Racing - tuning a 707

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Tuning

Ian Brown

The 707 is undoubtedly the ‘Sport Boat’ success story thus far, with its main strength being ease of operation and tight class rules. The class limitations on sail inventory make the boat simple to sail, fun, and affordable. With each of the three sails having to cover the whole spectrum of sailing conditions, it is important to be able to get the most out of them at all times. As with all tuning guides, this is just that, a guide. This information should not be taken as absolute. It is impossible to sail strictly by the numbers. Trim and tune are dynamic, requiring constant changes to get the most from the boat. It is more important to understand the concepts behind tuning and the effects of the different controls so that you can learn how to shift gears. Keep an open mind and experiment in changing conditions to determine the right combination for the moment, or simply what works for your sailing style. There is no one way to make your boat go fast. The single most important thing is to recognise when you are slow and to do something about it.

Rig Tune and Basic Set Up

There are three goals to achieve in basic set up:

  • Set forestay to maximum length
  • Centre the mast in the middle of the boat and ensure that the mast is in column athwartships
  • Set the correct amount of pre-bend and forestay tension for the conditions.

Forestay tension and mastbend are the key variables in adapting the rig setup to specific conditions. As with all fractional rigs with swept back spreaders, forestay tension is directly related to shroud tension. Strong winds require a tighter overall setup with more pre-bend. Medium winds call for a fairly tight rig with a straighter mast. Very light airs call for a softer rig but with more pre-bend again. In all conditions the forestay length should be set to maximum. Remember that in addition to keeping the mast in column side to side, the cap shrouds also help to control forestay tension, and the lowers act like checkstays and control mastbend. With this in mind the following should provide a sound starting point:

  1. Mast rake: Class rules prohibit the addition of toggles or any other means of altering the length of the forestay as supplied with the boat. However, the forestay should be set as long as is possible, thus providing maximum rake. With the rig tension set to base settings (see below) the distance from the top of the mast to the after edge of the transom should be 10.80m (this measurement was taken by hoisting a tape measure on the main halyard with the shackle pulled up hard to the sheave)
  2. Centre the mast: With the rigging fairly loose hoist a tape measure on the main halyard and measure down to a point at the chainplates on each side of the boat. If the measurement is the same both sides (or within a few millimetres) the mast is upright. Once the mast is upright, you can begin to tighten the cap shrouds, making sure that you wind an even number of turns on each side. Wind on about 8 turns past hand tight. Now you can begin to wind on the lowers, again winding on an even number of turns each side, but making sure that the mast is straight side to side. Winding turns on the lowers will straighten the mast. Put enough turns on until you are left with about 70 mm of pre-bend (you can check this by sighting up the aft edge of the mast).
  3. Shroud tension: Your mast should now be upright in the boat with approximately the right amount of pre-bend in it. The shroud tensions now need to be fine tuned. Using a Loos gauge (rig tension meter) the cap shrouds should be tensioned to read 37.5 measured at eye height. The lowers should be 35 at eye height, and this should give a forestay tension of about 34. Using these measurements, the pre-bend should remain at about 70mm. The critical measurement is the pre-bend, do not worry if the tensions are +/- a little. These measurements should be regarded as your ‘base’ settings.
  4. Rig tension for conditions: Remember that what we are trying to achieve is pre-bend in light air but with forestay sag, pre-bend in heavy air with as little forestay sag as possible, and a straighter more powerful rig for the medium airs. Use the following table as a guide

True Wind Speed

Lower Shrouds

Upper Shrouds

0-8 knots

Ease 3 turns

Ease 1 ½ turns

8-12 knots

Base setting

Base setting

12-18 knots

Base setting

Tighten 2 turns

18 knots +

Base setting

Tighten 5 turns from base

These changes are made for two reasons; firstly to control mastbend, and secondly to control forestay tension.

Upwind Trim: The Jib

Taking any single headsail through the complete sailing wind range is difficult since no one shape is perfect for all conditions, and so it is necessary to have a wide range of trim settings. In the 707 there are four tools at your disposal to control sail shape: halyard, sheet tension, jib lead position, and forestay tension.

