- 385m (1,270 feet) of 6mm (.25 inch) diameter polypropylene rope
- 148m (489 feet) rope for radials
- Sticky tape
- 1 x marker peg
- 52 x tent pegs
- 52 x short ropes/cord
- 12 x spars 4m (12 ft) long
- 1 x rope (spar circle) at least 35m (115 ft) long
- 12 x guys 7m (21ft) long
- Handy billy
- Additional tent pegs (optional)
- 3 x ropes 14m (46 ft) long
Arch and tunnel:
- 1 x spar 2.5m (8ft) long
- 2 x spars 2m (6ft) long
- 1 x rope 5.5m (18ft) long
- 3 x ropes 7m (23 ft) long
1. Constructing the net
The quantities of rope given in the equipment section include a generous knotting allowance. This is not included in the measurements below.
The net consists of 14 concentric rope circles, which should be 500mm (20 inches) apart. A gauge as shown in diagram A will help measure the distance between the circles. The length of rope needed is shown in Chart A.
The ends of the rope are joined using a fishermans knot (see knotting guide). It is important that the joins in all the circles line up. Tie these firmly but not too tightly, as they will need to be undone later in the construction. Ensure that you have long ends left.
20 equi-spaced radials are then added, with each radial rope approximately 7.4m (24 ft) long, plus an allowance for each knot. (Diagram B)
We suggest that the circles are marked with tape to ensure the correct spacing of the radials.
Position the first radial to lie along the line of fishermans bends but do not tie this radial to the circles. Space out the remaining 19 radials according to the measurements given.
Join the radials to the crown ring using a round turn and two half hitches.
Work outwards towards the base ring, joining the radials to the rest of the circles using a variation of the rolling hitch the hitch is started in the usual way by taking two turns round the circle rope but after the cross over, instead of simply tucking the running end through itself, it is passed through the lay of the rope and pulled tight. This should stop the radials sliding along the circles.
2. Erecting the main structure
Choose the location of the centre spot and drive in a marker peg. Select a large, fairly flat area. The dome, as described, is approx 14m (50ft) in diameter plus and allowance for guys.
Using a rope marked with sticky tape to a radius of 7m, set out the outside diameter of the dome by driving in pegs, There need to be 40 pegs equi spaced at approx. 1.1m centres facing outwards from the centre.
Set out an inner ring of 3.55m radius and mark it with 12 equi spaced pegs. These mark the position of the support poles and are approx. 1.85m apart.
Lay the net in position and tie the outer face firmly to the ring of pegs with the line of fishermans bends where you want the entrance to be.
Use a long rope – at least 35m to produce an 8.8m diameter circle with 12 equi spaced knots (we recommend the man-harness knot) with the loops adjusted to fit snugly over the 4m spars.
Attach a 7m long guy rope to each spar, 3m up from the butt end.
Lay the rope circle in position over the centre of the net so that the loops line up with the inner ring of marker pegs.
Stand the spars up next to the inner marker pegs with the butts through the loops in the rope circle, taking care to pass them between the 7th and 8th loops of the net, counting from the outside.
Slide the rope circle up the spars until it is just under the guys and seize it with sisal to each spar.
Place additional pegs around the base of each spar to prevent them moving.
Peg out the guys so that the spars lean outwards at equal angles and the rope circle is taut.
Tie three ropes lightly between opposite spars above the rope circle so that that they cross in the middle.
Rig a handy billy and make it fast to the centre of the net and to the three cross ropes.
Raise the centre of the net to give 2m headroom and seize it at each spar.
3. Entrance Arch and Tunnel
The dome follows the same proportions as The Dome at Greenwich but if we followed suit with the entrances they would only be about 600mm high. We have therefore opted for an arched tunnel. These instructions only allow for one entrance but if this was required for, say, a grand entrance to a camp, another could be added to provide a walk through with a spectacular reception area. In that case, each circle of the net should be constructed using two lengths of rope, knotted using the fishermanï¿½s bends, at the places where the entrances will be.
The two 2m spars are used to support the entrance arch, one at each side. The spars are linked together at the top by the 2.5m spar and are lashed to a peg at the bottom. They will need to be guyed.
A 5.5m rope is doubled and then the mid point is attached to the centre of the cross spar. The ends are fixed to the bottom of the uprights and sisal is then tied to the poles and used to hold the arch in shape.
To construct the tunnel:
Untie the fishermans bends on the outer 11 circles. Tie the loose radial which lay along the knots to the top of the entrance arch to form the roof of the tunnel.
Take the join of the 10th circle from the outside and the radial on either side of the loose one and attach a rope to each. Tie the other end to the rope forming the arch at point a) to make the side of the tunnel.
Take the ends of the circles that have been untied. Tie each one to the rope forming the side of the tunnel and the radial that now forms the top of the tunnel. The ropes may need to be extended.
The structure of the dome is now complete and can either be left as this or clad to make it actually useful.
As the surface area of the dome is approx. 165m2, cost is obviously an important factor in the choice of cladding. Any sheet material will do depending on the expected life of your dome.
Damp proof membrane can be purchased from DIY stores or polyethylene covers advertised in the press can be obtained from such people as Bradshaws. The main dome is covered using segments like an orange and we suggest you scale up the pattern below. The entrance tunnel can be covered using simple strips.
Start at the entrance arch and work back towards the dome with each strip overlapping the previous one by 50mm at least. Where strips meet the slope of the net they should be laid across its surface and will provide a lap with the segments. The edges of the covering panels should be turned over, stapled or stitched and then have holes punched for lacing up. In an ideal world these holes would be fitted with eyelets but as some 450 are required this may prove prohibitive. The lacing can be done with either 6mm rope or sisal. The lacing should be attached to the net periodically to secure the covering.
Fishermans knot and round turn and two half hitches
Rolling hitch (adapted) and manharness knot
To download the complete plan and design document please Click Here