Long skinny shapes (narrowest edge less than 1/2 the length of the
longest edge)
should always
be avoided.
A cable to a remote attachment point may extend one
corner; otherwise the corners should be fixed directly to a post or an
adequate fixing point.
Use of extending
cables allows the membrane to move too much which increases shock
loading and reduces membrane life expectancy.
Flat shapes such as triangles must be canted adequately to keep them
from "puddling" during rain. A slope of 1:4 is the recommended minimum. But
with larger triangles or
flat sails more slope is even more imperative. Failure
to have enough slope will cause puddling and excessive sag which can
cause a membrane to fail.
When possible, a twisted shaped is preferred such as a hyperbolic
parabola. This
imparts a 3rd dimension of tension into the membrane. Another way to
get this 3rd dimension is to have one corner of the quadrilateral much
higher then the other corners. (High Point Sail) Membranes
with 3 dimensions and are not relying on just edge tension, have a more
even distribution of forces.
Flat 2 dimensional
sails tend to concentrate forces at the corners and edges, A Shade Sail
is only as strong as its weakest point. Therefore,
a flat 2 dimensional sail is not as strong as a 3 dimensional form and
will not last as long when exposed to the same conditions.
Hyperbolic and “High Point” shaped sails should
have height difference that create a minimum 1:4 slope from high to low
fixing points.
This is the minimum
to start getting the 3 dimensional effects. Slopes
of 1:2 are recommended and are also more
aesthetically pleasing as well.
Sails should not be allowed to stay up in the event of snow. Long-term
loading will stretch the fabric. Shade
Sails do not shed snow well.
Overlapping sails should have a minimum of 18” of separation
to avoid chafe.
Movement in high
winds can cause close sails to touch and they will suffer chafe damage
in a very short time.
When these rules are followed you can expect much less movement of the
Shade Sail
and therefore longer life.
It is the installer’s responsibility to understand and follow
these rules and recommendations. When these rules are not followed then
any warranty given or implied by Shade Sails LLC becomes void.