The Boat
OriginsThe '3.7' was designed by Bruce Farr in 1971 as a single handed trapeze version of his successful 12 and 18 foot skiffs. It is believed he designed the first boat for Greg Elliott's Dad.
The class became established and has become a popular alternative to Lasers and such like for smaller lighter sailors interested in high performance sailing. At the present time over 400 boats have been built, most of them plywood. The 3.7 is a one design hull but with sufficient measurement tolerance to allow for amateur built hulls, which comprise the majority of the fleet. With a minimum hull weight of 50kg easily attainable this ensures the longevity of boats, and some of the oldest are also among the fastest. Bruce Farr's original 3.7 (XL, No. 1) is still racing competitively and is now over forty years old, a tribute to the designer. Although the 3.7 is a restricted rule class with a one design hull, there is plenty of latitude for a bit of ingenuity in other areas, particularly the rig. Various mast configurations are found at the front of the fleet; spreaderless, rotating diamond rigs and fixed spreaders. Since the introduction of carbon fibre spars the performance and ease of sailing has further enhanced the class's growth with new boats. |
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3.7 Tune and Technique Guide
Grab a cup of tea and get into the detail.
So you got yourself a 3.7... Let's get started!
The mast
Mast Rake
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If you have no reference for your mast rake, you can either start from Bruce Farr's diagram, or simply line up your boat level to another 3.7 and copy their rake to begin with. If you're a guru, mast rake will be all about feel... A perfectly balanced boat will have the lightest touch of weather helm which you can dial in over many sails and tweaks. Rule of thumb: Rounding up too much or sailing backwards through your tacks? Bump that rig forward. Bow being driven in too much and tacks a bit too frightening? Bump it back. Enlist a stick into your performance programme and mark your settings.
4mm on a forestay changes the rake quite a bit (check it out and see). Don't try to experiment by the power of your biceps when setting up the mast. The writer's experience is that even though in principle everything should be equal, the forestay sets mast rake, while the tightness of sidestays affects rig tension before it seriously affects mast rake. Sailing upwind, it is definitely the forestay that remains tight, and upwind is where the rake matters most. On the whole, rig tension does not need to be through the roof.
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Mast Stiffness
Mast stiffness is quite important, but it's another dark art specific to sailor style and bodyweight. Most serious competitors will spend a season or two on the rig they get initially, and upgrade to something more suited once they know what they want. Some sailors love a soft rig that does all the work for them, others love a stiff one which they can work precisely. Generally though, if you are a heavier sailor, avoid a soft mast. With HM masts now coming out of C-Tech, there has been a trend towards going stiffer, even for lighter sailors, who utilize their cunningham (and if you're really tricky, a few sets of battens) to its full potential to get a full range out of the sailshape. Softer masts are lightning quick if they are suited for your weight.
Foils
Bruce Farr designed the boat with a centreboard that was raked aft, and had the centre of effort aft as well. But some sailors have made boards that don't get slimmer with depth, and are not raked, and they have gone well in all conditions. Variable rake boards are pretty standard now, and in the ultra-light, gains in pointing and power are made by getting the board raked forward, and as the breeze picks up, kick it back, then pull it up maybe 200mm in the breezy stuff and go for boat speed.
Rudder setup is straightforward. No slop in your gudgeons or your stock, and a fair foil section are mandatory. Gantries of all shapes and sizes exist in the class, with a view to increase high-speed control and allow a bit more mast rake. Those that hang at max length often have troubles staying out of the water when the boat is bow-up, lest the stock be mounted up in the air. On the whole, sailors do get by without them so don't despair if you find a boat without one. They look cool though, don't they?
Rudder setup is straightforward. No slop in your gudgeons or your stock, and a fair foil section are mandatory. Gantries of all shapes and sizes exist in the class, with a view to increase high-speed control and allow a bit more mast rake. Those that hang at max length often have troubles staying out of the water when the boat is bow-up, lest the stock be mounted up in the air. On the whole, sailors do get by without them so don't despair if you find a boat without one. They look cool though, don't they?
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In light conditions, you are either unable to wire upwind, or can pull off a crouch by the chainplates. If your legs are stretched on the wire, move to 'medium conditions'.
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Upwind
Body position
Either:
Do things gently. Remember it is a 3.7m long boat. Throwing your body around in your boat will stop you dead in the water.
- Sit right forward, inside at the front of the cockpit, and heel the boat a little. This gets the transom out of the water and lets the sail fall away nicely.
- Hook into your wire and bring it high. Then with your feet on the centreboard or foot chocks, swing in and out of the boat to balance a heel as far forward as possible.
- Crouch high on the wire right up by the chainpate.
Do things gently. Remember it is a 3.7m long boat. Throwing your body around in your boat will stop you dead in the water.
