Sails work best when they are:
1. Under enough tension to give curvature
2. Not on a level plane
3. Are ‘twisted’ for stability
It is important to consider the slope of the fabric to ensure good shedding of water.
The shade sail is essentially pulled taut and twisted so one axis is convex and the other axis concave.
The best designs we have found are shade sails that have a significant difference with one corner much
higher than the other. This gives a striking look. Overlapping shade sails or a series of sails can also
give a dramatic sculptural look.
1. Measure The Shade Area
— decide where shade is wanted and measure the sides and diagonals of this whole area.
— consider the height of the sun and direction during the summer period.
— consider the size of the sail, location of any barbecue’s or tree branches that may also chafe or affect the sail.
— to help visualize the sail you can use a string stretched between planned attachment points.
— a scale drawing of the area to be shaded can be useful.
— rotate scale drawings of the actual shade to get an idea of actual layout.
— straight lines drawn through the centre or corners will give the fixing points.
—tensioned sails have curved or concave edges and the depth of the curve is about 10%. in from the outer of the sail.
— this curvature and the use of fixings means that the sail covers a smaller area.
2. Allow For Sail Curvature
The fabric needs curvature to maintain stability and it will be pulled taut and slightly twisted to achieve this.
—This curvature plus the sail not being on one level plane – will make the sail more stable in winds.
— A flat sail will not perform properly and can hold water. The most common method is to have each pair of diagonally opposite corners at sgnificantly different heights.
— Shapes that have little curvature and tension will deform under load and become unstable and move about.
3. Fixing Points
Finally ensure that any proposed fixing points are strong enough to bear the local wind conditions. If unsure consult a local engineer.
4.What Sort Of Fixing Methods?
4.1 Houses or Buildings
Always ensure that the existing structure or building can support the load of a sail under poor weather conditions. A sail under heavy wind can put considerable strain on the building. A local engineer or qualified builder can verify that the building can withstand such a load.
Galvanised steel will avoid rust and is a better solution for fixing shade to than wood.Wooden posts can warp which place the sail out of alignment and can rot over time.
If the post moves in its foundations as it is under strain it is usually hard to correct at a later stage. If the post moves during the initial construction of the sail it will be extremely difficult to tension the sail properly at the outset. A good way to look at the foundation depths is 1/3 of the post underground. Most sails sit 2.5m high so the post needs to be just over 1/3 again longer than this.