Posted: Tue Jun 21, 2016 8:00am

I am having a new boat built. my builder uses two-pack epoxy for this. Should I have the hull shot blast before they apply this or not? I have been advised that it doesn't need it as it fix's better to the surface if not blasted.

Posted: Tue Jun 21, 2016 1:37pm

I can not give you a definitive answer because I do not know exactly what two pack epoxy blacking the builder will be using and I do not know exactly what steel the hull builder used. The exact blacking is important so the manufacturer's application instructions can be scrutinised. If the application instructions say the steel should be blasted in some way (probably quoting a BS or ISO number defining the preparation) then that trumps anything the builder may claim. the steel is important because most steel used in UK boat construction is hot rolled and that creates a film of mill scale on the surface. When water gets under mill scale and starts rusting the mill scale falls off together with the hull blacking. some form of blasting is usually recommended to remove the scale. However steel can be obtained that has been treated to remove the scale before delivery so as long as there was no rust and any preservative oil was removed maybe blasting would not be needed. If you can get those pieces of information from the builder you can then look up the application instructions on the internet or phone the makers advice line to find out what they recommend.