Nirvana Race Tuning

Nirvanas are uniformly produced and regulated by a rule that prevents owners from modifying their boats in such a way as to gain a boat speed advantage.  Therefore, to get the best boat speed for the conditions, you need to understand tuning.

Tuning is a skipper skill that is learned and perfected with practice. Not all successful sailors agree on every aspect of tuning, but we generally agree on the basics.  Exact settings are not useful – it is the concepts that count, along with building experience.

 

Vocabulary/Definitions

I have laid out some terminology so that we are all talking about the same parts.

Stays – Stays run fore and aft on the Nirvana. They adjust the top of the mast forward and back. The forward stay is called the forestay! How odd. It can also be correctly called a jib stay in this case because it runs through the luff of the jib.

Shrouds – Often referred to as side stays but that is generally because you have forgotten the word Shroud. These lines/wires support the mast sideways.

Sheets – These are the lines that trim the sails. The line to the jib is the jib sheet, and the line to the mainsail is the mainsheet.

Outhauls – These are lines attached to the clew (lower, rear corner) of each sail. We have two lines attached to each clew on each sail. The aft one is the outhaul, the other is a leech tension line, or take down. Outhauls on Nirvanas are normally attached to O-rings on their respective booms.

Halyards – The line that holds the sail up.  In models we don’t actually have running halyards, per se, since we never lower the sails.  Instead we just tie them up, but for reference, that is the halyard. These lines are attached to the top (head) of each sail.

Downhauls – Downhauls are not generally needed on Nirvanas.  The stiffness of polyethylene sails does not allow the sail to bunch up along the luff, nor is the downhaul capable of stretching the luff (polyethylene does not stretch).  If used at all, a downhaul is simply a preventer to keep the luff of the sail down in place.  There is no downhaul on the Nirvana as produced.

Rake – Rake indicates the lean of the mast fore and aft. Not to be mistaken with mast bend.

Twist – If you look up (or down) the leach (trailing edge) of each sail, twist is the curve from side to side. A lot of twist appears as an “S”, where very little twist is nearly straight.

Slot – When sailing to windward (into the wind), slot is the amount of space the wind has to pass between the jib and main.

Balance – For the purposes of this article, balance refers to how well the boat self steers. A perfectly balanced boat has a small, but noticeable, demand to turn into the wind if the steering is left neutral. See Weather Helm.

Weather Helm – is the tendency of the boat to turn into the wind – actually the amount of weather helm is measured in the amount of effort put into holding the boat in a straight line. If you are turning your rudder any sizeable amount to prevent the boat from turning into the wind, the rudder is causing unnecessary drag slowing the boat down. To correct, you need to “balance” the boat.

Sails – The three edges of the sail are: leading edge – luff; trailing edge – leech; bottom edge – foot.  The three corners are: top (luff/leech) – head; bottom (luff/foot) – tack; bottom (leech/foot) – clew.

Draft – In this tuning article, draft is the amount of belly/camber placed in the sails by moving the outhaul connection on the boom forward ~ not the other meaning for draft (the amount of water that your boat needs to keep from running aground).

Boom Vang – When the wind strikes the sail, the boom wants to rise, allowing the sail to “twist” out of shape. The jib pivot attachment provides a cantilever effect to keep the rear end of the jib boom from rising but the mainsail needs a physical line connected to the boom and the bottom of the mast. That is the boom vang.

 

Tuning Concepts

These concepts are the same for most boats whether models or crewed boats.

Balance – For optimum performance, a boat must be balanced so that it has a slight tendency to turn into the wind if steering is left in a neutral position. If the boat turns away from the wind, or turns violently into the wind, balance is not correct.

Balance is affected by quite a number of variables. But we will only address those variables that you can adjust easily, mainly the rigging and the sail set.

The overall effort of the sails is consolidated to a single point called the “center of effort” (CE).  For you, the CE is someplace, and it is not worth figuring it out.  All you know is that you can adjust the CE forward and aft by changing the angle of the rig.

The boat itself has a center of collective forces, but you cannot change that as the position and size of the rudder, keel, and the shape of the hull are all fixed in the original design.

So all you can adjust is the rake (lean) of the mast, and the trim of the sails (draft, angle).