Sail trim
Your boom is on the centreline. Be careful not to pull the mainsheet in too hard - just enough to get the top of your sail working. A hooked headboard is draggy, even if it feels powerful. Build boat speed first, then take the height - This sometimes means easing the sheet for a bit of go-forward. Pull a touch of vang on if you are beginning to ease the sheet even slightly in light puffs. But in the ultra-light, keep it heeled, keep it sheeted.
Downwind
Body Position
Tucked in, infront of the raised centreboard. In very light conditions, with your leeward hand, keep the boom pressed into the sidestays and try for a bit of windward heel.
Sail trim
Everything off. Maybe a bit of vang on if the boat develops a nasty windward kick in light puffs.
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In medium conditions, you are fully stretched upwind, and able to get a good skip going on the reaches. If reaching gets from beam to broad, and you start stepping back in the boat to avoid harsh chop, move to 'heavy conditions'.
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Upwind
Body position
In lighter medium conditions, centre your body against a perpendicular line off the back of the centrecase. If it freshens up a bit, move your front foot to this line.
Do not drop your wire down too much. In gusty conditions, being able to bend both knees to crouch in will save you becoming a tea bag!
Do not drop your wire down too much. In gusty conditions, being able to bend both knees to crouch in will save you becoming a tea bag!
Sail trim
Try NOT to pull the mainsheet in too hard: this is all too tempting in a boat where you are using your massive thigh muscles to go out on the wire. Once you are out and feeling secure, let the main slip until the top of your sail starts to exhaust.. then pull it in to where you feel that maximum drive through the water. 3.7s love going low and fast before getting height upwind. In these moderate conditions, it requires fine movements, and plenty of practice, especially against other boats.
If you are letting your boom drop down, you need vang on to keep the leech in check. If you have a softer mast, you will run less vang than a stiffer mast, as you don't want to suck all the shape out of your sail.
If you are letting your boom drop down, you need vang on to keep the leech in check. If you have a softer mast, you will run less vang than a stiffer mast, as you don't want to suck all the shape out of your sail.
Downwind
Body position
Move your bodyweight aft, centreboard raised. If trapezing on a reach, stand as far forwards as possible; the bow should be lifted to avoid waves but the stern shouldn't be dragging.
Reaching at speed, or just rolling flat off, you can feel your boat speed up as a wave comes under the stern. Rather than madly throwing your body about and wildly pumping the mainsheet, you may well find you get more benefit by looking ahead for the trough to steer your boat towards. (Done any surfing?) Trim your sail or move your body in order to accelerate with the change in direction as you try to ride the surge. It is boring to just pump and ooch... (And illegal for the matter...)
In the gusts, especially if you are up to planing, try to bear away and head a little downwind. You stay in the gust longer, and your speed is good due to the apparent breeze. As the wind dies away, point up a little: you gain a little boatspeed by pointing up a bit on a reach in the light, and if you move upwind a bit, you spend less time in the hole because the next gust hits you sooner.
Trapezing on a reach can also gain you a lot in speed: once you are out on the wire with that extra speed, the new apparent wind can actually keep you there for a while.. If the gust is really marginal, you may need to point up a bit as you get out on the wire and get your speed up. You should then be able to come back to the right direction at your improved speed, and make some profit.. If, however, the wind dies too suddenly, or you need more practice in apparent wind, you may have been better off to stay stacking, and re-read the previous paragraph... You tend to slow your boat getting on and off the trapeze, so you need to develop a sense of when it is worthwhile.
The 3.7 planes best when it is level - not heeled.
Reaching at speed, or just rolling flat off, you can feel your boat speed up as a wave comes under the stern. Rather than madly throwing your body about and wildly pumping the mainsheet, you may well find you get more benefit by looking ahead for the trough to steer your boat towards. (Done any surfing?) Trim your sail or move your body in order to accelerate with the change in direction as you try to ride the surge. It is boring to just pump and ooch... (And illegal for the matter...)
In the gusts, especially if you are up to planing, try to bear away and head a little downwind. You stay in the gust longer, and your speed is good due to the apparent breeze. As the wind dies away, point up a little: you gain a little boatspeed by pointing up a bit on a reach in the light, and if you move upwind a bit, you spend less time in the hole because the next gust hits you sooner.
Trapezing on a reach can also gain you a lot in speed: once you are out on the wire with that extra speed, the new apparent wind can actually keep you there for a while.. If the gust is really marginal, you may need to point up a bit as you get out on the wire and get your speed up. You should then be able to come back to the right direction at your improved speed, and make some profit.. If, however, the wind dies too suddenly, or you need more practice in apparent wind, you may have been better off to stay stacking, and re-read the previous paragraph... You tend to slow your boat getting on and off the trapeze, so you need to develop a sense of when it is worthwhile.
The 3.7 planes best when it is level - not heeled.
Sail trim
Cunningham still off. Kicker on just enough to stop the leech twisting too much. If there is enough wind to get you planing, use either some kicker or main to tighten your leech enough to make sure you are getting maximum power out of your sail. The extra speed and acceleration you can get from planing better than the others is a crucial factor in this class.
