What is “tack knock”

[2copplane]

Looking at buying a preloved mainsail and have come accross the term “check the tack knock” but even the omniscient google couldn’t shed any light as to its meaning.

Hopefully someone with more amassed knowledge than google can advise. I’m guessing it is the offset required to allow for the gooskneck?

 

[pvb]

Also called "knockback", usually the distance from the aft face of the mast to the pin which holds the tack eye. Can also feature the height of the pin above the top of the boom.

 

[lw395]

As PVB says, but beware of subtly different definitions, I'm never sure whether everyone measures to the bearing edge of the mast slides/bolt rope from the bearing edge of the tack pin, or the centre of the hole or the centre of the bolt rope or whatever. A little diagram can help.

 

[2copplane]

Thank you thought it must something like that.

 

[William_H]

Ideally a main sail tack when fitted to the mast/gooseneck should be a straight line from head eyelet to tack eyelet with no load on the bolt rope or slugs. You may need to redesign gooseneck tack attach or add slugs if not fitted to get this straight line. good luck olewill