Spreader Sweep (Chris MacMurray)

Adjusting Spreader Sweep


Adjusting spreaders on the Jet-14 is a methodical procedure. It involves setting the spreader tip height on the stay, sweeping the spreaders naturally with rig tension, measuring to ensure even spreader sweep, pinning the spreaders, and checking the rig under sail in moderate winds.
Before starting, here are the materials and tools you will need.

Two simple foil spreaders about 17 inches in length. These are about $20 a set from Dwyer,
Two 3/32 inch copper stop sleeves – $2 for four at West Marine,
Tall ladder,
25 foot measuring tape, and
Masking tape.

Before starting on the mast, take a copper stop sleeve, place it a vise, and hacksaw longitudinally to the center hole in the sleeve. Repeat this with the other stop sleeve. Now set these aside. These sleeves will be used to keep the spreader tips at a constant level which will help with consistency in adjusting the rig.

Next, remove any spreaders attached to the mast. Step the mast, connect the shrouds and forestay, and raise the jib. Remove all chalks or release pusher-pullers at the partners. The idea is to allow the mast to float fore and aft as tension is applied or removed. Make sure the mast is snug athwart ships. Tighten the rig, but apply no measurable tension.

Set the ladder to reach the spreader bracket. Climb up with the foil spreaders and insert them in the spreader brackets. Affix the outboard ends to the shrouds. The spreaders should butt against the mast and be positioned as deeply in the brackets as possible. DO NOT PIN them at this point.

Next level the spreaders. Apply just enough jib tension to allow the spreaders tips to slide up and down the shroud and remain where they are placed. Level one spreader by eye. Crimp a copper stop sleeve on the shroud so it prevents the spreader tip from dropping. Be careful not to nudge the spreader tip while you are doing this. Measure the distance from the spreader tip – as it butts against the copper stop sleeve – to the shroud base.

Take the second stop sleeve and lightly crimp it on the other shroud at the spreader tip. The light crimp should allow the stop sleeve to slide on the shroud with sufficient friction to allow adjustment. Measure from the spreader tip to the shroud base. If the measurement is the same as the first shroud, crimp the stop sleeve in place. If not, adjust the stop sleeve and spreader tip achieve this. When you are satisfied the two measurements are equal, crimp the stop sleeve in place.

Now adjust the spreader sweep. Further tension the rig. Tensioning without the spreaders pinned allows them sweep evenly regardless of whether the spreader bracket itself is positioned squarely on the mast. Tension the rig until the distance between spreader tips is approximately 32 inches. Measure this from shroud to shroud at the spreader tips. Rig tension at this point may be significantly greater than when you sail. That’s OK. This is a spreader sweep adjustment only. Measure the distance from the shroud at each spreader tip to the center of the transom. You may need some masking tape to hold the tape in place. The distance from each spreader tip should be equal.

Step back from the side of the boat about 30 feet. With one eye sight with the shroud bases in range to the hounds. The shrouds should remain in range all the way to the top. If the measurements are not equal or the shrouds sight out of range, make sure one of the spreaders is not constrained in the bracket. Also check the distance between the forestay and shroud bases is equal as is the distance between the hounds and the shroud bases.

When you are satisfied with the alignment, climb the ladder, drill and pin the spreaders in the brackets. Double check the measurements to the transom and sight the shrouds to ensure they remain in range. Label each spreader as port or starboard, the length, and sweep distance, eg, port 17x32.

Finally, take the boat for a sail. If the mast sags to leeward between the shroud base to the hounds, make up a separate set of spreaders that are slightly shorter, maybe 1/4 inch. If the mast bows to windward, make up a separate set of spreaders that are slightly longer, maybe 1/4 inch.

Also look at the bend wrinkles in the sail close hauled in moderate winds (10-12 knots). If bend wrinkles are prominant above the spreaders, move the spreaders forward. If wrinkles don't appear until well below the spreaders, move the spreaders aft.

Adjust the spreader sweep of any new spreaders in the same manner described above. Keep all your labeled spreader sets. You may be able to make adjustments for crew weight and different sails with these. I currently have three spreader sets: 17x32, 17x32.5 (the one I'm using) and 17x33. Additionally, I have one set of spreaders that are not drilled should I want a different sweep any time in the future.

Chris MacMurray
Jet 1145

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