Pre Purchase Condition Survey of GRP Boats & Pleasure Yachts
Captain / John Noble
Every year many grp boats are lost at sea, many with reasons unknown However, the possible factors may perhaps be a lack of maintenance, unseaworthiness, improper use, defects developed in course of time and inferior material gone into making the hull.
The hull for a boat is like the foundation of a building. the hull may be likened to a long beam. when the boat moves in a calm seas the hull is like a uniformly loaded beam due to the impact of water on the bottom being even. when the boat moves over large waves the hull is like an unevenly loaded beam and different sections along the hull are subjected to varying stress and strain. Causes of losses are many and varying but major cause among all is hull failure.
The phenomenon of osmosis is the main cause affecting the fiberglass hull badly. the general conception is that fiberglass structures are water resistant and waterproof. this is the general understanding but not scientifically correct. Any fiberglass structure if immersed in a water, a possibility of osmotic problem developing over long period of time needs to be considered. because of the osmosis problem blisters develop on the surface of the gel coat thereby weakening the fiberglass material and also leading to marine growth.
Whenever two dissimilar liquids are separated by means of a semi permeable membrane the tendency for the lower solute liquid is to mix with the higher solute liquid by passing through minute pores in the semi permeable membrane. in the case of grp hull the water outside the hull seep into the laminate through the gel coat thus resulting in a chemical reaction with the molecules of the laminate and high pressure in the area of high density solvent causing blisters in the gel coat. blister repairs should be carried out with great care and needs high skilled workmanship to perform the job.
It is recommended that a marine survey expert may be assigned to supervise at the boat designing stage itself and during construction in order to ensure good workmanship and also to confirm only good quality materials go into building the boat enhancing its durability and seaworthiness.
