This comprehensive tuning guide will give you the key information
needed to stay in the front of the Sonar Fleet whether you are sailing
at local or national level. Our sails are designed with proven
technology in cloth as well as shape to insure durability and speed on
the race course. Our sails are also designed to keep things simple in
order to give you the confidence that is needed to keep your head out of
the boat while sailing in close One Design competition.
Before Stepping Mast
1. Forestay should be 25' 11" when measured from the bearing point of
the Tee fitting aloft to the centre of the turnbuckle clevis pin.
2. Clean and lubricate turnbuckles.
3. Spreader angle, set deflection at 2 3/4 - 3" (To get proper
deflection measure from the back face of the mast to a line extending
between the holes in the spreader tips, this distance should be 2 3/4 -
After Stepping Mast
1. Adjust partner to fit snugly side to side (so mast is centred.)
2. Mast step, measure the distance from the aft face of the mast
where it meets the step casting to the gel-coat edge of the centre of
the cabin opening lip near the floor. This should be set between 28 1/4"
and 28 3/4". (Ontario boats only).
3. Next, measure the distance from the forward edge of the mast
partner opening to the centre of the headstay anchor point. The class
rule limits this dance to 7' 11.5".
Fine Tuning the Rig
1. Centre the mast laterally using a tape measure on the jib halyard to a common spot on the port and starboard rails.
2. Remove any mast blocks as well as the lower shrouds from the chainplates.
3. Remove the slack from the backstay until the headstay just becomes
taut (no mast bend). Place a mark on the deck abeam of the aft face of
the mast. This is your reference point in the relaxed state.
4. Now pre-bend your mast at the deck with mast blocks on the aft
side until you have moved the mast 1" forward of the mark. Make a new
mark and erase the old. This is the new "Neutral" position.
5. Next, you want to tension your upper shrouds in equal increments
on both sides to between 230-260 pounds using a "LOOS-Model A" tension
gauge (cable size is 5/32" or equivalent). See Tension Gauge Conversion
Chart. Check the mast laterally again by repeating step #l.
6. Finally you want to attach the lower shrouds and adjust them so
that you can make 8 to 10" circles with them at shoulder height. This
requires some guess work but loose lowers are required to keep the tip
of the mast in column when you are sailing. Minor adjustments should be
made to your lowers when you first go sailing by sighting up the mast
track and tightening or loosening the lowers to keep the rig straight.
Now you have a great starting point and adjustments will be made from
and relative to this position depending on different wind strengths and
Trimming your North Sonar Sails
It's important to mark all your shrouds, sheets, tracks, outhaul,
backstay, etc. Keep records of your tuning set-ups for different
conditions in order to be able to reproduce settings when you know the
boat is going fast.
You want to make six 1/2" wide plastic blocks from the template shown
below, this will give you the proper amount of blocks to take up the
extra space and allow you to block the mast according to our chart.
Blocking is measured from the aft face of the mast relative to the
Mast blocking has two profound effects. First, the more blocks you
put behind the mast the less headstay tension you will have and the more
the headstay will sag. This results in a deeper and more powerful jib
for light and lumpy conditions. Secondly, blocking in front of the mast
will create more headstay tension thus a flatter jib for windy
conditions. The second effect is relative draft position of the lower
part of the main. In lighter air blocking to induce pre-bend (behind the
mast) will remove forward draft and decrease the depth of the sail. In
heavy conditions you will want to block in front of the mast in order to
power up the bottom part of the main in order to help you through
rougher seas. Remember blocking in front also gives you more tension on
the headstay for a flatter jib.
Trim the mainsheet hard enough to make the top batten parallel to the
boom. You can check this by sighting from underneath the boom on a
vertical plane. Once the boat has accelerated and you want to point
higher, trim harder (2-3") to cock the top batten slightly to weather.
If the mainsheet is too tight (evident by the top batten hooking to
weather), you will slow down. In light air and choppy water the top
batten should be parallel or twist off slightly. You may want to mark
your mainsheet somewhere in the middle so you have a nice reference
point for mark roundings and upwind sailing. Pull the traveller car to
windward until the boom is on the centreline. To check this have your
crew sight aft along the boom and line up the centre of the boom with
the eye that attaches the backstay to the boat (this should be in the
centre of the transom). Keep the boom on the centreline up to 12 knots
and gradually drop the traveller to keep the helm and heeling under
control as the wind speed increases. The lens foot allows the sail to
act as a loose-footed sail. Upwind the lens foot should not be fully
open. To set your outhaul properly, use the following guide:
0 - 5
Eased 1 1/2 inches
6 - 10
Eased 1 inch
11 - 14
Eased 1/2 inch
This chart is based on settings relative to the black band
On reaches and runs the outhaul is eased 1 - 2".
