Because of the nature
of the rig a junk sail works best on an
And with most junk rig conversions the mast will need to be positioned
of the bermudan mast position.
So, before you start to design the sail you need to check your boat for
suitable position mast, then design the sail plan to suit.
Positioning a junk sail is about getting the sail’s CE (Centre of
positioned in front of the hull’s CLR (Centre of Lateral
Too far aft and it will develop too much weather helm too far forward,
The CLR will be fixed by the shape of the hull.
The CE will depend on the size and shape of the sail plan.
The sail plan can vary enormously, depending on the aspect ration,
sails etc, and of course it will depend on the mast position.
Having said all that, it is rare for a junk rig to suffer from much lee
weather helm is much more common, so the further forward the CE the
However, this is not
exact science, the CE of a sail will alter as the wind strength alters
you trim or reef the sail.
The CLR of the hull will alter somewhat as the boat heels and the
It is because of the desirability of having an unstayed mast
that the junk
rig conversion of catamarans can be problematic, though some have
this by having a twin rig with a mast in each hull.
And shrouds can be used though this will greatly reduce the versatility
Tabernacles have been used on some smaller
boat junk rig conversions
still need as much bury between the pivot and heel as for fixed masts,
calls for an intrusive ‘slot’ extending below decks.
The CE can be moved forward by raking the mast forward.
Forward rake is seen on many Chinese
vessels but with a single masted junk rig conversion there is a danger
this may cause too much downwards press on bow.
For a single masted rig the recommended rake is 'plum'.
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