When installing a Shade Sail it is advisable to install posts first and then get a shade manufacturer to fabricate a sail to fit the position of the posts.
This is easier than trying to get posts into a position that pulls the corner of the sail in the correct direction which will keep all sides of the sails tight and not have one side over tight.
It is also preferable because the following can be achieved by placing posts first and then fixing sails second:
- factoring in the position of the sun
- achieving the design
- complementing the shape of existing landscape
- measuring the heights required
The size and thickness of the sheet post must be sufficient for the size of the sail to be fitted.
Always start with the highest point and then work diagonally outwards. A block and tackle set up is realy what you need to install your shade sail to the correct tension. If using turnbuckles please make sure that you grease the threads when tightning the turnbuckles when stainless steel is under tension it will lock up and your turnbuckle will be as good as dead. Remember to lock your nuts when your finished adjusting the turnbuckles. If posts are powder coated make sure you cover the posts with material or foam etc when winching to ensure you do not scrath the paint.
As the post height lengthens or the sail grows in size the posts must be stronger and the footings must be larger. The corner fittings (D Shackle Turn Buckles) must also be stronger to take higher loads. Depending on the size of your sail an 8mm rope should be strong enough to hold the loads until you lock off your stainless fittings, although some jobs you may need to use 10mm.
Shade cloth does allow water to seep through but in larger downpours water can bank up on the sail and stretch it.
In order to stop this happening you should have a fall of at least 1 metre for every 5 metres. This fall can be acquired by two high posts on one side and two low posts on the other side or a more attractive design is to create a hyperbolic finish in the sail by placing two high posts diagonally and two low posts diagonally. This design helps to equalise the wind loads on the sail but still allows for water runoff.
If you have installed your post you need to measure the distance between the eyes on the posts and the diagonal measuremenst as well.
You should also discuss what fitting you require to be installed in the corners of the sail so the manufacturer can allow for the stretch in the sail and the corner fittings.
The stretch worked out by the manufacturer is usually a standard reduction so if your posts are not up to the correct specification for their height and the sail size there is a good chance your posts will fail.
When installing your posts they should be installed at a lean of between 5 and 10 degrees away from the centre of the sail.
Hope you find these tips helpful. I’ll discuss the installing of sails from existing structures.