The cunningham is used to position the draft in the main. Your goal
should be to keep the maximum draft position 50% back in the sail or
just slightly forward of this. In a new sail we use no cunningham up to 6
knots, enough to remove most of the wrinkles in 7 - 14 knots and
progressively tighter in higher winds so there are no wrinkles. Pull the
cunningham very hard above 18 knots to move the draft forward in the
top of the sail. Under most circumstances you do not need much backstay
tension. The exception would be in breezy, extremely puffy conditions,
particularly when combined with flat water. In these conditions, you can
use the backstay as a power control. Pulling the backstay on reduces
the power in the mainsail up high by opening the leech, thus reducing
heel and weather helm. Remember backstay has a large effect on luff sag,
a tighter backstay equals less luff sag, more luff sag makes the jib
entry fuller and moves the point of maximum draft back, this is best in
light air and flat water. As the breeze freshens, a straighter jib luff
produces a flatter jib entry. Use the boom vang downwind and on the
reaches to control the amount of twist in the mainsail. The twist should
be the least amount that still permits attached flow at the upper
batten tell tail, stalling is unavoidable. From 100 degrees or so to a
dead run set the vang so the top batten is parallel to the boom. Your
mainsail is equipped with a leech cord, the primary function of the
leech cord is to prevent the leech from fluttering. In windy conditions
tension the leech cord to prevent the leech from fluttering. In light to
moderate conditions pull it just tight enough to eliminate flutter.
Your North Sonar jib does not have a wire in it. Therefore luff sag
is controlled by headstay tension (see blocking and backstay section of
this tuning guide). Luff sag is measured as an offset from the centre of
the jib luff to a straight line between the head and tack of the jib.
To trim the jib correctly you must have the lead in the proper fore and
aft position. This is accomplished by moving the lead forward or
backwards until all three tell tails on your jib lift at the same time
as you begin to pinch the boat above a close hauled course. If you find
that the windward tell tail on the top of the sail lifts before the ones
lower down, this is an indication that the lead is too far aft and
should be moved forward. Conversely should the windward tell tail on the
bottom of the sail lift before those higher, then you should move the
lead aft. After experimenting in say 8 to 12 knots and you have your
central lead position, you may want to move the lead forward a little in
very light air and aft a bit when the breeze is above 15 knots. The
most critical adjustment you will make with your jib is the sheet
tension. The best way to gauge this is to pull the sheet in when you are
going upwind until the upper batten is parallel to the centre line of
the boat at the back end, or perhaps points just to leeward from
parallel. In no instance do you want the upper batten pointing to
windward towards the mainsail. This will create backwinding and stall
the boat which will slow you down.
Spinnaker and Downwind Sailing
Set the vang so the top batten is parallel to the boom. Ease
the cunningham, outhaul and backstay. Trim the spinnaker so there is 6"
to 8" of curl in the luff. Keep the pole perpendicular to the apparent
wind. Keep the outboard end of the pole even with the free clew. On runs
you may want to use some leeward tweeker to keep the leeward leech from
opening too much. Remember over trimming the spinnaker (never allowing
the luff to curl) chokes down the slot between the spinnaker, leech and
main, the result is a boat driven sideways instead of forward.
The Sonar has a very big main, therefore, it is very important to
balance the boat for different wind strengths. If your boat is not
balanced, you will feel it in the helm. In heavy conditions you want to
de-power the main in order to reduce windward helm. Since hiking is
limited in the Sonar class, it is a good idea to sail with four people,
you can use these people to your advantage by moving them around in the
boat. Use crew weight to help steer the boat upwind as well as downwind.
In light air keep the crew weight low and forward in the boat as the
wind freshens move the crew weight to the windward rail and forward and
close together. In all conditions playing the mainsheet, traveller and
backstay will keep you in close tune with the helm. Remember, steering
fast is a function of concentration and balance of your boat.
Good luck on the water!