unfortunately some of the better colour pigments are being discontinued for environmental reasons.
The survey showed some preference for small buoys manufactured from polyethylene (moulded), or all foam, over GRP. This was based on cost and resistance to impact damage.
Cost is such that it will probably not be economic to carry out any repairs and a buoy will be replaced with new if subject to damage.
The particular advantage of plastic buoys in this size range, when compared to steel, is low cost.. Usually constructed from rotationally moulded thermoplastics (eg polyethylene) or totally foam - cost may be less than $ 1000-00.
LARGE BUOYS
Large buoys, probably classified as over 2 1/2m diameter, have traditionally been fabricated from steel plate and have not generally been superseded by buoys manufactured from plastics.
Steel buoys will often have a working life in excess of 50 years and with suitable paint systems remain on station for a period of 4 years. At this size it will be necessary for a plastic buoy to have a load bearing core structure to connect the mooring eye through the body to the superstructure and lifting eyes. The design of a load bearing core structure must be inherently safe taking into account corrosion and abrasion over the working life of the buoy. A 3m large plastic buoy of the skirt type with a substantial steel core structure will be of a similar weight to a conventional steel buoy. A deep tail tube of this size may be in the order of 50% lighter than a similarly proportioned steel buoy.
None of the authorities taking part in the survey operate a large number of plastic buoys in this size range. The French service is evaluating tailtube buoys 2.5m and 3m diameter, with foam filled rotomoulded polyethylene buoyancy units, steel tailtube and aluminium alloy superstructure. Tail tube buoys of this type are considerably lighter than conventional steel buoys which will enable plastic buoys of a given size to be handled by a smaller ship than would be the case for a steel buoy, however these plastic buoys have not been in service for many years and it is difficult to comment on their long term advantages.
Japan has been using 2.2m foam filled GRP buoys for 15 years although their poor impact resistance is noted as is the difficulty of disposing of the plastic materials from which they are built. These plastic disposal regulations wilI valy from country to country but may become a major factor in choice of buoy material.
SPAR BUOYS
Sweden has extensive experience over a 10 year period with plastic spar buoys. Although not generally a popular type of buoy they are particularly suited to areas with little tidal range and may well be worth investigation by other authorities as the fixed position of the buoy has particular advantage.
MAINTENANCE
