Farr 30 Tuning Guide
The Farr 30's carbon fiber rig with swept spreader and no runners has simplified sailing and boat handling but requires some different techniques in rig tuning. To fully understand how to tune the rig, first take a step back and look at what the goal of rig tuning is. The main objective with tuning is to insure that the rig fits the sails and that the sails work together. The mast bend and headstay sag should fit the sails as they were designed. (I'll assume the rig is centered side to side and that it has similar bending characteristics tack to tack, which could be an article in itself).
The basic concepts of setting up the Farr 30 rig is not that different from many other modern boats today. The basic philosophy is to match headstay sag and mastbend to fit the sails and then adjust the rig and sails to keep this relationship similar as conditions change. The key factor in accomplishing this balance is headstay length. The headstay length should decrease as wind increases.
This may seem backwards but the reasoning here is simple. It has to do with rig tension and sail shape not the location of the center of area of the sail plan. Changing the fullness/shape of the sails has a much greater effect on how the boat is balanced than a small movement of the center of area of the sail plan. A longer headstay reduces rig tension and pre-bends the mast. The looser rig allows headstay sag, fitting the jib's design parameters which allows it to set fully. The pre-bent mast allows the mainsail luff curve to fit the mast without using backstay tension to bend the mast. However, as the wind increases, the headstay will sag more. To reduce the sag, the headstay should be shortened. This will flatten the jib, straighten the mast and allow backstay tension to be applied. Doing this will maintain the same relationship between the headstay sag and mastbend.
Let's look at the sails individually. The jib is a tall and narrow sail which is greatly effected by headstay sag. As the headstay sags the jib gets fuller and has more power. This is fine as long as the conditions warrant it. As the wind increases the sail rotates back into the mainsail and starts to spill air into the main causing the main to luff. When the jib sag is greater than it is designed for, the sail acts more like flaps on an airplane wing. The resultant air foil is a high lift but also high drag air foil. To reduce the drag you have two options:
1. Move the jib lead back and pull the sheet in to flatten out the foot.
2. Tighten the headstay to reduce the sag.
The mainsail responds to the mast bend the way the jib responds to headstay sag except in the opposite direction. A full mainsail is similar to an airplane wing that has its flaps down, thus creating high lift and drag. To reduce this drag you need to add bend to the mast thus pulling material from the center of the sail and reducing the depth of the sail. This is accomplished by either tightening the backstay in heavy wind or loosening the headstay and the lowers/D1 in light air.
The goal is the same, get the perfect relationship between the mastbend and headstay sag and have that relationship fit the sail design so they work together.
The approach we use in the Farr 30 is to set up the rig with some prebend. A prebent mast is one that has some fore and aft bend mainly focused in the lower portion of the mast. This occurs without any backstay tension. Prebend is accomplished by the location of the mast butt and the mast chocks. Moving the mast butt aft and the mast chock forward increases prebend. Prebending the mast is a critical aspect of rig tuning for light air performance. Easing the headstay results in lower mastbend (with the mast butt and mast chocks properly positioned) and counter acts the shroud load. This balancing act loosens the headstay with small adjustments of headstay length. A looser headstay fits the jib's designed shape better in light air. As the wind increases the headstay length is shortened thus tightening the rig by pulling the rig forward, removing prebend and adding rig tension. Now with less prebend the mast needs to bend more to fit the mainsail. This is accomplished through backstay tension. Backstay tension bends the mast and adds headstay tension which is desirable as the wind increases.
Now that you understand why we change the rig tuning for varying conditions, let's explore some of the critical controls to play with in the Farr 30 rig. Lets rank the controls in two separate areas. First will be the on the water controls and second will be the on the land controls.
On the water controls:
1. Headstay length, vary + - 1 ¼" total about 2 ½"
2. Backstay, full on to full off
3. Lowers or D1, hand tight to + 5 turns
On land controls:
1. Mast butt and mast chock location HSM=6'
2. Cap Shroud tension, about + 15 turns (32 On Rod Guadge) D1 Tension 17 On Wire Gauge
3. Diagonal or D2 tension, hand tight +3 turns
Farr 30 Rig
With this basic understanding of what to look for while tuning your rig, making the critical decisions of where to put the rig should be easier. Some key items that will help you decide what to do would be as follows:
From the helmsman position look up at the top spreader and estimate where the headstay intersects the mast if you can see the luff tape of the jib the sag is correct. If the luff tape cannot be seen you'll need to reduce the headstay sag. If you see a lot of sail behind the luff tape you should add headstay sag.
While trimming the jib on the leeward side of the boat looking up at the jib the leech should come straight back. If you see the leeward side of the jib the headstay has too much sag. If you do not see any of the leeward side the headstay may be too tight.
For the mainsail in light med air, if the top batten is stalling a lot you will probably need to add some mastbend.
Fine-Tuning the Farr 30 Rig
This two step process that consists of at the dock measurements and sailing tune. At the dock you will want to measure the mast position side to side (athwart ships) insuring the hounds are in the center of the boat and then adjust the mast chocks to keep the mast at the deck is in the center of the boat. Step 2 is completed while sailing, and you will want to look at side bend on each tack.
At the Dock Tuning
To complete step 1; Step the mast with the mast but in the position recommended to fit your sails.
For Doyle sails measure from the center of the lifting ring to the aft face of the mast step to be 4'. A double check for this measurement is from the front edge of the mast to the center of the forward head stay bolt (see reference photos below).
