Jes,

I had hoped that chapter 4 and 5 should explain it for you, so I suggest you have another look.

• ·         The paper patterns should be lofted and cut to net size of each panel, including the barrel round.
• ·         The panels are given an extra 20mm stripe around the pattern. At luff and leech, these are used for putting on a simple hem. 
• Note: This hem at luff and leech is put on before one starts sewing together the panels at the battens.
• ·         The edges of the two top panels match each other quite well since the barrel curves are quite flat there. My method is to first staple the panels together at luff and leech (B is constant). Then I staple at the middle of the curve, etc. until the staples sit with 20-40cm distance. Remember, this is canvas, not steel plates, so millimetre accuracy is not needed.
• ·         The biggest difference in edge length along the curves is between panel 3 and 4 (from top). Here I often use a little trick; I cut the upper edge with less round and the lower edge with more round, so that the curves match better the adjacent panels (See chapter 4, Fig 4.2 on p.2).

Good luck
Arne

Whilst waiting for my mast and aluminium for spars to arrive I thought I'd get going with the sail.  I've made a lofting/sewing table 3.6 X 1.5m in my garage and have started making the panel templates.  One of the satisfying aspects of working on boats is the curves you create, and I enjoyed marking out the barrel curves!  I've ordered sail cloth from englishseadog which should arrive this week. It's good to be making progress

The one part of the sewing I don't understand yet though it may become clear is how the lengths of the panels matches up, eg between panel 1 and 2 where the round on panel 1 is half that of panel 2.  Surely that makes the  length of the seam different on the 2 edges?  Any clues as to how this works, maybe the difference isn't that significant, thanks.

Anonymous wrote:

This summer JRA member Paul Schnabel has successfully cruised his Maxi 77 with his junkrig set with up to 27% mast balance.
I have therefore made use of his findings and drawn a hi-balance sail for the Corribee, shown below.

The mast was put through the hatch, with its centre about 200mm aft of its forward edge.

I don’t think the sail will ever need to be moved forward of the shown position. If anything, it rather needs to be shifted aft a little to trim away any lee helm. There will be plenty of room for that.

The Corribee has a smallish rudder. This hi-balance JR brings its CE quite close to the JR mast, which again means that the CE will sit close to the boat’s centreline when sailing downwind. This should help the rudder to cope.

Just an idea.

Arne

PS:
It looks to me that the superstructure of the Mk 2 and 3 are very similar, so I used a Mk 3 version here.

(Hi-res diagram in Arne's sketches, section 8, photo11)

Hi Arne, can I trouble you again? I am getting back into my project after a bit if a break.  I went through the process of working out the CoL for my hull today and  I have transferred that onto your  sketch, see attached image. It appears that the CE is way forward of my estimated CoL. Is this cause for concern?  Thanks, Jes. 

I just went back and plotted the CE for the old Bermudan rig and compared it to the CE of your proposed rig and find they are identical...perhaps I'm trying to teach my grandmother to suck eggs, as we say!!

Anonymous wrote:

Hi Jes, i have just recently joined the JRA, as i have become interested in the junk rig. I have a home built Flicka sailboat designed by Bruce Bingham, I built the boat in 1993 and rigged her as cutter. I have started looking at materials for masts, yards battens etc. I live in Devon, England and came across a company called Aluminium warehouse, who seem to stock aluminium tubing that looks usefull. the only trouble is their maximum length is 5 metres. I am writing to ask if you could let me know the contact details of where you sourced the lampost for your mast. Many thanks. Best regards, Oz.

Anonymous wrote:

Yes, Jes, I think you are overthinking a bit.
The odd-looking number 1.98, has nothing to do with me being particularly accurate or bright. The number is just there to point you to the corresponding master sailplan

Ten years ago I produced a string of master sails, called the Johanna style master sails, with AR rising from 1.80 to 2.25 with 0.05 increments, and all with 70° yard angle. Only recently did I design a string of master sails with yard angles at 65 and 60°.

To make them, I started with the ‘Johanna 70’ master sails.
I kept the four lower panels and made new 3-panel top sections, doing my best to make the area of these top panels almost the same as in the lower panels.

I stick with the method in PJR for finding the AR: AR= h/chord, where h is the vertical height from peak to boom. In your case, this Johanna 60sail with AR=1.98 is thus a result of the Johanna 70 master’s  with AR = 2.00.

This is how I go about to find a suitable rig for a boat like yours.

• ·         I start with drawing a vertical mast line where the mast is supposed to go.
• ·         Then I draw a long boom line with 10° rise.
• ·         Then I play with this formula to find a possible combination of batten length and AR which gives the wanted sail area and a usable mast balance.
  SA = B x B x AR x 0.78. This formula hits within one sqm, but remember to, in this case, put AR = 2.00 into the formula.
• ·         In your case I end up with a 60° yard to allow a hi-balance sail to sit.
• ·         Then I go to the string of Johanna 60 master sails (found und MASTER SAILPLANS here: The Junk Rig Association - Arne Kverneland ) and pick the one with AR= 1.98. A quick check with the calculator make sure that the area will be right.
• ·         From the two sheets of that master sailplans you can decide how much camber you want (I use 8%) and by reading Chapter 4, find the right numbers for the needed Round, R.

Clear as mud, right?

Arne