There are many, very important considerations when planning your structure, and in fact this is the single most important aspect of the whole process. Proper planning will ensure that your sail structure performs in the way it was intended.
You will already have an area in mind that you wish to cover with a sail shade. It may be a paved area, a courtyard, a deck, a pool; regardless, the area is known but the “how to” remains in doubt.
There may be opportunities for creating attachment points for your sail on areas of existing structures, or you may need to install steel posts to create a totally free standing structure.
Always remember to ensure local building authority requirements for the structure are followed.
1. Movement of the Sun The sun rises daily in the east and sets to the west. As the seasons progress, it also moves from low in the sky during the cooler months to high in the sky during summer. Your structure should be planned to provide maximum shade protection for your particular requirements.
2. Sail Design & Architectural Twist Shade Sails work best when they are designed to have a “twist”, or architectural hypar effect. This is where the fixing points, being steel posts or brackets, are created at different heights, such that the sail is then twisted in order to fit. A flat sail or a triangle sail are harder to tension correctly, and in times of heavy downpour can catch and hold water for long periods of time, putting excess load pressure on the fixing points. Install your fixing points with diagonally opposite high and low points, to avoid these problems and create a great looking visually and functional structure.
3. Sail Size In order to fully tension the sail shade, It requires a space between the sail and fixing points for rigging tensioners, and also catenary curves in the sides of the sail. For larger sails, these tension gaps and catenary curves need to be quite large, to give maximum tension and longevity of the sail. It is strongly recommend that you install your fixing points further apart from each other than the actual shaded area you desire. As a general rule, your sail will begin about 300mm away from the fixing point, although this varies depending on the size of your sail.
4. Fixing to Existing Structures Caution is imperative when considering fixing to existing structures, such as your house. In instances of poor weather and strong winds, the loads placed on fixings by the sail are enormous.To ensure that your existing structure is adequate to handle such loads, you need to consult a local engineer or qualified builder. For the best safety practises, you should remove your sail when high wind conditions are forecast.
5. Post Footings Footing sizes vary dependant on the size of the structure and the height of the post out of the ground. An old conservative engineering principal is “1 third in, 2 thirds out”, which means posts out of the ground by 2400mm need to be at least 1200mm in the ground This is typically considered conservative. It is also a requirement to have the posts on an incline for better pre tensioning as correcting a post that has been leant over in high winds due to an undersized footing is a difficult job. Even a small movement of your footing will also compromise the ability to tension the sail. These hole diameters as a general rule, should be around 350mm however increasing as column sizes increase. Depth, however, is the most important factor
6. Underground Services Ensure your area is clear of underground services, such as sewage and water plumbing, or electrical cabling, prior to digging holes for your footings. Damages to services can be dangerous, and expensive to correct. Your local council will give you most underground services locations.