420 TUNING GUIDE
The mast step should be se at 9'-4 1/2" when measured from the transom along the floor of the boat to the back of the mast. Usually this places the butt of the mast in the first pin hole from the front.
To measure the rake hoist a tape measure to the top of the mast on you main halyard. Lead the tape measure over the top of the transom down the aft face of the transom to where the transom meets the bottom of the boat, For club/junior sailing the rake should be adjusted to fall between 2l'-6 1/2' for light winds and 20'-9 1/2" for heavy air, near survival conditions. Note that the shrouds and, therefore, the rig tension should be adjusted as well, as the rake is altered for varying wind conditions.
In general in heavier winds and as you become overpowered, rake the mast farther aft which will twist open the leech of the jib and depower the sail. This has the same effect as moving the jib lead aft. Raking the mast aft also moves the center of effort aft, which makes the boat naturally head up into the puffs instead of being blown over sideways. Heavy crews (over 270 lb.) will want to rake aft in higher wind velocities because they can use the extra power. Lighter crews (under 240 lb.) will tend to be overpowered sooner and should rake aft in lower wind velocities. Here is a good rule of thumb. If your boom is consistently out beyond the corner of the boat to maintain the boat balance when sailing upwind, you should rake the mast farther aft. In light winds you want the rig raked farther forward. In heavy winds it is necessary to rake it aft. Since you are not able to adjust the shrouds as the rig is raked aft, the result is a looser rig, but one that is still better balanced with depowered sails. By itself this set up is fine, but be careful of overtensioning the boomvang in a breeze. Too much vang tension without the tighter rig and mast blocks (see section on following pages) will lead to excessive headstay sag and overbending of the mast. This creates a jib that is too full, a main that is too flat and a badly balanced boat. Instead sail with a looser vang in heavy winds. With the vang more eased the mainsheet will control the amount of twist (the angle of the top batten to the boom). You can depower quickly by easing the sheet and twisting the main more open. This makes it easier to quickly balance the boat and pop it up on a plane when sailing upwind in a breeze.
The tension of the rig is effected through shroud position and channel adjusters and tension of the jib halyard, It is measured off the 1/8" sidestays with either the new Loos model PTI tension gauge or the older model A tension gauge. (These gauges are very helpful in tuning your Club 420.) While they are valuable in setting the tension close to that of other boats, they will only give relative tension numbers. We have found wide variances, even with new gauges. Take note of what we describe as the goal in setting the rig up with the proper tension. Remember, use the Loos gauge to got dose to the, specified tensions. If in doubt, use your gauge to measure the fastest boats and set your boat up accordingly!
While sailing your Club 420 in club/junior racing, your rig tension should be varied from 240 lb. in fight winds, to a maximum tension of 360 lb. in near survival conditions. When the rig is tensioned properly for upwind sailing the leeward shroud just starts to go slack (definitely not "dangling").
For the collegiate sailors, since you are not able to adjust your shrouds, go ahead and read on.
The best method to change your rig tension while on the water between races is to ease the jib halyard until the forestay is just taking all the load. This will allow the mast to fall back enough that it should be fairly easy to adjust the position on the leeward shroud. When completed, tack and do the other side, On some older boats it may be necessary to add an extender to the forestay to allow the rig to drop back enough to change the pin position. To pull the rig back forward, use the 3 to I purchase on the jib halyard, bowstringing the halyard above the purchase then taking up the slack created with the 3 to I purchase. For lightweight crews or those low in strength, it may be difficult to change the rake and rig tension on the water. Some may find it helpful to tension the jib halyard through placing your feet on the bow while the crew tightens the halyard inside the boat.
Mast blocks are usually not supplied with the boat. Mast blocks are either wood or plastic spacers that are cut to fit into the mast partners in front of the mast, Placing mast blocks in the slot in heavy winds will help prevent the mast from overbending too much down low. In fight winds mast blocks are not at all necessary. As the breeze builds, especially when more boomvang tension is applied, the mast will bow forward. if unrestricted it can bend too much below the spreaders. Overbending creates two major problems. First the jib luff will mg more which reduces your boat's pointing ability and it will overpower the boat by making the jib too full. Secondly, overbending the mast down low will overflatten the main in this area and greatly reduce its drive and power. Ideally in windy condition where the boomvang is tensioned, mast blocks are placed in front of the mast in the partners to the point where they fill up the space less about 1/8" to 1/4". If there is the possibility of a capsize, be sure to use some type of retaining line or duct tape to hold your blocks in place.
When sailing collegiately, unless the entire fleet is fitted with mast blocks and their adjustment is specifically allowed, this tuning technique is not applicable.
