MC Scow Tuning Guide

  • Last Updated: March 10, 2021
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Take the time to check all of your pins, shrouds and spreaders for wear. Clean your mast and spreaders with soap and water or Acetone. Also, please check your wire halyard. Most wire halyards fail near the shackle so please review. Clean and lubricate your sta-master turnbuckles. Also, be sure to tape all pins and spreader ends to prevent tearing the sail.

With the mast on some stands or sawhorses, compare the length of the two side stays. If they are not identical in length the mast will not be in the center of the boat. Lay the shrouds along the side of the mast and adjust the stay masters so that they are the same length down to the bottom bolt.

Check your spreader length and sweep. To measure the sweep, tie a thin piece of shock cord to each side stay and measure to the back of the mast. Less sweep stiffens the middle of the mast, more sweep allows more bend and as a result a flatter sail.

  • Standard Spreaders we recommend 4” of sweep.
  • Max length spreaders (18 inches) we recommend 4.5″ of sweep.

Be sure to install shroud tell tales!


Items you will need:

  • Sharpie
  • Tape Measure
  • P-1 Loos Gauge
  • Tape

Install your sidestay turnbuckles in the forward hole of your chainplates. Ensure the numbers of the sta-master are facing inboard to see them. Tighten the bolts with a 7/16” wrench. Have the bottom of the spar held down on the mast step plate while you walk the spar up. Before you hook up the forestay, lay it along the front of the mast and put a mark where it intersects the top of the black band. Hook it up on the aft hole in the forward chainplate. Measure up from the deck to this mark and adjust the sta master so that the measurement is 742mm or 29 7/32”.

Another way to double-check the rake is to take a 50ft. steel tape measure and attach it to the shackle on the wire main halyard. Pull your rope halyard so that the tape goes all the way to the top of the spar and latch the ball into the halyard lock. Pull down on your halyard so that you know it is locked in place.

Measure down to the center portion of the deck at the stern. This measurement must be taken from the point where the hull and deck meet. The fast measurement for your Z Max, Magnum, and Rocket mainsail is 28’ 3”. Now you are ready to set your side stays.


After you have set your mast rake at 28’ 3” the shrouds will need to be set. Put a P-2 tension gauge on the side stay and tighten each side evenly until the gauge reads 15 units. Then take two full turns off of each side. This is a good base tension setting.


MAST RAKE With a 50’ tape, have your AP mast rake set a 28’ 3”
SIDESTAY TENSION 15 on Loos gauge minus 2 full turns (Base setting)
SIDESTAY PLACEMENT Place sidestay in forward hole on chainplate
  Sitting on Leeward Full time on deck, not hiking Just starting to hike Max hike, overpewered
MAST RAKE 28’ 3” 28’ 3” 28’ 3” 28’ 3”
UPPER SHROUD TENSION Base lets a 1/2 turn BASE Base plus 1/2 to 1 full turn Base plus 1 to 2 full turn
OUTHAUL Remove wrinkles,
slight shelf on foot
No wrinkles,
more shelf on foot
Pull to black band,
defined shelf on foot
Max outhaul
CUNNINGHAM None None Full cunningham tension None
OUTHAUL / CUNNINGHAM DOWNWIND Cunningham off / Outhaul eased Cunningham off / Outhaul eased Cunningham off / Outhaul eased Cunningham off / Outhaul eased
VANG TENSION UPWIND No vang tension Vang tension in puffs 75% vang Full vang tension. Pull hard!
VANG TENSION DOWNWIND No vang tension Just enough tension
to straighten leech of sail
Play vang downwind w/ waves. Eased when by the lee, pull on when higher Play vang downwind w/ waves. Eased when by the lee, pull on when higher
TRAVELER Centered Centered 0-6″ below center 6-9″ below center
BOARD HEIGHT All the way down, 103 degrees
flush with deck
All the way down, 103 degrees
flush with deck
1″ above deck 2″ above deck
BOARD HEIGH DOWNWIND 1/4 way down 1/4 way down 1/4 way down 1/4 way down


Your new North Mainsail is the fastest around the track. By following the guidelines noted below you will optimize your chances for a distinct speed advantage over your competition. You can make the sail full and powerful or you can flatten the sail so that your MC is easy to handle in the breeze. Please practice the following techniques and watch your MC sailing improve!

