Thought for the day - Problems with the jib. It's all in the geometry.

How many of you have the problem of the jib boom flicking out one side or the other in calm conditions, making it impossible to sail. I have encountered this problem since I first launched my first boat boat. It was only in a discussion with Dave Potter last week that I found the solution. It's all in the geometry. See the picture below.





The diagram on the left shows the configuration I used last year. My leech line had caught around the spreaders a few times I thought it best to use a line and tie it forward at the head of the jib not realising that this impacts the geometry and caused the boom to kick out one way or the other when there is little or no wind.

If you want to see this in action, set the headsail up loosen your current leech line and tie a loose leach line onto the end of the jib boom. Make sure the line is long enough to reach the entry point on the mast. Put the luff and leach line under some tension. First move the top of the leech line to the right of the mast (i.e. aft) by an inch or so as set up in the picture and you should see the jib boom pull into the centreline of the boat. Now move the leech line in the opposite direction, forward of the mast and you should see the jib boom move as far away from the centreline as it can.


Talking to Dave Potter, he told me that he and Deve Creed solved the problem by tying the jib luff and leech line to a self tapping screw thus ensuring the leech line and jib luff tension line intersect the mast at exactly the same point allowing the jib boom to rotate freely in any direction


I pondered this for a while and came up with another solution using wire and a bowsie. The wire leech line and jib luff eye are attached to a bowsie inside the mast. They exit the mast and the jib luff can be hooked onto an eye fashioned out of the wire. Both enter the mast at the same point setting up the correct geometry.


Fingers crossed this will mean the jib boom will swing easily from one side to the other in calm conditions. I will let you know at the end of the week if it works.




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