Mast - 11mm Alloy Round Natural Anodised (0.6 mm wall) 1.5 metre


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Product Description

11mm Alloy Round Genuine SAILSetc Natural Anodised (0.6mm wall) - 1.5 metres long

Suitable for B Rig - IOM

Weight - 75 grams

Q  Why are your mast tubes not as hard as some others?

A  Simple question, long answer. The best fore and aft tension in an IOM rig
can be obtained using a mast that is pre-bent so that more forestay and
backstay tension is required to pull the mast into the right shape to match
the mainsail luff curve. The extra tension this pre-bend permits allows the
rig to work at higher wind speeds without distorting and so maintains sail
shape to a better degree than a mast without pre-bend.

Pre-bend is normally added after the mast has been drilled and before the
fittings, rigging and sails have been added. It can usually be adjusted once
the rig has been set up on the boat if fine adjustment is required to get
the sail shape spot on.Aluminium alloy extrusions are available in a range
of hardness varying from soft through to hard.

It is important to understand the difference between hardness and stiffness.
Hardness describes the ability of the item to resist loading without taking
on a permanent deformation. Stiffness describes the ability of the item to
resist deformation for a given load.  Spring steel, for example, is very
hard but may not be very stiff.It is also important to understand that the
stiffness of the metal and the tube made from it is the same regardless of
the hardness of the metal.

So, for a given diameter and wall thickness, the stiffness of all aluminium
tubes will be the same (within a very few %) and they will resist the
bending loads of the rig in the same way.  However a mast that has had
pre-bend added will be able to have higher rigging loads that will permit
the rig to work better at higher wind speeds.

So, where does hardness come it?An alloy tube that has been hardened
(usually by heat treatment) will often break before it can have permanent
bend added to it. For example the tubes we use for IOM headsail booms are
like this - it is virtually impossible to bend those tubes. However, we
specify a medium hardness for our mast tubes so that adding pre-bend is a
relatively straightforward task.


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