It sounds as though you were previously using the forestay to support the sail,  which is yacht practice,  and outdated (1950s and older) dinghy practice.   In dinghy practice over the last 50-odd years there is considerably more tension on the genoa halliard,   and if you have sufficient tension on the genoa luff the forestay will become slack.

I remember when I was teaching sailing in the sixties asking myself why we bothered to hank the headsail onto the forestay,  when the headsail luff had the greater tension;   what purpose was served by doing so?

So the first step is to adequately tension the headsail (whether genoa or jib) halliard.   Just how much depends on the age of your boat;   for all modern (i.e. series 2) boats you can (and arguably should) use either a muscle box or a cascade tackle (giving either 8:1 or 9:1 purchase),  and keen racers will then lead the downhaul on that to a 2:1  in the cockpit,  which is led back to the two sides of the boat at the thwart;   this will give a 16:1 or 18:1 purchase overall.   However you may need to adjust your shroud settings at the same time to compensate for this;  modern practice is to set the shroud adjustment first,  and then apply tension to the rig.

There are tuning guides in the Members’ Area of the site which are worth a read even for non-racing.

For the oldest series 1 boats this amount of tension is vastly more than the boat was originally designed for,  and is potentially dangerous,  as it risks structural damage to the hull,  unless the official mast step conversion has been fitted.    However you can safely use a Highfield lever (typically about 6:1 by the point at which it is fully closed) to tension the headsail halliard.   (Be aware of correct technique for using this,  and of the danger to fingers if this device is operated incorrectly!)

With the headsail correctly tensioned,  which thus tensions the entire rig,  the forestay will go slack.   You then need to ensure that the forestay is kept out of the way of the headsail as it is furled;   if not kept out of the way it will wrap up with the furled sail,  and jam the furling after only a few turns.

The first step to keeping the forestay out of the way is to take the slack out of it after the halliard has been tensioned.   One way is to simply tighten the lanyard until it is just taut;   note that this will result in there being significant tension remaining on the rig when you later drop the sail.   An alternative,  and probably better,  way is to use a short piece of light shockcord to keep the forestay just taut.

The second step to keeping the forestay off the furled sail is to use some form of spacer at the head.   See the paper on Reefing Systems (also in the Members’ Area) for methods of doing this.

Hope this helps,

Oliver

• This reply was modified 3 years, 4 months ago by Oliver Shaw.