Hi Roger,

It’s easy to get more lift from a sail. You just make it bigger. But what happens when the wind increases? We have to reef and make it smaller. It is not the lift that is important in a rig (or a wing), but it is the lift/ drag (L/D) ratio. Leading edge slats help delay the stall, but at the price of higher drag and therefore lower L/D or efficiency. Slats, drooped leading edges, flaps and Gurney flaps all are useful at slower airspeeds which you would think are what is needed in a sailing rig, particularly in light wind conditions, but the overall efficiency of the rig is lower and does not help the windward performance.

Take the real life condition of an aeroplane overshoot from an approach. The first action is to increase power, but rather than raise the undercarriage to reduce drag, the second action is to reduce the amount of flap in use. This will decrease the lift a little, but it will decrease the drag a lot and make the wing more efficient with a higher L/D ratio.

The slats are useful on an aeroplane where, if it flies too slowly it can stall, and people get hurt when that happens close to the ground. It does not matter if the rig on a boat stalls as it will just slow down and only the helmsman’s ego will be hurt.

The spats are generally set to open automatically as on the de Havilland Tiger Moth, or even the Boeing 737 200, but they are automatically retracted during normal flight. We don’t want such complication on a boat rig.

Cheers, Slieve.

Thanks Slieve

Hi All,

I'm in the process of negotiating over a Freedom 40 Centre Cockpit. The sails are shot and it seems and ideal moment to convert to Junk rig. I am currently reading through the various threads on this.

However, one thing I want to look at is the possibility of a split junk rig, at least on the foresail if not both. The issue here being sail balance - with over 30% balance a split rig will presumably bring the centre of effort well forward.

So, two possibilities spring immediately to mind (there may be others which might turn up here!):

1) have a larger Main than Foresail. The Freedom masts are plenty long and I've seen suggestions that they be kept long. With the yard not going to the top of the mast, a kind-of permanent parrel for the halyard is suggested some way from the top to reduce side loads on the top of the mast. Makes sense.

But this implies there is enough space at the top of the mast to have a taller (and possibly wider) main. So, one way perhaps to bring the CofE aft again.

2) The other way could be to reduce the amount of balance to something more like the HM sail and have smaller, high aspect ratio jiblets.

Slieve McGalliard mentions in his article about split junk rig that one of the main reasons for the extra balance is to reduce sheet loads and tame the gybe somewhat. I get this but wonder if there's something else I'm missing, which might make a reduced balance area unsuitable for split junk rig?

Many thanks in advance for any forthcoming help!

Cheers,

Roger.