Usually my husband Fraser and I sail our 1984 Maurice Griffiths-designed Barbican 33 Barberry around the coasts of Ireland and Scotland, but in preparation for a more challenging journey, the boat needed to be upgraded.
One of the last jobs on the list was the replacement of all below-waterline through-hull fittings. Barberry’s appeared to be original, or at least very old. They were of good quality bronze, and there was no sign of ‘pinking’ visible, but as we were planning to set off on a long voyage, and as there could be all sorts of degradation going on where we could not inspect, we decided we’d sleep better if we replaced them.
Once that decision was made, the debate began about what type to replace them with. Fraser is a retired professor of materials engineering (albeit medical materials involving implants), so he applied decades of research into hip joint replacement materials, where the object is to find one that gives 20-plus years of useful life in a body (in this case, a body of salt water, but the principle is the same).
Composite fittings
One option was to replace like with like. That was our first intention, but Fraser was concerned that modern bronze might not be of the same quality as the original bronze fittings, and it seemed difficult to find information on the exact composition of bronze fittings currently available.
In addition to that, metal fittings are potentially vulnerable to electrolytic or galvanic corrosion.
We had read about composite through-hull fittings, and these looked attractive. My concern was plastic becoming brittle with age, but Fraser assured me that these were not plastic but glassfibre nylon composites, not dissimilar to own hull construction.subject to much UV light, which is a major cause of degradation in plastics.