Advice from Martin Egan. UK Mirror Class Technical Officer


Complying with the ISAF interpretation on adjustable forestays

This is a note for owners with adjustable forestay systems to set out some options for complying with the ISAF interpretation.

1)    The purchase system can be removed from the boat and replaced with

a.    A dyneema/spectra line which is the traditional system. 3mm line running around a straight pin on the forestay channel and the swaged eye on the end of the forestay works well. If the line is tied to the forestay eye, then around the pin in a aft to forward direction then through the eye in a forward to aft direction. If 3 complete loops are made, each in the same direction, the line binds on itself when tightened so the tension is held on while a knot is tied. Looping the line in the direction indicated makes it easy to apply tension by pulling down on the line between the end of the forestay and the foredeck (so can be done with your shoe if necessary).

b.    A “boat buster” purchase (8:1 is popular in Australia) which is temporarily attached to the jib halyard and forestay attachment fitting and used to apply tension to the shrouds. The forestay is then attached to the forestay attachment fitting directly with a pin (if the forestay is long enough) or the pin inserted into a vernier style shroud adjuster which is attached to the forestay fitting, or a dyneema/spectra line is rigged, tightened to take the tension and knotted. The purcase system is then removed. To take of the rig tension the process is reversed.

c.    A bottlescrew or “staymaster” which is then wound up to achieve the tension required.

d.    A highfield lever

2)    The purchase system can be disconnected from the forestay while the boat is racing. One way to do this is to rig a dyneema/spectra line as in 1) a) above. Use the purchase system to tension the rig. Then tighten the dyneema/spectra line to take up the tension and knot it off. Uncleat the purchase system and disconnect it from the forestay by disconnecting the 1st block in the cascade, or untying or unshackling or unhooking the purchase system from the forestay.

I will be on hand on Saturday and Sunday morning with a reel of 3mm dyneema to help owners with this.

Martin Egan

Technical Officer UK MCA