[Public-List] Genoa sheet blocks

Don Campbell dk.campbell at sympatico.ca
Sun Oct 4 17:33:48 PDT 2009

For those of you who do not have a catalogue that includes winches, (it 
might be a good idea to get one for reference) every winch in say the 
Harken catalogue has a specified line entry in inches (measured from the 
base of the winch) That means that one has to mount the foot block or 
cheek block accordingly so that the line entry to that particular winch 
is always fixed at that height. The only way to achieve this with genoa 
sheets where a sail trimmer may change  the sheet block position for a 
given sail depending upon apparent wind direction is to have a fixed 
block, independent from block on the car, for the  line leading to the 
winch.   It should also be on the correct angle so that the lead is 
without twist as it leaves that sheave so one needs to make a pad in at 
least two planes to get the angle correct for most turning block 
placements. The line in and sheave at that point is aligned with the the 
locus of a point from the base of the block on the car, and the line out 
is aligned with the angle specified by the manufacturer. Thus the block 
is angled to get the differences in those two alignments which may 
include side to side and back to front.
    Any other rig set up will change the entry angle of genoa sheets 
coming into a winch as the position of the car changes. Just draw out 
the geometry to scale to see the changes.


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