not seem to be overwhelming in complexity or number.