One thing to mention is that the driver will want to always sit forward in the boat (right next to your mainsheet cleat) in all conditions, upwind or downwind. Only move aft when the bow tends to submarine in big waves.

The order in which to adjust your sail controls will be in the order described below. Please follow this sequence in order to achieve the ultimate speed with North MC Mainsail.

FULL POWER (0-8 mph)

Your North Mainsail will be fast in this condition.  You are trying to get the boat to maximum heel to where you start having to use the hiking straps to hike the boat down.


Before sailing it is best at some point to turn the boat on its side to measure and mark the board angle. First, check to make sure the board cannot hit the front of the case by pushing forward on the board and adjusting the line in the cleat accordingly. Then take a protractor and measure the angle. We suggest 103 degrees is a full down angle for the boards in light air. Mark each side on the deck so that you can easily repeat this angle while racing. Also, take time to mark the boards for downwind. Pull the board up so that the aft knuckle is just tucked into the hull. Having these marks will ensure that the board is even from tack to tack and allow for optimum sailing.


You want to heel the boat to reduce wet surface area and also to get the boards basically vertical. Use the leeward rail as your guideline in all wind conditions. Maximum 15 degrees of heel is what you are aiming towards.  Never allow water to run over the edge of the leeward side rail.  When you over heel the boat develops too much weather helm and you go slow.  CONSTANT ANGLE OF HEEL IS KEY FOR SPEED!


In the light air, most MC racers choose to trim and head up the moment they get new pressure. The exact opposite is the case if you want to go fast. When you get hit with a puff you want to ease a bit, keep the bow down, go for speed and then trim the main. After this, you can head up and point a little higher. The #1 goal is to achieve boat speed in this light air condition.

Mainsheet Trim

The mainsheet is your accelerator. Never cleat your mainsail. Always have the mainsheet in your hand so that you can trim in the pressure and ease in the light spots. Constant mainsheet trim / working is key to ultimate boat speed. Put a good mark on the sheet where you can see it so that you can easily repeat fast trim settings. In the very light air (when sitting on the low side) a great reference for mainsheet trim is to have the back of the boom over the back leeward corner of the boat. As you get more wind trim from there and feel the sail and boat respond. If the boat does not respond then ease your sail back out. You will see a response in the boat from the angle of heel.

TIP – Install the 5:1 mainsheet system. It allows you to hold the sheet easier and also allows for finer adjustment!


Your outhaul should be fairly tight along the boom. You should have a shelf in the sail even in these light conditions, especially if the water is very flat. Pull the sail to the inboard edge of the white band on your boom end. This creates a small wrinkle-free shelf foot and is very fast. This will help you with speed and pointing. In very choppy conditions you might experiment with a little less outhaul tension to help power up the boat.


Do not have any vang tension on at all. In fact, be sure your vang is un-cleated so that when you ease your mainsail your vang does not tension up. This is very important while working your mainsail upwind. Vang should never be applied in such light conditions.


Be sure this sail control is off so that there are horizontal wrinkles in the luff of the sail. You want these wrinkles in this type of wind condition.


Keep your traveler on centerline at all times. The only time you drop the traveler down is when you are fully hiked out and you cannot hold the boat down.

Downwind Sailing

Once you have rounded your weather mark be sure to pull your leeward board up 75% of the way up. Begin to look for wind behind you. Speed is king downwind and the only way to have speed is to be in the breeze. Set yourself up so that you have clear air and that you are in line for more breeze moving down the lake. This is very important.


You must heel your boat to leeward in order to reduce the wetted surface area in these conditions. The end of the boom should be kissing the water. If this is not happening you are not maximizing your speed.

Your mainsheet trim is critical as well. Just like upwind, you absolutely must work your mainsheet downwind. Grab your mainsheet directly from the aft block on the boom. This eliminates the ratchet and it gives you quick and direct pull.

In the very light air you must reach the boat more so that the boat picks up speed. Heel and head up to generate speed while trimming in your main. As the boat builds speed begin to head down, continue to heel the boat and begin to ease your main back out. The second the boat feels like it is going to slow down, repeat the process. In order to go fast downwind in the MC you must work just as hard downwind as you do upwind. Stay prepared to keep the boat moving and always be looking for fresh wind.

