These two models were designed for the specific needs of a particular area. They require a great deal of skills and therefore are only suitable if none of the other rafts can be used.
How to build a welded raft
The designs shown below have proved to have an estimated life of at least 12 years with minimal maintenance.
These two types depend on availability of suitable welding equipment and skills, and sheet-metal float tanks used by gravel companies for ferrying electrical equipment around wet pits.
Weld together three float tanks and attach a rim of logs with welded metal straps. To moor the raft, fix a wire anchor rope to a 50kg scrap iron or concrete anchor. This simple but strong raft gives a surface area of 6.7 sq m. It successfully attracts ducks and geese, but has two disadvantages.
It is so buoyant that the nest floats at least a foot above the water so that, unless a ramp is attached to help them, once the chicks leave the raft they cannot return. Soil ultimately dries out or is dislodged and must be replaced at intervals along with fresh vegetation.
This rather elaborate design features a semi-flexible welded frame, which makes the raft very durable in exposed conditions. The float tanks are the same size as in the previous design – the sleepers are topped with a grid that holds nesting cover.
How to construct this raft:
- Weld the frame together and to the float tanks. Weld two anchor bolts to opposite corners.
- Manoeuvre the completed frame into the water.
- Slide the sleepers into position. Leave gaps between the pairs of sleepers so that plant roots can reach the water.
- Cover the top of the frame's central section with narrow-mesh galvanised metal.
- Fix the nesting boxes on top of the floats.
- Cover the mesh with mulch or soil and suitable plants. Plant up the nesting boxes.
- Tow the raft into position and anchor from the anchor bolts.