When sailing upwind the centerboard is usually in its maximum down position. In the near survival conditions when the boat is greatly overpowered, it is helpful to pull the board up as much as 2 or 3 inches to balance the helm and make the boat easier to steer. Downwind and on a reach with or without the spinnaker, the board should be positioned high enough so that the helm (whether the tiller "tugs" or "pushes") is neutral. If the board is down too far and there is too much windward helm the boat will tend to "trip" over the board and will not plane as fast.
Main Top Batten Tension
While the proper tension on the upper batten is not critical, it is important that the batten is neither too loose or too tight, Ideally the batten would be tensioned just until the vertical, perpendicular wrinkles to the pocket are just barely removed. Overtensioning the batten past this point will make the sail too full and the leech will be too closed. Undertensioning the batten in heavy winds will allow the batten to slide aft in the pocket and the leading edge will poke through the front of the pocket.
Tension on the luff of the main will affect the draft position and to a lesser extent the depth of your mainsail. A loose luff with wrinkles all the way from tack to head is necessary in fighter winds to allow the draft to move aft and flatten the entry of the main. In heavy winds tension the luff until the wrinkles are almost completely gone. This will help maintain the proper draft position, You can adjust the luff tension on your Club 420 main with either your main halyard or cunningham. If you expect to be sailing in a constant, relatively unchanging condition (is that ever possible?!), then it may be best to use the main halyard to tension the luff of the main. On the other hand, if the conditions are puffy yet still leave enough time to adjust the luff tension, you may want to initially set your main halyard so there are slight wrinkles all the way up and down, Then use your cunningham tension (through the grommet just above the tack), to fine am the luff tension for the proper wrinkes and draft position.
For lighter winds tension the outhaul until vertical wrinkles just disappear and the sail is smooth. As the breeze picks up and the boat becomes more overpowered progressively tension the outhaul. The foot tape on the bottom of the sail should be standing straight up from the boom in very windy, near survival conditions. Downwind if there is an opportunity to adjust the outhaul, case it until the bottom of the sail is just smooth.
Be conscious of overtensioning the outhaul in any conditions, as this will overflatten the bottom of the sail and depower the boat which harms the boats pointing capability.
Ideally the mainsheet should be tensioned so that the last 18" of the top batten is set nearly parallel to the boom (sighted from underneath the boom looking up the sad vertically). Trimming the mainsheet harder will hook the top batten in relation to the boom which will provide the boat with short bursts of pointing ability at the expense of power and acceleration. Easing the sheets so that the top batten twists open (falls away) from parallel to the boom will compromise top end speed and pointing ability, but greatly increase the boat's power to punch through waves and ability to accelerate out of a tack. The mainsheet will never just be cleated and left alone. It is one of the more critical adjustments on the boat. Play it constantly to allow the boat to point and power up and to sail with a balanced helm.
Downwind the boomvang is tensioned just enough so that the last 18" of the top batten is nearly parallel to the boom. Be careful of overvanging in fight winds and undervanging in heavy winds.
Upwind in fight winds, the vang needs to be loose enough so that the leech Will twist open (upper batten angled outboard) to help the boat drive through waves and accelerate out of a tack. The Yang should not be totally loose as this will compromise the boat's speed and acceleration out of tacks. The vang should be set loose enough so that when the mainsheet is eased out the upper batten a good 15 to 20 degrees open from parallel to the boom, but no looser.
As the breeze picks up, increase boomvang tension to help bend the mast and flatten the sail. At maximum boomvang tension there will be slight overbend wrinkles running from the mast toward the clew of the main. These should be just below the spreader and just barely evident in the heaviest of winds, In very heavy conditions, near survival, it may be advantageous to ease tension on the vang allowing the top of the main to twist way open reducing heeling moment.
Jib Sheet Tension
The jib leads are fairly far outboard which makes it necessary to use windward sheeting in fight to medium winds to bring the lead closer to the centerline. The leeward sheet is d in tight until there are slight creases from the tack to the clew. Trim the, windward sheet hard enough so that the creases just barely disappear (approximately 1 1/27" to 2"). In light to medium winds when trying to accelerate ease the leeward sheet and not the windward sheet. In breezy conditions do not use the windward sheet.
An overtrimmed spinnaker will close the slot between the spinnaker and the main. It will not only make the boat sail much slower, but the spinnaker will also become more difficult to fly. Set your pole topping lift height so that it is roughly parallel to the horizon. In light winds it is necessary to lower the pole, in a breeze raising the pole will keep the 2 clews even. Set the pole position nearly perpendicular to the wind when selling on a broad reach or a run. A telltale on the topping lift 1 ft. up from the pole will greatly aid in setting the proper angle of wind to pole position. Finally, ease your halyard off the top of the mast approximately 6" to help open up the slot between the spinnaker and the upper sections of the main.
