Barry has just published initial drawings of the new junk rig for Flutterby, our Freedom 33 (F35 in UK/Europe) cat ketch. His design process involved putting every variable into an Excel spreadsheet (took several months) and then telling Excel to draw the sails using the graph function.

Those who are interested can find the drawings and specs on our website at this link: http://www.mepsnbarry.com/adventures/2011/02/time-for-some-new-junk/

(there was also a version of this posted to the Yahoo Junk Rig Group on Feb 21)

Notes on the drawings and design follow (all dimensions are in square feet)

Given that our masts are fixed in position and height, here are the variables considered in the design:

• Yard angle
• Number of panels
• Shape/size of panels
• Amount of balance
• Clew positioning
• Boom angle
• Length of yard
• Length of battens

The line in the sand: The following decisions are (pretty) final

These drawings show the most sail area we can reasonably fit on existing masts and deck: 58% more sail area than the original two sails. However, it keeps the Center of Effort in line with the original CE of the Freedom 33 rig. The original design showed a mizzen staysail which can be sized like a spinnaker, which we won't be using (so no need for running backstays).

In the drawings:

• Black circles are CE of each sail and the whole rig
• Red triangles are the CE of the original cat ketch-rigged Freedom 33
• Red diamonds are the CE of the tall cat ketch rig-rigged Freedom 33
  

The sail shape is more-or-less Hasler-McLeod, with the top two panels adjusted to give each one about the same sail area as a lower panel.

To improve upwind performance, the mainsail will use a split rig and will have camber sewn into both the fore and aft sections. The mizzen will not be split, but will have camber sewn into the panels.

• Mizzen: Little balance, 60-degree yard, 11-foot yard and battens.
• Main: Lots of balance, 50-degree yard, 16-foot yard (cut from original F33 wishbone), 18-foot battens.
• Sheeting arrangement: Simple, 6 or 7 parts. May use split sheets.
• Would prefer to avoid downhauls for either sail.
• Would prefer to avoid panels over 4 feet high
  

The sand itself: The following items are still under discussion (as of 23Feb2011)

The number of panels for both the main and mizzen is still open to debate. More battens means more weight, but shorter panel height. Fewer battens would be lighter, but make for a taller panel height and more need for downhauls. Material cost for either option is similar.

• Should the main be 7 or 8 panels? The aspect ratio is reasonable for either.
  
• Should the mizzen be 7 or 8, or even 9 panels? It has a very high aspect ratio, which might also justify a reduction in the overall height. It has a panel height to batten (P/B) ratio of 0.36  (7-panel) or 0.32 (8-panel).
• With a SA/D ratio of about 23.1, is 8% camber the right amount?
  
• How far aft should the maximum camber point be?
  

Thanks very much for any suggestions, comments, questions, or input.

Barry Stellrecht and Margaret "Meps" Schulte
s/v Flutterby
Freedom 33 cat ketch undergoing conversion to a junk rig
Moored Vero Beach, Florida, Feb. 2011
www.mepsnbarry.com