Mast Tuning 101
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MAST TUNING 101
(December 1996)

The first in a series by John Clark of JC Sails, Kingston.

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The Shark attracts many sailors looking for quality One-Design sailing, as it is an easy boat to handle, crew weight is not critical and it has an affordable price tag. Whether you purchase a used or new boat, you will usually find solid construction in each alike. Many of the older boats are equally as competitive as the recently built boats for example, the current Shark World Champion was built in 1969. There have been three builders of the Shark, Hinterhoeller, C&C and Halman There are slight variations among them, but no true favourite exists. Each of the builders have produced boats that win at regattas. With a strong Class Association, regattas are well attended after some 25 years since its inception. The Class continues to work diligently at bringing the boats in line to provide for a true One-design racing class. So whether you start with an old or new boat, here are my suggestions for a deck layout and tuning guidelines, designed to assist you in achieving the most out of your Shark.

Getting Started

If you're new to the Shark fleet, the most important consideration is weight (the boat's, not yours). Although the class is in the process of bringing all of the boats to a common "all-up racing weight", it still has to be considered at the present time, the most prominent feature. There are many older boats which have never been weighed, so it is imperative that you get a hold of the scale through your regional measurer. A word of caution however, some of the early boats are extremely light and fast, but their bulkheads will be on their way out and will require replacement. The keels, constructed of cast iron, can at first glance appear extremely crude and rusted, but with effort can be brought up to norm and seated. The rudders, in the past five years, have taken on numerous shapes and forms, and have improved the performance and handling of the boat considerably. There are some reputable rudders on the market, or like many Shark sailors, you can build your own. The new rudders are elliptical and are being constructed of a variety of materials from mahogany to Laminated plywood to foam-core carbon fibre. In any event, you will always have the benefit of shared knowledge if you need to consult fellow Shark sailors

 

Tuning Up

Check your mast before you put it on your boat. First, make sure your spreaders are fixed and have no wobble. Second, the jumpers must be adjusted. Lay the mast on two wooden horses, back side down. Now tighten the jumpers by hand until they are snug. Sight up the mast from the bottom end and re-adjust them to make the mast straight. Use a string if necessary. Place two fingers on the jumpers 6" above where they join at the mast near the spreaders. You should be able to touch them to the mast without much effort. If your mast is already up, tighten your backstay until it is approximately 3/4 on, then tighten the jumpers to hand tight.Release the backstay and check to make sure the top of the mast is straight.

Once the mast is up, loosen off both shrouds to check the amount of mast rake. To do this, put a tape measure on the main halyard and hoist it up to the top of the mast. Measure to the centre of the wood combing on the transom. Your measurements should be within 1" of 30 ft.

Now it is time to find a constant on both sides of the boat. Take a measurement from the tack pin to. a point where the deck meets the hull on each side of he boat near the shrouds(don't use the shrouds as they are probably not in the same place form one side to the other). Now measure from these points to the bottom of the mast and the top of the mast, to ensure that the mast is not only in the centre, but straight as well. Start tightening your shrouds careful to get the mast straight. Sight up the mast to make sure it is straight and use the main halyard putted down to the gooseneck for a reference if necessary.Once the mast is straight, tighten the shrouds equally until you carry between 150 and 200 lbs. on the lowers and 400 to 450 on the outers, using a tension gauge. Again, these are middle of the road settings. In lighter air, we will carry 150 on the Lowers and 250-300 on the outers.

Now it's time to go sailing and check the rig with the sails up. Sail upwind in approximately 12 knots of wind.Sight up the mast and check for bend (side to side). You should see a relatively straight mast. If anything,the top will bend off to the leeward side. If you see the middle bending to Leeward or the top bending to windward you need to tighten tighten your towers or Loosen your uppers. If your mainsail is older and fuller, loosen your uppers. If you have a new mainsail, tighten your lowers.

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