Adjustable spreaders

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I've been very keen to make spreaders which are adjustable, particularly in terms of the "V".  This is about the 10th design I've come up with, after help from Graham Bantock made me keep it as simple as possible.  It is pretty crude, but gives an idea of how this might work.  The mast fitting is, at the moment, free to ride up and down the mast.  I may decide it needs to be pinned in place.

The view on the right shows the spreader at maximum "V" angle of about 120 degrees, and gives a good view of the adjustment screws.  To change the "V" angle, the screws are slackened off and the spreader moved to a new position.  The "pivot" screw is tapped into the mast fitting, and operates through a slot in the spreader.  The "locking" screw operates in a slot in the mast fitting, and has its nut running in a recessed channel.

The recessed channel for the locking nut is shown in the picture on the left, where the spreader is set at about 180 degrees.  The shroud is very simply clamped to the spreader by a screw, since the new SAILSetc "aerodynamic" spreader can be tapped quite nicely for a M2 thread.

The slots are needed in the spreader arms and mast fitting in order for the spreader length to stay roughly constant when the "V" angle is changed.  If the slot in the spreader is not present, as the "V" angle is tightened up from 180 degrees, the shrouds are pulled in.  This may be undesirable.  It turns out that the slot of the mast fitting needs to be angled at about 45 degrees in order to keep the overall spreader width roughly constant.


2011 Lester Gilbert