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In heavy conditions, you are getting into full planing and apparent wind territory. Woohoo!
The 3.7 is THE ultra-exciting one-man boat. You can get all upwind thrills while the trapeze allows you to partially relax at the same time. Downwind thrills take all your energy, brainpower and reaction speed..
Tacking: Dump main as you go into the tack, and get across fast as to stop the boat stalling. You should pop out with a healthy ease in the sheet, hook on, and get on the plane as soon as you are on the wire again. Then bring the boat back up to VMG.
Capsizing #1 tip: EASE VANG in recovery!
The 3.7 is THE ultra-exciting one-man boat. You can get all upwind thrills while the trapeze allows you to partially relax at the same time. Downwind thrills take all your energy, brainpower and reaction speed..
Tacking: Dump main as you go into the tack, and get across fast as to stop the boat stalling. You should pop out with a healthy ease in the sheet, hook on, and get on the plane as soon as you are on the wire again. Then bring the boat back up to VMG.
Capsizing #1 tip: EASE VANG in recovery!
Upwind
Body position
Drop that trapeze down as low as you can go. Body positioned with your front foot around the perpendicular line off the back of the centrecase, or even further back if getting into a low-mode in waves.
The centreboard can come up 200mil. Get that boat skipping upwind, drive the boat low and flat.
The centreboard can come up 200mil. Get that boat skipping upwind, drive the boat low and flat.
Sail trim
Compared to most other 1-man boats, the 3.7 tends to plane and perform better in strong winds if you sail free and go for speed, rather than point high up into the wind. Your mainsheet should be eased as to see the boom end on the aft quarter. If the top is inverting when you do this, vang on. The way you trim your sail is dependent on your type of mast:
Both stiff and soft masts have gone well in heavy conditions. Softer rigs are definitely easier on the sailor.
- Stiff masts. The most recent rigs in the class are moving this direction - High vang loads, and flat-cut sails. You adjust the passive power in the rig through outhaul, and actively sheet like mad in the gusts. Pull on max vang and if you are still overpowered, cunningham is the master twist-control, and should be utilised instead of leaking power by under-vanging. Ease a touch of vang for 30kt+ conditions.
- Soft masts. Over-vanging can kill all your power, even in heavy conditions. John Elliott wrote of the soft-mast fashion a few years back: "People are tempted to set their rigs up too powerful so that they can get out on the trapeze as early as possible in moderate airs. You need to make your rig just powerful enough for this, but also still flexible enough to bend a bit, flattening the sail for you when gusts hit in strong winds. Basically, your rig should flex enough for you to be able to cleat the main, and just use a little tiller to keep the boat flat and pointing the right way when the gusts hit."
Both stiff and soft masts have gone well in heavy conditions. Softer rigs are definitely easier on the sailor.
Downwind
Body Position
Reaches on the wire in strong winds are ultra-exciting, and whatever shortcomings the 3.7 may have as a design in other areas, this is where the 3.7 rulz!!
Board half up, traveller (if applicable) right out. In strong winds, use your lower ring instead of the usual upper one, or lengthen your adjustable trapeze wire a little. As you swing way out near the stern of the boat you lift the bow, getting extra leverage and control over the boat, for a truly thrilling ride. (Don't lift the bow like this unless the wind is really strong.)
When dead-running, you'll often find yourself sitting as far back as you can to prevent an unwanted journey down the mine. It is still high adrenaline/thrill sailing, but you tend to be huddled over the tiller at the back of the boat, making critical 1cm tiller movements, and balancing your weight with lightning precision against the hull....
Board half up, traveller (if applicable) right out. In strong winds, use your lower ring instead of the usual upper one, or lengthen your adjustable trapeze wire a little. As you swing way out near the stern of the boat you lift the bow, getting extra leverage and control over the boat, for a truly thrilling ride. (Don't lift the bow like this unless the wind is really strong.)
When dead-running, you'll often find yourself sitting as far back as you can to prevent an unwanted journey down the mine. It is still high adrenaline/thrill sailing, but you tend to be huddled over the tiller at the back of the boat, making critical 1cm tiller movements, and balancing your weight with lightning precision against the hull....
Sail trim
Kicker hard on if you want maximum power - and you can handle a lot more power on a reach than you can upwind. But if you are getting knocked over instead of accelerating (is your board half up?) let your kicker off so that the sail twists, and you sail off the bottom half of it. It is perfectly good (and safer) to do this in strong winds on reaches. But pull your kicker on again for upwind or flat off downwind. Keep the boat vertical. You have less control if you heel the boat at speed.
Basically, if you're feeling the rig kick you to windward when eased, van on to get that leech under control.
Basically, if you're feeling the rig kick you to windward when eased, van on to get that leech under control.
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