Rig Selection 

The most difficult part was designing the rig to fit the boat. There are some controversies around how much lead junk rig needs on a monohull. With a multihull it is easy as they don’t heel and therefore a Centre of Effort (CE) of the rig can be placed over the Centre of Lateral Resistance (CLR) of the Hull.

Once the lead has been decided one of the next major considerations is where the mast is going to go. We used PJR and the designer’s original sail plan to determine an appropriate lead. Time will tell whether or not this was decided correctly.

How did we determine the lead? We used the original boat plan but then noticed that the boat’s actual dimensions differed. She was stretched during the build. All calculations had to be based on the current photograph of the hull with the rudder included.

Where to place the mast? 

Francis has a very shallow forefoot with a narrow keel/stem timber. This made placing the unstayed mast any further forward than the original bermudan mast position difficult, due to structural problems with the mast step and getting enough bury for it.

Having decided to keep the mast in its original position, this dictated a larger than usual balance in the sail. The available rig designs were a Hasler / McLeod sail (with or without camber), a split junk rig or an aero junk. 

The most suitable rigs are either Slieve McGalliard’s split junk sail or Paul McKay’s aero junk. Linda liked the aero junk rig the best, especially the sexy curved wishbone battens. Having sailed on Oryx for 900 miles in all sorts of conditions she was impressed with the way the rig worked, its ease of handling and how it responded to the sudden wind changes. And nothing broke!

Using the formulas in PJR, I worked out the CLR and gave the rig a 7% lead (not taking the rudder into account)!

Mast 

Getting a mast in New Zealand is not easy. Good spar timber is very expensive and there seem to be no suitable grown sticks available. In the end Linda had decided to go for the aluminium tube (125mm x 3mm 6063 T6). After much searching we found a suitable Douglas Fir (Oregon Pine) roof truss (demolition wood from the earthquake in Christchurch). This was 150mm square, 4m length beautiful close grain with only a couple of small tight knots. When planed down it looked like new timber and it smelled beautiful. 

The top of the topmast has a 25mm thick plywood disc glued and fibreglassed to it with three stainless steel 8mm U bolts for the halyard and topping lifts. The topmast has 300mm of bury and extends the mast to 7.5 metres. The topmast was coated with a layer of 300g glassfibre cloth and epoxy before painting.

Mast Fitting / Stepping 

Fortunately there was not too much to do to strengthen the deck/cabin because the cabin had a substantial hanging knee as had the deck beneath it. Two layers of 6mm plywood were glued up under the deck between the deck beams and a 18mm oval plate glued on top of the deck, together with a plywood collar for the mast boot. The mast step consists of a 40mm plywood plug that fits into the base of the aluminium tube. This is glued to a plywood base with a timber wedge underneath to make it level. Two 10mm x 120mm galvanised coach screws through the plug connect the mast step to the inner keel (over the old mast base).

Building the Battens  

We could have used aluminium for the battens but it is quite expensive here and also I prefer wood anyway since my boat is wooden. Not to mention how they look alive when in action! The timber for the yard and battens is clear pine (yard: 40mm x 20mm, battens: 30mm x 20mm). The most economical way to buy the timber dictated that we had to saw each plank in half to form the two halves of the wishbone. You need to remember to keep the two cuts to use as a pair for a wishbone to ensure that each bends at the same rate. See the drawing and photos for the construction details. The triangular piece supporting the main cross member was a design failure because – it was fiddly and not very strong. We added the rebate and probably the triangular piece serves no purpose. The yard is only a variation on the batten. With these shapes Francis definitely looks very feminine.

Sail Design and Making 

The sail material is 300g/sq.m PVC on nylon, a bit too heavy but the price was right! 

I set to making the sails. I used Pete’s Sailrite sewing machine on Rob and Maren Prince’s garage floor. Sewing it together was straight forward because the sail is flat. Measuring extremely carefully was important and it was essential to put the jib over the mainsail to make sure that the battens lined up perfectly. This meant laying the jib on the top of the main, luff to luff. 

The sail has small battenlets (4mm fibreglass rods – as used for carnival costumes!). This is to stop excessive flogging of the sails when head to wind. These fit into pockets on the sail at every batten position. Each batten let end was protected with heavy sailcloth padding to stop them poking through.

Rather than have metal rings to attach the sails to the battens, webbing tabs were used instead.

The main and jiblet each have a sail-catcher/sailcover sewn to the bottom of each sail. They are not working perfectly and will need some fine tuning with more rigid supports at the top of each sail catcher. 

Stitching up the sails was quick and easy. To do all the finishing work took at least as long again. This was because of all the detailed work required instead of just long runs when stitching the panels together.

Rigging 

Of course putting this all together took much longer than planned but eventually the mast was finished, the battens and yard built and painted and the sail sewn up. Francis came alongside Oryx and using Oryx ’s port mast to lift it, the mast was lowered into place. The mast hole in the deck gave a 12mm gap all around, a strip of 6mm conveyer belt rubber was placed around the mast and then a couple of turns of 8mm bungee cord was driven into the remaining gap giving a nice tight fit, then the mast boot was pulled down over the collar giving, for the moment at least, a watertight seal. 

The sails are hoisted with a two part purchase using the latest low friction, hard-anodised “rings” instead of more normal blocks. The main sheet is a single part from the yard through the end of each batten and down to the horse at the stern.

The original sheeting was a multi part to sheetlets. This proved to have too much friction and miles of rope in the small cockpit was mayhem. The new system is yet to be tried properly and we will have to wait until next summer. 

Originally I used 10mm rope (the price was right!) for the halyard and the sheet but it proved it had too much friction for the size of the rings. I now changed it to 8mm rope which seemed to solve the problem. Also the original halyard was 3 part and it was extremely difficult to raise and lower the sail. The halyard seems to work well with 8mm rope (I bought the largest size of ring available) but maybe traditional blocks would work better. However I did not want to have metal clanking on top of the mast. The rings are attached to the U-bolts with Dyneema line. 

Sail Testing 

The winds were light but there was sufficient to see how the rig worked. You would expect a Francis Herreshoff design to sail well and Francis with her new rig performed even better than expected. The rig was almost perfectly balanced with just a touch of weather helm and steering was fingertip light. She seemed fast in the light winds, pointed high and tacked on a sixpence. There were a lot of big smiles all round on that day. Much more testing will need to be done in varying conditions to evaluate the rig properly.

Unfortunately we had no time to test the new sheeting and halyard arrangement fully nor to take a single photograph! Francis needed to be put to bed on her winter mooring – and this required some mud digging and pontoon adjustments, which took priority.

Technical details: 

Sail area 16.72 sq. metres, with the jiblet being 26

• LOA 5.63m 18’ 6” 
• LWL 4.69m 15’ 5” 
• Beam 1.90m 6’ 3” 
• Draught 0.76m 2’ 6” 
• Displac. 770kg 1700lbs 
• Ballast 363kg 800lbs 

Mast length 7.5m overall, 6.5m above partners 

Lower mast: 125mm diameter, 3mm wall thickness, 5m aluminium (6063 T6)

Top Mast: Oregon Pine (Douglas Fir), 2.5m (solid) Mast weight 25Kg 

Battens & Yard 10kg 

Sails 8kg