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The standard raft
This raft is made of 3 m tanalized soft wood and is 3 metres square. Design includes chick shelters, a re-entry ramp and an optional security fence.
Buoyancy is provided by two high-density polystyrene blocks. Raft is anchored to concrete blocks by a chain attached to a marker buoy. It is covered with gravel and rocks, and any plant growth is removed each winter.
Raft platform
Mainframe: 100 x 200 mm timber, bolted together in each corner through overlapping ends (two upper, two lower), one top inset 150 mm to allow for re-entry ramp.
Deck: 25 x 150 mm planking, laid on and nailed (75 mm galvanized nails) to lower mainframe timbers.
Sub frame: 50 x 75 mm runners to support flotation and strengthen deck, nailed (150 mm nails); main flotation holders/deck support 50x100 mm runners; slides 25 x 150 mm planking, nailed flush with top of upper mainframe timbers along the lower sides to hold in gravel etc, and flush with the bottom of the mainframe timbers along the upper sides to hold the flotation devices in place.
Buoyancy
Blocks of 380 x 600 x 2700 mm high density polystyrene foam, painted (optional) with BP Aquaseal 44 bituminous paint (as suitable for use inside cold water tanks) to water seal and strengthen the polystyrene; two optional straps per float block, 1420 mm strips of polystyrene webbing (or 50 mm chair webbing as a temporary measure, eg. during launching) with eyelet holes for nailing to frame.
Once in the water, the weight of the raft is sufficient to hold the polystyrene in place without any additional fixings, even in extreme conditions.
Mooring
Mooring ring bolted through center of mainframe timber (bolt fixed with two nuts so that it can swivel freely), connected preferably to a chain (expensive), or a 20 mm diameter hawser-lay polypropylene rope (which will not rot, but can be chafed), with hard eyes and shackles each end.
Tether a 30-inch circumference marker buoy to the raft end of the chain or rope with a length of polypropylene rope to allow the raft to be detached, without having to pull up or lose the anchor.
Anchor
Multiple small weights (up to 1m3 concrete as a total) for ease of transport. Four buckets 250mm high by 300 mm diameter of concrete, eyebolt set in centre; weights connected in pairs by shackles to 300 mm lengths of chain; fixed to mooring by placing two pairs of weights together with the connecting chains forming a cross, and attaching the mooring rope shackle to the point where the chains cross. Exposed sites where wind and waves are strong may require more anchor weights.
Shelters (to protect from rain)
These comprise 1 m long 25 x 150 mm planks located in opposite corners, nailed flat onto end of upper mainframe timber, side plank and 50 x 75 mm end block.
Gravel covering
Preferably of 15 mm - 25 mm gravel with larger pieces and rocks to provide shelter, and give sufficient weight to push running board down to water level.
Re- entry system (for chicks falling overboard):
These are located on opposite (lee) side of raft to the mooring ring: running board 3 m, 25 x 150 mm plank nailed to bottom of the two lower mainframes. Ramp (1.5 m, 25 x 150 mm plank) sloping up to top corner of mainframe, supported by up stand, nailed. Block gap under raft behind ramp with 25 x 150 mm skirt plank.
Optional removable security fence
These comprise four frames 230 mm by 0.3 m, made from 50 x 50 mm planks covered with 25 mm chicken wire, bolted along each side and fixed at top corners.