About thirteen years ago I built a fifteen foot cruising dinghy with an unusual version of the gunter rig. Since this boat has been generally satisfactory I thought a description of the rig and the reasons for choosing it might be of interest.

The idea was inspired by my previous boat which was a Mirror dinghy. The main advantage of gunter rig for a boat like the Mirror is that the mast is short so that the whole rig will fit inside or on top of the boat without overhanging. This means easier preparation for trailing and launching, less storage space required on shore and it makes it easy to lower the mast into the boat for rowing under bridges, or for some bridges it is only necessary to dip the gaff. Those who have sailed a Mirror dinghy will appreciate just how much handier it is than a comparable Bermudan-rigged boat.

However, the performance of the gunter rig may be inferior to that of the Bermudan rig due to a combination of factors including the extra weight and windage where the mast and gaff are overlapped and perhaps also the slightly quadrilateral shape of most gunter sails. Having said that, there are some who would claim that a quadrilateral sail is actually more efficient than a triangular one and there have been some tests which demonstrated this, although not conclusively. Another disadvantage of many gunter rigged boats, including the standard Mirror dinghy, is that they have no proper arrangements for reefing.

In constructing a gunter rig for my boat, I attempted to keep the advantages whilst minimising the disadvantages.

Firstly, the attachment of the halyard to the gaff was arranged as shown in fig. 1, giving minimal gap between the mast and gaff. When fully hoisted the gaff becomes a straight line extension of the mast and lies close behind the mast where it causes minimal extra windage. The sail is almost the same shape as for Bermudan rig. I first used this method on my Mirror dinghy.

The next point is the weight penalty of the gunter rig due to the greater combined length of the mast and gaff. However, when a Bermudan rig is well reefed there is a considerable length of bare mast above the sail which does nothing useful. This led me to think in terms of a rig which would be a gunter when full sail is required but when deep reefing is needed the gaff and full mainsail would be stowed away inside the boat and a small Bermudan mainsail hoisted on the short and light mast. Although there would still be a weight and windage penalty when full sail is set, when deep reefing is required there should actually be an advantage over a conventional Bermudan rig. For racing this would not be helpful since racing dinghies are hardly ever reefed but for cruising one might prefer to have maximum sailing efficiency when deep reefed rather than when under full sail.

Another feature I have adopted to hopefully improve performance is a rotating mast. I really do not know how much this really helps performance, but for a gunter rig it offers a secondary advantage in that the mast and gaff rotate together so that conventional gaff jaws are not required. Rotating masts have been tried on a few monohulled dinghies including the Firefly, but have never become popular. Some lift and drag measurements have been made for rotating and non-rotating masts, but I do not think that the results so far are conclusive. Perhaps the best advertisement for the rotating mast is the modern type of daysailing catamaran for which mast rotation is almost a universal feature, and I do not think this would be so if it were not at least a little bit faster.

Having outlined the principles I shall describe some of the details. The mast is aluminium, and has a luff groove which carries a slider to support the lower end of the gaff, slides to support the gunter sail below the gaff, and also slides for the small mainsail which is used in windy weather. Fig. 2 shows the attachment of the lower end of the gaff to the mast using a special slider consisting of Tufnol parts riveted onto a short double thickness of car seat belt webbing. Aluminium rivets clamp the webbing between the Tufnol parts. Two small strips of Tufnol form a slider to run in the luff groove, and the larger Tufnol blocks run on the outside. The arrangement works very well and shows negligible wear after years of use. I think that it is neater than gaff jaws, and it does not seem to damage the anodised mast which gaff jaws might do. The webbing flexes to accommodate misalignment between the mast and gaff, but because the mast rotates this misalignment is not great. I have used a stronger version of this arrangement to make a gooseneck for the boom.

Fig. 3 shows the mast foot. The mast is deck-stepped, which keeps it as short as possible, almost exactly the overall length of the boat. A stainless steel peg on the end of the mast slots into a deck fitting and is retained by a pin and tension in the rigging. The kicking strap tackle is attached to a strong bracket fastened to the mast foot and this constrains the rotation of the mast to a little more than the boom angle. Without the kicking strap tightened the mast tends to rotate rather too far.

Lifting and lowering the mast is easy since it is short and light enough to be lifted into position without any tackles, tabernacle or the like. The standing rigging stays permanently attached. As one considers larger boats there must come a point at which it is no longer convenient to manhandle the gunter mast in this way, and I think that much of the advantage of a gunter rig would then be lost.

Although the mast is aluminium, the gaff is of Sitka spruce. On the whole I prefer aluminium spars, but using wood for the gaff made it easier to taper for lightness. It can be a very light spar, being only used in fair weather. A luff groove in the gaff holds the gunter sail; a possible alternative would be to have the sail made with a pocket for the gaff, as seen on sailboards. Indeed, the gaff could perhaps be made from a sailboard mast. When not in use, the gaff stows on the floor of the boat, a tunnel into the forward buoyancy tank providing the necessary length. There are two attachment points for the halliard to the gaff, one above the other, and this provides for one reef in the gunter sail before changing to the Bermudan sail. This method of reefing a gunter sail requires the sail to be lowered for reefing so that the halyard can be repositioned, but I find this little disadvantage since a gunter sail can be lowered and raised very quickly.

The small Bermudan sail which replaces the gunter sail in windy weather was made with a straight leach and no battens, common practice for storm mainsails for yachts. I think this was a mistake: the sail has never set particularly well and I think this is at least partly due to the absence of battens. This is a point worth considering if making a ‘storm’ mainsail for a Bermudan rigged dinghy. If a curved leech and battens are desirable for the full sized sail, then probably they are also desirable in the small sail; they do more than just add a little extra sail area.

Altogether this rig does work well, but is more complicated to construct than a Bermudan rig. I really do not know how the performance compares since the boat to which it is attached is an unconventional design making a straight comparison difficult.

Converting an existing boat from Bermudan to gunter rig may not be worthwhile, but if building a new boat or re-rigging, one can take the opportunity to experiment with alternatives to the conventional Bermudan rig. One of the nice things about boat building is that it is one of the few areas of technology where there is still scope for experimentation by amateurs with small budgets. Another example of this is my long-term project building a sailing boat with hull-lifting hydrofoils, but this is definitely not intended for dinghy cruising!