Now that the mast butt is properly located, set the headstay to 5'11 ¾" then attach the backstay and pull some tension on it. Attach the uppers and lowers, hand tightening the uppers but leave the lowers loose. Then release the tension off of the backstay. This is now the starting point, use the topping lift (centerline haylard), as a tape measure and measure the mast position from side to side. This is accomplished by easing the topping lift off until the snap shackle touches the chain plate on one side, then cleat it off. Applying the same tension on the topping lift measure the other side. Adjust the shroud turnbuckles to get the hounds centered in the boat by easing one and tightening the other. Now the mast in centered in the boat the key points to look at are; The D2 or the second diagonals, should be sufficiently slack to allow the center point to move about 1" off the straight line.
By sighting along the luff grove from deck level check that the masthead is directly over the hounds and that the middle of the mast is straight. At the deck place the mast chocks in making sure the lower portion of the mast is straight side to side. Place the fore and aft chocks in at the recommended position to fit your sails. (Doyle Sails like the mast 1/2cm Forward of center) The most important item at this point is to keep the mast in column side to side. You may need to shim the mast more on one side than the other to accomplish this. Now take up 11 turns on each shroud, your D2 should just come taught. You should be able to adjust them by hand still and if they are not even you should adjust them at this point to even the tension out. The lowers or D1 should now have the slack taken out of them to be hand tight. Sight up the mast, it should still be straight from side to side with a little fore and aft bend.
Take up 5 additional turns on the uppers (Bringing the Caps to 32 on the Rod Gauge) the diagonals D2 should just become tight. And the mast should be straight side to side. Take up 6 turns on the lowers D1 making sure the mast is straight side to side. You may need to take up one side more than the other to keep the mast straight side to side (17 on the Wire Loose Guadge). Now you can tighten the forestay to position correct for the conditions and the cut of the sails. Now your set to tune the rig undersail.
With the mast tuned the mast chocks can be place in the mast partners. The for and aft position of the mast should measure 10' 10" from the front edge of the mast to the headstay pin (Generally its 1/2cm forward of centered in the partners). Add chocks to the side of the mast to keep the section in colume. Sailing at Max J is not important.
Place the topping lift shackle to the top of the mast band at the gooseneck. Then swing the topping lift to the forestay and mark its intersection. This mark will be your referance point to measure from. Measure from this mark to the center of the headstay pin. Heavy air min 5' 9 ¾", light air max length 6' ¼".
For most headstays the light air setting will have the turn buckel backed off all most all the way 2 - 3 threads showing, as shown in this photo below.
Tuning Under Sail
Before we look at the mast side to side profile keep in mind the following.
1. The leeward side cap shroud should never become loose while sailing. If it is loose or dangling the rig is too loose, thus causing poor stability side to side and inadequate headstay tension.
2. While sailing the objective of adjusting the diagonal shroud (D1 & D2) is to keep the masthead, hounds, spreader positions in a straight line, when the boat is heeled at least 20 degrees.
While sailing it's very important to check the mast at regular intervals to insure the mast is kept straight, as the tune of the rig can change over time. To accurately test the straightness of the rig you will need wind conditions strong enough to heel the Farr 30 over approximately 20 degrees.
Sailing in upwind trim, with the sails trimmed in and crew hiking. Have one person go up to the mast and sight it two ways. First look up the mast from behind focusing on side bend at each spreader (not fore and aft). Then go in front of the mast and sight up the leading edge of the mast and see if you see the same deflection. Then tack the boat and look up the rig the same way as the other tack. Noting the side to side bend. Diagonal shroud adjustments at this point are simple, but do require some time and fine tuning.
Focus your attention to the rig at the spreaders, if the mast is straight sideways nice job you have followed the instruction perfectly. But most of the time you will need slight adjustments to the rig. If the mast at the spreaders is sagging to leeward the diagonal's at that point needs to be tightened and on the other hand if it is bending to windward the diagonal should be eased. The adjustments should be small ½ to 1 turn and then check the rig tack to tack. Start adjusting the D2's first and then the D1's.
Once you get the rig tune straight make sure you mark the shrouds and the diagonal position with tape or marker and port or starboard if you remove the lowers from the mast. This will help you insure proper tune when you set up the rig again. I hope these hints are useful.
The mainsail has two different modes of tune, powered up and de-powered. The powered up condition is up to about 10 knots (all the crew hiking). In this condition you have a fairly tight leech with the telltales just flying. As the wind increases you start pulling on the backstay to keep the boat on its feet. The mainsheet stays in relatively the same position. As you start to get overpowered, use enough backstay to allow the upper luff portion of the mainsail to luff, freeing up the leech and keeping the boat flat (rail 6" + out of the water).
The photos above show the Farr 30 main in a powered up condition, light backstay and a small amount of mast bend. 3-12 knots.
The photos above show the Farr 30 main in a moderatly depowered setting with moderte backstay bending the mast thus flating the mainsail, starting in 14 knots.
The jib should be trimmed with the aid of leech telltales, marks on the spreaders can be misleading. Put some telltales on the leech of the sail at the top spreader. Trim the jib in until these telltales stall, then let the jib out slightly, allowing the telltales to fly. Make sure you check the jib trim as the wind velocity changes. The Code 1 jib should be trimmed with the use of the in hauler (2-3") in air under 7 knts. The photos below show our light air jib (Code 1) left & med air jib (Code 2) right.