Mirror Tuning Guide by Sailboats Speedsails

Although the Mirror dinghy is often used as a beginner's boat, the rig is less straightforward than many other classes and allows quite a bit of scope for tuning. While individual boats may require some alterations to the following settings, this guide should give you an excellent starting point.

Mast Step Position

Rig Type	Mast Step Position
Gaff rig	2174mm from forward face of transom to centre of mast step (class rule: 2160mm ± 15mm)
Bermuda rig	2174mm from forward face of transom to intersection of foreside of spar and surface of foredeck butt strap

Rig Tension

Measure the tension on the side shroud at the same height each time (eye level).

Rig	Tension
All rigs	160–180lbs (No. 15–18 on Superspar rig tension gauge)

Mast Rake

Rig Type	Mast Rake Setting
Gaff rig	3540mm – 3570mm (top of mast to top of transom with 180lbs forestay tension)
Bermuda rig	4921mm (tape to 4102mm datum at back band at gooseneck, then swing to top of transom). Shroud tension: 160lbs (15 on Super Spars gauge). Move shrouds down one hole to increase rake; up one hole to decrease.

Jib Halyard

The jib halyard should be pulled on just tightly enough so that there are no creases appearing between the hanks. Be careful not to use too much tension — a long vertical crease or bump running parallel to the forestay indicates too much tension.

Jib Sheeting

Conditions	Jib Sheet Setting
Above 12 knots – both fully hiking	Bar tight
Crew sitting to windward but not hiking	Eased 5–10mm
Crew progressively lighter / moving inboard	Eased progressively up to 25mm maximum
Very choppy and light	Ease a further 5mm

Put a mark on the jib sheets (waterproof marker or whipping twine) to show when the jib is in tightly, so the setting can be reproduced easily.

Jib Fairleads

Recommended position: bearing surface of fairlead 30mm from the side-tank, as far aft as possible on the thwart.

Jib Tack Height

Conditions	Jib Tack Height (above bow knees)
Light winds	Up to 25mm above bow knees
Strong conditions	10mm above bow knees

Raising the tack decreases tension in the foot and increases tension along the leech (upper windward telltale breaks first). Lowering the tack increases foot tension (lower telltale breaks first) and opens the upper leech to prevent the slot getting choked.

Kicker

The kicker is the most critical sail control when racing. It controls sail twist and can be used to de-power the sail.

Conditions	Kicker Setting
Very light winds (crew to leeward or middle)	Just enough to remove the slack. Use mainsheet tension to control leech profile.
Wind increasing (crew to windward deck or gunnel)	Aim to have top leech tell-tale flying ~80% of the time (occasionally flicking behind the sail)
Above 15 knots (both fully hiked)	Top tell-tale flies continuously — use as power control (more on if overpowered, less if underpowered)
Downwind	Ease so leech tell-tales fly continuously; let off significantly on a run

Downhaul

The downhaul should only be used to pull some of the large creases out of the luff of the mainsail. With the downhaul on, the lacing should be tight enough to hold the luff of the mainsail about 30–40mm from the mast all the way down.

Outhaul

Point of Sail / Conditions	Outhaul Setting
Upwind	~100mm between foot of mainsail and boom
Reaches	Eased a further 38–50mm (leave on in windy close spinnaker reach)
Run	Eased only 5–10mm to keep more sail area to the wind

Spinnaker

Stopper knots can be placed in the spinnaker sheets so that in light winds the pole is just off the forestay. 90% of the time, the spinnaker pole should be set so that the clews are level — look at where the spinnaker breaks when eased (top, middle or bottom): if the leech curls at the top first then the pole needs to be lowered and vice versa. If the wind drops so you are struggling to get the spinnaker to fly, dropping the pole a few inches can support it and help it set.

Once the boat is set up, it is important not to get overly immersed in boat tune. What is critical in all conditions is having your sails correctly trimmed.