SJ23 Tech Tip F12, (Issued 1998-10-26) Art Brown


Boom Topping Lift - Factory Kit.

The part numbers for this kit are from the early 1980s and may still be in the Ronstan catalogue.  Thanks to Art Brown for preserving this document from the Seattle SJ23 Club. 

When the mainsail is raised on an SJ23, it holds the boom up.  As the mainsheet, boom vang and gravity pull the boom down the mainsail leech is pulled tight.  When the mainsail is lowered, the topping lift holds the boom up, otherwise the boom would fall into the cockpit, creating a hazard to crew below and possibly stressing the gooseneck at the mast.  The SJ23 topping lift option shown above is adjustable, allowing the sailor to adjust the height of the boom.

There are several situations where you should shorten or tighten the topping lift to support the boom. 

  1. Prior to reefing the mainsail. 
  2. To support the boom prior to dropping the mainsail. 
  3. To raise the boom slightly for sailing with a reefed main.
  4. To raise the boom above head height for a cockpit party.
  5. To support the boom for a boom tent. 

Reefing is the process of reducing the size of the mainsail (to a reef point) to use less sail area when the wind is blowing too  hard.  A supported boom makes it easier to lower the mainsail.  After reefing the sail you should loosen the topping lift a bit so the weight of the boom pulls the sail tight and the wind pulls the topping lift away from the leech.  If the topping lift is lifting the boom, it causes a loose leech that is inefficient for sailing.  If the topping lift is too loose the line flops around and snags battens, leech tell tales or other rigging.  Being just a little loose is perfect and offers another advantage: if you forget to snug it up before lowering the mainsail, the boom cannot drop into the cockpit, eliminating the risk of hitting someone’s head!

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