These fittings are available in a wide range of quality and performance specifications. They range from (in order of strength and price):
- Gal fittings found at retail outlets
- 304 grade stainless steel
- 316 grade stainless steel
- Commercial Grade Rated Alloy fittings
If using stainless it is recommended that all fittings are 316 grade stainless steel (304 grade will stain).
It is essential that hardware be suitably sized to provide an adequate margin for safety. For example a 10mm eye/eye turnbuckle has a breaking load of 3,300kg but a maximum safe working load of 1,650kg.
Beware and avoid the hook style turnbuckles (shown in the picture) which are often used for their convenience during installation. Aside from the danger posed by one of these coming un-hooked in a storm, they have very low strength – the capacity of a 10mm hook turnbuckle is only 350kg.
In our opinion, hook turnbuckles are completely unsuitable for use in shade sail applications.