Upwind in very light winds the helmsman should sit just in front of the traveler with the crew placed just forward of the centerboard thwart. In medium winds the helmsman will move aft slightly just straddling the traveler. The crew will be anywhere from just behind the thwart to just forward of the helmsman. In a breeze the helmsman will move aft of the traveler. When on the trapeze, the crew will have his/her aft foot just forward of the helmsman's body. When hiking the crew will be just forward of the helm and hopefully leaning aft and angled behind the helmsman. Remember to keep the weight centered so the boat proper balance through chop.
STEP 1. MAST STEP 2790 - 2810mm
Measurement from the inside of the transom to the pin retaining the aft of the mast heel.
STEP 2. SPREADERS L = is the length of the spreader from the side of the mast to the side stay.
P = is the Poke or deflection of the spreaders, measured using your top batten across the shrouds at your spreader tips to the back edge of your mast.
1. Hoist the tape measure up your mast. Adjust the halyard and lock it when the tape reads 4900mm to the top of the lower black band near your goose neck. This is very important!
2. With no chocks (CHOCK) in the mast gate, pull the rig tension (TENS) on until it reaches approximately 40 on the Loose Guage. Now take the tape measure to the transom and see if it measures between 19’101/2” to 20’0”. If not, adjust your chainplates (CHAIN) to achieve this ball park measurement. Most chainplate fittings have 2 sets of holes, and the front ones should be referred to as F and the back as B.
STEP 4. CALLIBRATING YOUR “HOOK”
Once done, then pull the rig tension on until you get the most upright rake setting to suit your weight as listed below (dia.1.2) At this point, you should put a mark on the side of your mast where your jib halyard connects to your rig tension system. THIS IS THE “HOOK”. From this mark, working downwards put 4 additional marks every15mm and working upwards an additional 5 or so. Then number each of the marks from top to bottom. Alternately, you can use “stick on” calibrations that many fitting companies sell.
STEP 5. CALLIBRATING YOUR RAKE & TENSION SETTINGS
Now simply work your way down each RAKE setting, recording your CHAIN, HOOK & TENS on the draft easytune chart provided. If you cannot achieve ball park tensions for the rakes prescribed, you may have to change your CHAIN until you get it right. (go down for more tension, same rake or up for less tension, same rake)
STEP 6. PREPARING TO CALLIBRATE CHOCKS
Once your settings are finalised, tip your boat in it’s side, and with your most upright rake setting, measure the mast bend, with NO chocks at spreader level. This is done by placing your main halyard to your goose neck at the aft side of the mast, and tension it. Then measure the bend from the aft side of the mast to your halyard. You should have at least 30mm of bend with 0 Chock. If not, wind your spreaders back a little. Remember, every boat is a little different!
STEP 7. CALLIBRATING CHOCKS FOR MAST BEND
This “0 Chock” setting at upright rake has now become your 0 – 5 knot setting. Next, go to your 5 – 12 knot setting, and add chocks until the mast becomes straight – 10mm of bend. Record the number of chocks on your chart required to achieve this. From here, simply remove 1 chock for each increased wind range.
PLEASE NOTE – Chocks control mast bend and therefore mainsail depth. The above settings are guides only and you may have to adapt how much “POWER” you get from your mainsail “DEPTH”, via the “CHOCKS” to suit your weight, sea state, wind conditions etc.
STEP 8. CALLIBRATING THE CENTERBOARD
While your boat is on it’s side, pull the centerboard all the way down. You should notice that it is raked forward in this position. Put a mark on the back of the C/B “handle” on the inside of the hull at this maximum down setting and label it “8”. At 30mm increments mark another 3 settings labelled “7, 6, 5”. Now pull it up until there is 400mm protruding under the hull. Put a mark or draw a line on the centerboard, on the INSIDE of your boat to record this position, and label it “4”. Repeat the process at 300mm, 200mm and 100mm.
THIS WILL ALLOW YOU TO GET A FEEL FOR C/B POSITION. AS A GUIDE: 0 – 14 KTS
14 - 18 KTS 7 – 6
18 – 22 KTS 6 – 5 +
SETTINGS WILL CHANGE WITH CREW WEIGHT, SEA STATE, GUSTINESS OF WIND, AND POWER IN THE RIG. TRIAL AND ERROR WILL SEE YOU BECOME FAMILIAR WITH YOUR FAVORITE “NUMBERS”!
Damian Saponara Sailing Coach
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