Harken 7413.10 MKIV Jib Reefing & Furling built after Feb. 2009 - Manual (Page 32)

Operation Spinnaker Halyards/Headstay Tension/Backstay Adjuster
Backstay Adjusters
Backstay adjusters allow headstay tension to vary so sail shape can be changed to
match conditions. They permit a very tight headstay to be eased when boat is not
in use. For best performance, consider adding a backstay adjuster; either a block
and tackle, or a mechanical, or hydraulic adjuster like those offered by Harken.
Remember to keep headstay tight for best performance when furling or reefing.
If your boat is fitted with an adjuster be sure that it is tensioned before the halyard
is tensioned. If not, backstay adjuster may increase halyard tension and could
damage the sail or furling system.
Racing boats often slack the headstay completely when sailing downwind. Check
to be sure that foil does not jam against upper headstay terminal when backstay
is released. To prevent this, it might be necessary to shorten foil slightly.
32 MKIV units 3, 4
On many boats, it is not possible to attach spinnaker halyard to
bow pulpit or it may be "sucked" into jib when furling.
On some boats the spinnaker halyard lays across headstay
and will catch on halyard swivel, foils, or jib halyard. To prevent
problems, it may be necessary to install a masthead bail to
move spinnaker halyard block forward and to one side.
Boats with external halyards might find it necessary to flip both
ends of spinnaker halyard behind spreaders to prevent fouling
with furling system.
Headstay Tension
A furling system will work best if headstay is tight.
A loose headstay is difficult to rotate and can cause unusual
wear on foil joints.
To adjust headstay tension, remove sail and furling line from
unit and follow instructions on page 27.
Tip: Before adjusting headstay tension, slack
mainsheet and vang.
Spinnaker Halyards
Spinnaker halyards occasionally cause problems with furling.
WARNING! In severe cases, spinnaker halyards can
jam furler, causing loss of control of boat. Make sure
halyards are clear of top of foils and halyard swivel.