# Shade Sail Mounting Post Strength Calculator

This post strength calculator will calculate the maximum horizontal force (F in kg) that the post can withstand before bending.

The inputs that are required are:

- outside diameter of the post D in mm
- wall thickness of the tube T in mm
- height of the post H in m

Enter the dimensions in the spaces below and click on calculate.

The calculator uses the material properties of Stainless Steel Grade 316L, which has a Yield Strength of 205 MPa and is the material from which our shade sails posts are manufactured. To calculate the maximum force for other materials, see the sections below.

## Aluminium Post Strength Calculator

The calculator uses the properties of Stainless Steel 316L with a material yield strength of 205 MPa. If you wish to use the calculator for another material, such as Aluminium, then a correction factor must be applied to the result.

It is important to identify the correct yield strength for the material you are using and there are many different grades of aluminium alloy. For example 6061-T4 has a yield strength of 110 MPa. This is a lower yield strength than the 316L grade stainless steel and the corresponding force that it can resist will be lower. Typically Aluminium tubes will have a greater wall thickness to compensate for the lower strength.

The correction factor to apply to the calculated result is simply the ratio of the two yield strengths 110 / 205 = 0.54. The maximum force an aluminium tube in 6061-T4 can withstand will be 0.54 times that calculated for a 316L stainless steel tube - for the same tube dimensions.

## Wooden Post Strength Calculator

The calculator uses the properties of Stainless Steel 316L with a material yield strength of 205 MPa. Wood typically has a yield strength of 55 Mpa, but this varies with the type of wood - pine, oak, douglas fir. The result from the calculator would need to be corrected by a factor of 55 / 205 = 0.27.

It is important to note that a wooden post is solid and not hollow like a metal tube. The calculator will still work for a solid post but, in this case, the wall thickness T in mm will be half of the post Diameter D in mm. T = D / 2.

## References

The following references to material specifications were used :

- Aluminium alloy 6061 material specifications
- Douglas Fir material specifications
- Stainless Steel 316L material specifications - Download pdf data sheet