  1. Halyard tension: In normal conditions (10-12 kts) use just enough halyard tension to remove the ‘scallops’ between the hanks. Halyard tension should be eased as the breeze drops, and in less than 10 knots of breeze it is o.k. to have scallops in the luff. This makes the entry finer which will help with pointing, and will also power up the back of the sail. In lighter conditions it is better to be slightly slack than over tensioned. As the breeze increases, you need to use more halyard tension. This will round up the entry, which makes the steering groove wider and will also flatten the exit of the sail, which in turn de-powers it. Small high aspect jibs such as that used on the 707 are prone to ‘going round’ as the breeze increases, which produces excess drag causing the boat to heel over. Using lots of halyard tension helps to prevent this. It is vitally important that your jib halyard is marked so that you can easily re-produce fast settings.
  2. Jib Sheet Tension: the jib sheet is perhaps the most important headsail control and must be played constantly, easing to accelerate, trimming to point. Sheet tension will change with every change in wind speed, but the basic premise is to trim as hard as possible without slowing the boat down. Remember speed first, then point. Adjustments are not as frequent in steadier breeze, but the sheet still needs to be adjusted for changes in wave patterns or to duck other boats. Sails can be sheeted harder in flat water than they can be in lumpy seas for the same windspeed. If you are fast sheet harder, if you are slow, try easing it slightly. Remember that small changes in sheet tension make big changes to the sail because it is so small. Quite literally, a ½ inch change in sheet tension can be the difference between fast and slow.
  3. Jib Lead: The base setting for the jib lead should apply equal tension to the foot and the leech of the jib. On the 707 this should be with 2 holes showing from the aft end of the track. Moving the car forwards from this closes the head of the sail and makes the foot more round. Personally, I would never move the car any further forward than this when sailing to windward, and would have the car in this position up to about 12 knots of breeze. In 12-20 knots of breeze move the car back one hole, which will flatten the bottom of the sail, and de-power the top of the sail. In more than 20 knots of breeze move the car back as far as it will go. Remember that these figures are guides and will differ depending on waves and sailing style. Basically, as you become over powered, move the lead aft, and do not worry if the top tell tales don’t fly properly as you open the leech up. If your jib is trimmed so that the whole sail is working, but the mainsail is flogging to keep the boat on its feet, ease the jib. Give away the top of the sail to balance the boat allowing both sails to do some luffing.
  4. Forestay Tension: In light conditions you will need more forestay sag to make the jib fuller and this is achieved through loosening the lowers and cap shrouds as detailed above. Similarly, in heavy conditions the rig is tightened which tightens the forestay thus helping to prevent forestay sag. This de-powers the jib and helps pointing. Remember we said that we needed pre-bend for windy conditions to de-power the main, and this was achieved by tightening the cap shrouds. You could actually achieve pre-bend by loosening the lowers instead of tightening the caps. The big disadvantage of this approach is that you end up with excessive forestay sag which is exactly what you are trying to avoid.

Upwind Trim: The Mainsail

The first thing that you notice when you step aboard a 707 is the absence of a backstay. In some ways this restricts the amount of control that you have over sail shape, but in other ways it makes the other sail controls even more important. Mainsail trim has two primary goals. First, balancing speed versus pointing by controlling the twist or how open the leech of the mainsail is. Second, keeping the right amount of overall power, helping to maintain a constant angle of heel and the right amount of weather helm. This section will address adjustments to mainsheet, traveller, outhaul, halyard, cunningham and vang.

  1. Mainsheet: like the jib sheet, there is no one magic setting for the mainsheet. It should be adjusted continually with each change in wind speed and/or wave pattern. Basically, increasing mainsheet tension reduces twist and tightens the leech, which makes the boat point, but also slows it down. Easing the sheet induces twist, which accelerates air flow across the sail. This allows the boat to bear away and accelerate. Initially, the main should be sheeted until the top batten is parallel to the boom. At this point the top tell tale will be on the verge of stalling but should be flying about half of the time. Once the boat is up to speed, increase sheet tension until the boat starts slowing. Remember, speed first then pointing. The art is to find the delicate balance between speed and pointing, always trying to trim as hard as possible without giving away too much speed.

