There's been quite a lot of interest in a Balance Lug sailplan for Navigator lately. John Welsford drew plans for a Cat Yawl with a Balance Lug main and mizzen a while ago and posted it online. He granted me permission to post the plans here to make them easier to find, so here you go.
The Balance Lug is a very popular sailplan for small boats. This rig, with its unstayed mast and lack of a jib & bowsprit, is much simpler and quicker to set up and take down. The mizzen provides its usual advantages such as heaving-to and balancing the helm. Several Navigators have been built using this rig with their owners giving it an enthusiastic thumbs up. Personally, however, my preferred rig is still the Gaff rig for its ability to instantly drop the main and sail deep reefed under jib and mizzen. That's well worth the extra setup time to me. For those accustomed to conventional sloops I recommend the cruising sloop rig for slightly better upwind performance. With so many Navigator sailplan options (7 total I believe, although some are unpublished) surely there's one to suit anyone's needs.
Note that the main mast on this Balance Lug rig is located forward of bulkhead 2 whereas the Standing Lug and Gaff rigs have the mast located aft of bulkhead 2.
Some builders have asked if it's possible to retrofit an existing yawl rigged Navigator over to use this sailplan without moving the main mast forward of B2. John says No - the result would be an excessive amount of weather helm. I asked him if the sail area of the mizzen could be reduced to compensate. He said the mizzen would then be so small it would become ineffective. A new mast may be required as it's taller and may need to be stronger as it's unstayed. So yes, anything's possible but it would require some considerable rework.
