Nesting rafts

For small sheltered ponds a raft can be quite a simple affair; made from an old wooden door, for example. But for open waters the construction must be fairly heavy to make them stable and the moorings must be strong and secure. Various methods of providing buoyancy have been tried, such as metal drums of different sizes, but for preference pieces of expanded polystyrene scrap are used, packed in plastic fertiliser bags, since the duck like to eat it if it is accessible.

If metal drums are used it is better to have a large number of small ones rather than one or two big ones. Eventually they will rust through and obviously one or two small drums leaking will not effect the buoyancy so much as a big one. The small sizes are also more easy to replace. Plastic containers such as those used for chemicals and detergents are better.

We have found that old telegraph poles, usually obtained quite cheaply from British Telecom or local Electricity Board, provide the best basis for large raft construction, being heavy and pressure-impregnated with creosote. A simple framework or angle-iron fastened with coach screws makes a very strong, durable and cheap raft that will last for some years. Sloping ramps with 'footholds' or wire netting must be fitted to provide access for ducklings, otherwise some will be unable to follow their mother back 'on board'.

Raft construction

1. Cut a telegraph pole into two equal lengths and lay them out parallel; 5 ft. ( 1m.) apart and as close to the water as possible.

2. With a brace and bit, drill holes 3.5-in. (92 mm.) diameter where the angle-iron is to be fastened.

3. Before fixing, the iron frame should have s-in. (16 mm.) diameter holes drilled at each end for the fastenings and an additional hole in the middle of the angle-iron to take the mooring wire.

4. Place the iron frame in position and fasten with 6 in. X 0.5 in. ( 15 cm. X 1 cm.) coach screws driven into the prepared holes.

5. Turn the whole raft upside down.

6. Spread a length of 6 ft. (2 m.) 12-in. (3 cm.) mesh, 18-gauge wire netting over the raft and fasten with staples. In the event of a plank rotting, the wire netting will act as a safeguard to prevent rooted plants, etc., dropping through.

7. Nail planks across. These can be an expensive item (slabwood can be used as shown in Figure 125), but they can be spaced 6 in. ( 15 cm.) apart if used in conjunction with wire netting. Netting on its own would be forced up by the buoyancy material. Two planks should project 9 in. (23 cm.) beyond the poles on each side to form bottom supports for the duckling ramps. These boards should be 6 ft. (2 m.) apart and at roughly equal distances from the ends of the poles.

8. Secure the buoyancy material in position. The fastening need not be very strong (small-gauge lacing wire is adequate ) since it is only to hold the material when the raft is launched, after which it will be held by its own buoyancy.

9. Turn the raft right side up, at the same time lowering it slowly on to the water. This can be done by running a supporting rope from a nearby tree or vehicle. It is important to carry out this manoeuvre gently and to see that there is enough depth of water to float the whole structure, otherwise the buoyancy material may break loose or be damaged.

10. Nail a board 6 ft. 6 in. (2 m.) long across the centre of the two telegraph poles and projecting 9 in. (23 cm.) each side. This will be the top support for the duckling ramps.

11. Fit the ramps, and nail in position to the top boards. The bottom boards will be below water level and the lower edges of the ramps will have to be fastened to them with wire unless the raft can be tipped over to bring the boards clear of the water. Fill the space between the poles with straw and plant up with soft rush (Juncus effuses) or suitable reeds, and tow to the mooring position.

It is important to see that the moorings are really strong. At Fording-bridge 1-in. (22 cm.) circumference flexible steel wire rope is used with a breaking strain of about 4 tons (4,050 kg.). It is unlikely that this strain will ever be exerted, but deterioration must be allowed for. The rafts are moored in 'strings', usually with one end attached to an iron stake on the bank and the other to a mooring on the bottom. This is made up with concrete sinkers of convenient size can makes a good mould). One is fastened to the end of the wire and four more threaded on and allowed to slide down to the bottom - after which the end of the wire is shackled to the raft. Moorings must be regularly inspected. Chafe invariably occurs where the wire is fastened to the raft and the shackle must be moved to a new position further down the wire. For this reason there must be some slack in the moorings at first launching.

With large rafts it is possible to support the anchors on the raft while it is floated into position. If they are attached to the raft by a sufficiently long cable they can simply be pushed `overboard' when the raft is in the desired position.

If more than three rafts are moored together, there should be additional moorings from rafts in the middle of the 'string' to prevent it from sagging before a strong wind and dragging the main moorings. When planted with rushes they look most attractive. Some of the rafts at Fording-bridge showed no signs of deterioration after nine years afloat. By this time the wire netting and planking had rotted away but the rushes had formed a solid root mass which floated on the polystyrene and was held in place by the telegraph poles.

On these larger rafts, nests of Canada geese and tufted duck have been found among the growing vegetation, and on an unplanted raft a roosting pair of common tern have successfully nested for two seasons.

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