    In light air, the sail will be eased and twisted from the base position. In moderate air the sail will be sheeted hard with the top batten at least parallel. In heavy air the sail should be sheeted as hard as the angle of heel will allow. Bear in mind that in choppy seas, more twist is required to keep the boat moving, and on flat water you need harder leeches for pointing. Broadly speaking, the biggest mistake that people make in moderate conditions is not enough sheet tension. I am 5’11" and weigh the best part of 14 stone, and when the boat is fully powered up in 10-15 knots of breeze I physically cannot pull the mainsheet on hard enough. The mainsheet should be pulled on hard enough so that the top tell tale is only flying about half the time. When it is windy, the mainsheet also helps to bend the mast, which flattens the sail. This means that if you ease the mainsheet in the gusts, the mast straightens and the sail becomes more powerful, which is exactly what you are trying to prevent. It is possible to help control this with careful use of the traveller and vang.

  2. Traveller: the traveller serves two functions. Firstly, it controls the booms position relative to the centreline of the boat, and secondly it helps to steer the boat by controlling the helm and angle of heel in the puffs and lulls. To position the boom, set the twist with the mainsheet and use the traveller to put the boom on the centreline for maximum power and pointing. In light air the mainsheet will be eased to promote acceleration and keep the leech open and the traveller will be well to windward to keep the boom close to the centreline. In moderate conditions small adjustments will be necessary to control helm balance. It is important to dump the traveller quickly when a gust hits and you begin to get over powered, but equally important to pull it back on again as soon as the heel is controlled or the gust has passed. Wait too long and you have missed the opportunity to point once the boat has accelerated. As the wind speed increases the average position of the traveller will be further down the track. In over about 18 knots of breeze you may need to ease a little mainsheet as well. However, before you ease mainsheet in windy conditions you need to have the vang pulled on hard to prevent the mast from straightening too much. Think of the traveller as the ‘tip meter’ once the mainsheet has been set for twist. The traveller should be adjusted with every change in heel or any time the mainsheet is adjusted.
  3. Vang: the vang is primarily an offwind control. It takes over the job of pulling down and providing leech tension when the boom is eased out and the mainsheet no longer controls twist. However, upwind in heavy air the vang should be used to help out the mainsheet with the job of pulling down the boom and maintaining leech tension. If the vang is hard on, the mainsheet can be eased in big gusts without giving up the leech and without straightening the mast too much. In light air make sure the vang is off using only enough tension to stop the boom from bouncing. In heavy air it may be necessary to ease the vang at the weather mark to assist with bearing away. Easing the mainsheet may not be enough.
  4. Luff tension (halyard and cunningham): halyard and cunningham both tension the luff. Initial luff tension should be just enough to smooth out the wrinkles in the front of the sail. Leave a few wrinkles in the bottom third of the sail in light to moderate air. As the breeze increases more luff tension is required to prevent the draft in the sail from moving aft. Use the halyard first, and when the sail is at the black band use the cunningham. Do not under estimate the usefulness of the cunningham, it is one of the primary sail controls that many people choose to ignore. As soon as the boat is overpowered start pulling the cunningham on hard upwind. It is easier to adjust and fine tune the cunningham when sailing than the halyard.
  5. Outhaul: the outhaul controls the depth in the lower third of the mainsail. If you need more helm and feel, ease the outhaul. Power in the bottom of the main will increase weather helm. In light airs (less than 5-6 knots) the outhaul needs to be pulled out fairly hard in order to prevent flow separation in the mainsail. If the sail is too full in light airs it will stall. In 7-12 knots the outhaul can be eased slightly to increase power. Once the boat is fully powered with all the crew hiking (normally about 12 knots of wind) the outhaul should be maxed out. The outhaul should not be eased much when running, the object is maximum projected area. The outhaul should be eased however when reaching (unless you are over powered). Make sure that you have the outhaul calibrated so that you can repeat known fast settings (make sure all sail controls are calibrated for the same reason!)

