Although rafts vary in character and design, some basic considerations apply to each.
Main factors to consider when making a raft
Rafts are unlikely to attract terrestrial predators and so are useful where islands would be too close to shore for safety.
Rafts also provide wildfowl with loafing spots and are often used as resting places by various bird species during the winter. It is difficult to make them as effective as islands because there are many conflicting requirements.
Factors to consider include:
- The ability to float, preferably with the deck just above the water line.
- The ability to rise and fall easily with the water over the maximum flood range.
- Stability, so that the raft is not tipped or spun by current, waves or wind.
- A dry, sheltered nest site, which does not attract the attention of crows or other avian predators. The nest area must be high enough not to be swamped by storm waves.
- Means of access and some protection from waves and current for young birds.
- Harmonious blending with the surroundings, if possible.
- Practical factors, for example water not excessively deep, lake shore accessible by vehicle for bringing in boat, raft and materials, and for regular maintenance checks.
- On Sites of Special Scientific Interest, formal consent may be required from Natural England, Scottish Natural Heritage or the Countryside Council for Wales.
- The area and water characteristics determine the best design for a raft.
Whichever raft you choose, some basic considerations apply to each.
These tend to absorb water and sink, although pine or other light wood floats better than heavy timber. In most cases, additional floats must be used if the raft is to last for more than one season.
Small rafts can be floated with plastic 4.5 litre containers. Slightly larger rafts will stay afloat with 22 litre plastic drums. Rafts in the range of 1.2–1.8 m in dimension require closed cell polystyrene blocks, polystyrene scraps, airtight metal drums (including old oil drums). Polystyrene is easily held in place and can be adjusted to achieve the correct buoyancy.
It should be packed into strong polythene to prevent it from breaking up and littering the environment. Metal drums need to be weighted so that they do not float too high. The flotation blocks must be thoroughly cleaned before they are brought to the site to prevent pollution. Annual checks and maintenance is important to ensure that the raft remains secure and firm, and that the flotation devices are not disintegrating or leaking.
Two anchors are better than one and should be attached to opposite corners of the raft to keep it from swinging in the wind. Anchor to the bottom, not to the shore, to prevent vandalism and to keep rats or weasels from getting to the raft.
- Anchors can be made from breeze blocks, concrete blocks etc. The wire anchor rope should be tied to a short section of chain or to an eye bolt. For large rafts, use 19mm circumference flexible steel wire rope with a 4 ton breaking strain to be sure that the mooring is secure.
- The anchor can weigh about 50kg and is suitable for larger rafts. It can be made in a large polythene garden tub half-filled with scrap metal or rocks. Wrap one end of an appropriate length of chain around the scrap and fill the tub with concrete. Once the concrete has set, the anchor can be turned out of the mould and the chain bolted to the raft.
- Three thicknesses of heavy gauge (24mm) polypropylene rope can be used instead to save money. Similar rope will be needed for mooring lines in deep water as chain is very expensive. Where strong winds or icing is likely, several 50kg anchors will be needed to securely hold a 3 x 2m turned raft.
- Where such an anchor is too cumbersome to manage, a smaller (eg 9 litre) container can be used as a mould, and concrete sinkers can be cast with holes through their centres. One sinker can be fastened to the end of the wire and others can be threaded on and allowed to slide to the bottom before fixing the other end of the wire to the raft.
Where more than three rafts are to be moored in a string, there should be some additional anchor points from the middle rafts to keep the string from sagging before a strong wind and dragging the main moorings.
Duck baskets and duckling ramps
Various nest boxes and duckling ramps can be added to the raft superstructure depending on the species of birds that will use the raft. Duck baskets should be at least 1.2m apart and facing away from each other. They should be tilted slightly upwards at the front and lined with dead grass or some wood shavings. Baskets should be positioned in early January and left until early September, when they should be taken up, cleaned of nesting material and stored under cover.