Traveler is centered, vang off, Cunningham off for maximum power.

Outhaul must be eased so that the shelf is gone. Do not ease to the point that the foot of the sail has vertical wrinkles.

Powerboat waves: Always trim in and build up speed so that you can blast through waves. If they are very large you can pull on some boom vang so that the rig stays snug and so that the boom stays in place. Be sure to uncleat the vang after the waves have passed.


The MC can be overpowering (difficult to hold down upwind) for some sailors. By following the set up described below you will begin to see major speed improvements in your MC sailing. Practice these things so that you are smooth and prepared for the change in velocity.


Be sure that the head of your boards is flush with your deck or 1” up as the wind increases. Pulling the boards up helps reduce weather helm. Some sailors have success pulling them up as much as 2 inches when it’s really windy.


Again, the benchmark is your leeward rail. Never allow this to get wet while sailing upwind. As the wind begins to build, you must hike harder, use your sail controls to flatten the main and then feather the boat lightly into the wind with your steering technique.


For maximum speed you need to really work the boat. Hike in the puffs in order to hold the boat down. However, always keep your back vertical to the water or just aft of vertical so that you can see your horizon line. The horizon tells you just how much heel is indeed on your MC. Also, by being vertical you can trim and ease your mainsheet helping you to balance your boat.

Mainsheet Trim

You can trim harder in these conditions so long as you can hold your boat down. Once you become overpowered in this wind range you must begin to ease your mainsheet in the puffs. You never want the boat to overheel. When the boat does heel up you must have boom vang on so that the sail remains flat as you ease the sail. In this condition, you should sail off the angle of heel. Meaning, if you have to ease your mainsheet a foot in order to help hold the boat down then do this. The worst thing you can do is trim hard, overheel and then stuff the boat into the wind. By easing the mainsail you are able to sail at a ‘fast angle’ –not stuffed into the breeze. The boat will accelerate and begin to build speed. Never cleat your mainsail. Constant angle of heel translates into constant fast speed.


The foot of your sail should have a shelf in it which you achieve by pulling your outhaul maximum outboard. This helps to flatten the bottom portion of the main, which is quite full. Make sure you pull on this hard taking the sail to the inboard edge of the black band on your boom end. Do this before your leeward buoy rounding.


Due to different weight ranges we will all become overpowered at different times. Overpowered again meaning that it is difficult to hold the boat down. So, someone weighing 150 pounds will become overpowered in 10 m.p.h. of wind where someone weighing 200 pounds will become overpowered in 15 m.p.h. of wind.

As soon as you become overpowered you need to apply your vang so that the mast will bend and the sail will flatten. Also, now you can ease your mainsheet so that you can keep the boat from over-healing in the puffs. The more wind the more vang you will need to apply going upwind.


With the North designed mainsails you can apply much more Cunningham in order to flatten the sail. By applying the Cunningham you will move the draft of the sail forward and the sail will become much flatter overall. This too will bend the mast when pulled on hard – helping you to point. When it becomes very windy you must pull the vang on very hard.


As the wind builds you can drop your mainsheet traveler as much as 6”. Mark your traveler track so that you know the distance. Once you have dropped the traveler, pulled on your vang and Cunningham then you need to work your mainsheet in the puffs, easing when the boat wants to heal too much.

Downwind Sailing

With the breeze up now it is time to sit on the high side going downwind. You do this to eliminate helm on the rudder. When sailing downwind in these conditions you want the weather board to be down ¼ of the way. The leeward board is all the way up.

Upon rounding your weather mark or offset you will want to adjust the board first and then ease your outhaul so that the shelf in the foot is gone. When sailing straight downwind be sure to ease your mainsail so that it is all the way out. Your boom will actually rub against the sidestay.

As the wind builds, apply more and more vang. Downwind this becomes the stabilizer for the boat. When the boat feels very jumpy or tippy, apply more vang in order to stabilize your boat. Vang is crucial to downwind speed and acceleration. Please work your vang in the puffs. Applying more as the wind hits and the boat speeds up. In the lulls, ease the vang. Always keep your weight forward and outboard. Lean out as much as possible so that the boat rocks up downwind. This helps to reduce the wetted surface area and it prevents you from ever nose-diving in large waves or chop. Even lean out when adjusting your boards after a gybe. The board lines are tied together so that you can sit on the high side, lean out and pull the leeward board up. Doing these types of things make a big difference over a long race.

