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Jib Car adjustments

There are two Jib cars for port and starboard Jib sheets.  The cars are set at an angle to the dinghy centreline. As the Jib car slider moves forward the Jib block position moves closer to the dinghy centreline.  Moving this slider forwards has two effects; the Jib slot (the gap between the luff of the mainsail and the leech of the Jib sail) narrows and the tension down the leech of the Jib increases. The effect of this adjustment is to increase the speed of the wind through the gap (slot) between the sails. This will increase the efficiency of the mainsail.... up to a point. If you overdo this adjustment  you will see the wind through the slot creating a dent in the mainsail. This is called 'backwinding' and reduces the efficiency of the mainsail. Two options to solve this issue; ease the Jib car backwards slightly, ie widening the slot, until there is the merest hint of backwinding, or tighten the downhaul control line which may remove the dent in the mainsail (it has the effect of flattening the leading edge of the mainsail and thereby providing another way of widening the slot between the sails).

As the Jib car moves rearwards the Jib block moves both rearwards and away from the dinghy centreline, thus increasing the gap between the Jib leech and the mainsail. Importantly this also has the effect of increasing the tension along the foot of the Jib sail.


Changing the Jib car settings alters the performance of the Jib in various wind conditions. As a general rule the  Jib car should be moved slightly rearwards in light winds (allowing what wind there is to flow freely across the sails), slightly forwards in moderate winds (this narrows the slot between the Jib and Mainsail and increases the speed of the wind across the mainsail thereby developing full power) and rearwards in strong winds (to open the slot wide, reduce 'backwinding' and the upper part of the Jib will twist open -top tell-tale flies up - and reduce the heeling forces).


When both the Jib car and Jib sail are set correctly for the current wind conditions the Jib will be operating at its maximum efficiency. This can be readily seen by all three pairs of Jib tell-tales flying in parallel.  I am in the process of monitoring the settings for different wind conditions over a period of time and these will appear in the table below. If you have found ideal settings please contact us.

Average Wind Speed Mast Rake Setting Jib Car setting hole (rearmost =1)

Wind Speed and Jib Car settings for sailing


11 knots 3rd hole down Hole = 3


The above table shows the average wind speed and the Jib car hole setting that will contribute to maximum efficiency but note the