fibreglass expert needed

[a.t.park]

Bought a new 8.5m rib this year, but recently large black marks (seem to be a brush type mark) have been appearing behind the orange gel !!!!! has anybody had similar problems and if so what is the cause

[John Kennett]

I don't know the answer, but it doesn't sound good! If you bought the RIB new this year then your first stop should be the manufacturer to see what they say!

John

[a.t.park]

Thanks John

Agree it does not sound good but I would like to be one step ahead before confronting the builder so maybe someone might know the reason for these marks. Heres Hoping...........

[Alan Mckewan]

The "black marks" you refer to are most probably voids. After brushing the gelcoat onto the mould (assuming the manufacturer does not use grp spray equipment) and leaving it to set, the "inside" of the gelcoat is bumpy from the brushmarks. It is then most important that the first layer of resin and fibreglass is stippled well into the bumpy gelcoat, other wise voids form as the grp sets. These can easily follow the brush strokes of the first gelcoat layer. In a previous life I saw many of these problems at a small moulding shop in Lisburn which made clinker-style dinghies. The only cure is to grind the areas off, re-apply matching gelcoat and then sand and polish the area. Lots of work!

[tsunami]

I'm not sure if this would be because of voids. If it was you would be able to crack the gelcoat in that area by applying pressure to it! I would say that it is more likely colour separation in the orange pigment of the gelcoat. This can be common in orange and red gelcoats through no fault of the boat manufacturer! Unfortunately it is undesirable and there is very little that can be done with it.
Pigment separation can occur in other gelcoat colours but orange and reds seem to highlight the problem more because of the contrast in the colour!