compression in way of fittings, bringing with it another range of potential defects and failures for the surveyor to identify.


Here we are considering the single outer skin of a moulding.


In the early years Orthopthalic Polyester Resins were the norm, these were the cheaper resins, which continued to be used deeper in the laminate even on more modern lay ups to save costs.


In the 1980’s Isophtalic resins were used, some with Propylene Glycol, (commonly used as a food additive) and more especially those with Neopentyl Glycol, (NPG) and these were more blister resistant, but at increased cost.


A further development was the Vinylester Resins, which have better bonding, improved water resistance, better fatigue properties and allowed for improved secondary bonding, I.E the attachment of internal stiffening, bulkheads etc. but again there was an increase in cost.


Boat Manufacturers dealt with the potential increased costs of construction in different ways. Some embraced the technology and used the best materials throughout and usually advertised the fact, others used the more expensive materials sparingly and only in the outer laminate and used the cheaper materials where their effects would be less apparent for example deeper in the layup.


THE PROBLEM


Water Soluble Materials GRP laminate is not water proof. Without getting too technical, the Unsaturated Polyester Resins (UPR) containing Maleic Anhydride use Organic Peroxides as a catalyst, Polymeric Amine or Cobalt Soap in Styrene Solution as hardener and Organic Acids and Polyhydric Alcohols’ as solvents plus other materials depending on the requirements of the cured resin compound.


WSM’s (Water Soluble Materials). These are amongst the accepted level of 1% to 5% of WSM’s present in cured resin, some of which are Hydroscopic (attract and absorb moisture), which could include:


• Catalyst Elements (Organic Peroxide)


• Solvents (Polyhydric Alcohols) Methanediol or Methylene Glycol


• Shelf Life Inhibitors (Quinones Aminel)


• Ultraviolet Stabilizers • Colourants / Pigments • Binders (Polyvinyl Acetate Emulsions)


• Thickening Agents • Fillers • Fire Retardants • Wetting Agents • Impurities (including free moisture)


The water outside the hull will be attracted to any of these free WSM’s, present within the laminate as a result of any of the following manufacturing defects:


• Incomplete Cure • Overheating (cooking) • Chemical Reactions • Poor mixing


Voids / Bubbles / Air Pockets - These are the result of poor wetting out of the laminate resin, or is beginning to cure during the laminating process or where the mat has failed to follow the contours of the mould. Moisture will condense within these voids and attract WSM’s from the surrounding laminate / resin.


42 | The Report • September 2019 • Issue 89


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