Hi Rick, PJR has a table for calculating mast specs for solid timber masts.  Some folk think this table is too conservative but for offshore sailing I think it is accurate.  For my sail area of 35-6 sq metres, I seem to remember the table suggested 10 inches at the partners, tapering 50% at the truck.  My sistership, Minke, has a mast built to these specs and has made successful ocean passages.  I decided to use alloy for my mast on Arion and fitted a mast that was 200mm at the partners and 110mm at the truck.  It is probably stronger than Minke's mast but I am not certain, since no engineering assessment was done.  I am a bit of an empirical boatbuilder, or to put it more bluntly, monkey see, monkey do...

As for the positioning of the masts, there are once again some different opinions but I believe that if you make sure the CE or balance of the sails is in the same place as that of the original design, you cannot go wrong.  Calculating that requires some basic maths, once again explained in PJR or in any basic text on rigs.  Basically, you find the centre of the area of each sail, assuming you have a two-masted rig, then the combined centre.  This should be about 10-12% forward of the centre of lateral resistance of the hull.  Your plans should have that information on it, or you could get it from the Benford office.

There are numerous steps in the procedure and it is not possible to exhaustively canvas all of them here, but essentially you have to decide how much sail area you need, then what type of junk design you'll use, (I'd recommend the type Arne uses), then what percentage of the sail area each sail will have.  You need enough of a gap between the luff of the aft sail and the leech of the forward one if you are using single sheets.  All of these things will influence the positioning of the masts.  All of this information is in PJR and you can hopefully nut it out by doing a lot of reading and thinking.  It will be easier for members to answer specific questions once you have done some of this research.  At the worst, if you cannot understand it, you can pay a designer to draw a rig for you.  Benford might do it, or others.

Good luck and happy reading!

 Hello everyone! I'm a new member as of a few days ago and I have some questions I'm hoping to get answered by the learned and much smarter people than I am group here. I have a 35' Jay Benford Design "Mercedes" she's just about complete...all but the mast and rigging....and I've been convinced that a Junk Rig is the way to go. I think I will go with a wooden mast (or masts) but have no idea how to go about figuring out how tall they have to be or diameter at the base or top. Ive ordered the book The Chinese Sailing Rig - Design and Build Your Own Junk Rig .. and have already bought the Practical Junk Rig. Im having difficulty in understanding how to go about positioning the masts on the boat and how to figure out size of the masts. If someone could give a land locked sailor a hand it would be much appreciated.