Specifically, there are three adjustments that move the center of effort of the sails fore and aft – the draft of the sails, the rake of the mast, and the position of the jib (forestay).

Rake – If you find that your boat has too much weather helm (wants to round into the wind violently), your rig may be raked too far aft.   (top of mast behind the foot of the mast). If your boat tends to turn away from the wind when your steering is centered, then you have lee helm. In this case, your rake is too far forward.

I highly recommend with Nirvana that you stand the mast straight up and down to start, as best you can see it – not leaning forward or aft. In this position, the boat is fairly well balanced in most conditions.  Step back from the boat and view the mast in relation to the keel fin.  They should be parallel.

To adjust rake, concentrate on the direction you are moving the head of the mast.  Move forward if you want to lessen weather helm, aft to increase.  How much is the question.

You can only know this by actually sailing the boat.  It helps to have a steady breeze the day you experiment so that the wind velocity factor doesn’t muddy the waters.

One thing I like to do is test the extremes, so I will normally rake the mast forward about an inch from vertical.  That should produce a marked difference in helm.  And then slowly move the rake aft until I get the desired gradual heading to windward with the rudder in neutral position.

Jib Pivot – We all jest over what the pivot line that connects the jib boom to the foredeck is called. Some call it the jib tack, some the jib takedown or downhaul, some (like me) simply call it the jib pivot. Whatever you call it, the deck fitting it attaches to cannot be moved (by class regulation), but the connection to the jib boom can be made adjustable. As the boat is delivered, the jib pivot line is tied through a hole in the jib boom, but you can substitute a string ring connector to help with what follows.

If the pivot is further back on the boom, then that means the sail is further forward in relation to the boat. The sail being further forward moves the center of effort of the jib further forward, which, in turn, moves the entire sail plan’s center of effort further forward. Remember that moving the center of effort further forward lessens weather helm, the same as raking forward.

Draft – Drafting your sails is a double-edged sword. In light winds, you need to draft your sails (put belly in them) because these sails have no shape of their own. Curvature (draft) is power to drive the boat through the wind and water in lighter winds.   Another aspect of draft is that it moves the center of effort aft – increasing weather helm.  This is fine in light winds but when the wind starts to blow harder, if you don’t remove draft from your sails, you will find your boat fighting to head into the wind (weather helm) and she will bog down with all the rudder drag.

To put draft into your sails, move the clew adjustment ring on the booml forward.  This will allow the foot of the sail to develop more curve (camber) while maintaining leech tension. On the Nirvana, as initially rigged, the outhaul goes to an O ring which you slide forward. The leech tension line stays a fixed length (around the boom and through the clew grommet)

Drafting is done on both sails with more draft used in light winds and less and less as the wind velocity increases. You will know when to reduce the draft in your sails by the trouble you are having steering the boat.

Sail Twist/Boom Vang – The rig on the jib boom of a model is considerably different that on a crewed boat.  The jib pivot is connected part way aft on the boom.  Therefore the tension on the forestay at the forward end of the jib boom uses the jib pivot to cantilever tension into the leech of the jib which helps with sail shape in most wind conditions.

Often we talk about leech tension on the mainsail using the term “twist” ~ more twist or less twist. So let’s make sure you know what you are trying to do with the amount of twist you allow.

Generally, in light winds you want very little twist in the leech of your mainsail. That is because the leech of the sail is your driving force to windward and you need the sail from bottom to top. As the wind increases and you start sailing the boat with the rail down, it is wise to add more twist. This allows the top sections of the sail leech to “open”, spilling wind from the top of the sail. This keeps the driving force of the bottom of the sail while spilling wind up high where it does more to heel the boat compared to driving it.

Two things affect twist in the mainsail. The first is the angle of trim on the outhaul. If equal tension is placed on the foot and the leech of the sail (45 degree angle on outhaul), then the leech of the sail will tend to twist more because the leech of the sail is much longer than the foot.  So in light winds, sliding the outhaul forward a bit will put more tension on the leech than on the foot, keeping the twist in the sail to a minimum.

Second is the tension on the boom vang. The boom vang holds the boom down which maintains the tension you have set in the leech of the. Without the boom vang, the boom will rise, slacking the leech and cause the sail to lose all power.  When talking about the jib, the jib pivot cantilever acts like a boom vang keeping the leech taught as the wind increases.