Downwind Trim

As a relatively small all purpose deign, the spinnaker requires a variety of trim techniques in order to get the most out of it across the breadth of sailing angles. This is actually made somewhat easier by the fact that most racing now is windward-leeward which is far more tactical than reaching everywhere. The key to running effectively is to project as much area to windward as possible away from the mainsail, thus facilitating sailing deep. Do not get pre-occupied with having the clews at the same height as depicted by most sailing guides. You should start by altering the pole height so that the luff of the sail isn’t breaking too high or too low. You should then set the leech accordingly by using the tweaker lines. Pulling the tweakers on will stabilise the spinnaker when it is windy but don’t overdo it or the sail will stall. Use the centre seam as a guide to trim, which should be approximately perpendicular to the horizon. If it feels right it probably is right. The main thing when sailing downwind is to make sure the spinnaker is pressured up all the time. The trimmer and helmsman should be talking to each other continually so that the helmsman can get the boat really low when he has pressure and he doesn’t sail too high when he needs more pressure. Twisting the mainsail will also help you get deep, but at the same time it will make the boat more unstable and less forgiving. Be prepared to adjust the vang continually downwind and sail where you are comfortable. Sailing downwind is at least as tactical as sailing upwind with huge gains to be made by sailing at the right angles on the right shifts. If you tack on shifts going upwind you should gybe on them going downwind.

The crew should be well forward in light air, gradually moving aft and to weather as the breeze builds. The boat should ideally be heeled slightly to weather when going downwind which helps to project the spinnaker and helps the boat to drive off in the puffs. Weight should be shifted to stabilise the boat and promote surfing and planing in heavy air. When it is breezy all the crew should be well aft, with one person being allocated as ‘vang man’ to de-power and power up the main as necessary.

Miscellaneous Tips

  1. Crew weight upwind: sail with a constant angle of heel, and with as little weather helm as you can stand. Generally this will mean sailing as flat as possible. In light air the weight should be to leeward and forward to induce feel and helm. In less than 5 knots of breeze it pays to put a couple of crew members down below particularly in sloppy conditions when it will help prevent pitching. Once the boat is powered up with all the crew hiking, the furthest forward crew member should be sat immediately aft of the shrouds, with everybody else sat as close as is comfortable. Again keeping the crew weight together helps to reduce pitching (a common mistake in many boats is to have the bowman sat forward of the shrouds). There is no weight limit in the 707 class, but you are allowed to sail with a maximum of five people on board. You will be disadvantaged if you do not have five on board even in light airs. In boat speed terms the difference between having four and five people is probably about 0.2 or 0.3 knots upwind. This does not sound like much but 0.2 knots equates to 400 yards an hour which is approximately 130 yards in a typical 20 minute beat!
  2. Remove all unnecessary items of kit from the boat. Encourage the crew to bring only what they are going to wear. You don’t need to have a pair of boots and a pair of shoes on the boat for example. Stow any spare kit, fenders, fuel etc underneath the cabin step. This is approximately where the balance point of the boat is.
  3. Make sure the bottom is clean and smooth. The rules require the boat to have a coat of anti fouling, but this can still be rubbed down smooth with increasingly fine wet and dry paper.
  4. Make sure that all sail controls are visibly calibrated so that you can repeat known fast settings. This includes halyards and sheets.
  5. Similarly, put marks on the spinnaker pole controls so that you can pre-set it accurately before hoisting.
  6. Put a cover over the jib halyard at the point where it goes through the jammer. Maintaining halyard tension is vital when it is windy and most halyards will gradually slip as you progress upwind.
  7. Keep an open mind and do not be afraid to experiment. Perhaps the most important point to recognise is when you are slow, and then to do something about it!
  8. Have fun!

Resources

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For news, tips and chat visit one of our active Facebook groups

707s on FaceBook
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707s on FaceBook
Scottish 707 Facebook Group

2016 AGM Documents

2016 Minutes

Rachel Alvarado's
YouTube videos

Added March 2017 - A series of 3 winter talks from the guys at the front of the Scottish 707 fleet- Upwind, Downwind and Starts.

Talk 1
Talk 2
Talk 3

2012 Northerns
Spinnaker Rigging
Spinnaker Handling

Class Rules

The current class rules can be found here (pdf file)