Most important, always look behind you for the next available wind. Staying in the wind makes all the difference. However, being in the breeze will help even more. Be aware of the new wind coming down the lake.

CONTROL & DE-POWER (15-25 mph)

The Z Max, Magnum and Rocket mainsails are truly the best all-around sails because they can be flattened in these conditions. You can bend your mast and flatten your sail for great upwind speed and control. With the custom material we have chosen for the body of this sail, you really can have 2 sails in one. You can flatten this sail to be just like a heavy air sail. Follow along and see what you can do to reach better performance and have more control in this type of wind condition. One of the very best things that you can do, of course, is to go out and practice in this wind range so that you feel comfortable in the boat. Your boat handling will improve for all conditions as well.


Raising the board in this breeze can be advantageous. Especially if you are sailing alone. Please try moving the head of the board 2” above the board box. Or on the new boats watch the line move 2 inches forward as you pull up. We feel that you will experience less helm and more maneuverability. This is a good thing to try and to practice.


Over-heeling is the biggest mistake made when it is very windy. When you have all your sail controls on hard you must “feather” the boat into the wind. Do not stuff the boat – you must keep the boat moving fast through the water. Easing your mainsheet as much as 2 feet may be needed in order to keep your boat on the proper angle of heel. Do not be afraid to ease the sail this much when it is windy.


The mainsheet is your accelerator in light air and the controller of your angle of heel in the heavy air. Practice not cleating your mainsheet. Have the mainsheet in your hand and be able to ease the sail in the puffs and trim back in as the puff leaves. This will de-power your boat. The Z designed mainsails are a flat sail when all of your sail controls are pulled on so now it is up to your mainsheet tension and steering to keep the boat on its lines. Hiking out is important as well. If you have a crew in these conditions make sure to call out the puffs early so that the crew is fully hiked before the breeze is on.

Mainsheet Trim

There is no set trim guideline in this much breeze. You do not need to trim hard that is for sure. With a lot of vang on you can ease the sail as much as 2 feet and not loose any speed at all. The mainsheet just controls your heel in this much wind. So, if you are over-heeled then ease until the boat settles down. While easing keep the boat on its lines – a normal course. Do not stuff the boat into the wind because then you will stop. Sail the boat fast by easing the main. Always feather the boat into the wind.


Pull hard out to the black band on the boom. Never ease in from this point with this much velocity.


When you are trimmed in going upwind you need to pull the vang hard. This will bend the mast, flatten the sail, and then open the leech. The boat will become very controllable. You may need to ease this a bit on the tacks and always be sure to ease the vang at least an arms length before rounding the weather mark. Otherwise you could bend your mast.

Vang tension is very critical in heavy conditions like this. Apply plenty when racing upwind. At the start, it does hurt your pointing ability so you may want it eased a bit, but not completely off.


Pull this as hard as you can. The sail will flatten right out, especially along the front of the spar. You could never pull too hard on this control in this much wind.


You can drop this up to 9” if it is this windy and you do not have the weight on the boat to hold it down. If you have a crew do not drop the traveler more than 6”. When sailing alone you could go 3” further. Set this control, leave it, and then work your mainsheet.

Downwind Sailing

Certainly, in this much wind you must reverse heel the boat. Your board should be dropped just ¼ of the way down. Do not sail downwind with both boards down. It is slow and it could cause you to tip over upon maneuvering.

Apply vang downwind so that the boat is more stable. However, be sure to not over- steer on your gybes. The boom could catch the water and take you for a swim. To be safe, ease the vang a bit before a gybe in big air. Leaving the outhaul on when it is windy will not hurt your downwind speed. So, do not worry about this control. Worry about being in the wind, sailing safe and going fast.

When you are sailing in waves keep your weight in your normal position. To avoid nose-diving just lean out so the boat is heeled. This will help to prevent nose- diving. If you see a big set of waves do not be afraid to trim in and head up 10-15 degrees to reach around them. Trim your sail, accelerate and then head down with your extra speed after the set of waves.

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