The only variation to keeping the boom vang set tight is in rough seas or puffy wind. In these conditions, the boom vang should be slackened slightly to allow the sail to twist (breath). As the boat hobby-horses through the waves or is hit by puffs, the sail will twist and straighten which pumps the boat through the water, while keeping her on her feet.

 

Boat Speed

As I mentor other model sailors, the thing I emphasize most is BOAT SPEED!!! Without boat speed it doesn’t make any difference how good a tactician you are, or how well you have tuned your boat.

So what is boat speed – how do you measure it? Unfortunately when you are out sailing by yourself, you don’t always recognize subtle differences in boat speed. So you usually need to be sailing with another boat close by so you can gauge relative boat speed. There are some visual clues that you should learn, things you can see when you are not right next to another boat.

Heel angle – Often when you are sailing to windward, the angle of heel is an indicator of whether you are sailing with your sails at the right angle of attack (angle to the oncoming wind).  It is possible to sail on an angle too close to the wind, but still with the sails not luffing.  In this case, it is the change in angle of heel that is the indicator.  So whenever your boat is sailing along and then stands up, only two things can be the reason.  One is that the wind, or the boat, has changed direction and the pressure in the sails has reduced because the angle of attack is not correct.  You will hear the term “pinching” to describe sailing too close to the wind.  Your reaction must be to turn away from the direction of the wind slightly and see if the boat heels again and picks up speed.

The other reason for an abrupt decrease in angle of heel is that the wind has momentarily decreased.  So if you turn away from the wind as above, and the heel does not increase, resume your original heading until the wind returns.

Unfortunately, observing the angle of heel does not help sailors understand that they are not pointing high enough (close enough) to the angle of the wind.  In this case, your sails are full, and they look good, and you have an angle of heel based on the wind velocity.  Even though the sails become less efficient in this position (to big an angle of attack), it is not boat speed that is the problem but the boat direction.  So if you are sailing with other boats, and you are sailing at a different angle to the wind than a boat near you, and about the same speed, the boat sailing closer to the wind will clearly arrive at the windward mark first.

Both the issue of sailing too close to the wind (small angle of attack), and two far off the wind (wide angle of attack) is almost impossible to read in the sails.  In the “too close” to the wind issue, use heel to help you.  In “too far off”, you must rely on others sailing near you to see if you are close enough to the wind.  Of course a good technique when sailing to windward is to occasionally head closer to the wind to see for sure that you are maintaining your proper angle of attack.  If you head up and your boat stands up, you know you were sailing at the best angle of attack, and you should immediately fall off and continue sailing.  This is often called “feeling” for the wind.

I have not mentioned telltales.  Properly placed telltales can help you with being too far off the wind, but do practically nothing to help you with being “too close” to the wind.  When you are too far off the wind telltales attached to the jib will show you by “winding up” the leeward telltale.  When both jib telltales are streaming you know you are close enough to the wind, but unfortunately, they will both stream if you are headed right into the wind!

Side-slip. If you see your boat going slightly sideways compared to similar boats nearby – we sometimes call this “crabbing”, you need to slack your sails a little, turn away from the wind slightly, and get your boat speed up. Proper boat speed keeps the fins in the water (keel and rudder) from stalling. When the boat slows and you have wind pressure in the sails, the fins can stall causing side-slip or crabbing. You will learn to see this and avoid it.

Over steering – Many sailors slow their progress with way too much steering.  Practice steering with a steady hand so that your boat changes direction without jerky movements.  Rapid steering adjustments are just like putting on the brakes because when you turn the rudder quickly, it drags through the water momentarily.  Besides, there is less distance between two points if you sail a straight line!

Practice, practice, practice – Adjustments to your boat and proper handling based on your visuals of the boat, all take practice. NOTHING takes the place of “stick time”. The more you sail, the more you will learn the visual clues talked about here. You will learn the adjustments we have spoken about above because you will have done some trial and error. And, you will have learned to keep your Boat Speed up so that your boat will handle better and win more races for you. Good luck.

Your comments or questions are always welcomed, as I can never seem to remember everything I want to write.  But these guides will help you get to the top of the fleet if you practice, practice, practice!!!!