GOOSENECK DOWNHAUL AND BOOM VANG ANCHOR

Light winds=low tension/ Strong winds=high tension

Having a tight mainsail luff in strong winds, is essential to a MATILDA or any other sailboat performing well.
The secret to having a tight luff is to not only have the mainsail halyard pulled as tight as possible, with the sail pulled as high as practical, but to have a system to pull the gooseneck fitting down as well, and to hold it down securely. I am always amazed that even though the main halyard is pulled as tight as feasible, it is always possible to pull the gooseneck fitting down 6-8", which assures that you have a tight luff for strong winds. It is even more critical to have a gooseneck downhaul if your mainsail does not have slugs in the sail track, which allow the sail to slide more freely in the groove.

If the luff is not tensioned properly (low tension in light winds/high tension in strong winds), you will observe the following results.


#1 If the luff tension is too high in light winds, your sail will be very flat and not have much "belly" (draught) and consequently you will have not as much power as you could have to propel your craft and you will probably have a vertical crease right behind the mast.
#2 If the luff tension is too low in stronger winds, you will notice deep creases up the luff of the sail and as well you will have a sail with a very deep "belly" (draught) which will be drawn aft as the wind strengh increases. This powerful sail will cause you to heel more than a flatter sail would and as well, having the draught further aft will cause the boat to round up more readily than with a flatter sail.
#3 The same principles that apply to the luff of a sail also apply to the foot of a sail. Proper tension on the OUTHAUL will also affect the shape of the sail (light winds=low tension/strong winds=high tension).


A gooseneck downhaul, in my opinion, is much preferable to a CUNNINGHAM system for tensioning the luff of a sail.
P.S.One needs to devise a system of supporting the boom, when installing the sail cover so that the lowest slug does not take all the weight of the boom.

The following is an excerpt from "UNDERSTANDING RIGS AND RIGGING" by Richard Henderson, concerning downhauls.
The lines that pull down on a sail are important because they apply tension to the luff, thereby affecting the sail's smoothness and, more importantly, its draft or camber. Considerable tension on the luff tends to flatten the sail and move the draft forward, a great benefit when beating in fresh winds. A slack luff increases draft and moves it aft, such a shape being beneficial in light breezes and for reaching or running in almost any strength of wind.
I prefer that the forward end of the boom be attached to a mast track (at least a short one) with the downhaul pulling the boom, rather than just the sail, down. However, many racers have their booms fixed in the vertical direction to optimize their handicap ratings. With a mast track, the luff length is measured to the bottom of the track unless a black band is put around the mast at a point beyond which the foot of the mast cannot be lowered. When the vertical movement of the boom is fixed, a cunningham downhaul is used. This consists of a line passing through a grommet several feet up from the tack of the sail, the line being used to haul the grommet down, thereby tightening the luff. A minor problem with the cunningham alone is that it will form a prominent crease in the sail's foot. This does little harm, but the sail would set better and perhaps be a trifle faster without the distortion.






HALYARDS



Reasons for a Tight Luff (from page 11, Aug. 2007- Practical Sailor)

Regardless of sail type or deck gear, one factor always affects the choice of line for any halyard, and that is stretch. When the goal is to get the best performance out of a sail, its halyard should stretch as little as possible when it comes under additional load from a freshening breeze or sailing closer to the wind. When a halyard stretches, it allows the sail fabric to move aft. The draft of the sail moves with it. This results in the driving force rotating aft, creating more heeling moment and more weather helm. The boat is sailing less efficiently than it could, and you may be forced to reef earlier than you otherwise would..
As its fabric pulls aft, a sail on a mast track will scallop between the slides, and horizontal wrinkles will form at the slides. Apart from looking unseamanlike and making life less pleasant aboard, this also puts uneven stress on the sail fabric, which could—depending on how much sailing you do under these conditions—shorten its useful life
By the same token, if you have an aging sail that’s rather stretchy along the luff, you could eke another season or two out of it while you save up for a new one by spending a couple of hundred dollars on a less stretchy halyard. The halyard you bought will still be good for the new sail a few years down the road.
Creep is a fiber’s taffy-like gradual elongation over time while under a static tensile load, and given how most sailors today are relying on at least one permanently hoisted sail, this factor will likely come into play.



Matilda's are most fortunate to have wire halyards with almost zero stretch (0.1%).

Other boats are not so fortunate in that they have an all rope halyard as original equipment and many of these boats have been converted to having the ability to control the main and jib halyards from the cockpit. As a result many of these boat's owners have resorted to extreme measures to ensure a tight luff but the simplest of these is the adjustable gooseneck or a cunningham control system. One W.S.C. member, with a Siren, would tie a trucker's hitch in the main halyard which gave him a 2 to 1 advantage in tensioning the main halyard but then he had the problem of removing the hitch when he was done sailing for the day in order to install the main sail cover.

The new HIGH-TECH ropes for halyards can definitely improve your windward sail shape as compared to dacron double braid which will stretch by approximately 4% quite readily. On a 30 ft. halyard, 4% stretch means that the top of the sail can slide down the mast by as much as 14 inches.
P.S. You can always tell who has low stretch halyards, after boats have been sailing in strong winds for a while, by the size of the creases in their sails. So if you notice your mainsail exhibiting lots of creases up the luff after sailing in strong winds,
#1 Turn into the wind.
#2 Slacken off gooseneck downhaul and vang.
#3 Tighten main halyard.
#4 Tighten gooseneck downhaul and vang and enjoy the benefits of a tight mainsail luff in strong winds.












HARDWARE
It was found that the original fitting for the boom vang anchor was excellent for the purpose it was designed for (to act as an anchor for the vang, pulling at 45degrees to the mast) but if the pull on it was straight up, it might not stand up to the stresses involved. It was elected to use the aft pivot hole in the mast step, with a 3/8" stainless pin, with sleeves to hold the special fitting on center, to perform as a suitable anchor for a 45degree pull as well as a pull straight up the mast.









The pin is held in place by a pivoting stainless plate that swings out of the way for pin removal or insertion.















The pin and sleeves must be removed any time the mast is installed or removed from the mast step.


















The original boom vang hardware was used ( with the exception of the fitting that attaches the vang to the boom bracket-an improved replacement fitting -HOLT-ALLEN #HA4002- was found).







The gooseneck downhaul was made up of readily available RWO fittings. The original thumb screw lock was replaced with a stainless steel threaded stud (with a 3/16" hole in the outer end) and a sleeve threaded into the original lock threads.










Downhaul attached to gooseneck stud.









BOOM VANG
Having a boom vang that is properly designed for your boat is essential for running before the wind (broad reaching and running).
Without a proper vang that is well tensioned, you will find that the end of the boom will rise as the wind increases when you are running. The more sail area you can present to the wind, the faster your boat will go. A flat sail has more effective sail area than a curved sail on a run.
Another factor to consider is the dreaded "ACCIDENTAL GYBE". If the mainsail , when on a run, is allowed to swing wildly from one side to the other, (if the wind shifts direction) CATASTROPHIC RESULTS could occur.

You may find that
#1 The boat will swing wildly onto the new heading, if you are lucky.
#2 If you aren't lucky, the boat could BROACH and you may find yourself and your crew in the water.
#3 You may also find that if you are still sailing (for the moment) that you have broken some essential piece of sailboat hardware e.g. rudder blade, tiller, pintles/gudgeons or gooseneck.

A gybe under controlled conditions is a very useful sailing technique, an uncontrolled gybe can spell DISASTER.