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Block and tackle / hoist: what it is and why it is used in shade sails

Block and tackle or hoist

What it is and why it is used in shade sails

Whether it is called a tackle, winch or a hoist, it means an effective combination of lever and wheel.

But who invented it and what does it have to do with the world of shade sails?



“Two blocks, one fixed and the other mobile, and a cable inserted in them form a hoist”

This is how George S. Nares describes it back in 1862, in one of the most famous books on seafaring art. George was a Royal Navy officer, he was a British navigator, admiral and polar explorer. A great man who brought innovation to boating and is still widespread today in various other areas.

Over the years, sailors from all over the world have handed down the secrets to create those machines that now operate sailing boats. Among these there was also the method of two blocks and a long rope. Those few components, suitably upright, would have given life to the hoist, but let's see how it works!

WARNING: THIS ARTICLE CONTAINS ALGEBRA AND TRIGONOMETRY TRACES.

PROCEED WITH CAUTION

Newton's first law

For a body to be stationary, the sum of the forces in each direction must be zero.
For simplicity, we will stick with the forces in the x direction.

Looking at the pulleys we notice that the force of the sail is balanced by the force applied to the fastening.

This result obviously also applies to the other side, assuming that the force of the sail and the force 'discharged' into the anchor are identical.

We can assume that the tension applied to the string is evenly distributed: The pulling force pointing down is the same as the tension in the rest of the string. Therefore, to apply the necessary tension force to your shade sail, you only need to pull the rope with 1/4 of that force. This is called a 4: 1 mechanical advantage.

This happens thanks to the 4 different vectors that will help multiply the force we apply! Obviously the 4 'pieces' of rope that we are going to move will move for the distance of 1/4 each with respect to the movement applied to the 'mother' rope that they operate. This is the secret of pulleys: we pull the rope for a longer distance but apply less force.

The purpose of the hoist is therefore to reduce the effort required to lift or pull a weight.

Application of the hoist to the world of shade sails

A well-tensioned sail undoubtedly has many advantages, if you don't remember them we recommend this article.

Tensioning the fabric without any help from the hoist is a very difficult task.

Our research and development team decided to replicate the simple but brilliant invention of George S. Nares, creating our system that we called Muscle.

The Muscle kit, thanks to blocks inserted inside a steel body, is able to triple the force applied to the rope.

It is certainly the simplest and most effective way to set shade sails.

Also, together with the adjustable straps, we can boast the only system to make our Saill and Solaria safe in case of strong wind (find out more why Maanta sails are considered the best shade sails).

Muscle is a specific product, but easy to install. It has a great tolerance: it will not be necessary to be very precise in calculating the dimensions. Thanks to the top you can always be effective by perfectly adjusting every situation.

Now that you too have learned about the hoist, you just have to wait for the next article that tells about the installation of a truly immense shade sail in one of the most famous restaurants in the world: Hosteria in Certosa di Alajmo in Venice, Italy!

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