Rob wrote:

Thank you, Arne. As always you make some good points. We are tending towards a split junk rig with a balance of around 25%. Before we do so, could we use your rig with 25% balance and adjustable parrels? What happens if we have too much balance?

Rob

Rob,

no, you will most probably run into problems if you try that. If you look at the diagram below, left, you will see that the slingpoint of the yard will have to be moved too far aft. To allow a mast balance of 25%, now I sketched up a new two-panel top section. With a yard angle of 60° or lower, that 25% balance should work.

Note: I haven’t tried it hands on, so this must be armchair speculations:

My guess is that the modified sail will behave and weathercock with the sheet released, but we are approaching a limit, here: What I don’t like is that the mast has now moved very close to the max camber points in the lower panels. That was my reason in the first place to keep the balance down to around 10-12%. Later, when Paul Thomson reported about good performance with 18 and 22% balance in La Chica’s sails, I have relaxed this ‘rule’ a bit.

As can be seen on the same diagram, the original sail with 70° yard can be set with 15-17% balance. Maybe it will work to move the slingpoint on the yard from 5% to 10% aft of the middle. In that case, one can approach 20% balance in the sail without lowering the yard angle.

On the diagram to the right I have tilted the modified sail until 40% balance at the boom. Who knows, maybe it will work. At least, the initial 10° boom rise helps to keep the boom from drooping.
Personally, I would much rather take the trouble and make a big, powerful rudder, and save the trouble of canting the sail back and forth (in particular since I don’t sail for three days on the same leg...).

Hope this makes sense...

Arne

Rob,

The best sail for reaching and running, from a steering balance point of view, is no doubt the symmetric squaresail. Since this sail dominated for so long in Europe, the ships tended to be made with small rudders.

The Chinese started rigging their sails fore-and-aft fashion very early. In addition, since they didn’t make their boats with fixed keels, they soon developed centreboards and (in our eyes) oversize rudders. This way they managed to control their boats and ships downwind, with their offset rigs.

During my years in JRA, I have seen many examples of boats that struggle downwind with their sloop JR. This is mostly because the rudders have been small and in-efficient. I keep nagging on this: Choose boats with a big, efficient rudder, or be prepared to fit one.
There are other methods:

·         Go for a (sloop) JR with plenty of balance. My Johanna-style sail can hardly be set with much more than 17% balance. Paul Thompson’s sails with lower yard angle, have been used with 22% balance, as far as I remember. Slieve McGalliard’s Split JR can have 30-35% balance, which offloads the rudder a lot on a reach (and have light sheet-loads)

·         Make the sail with long Batten Parrels and a running Tack Parrel, so the sail can be centered somewhat when reaching and running. I’ve never used it, but they say it works.

·         Rig the boat as a yawl, with the CE of the (short-chord) mainsail far enough forward to cause a lee helm alone, and with a little mizzen way aft to balance the rig. When falling off to a reach or run, the mizzen sheet can be eased and thus help keeping the  steering easy. This method was in use on some elegant little gaff-rigged yachts, over hundred years ago (Albert Strange).

·         Reef!

For my own part, I have decided to live with my sails with moderate balance in them (10-17%). As long as I can easily control the boat at speeds up to about 10% above the hullspeed before reefing, that is good enough for me. Actually, for my sailing, in and out among islands, it makes little sense to carry more sail downwind than my boat can carry when close-hauled.

Arne

PS:  When having a closer look at photos of Blondie on the hard, it strikes me that her rudder is begging for an endplate, both at the lower and upper end. I would go for a ‘wingspan' of 60% or thereabouts of the rudder’s chord. I bet that will make Blondie cope better on a screaming reach.

I am having problems getting my head around how much balance a sail or a boat could handle? In PJR they suggest a balance of between 5% and 30% but favour 10%. Arne also opts for 10% but thinks between 5% and 15% is acceptable for his style of sailplan. We have an Arne sail on our boat Blondie and the balance is around 15%. We are very happy with the sail but there is some weather helm when heavy reaching. Maybe more balance would solve this?

Our new boat is a Robert Tucker Beagle design. I have attached a photo. We have placed the junk rig mast 1.2 metres forward of where the Bermudian mast was stepped, which is 1.2 metres forward of Bermudian sailplan's centre of effort. We couldn't go much further forward because of the forward berth and the foredeck hatch.

We were thinking about an aero junk rig with a balance of 25%, which would fit the new mast position perfectly. All the local JRA members want us to have a split-junk rig. Slieve favours a balance of 35% on the split junk rig. How can all these balances be so different?  Am I missing something? Would an Arne sail with more balance work?

Rob