Following some interesting articles on the subject of outriggers and things-multihull, I thought I would add my ‘two-penn’orth’. Several years ago, in the Bulletin, I read an account of a successful cruise in a two-man kayak fitted with an outrigger and sails. The author finished the article wondering if his contrivance could be developed into a proper type of sailing boat. I thought it could. In fact, I thought about it for years before I had the opportunity to design and build my interpretation.

At the time I had a light dinghy to which I had added 50 lbs of ballast beneath the bottom boards. It had improved the stability a little but imagine how much more effective this weight would be if it were applied on a lever 6 ft away from the hull. The Polynesians were doing this two thousand years ago and added cross-beams (akas) to their canoes (vaka) to mount the outrigger float (ama) on one side.

I wanted to create a stable boat that I could carry on the roof rack and that I could dance around in at anchor without the water coming up to meet me. 14 ft catamarans were (as a sweeping generalisation) too sporty or only offering a crouching or sprawling seating position. 16 ft plus catamarans were a little too heavy to car-top although I still covert several types. The only trimaran I knew of, the 15 ft Supernova, was again a little too sporty without much space for cruising gear. On the basis of my criteria, the outrigger-canoe/tacking-proa concept seemed promising and offered greater simplicity than a trimaran. I believe that the outrigger canoe concept is particularly useful in this size of boat. Shorter versions would struggle to carry sufficient weight without becoming slow. Longer boats which would necessitate a trailer in any case could become tris or cats or a heavy dinghy without any extra shore handling difficulties. Putting to one side any natural desire for symmetry, I took up my pencil!

The sailing outrigger concept was:-

Vaka (main hull) Length 16’4” Beam 4’ WL beam 1’9” Draught 1’ Disp 466 lbs Weight 110 lbs

Ama (Carried to starboard) Length 12’6” Beam 6” Draught 4” WL disp 50 lbs Submerged Disp 180 lbs Weight 30 lbs

Beam overall 8’10”

Sail Area 80 sq ft

The features I chose were: a vee section with shallow fin for trouble-free beaching and lack of clutter in the narrow cockpit; a built in flat floor (draining into a bailing well) to provide torsional stiffness to the hull; projecting side decks to give somewhere to sit, mount the shrouds, add torsional stiffness and reduce the bending stress on the akas; a high degree of rocker on the main hull and ama to aid going about (however this tends to reduce prismatic coefficient — see later); low displacement ama so that it sinks when capsized (leaving the mast parallel to the water) but with sufficient static displacement (50 lbs) to counter balance my weight on the port gunwale. Using the DCA boat safety recommendations, this would classify her stability in the order of a 12 ft dinghy. On this basis I specified the sail area as 80 sq ft.

Dinghies I have previously owned have never achieved the DCA recommended stability and sure enough they didn’t inspire the confidence to do much serious cruising. This boat had to be different. I tried, principally, to design in ‘cruising capability’ but I didn’t want to end up with a boat that was sluggish in the water, refusing to move unless a gale was blowing. So I tried to avoid anything obvious which would cause the boat to be slow.

During the two years of building, I was learning more about multihulls from various sources including the Bulletin. Some of this new-found knowledge supported my design decisions but other parts of it did not. This became a major worry because of the time and effort I was expending on a ‘leap in the dark’. Was my hull prismatic coefficient (0.62) high enough for good speed and low wave making? Prismatic coefficient is given by:-

Hull Displaced Volume x (Major Section Area x WL Length)

As you can imagine, this ratio gives a representation of the fullness of the ends of the hull. Full shaped ends (higher coefficient) tend to reduce the power required to drive the hull at maximum displacement speed at the expense of low speed drag. Since multihulls are relatively slender in any case, the prismatic coefficient can be made higher to the advantage of speed. Generally, modern cats are around 0.7 or more, racing kayaks are about 0.7, yachts are around 0.55 and I guess that the wide variety of sailing dinghies are somewhere in between. My concern was that my boat should have been nearer 0.7. Would the mast position, central on the main hull, cause lee helm on one tack and weather helm on the other? Was the displacement to length ratio (51) too high for reasonable performance? Length Ratio given by:-

Displacement in tons x (0.01 x WL Length in ft)³

This is another measure for speed potential and successful catamarans tend to be around 50 or less. However, I know of a 24 ft tri that rates at 66. (Monohulls apparently need to be less than 150 in order to be able to plane). Anyhow, by the time my concerns built up all this was already cast in stone and I had only one choice — to see it through.

After more delays, with life interfering with ‘precious’ building time, I finally launched Geese at Bosworth Water Park on 13th September. (It was a Saturday so I hope that was OK!). There was a magic moment when I pushed her off the beach to support her own weight in the water and she came alive… no longer a dream… no longer pieces of plywood and sticks… now a boat lightly sitting on the surface waiting to go. She looked good, anyway!

With a great deal of trepidation I waded in and collected my thoughts. Would I be able to get her to go about before I hit the opposite bank? One or two people were watching; I couldn’t just stand there, knee deep, any longer. I had to go. I stepped aboard, reassured by the feel of stability, sat on the side deck, pulled in the sheet and accelerated quietly away feeling quite in control (to my surprise!).

The first thing I wanted to try was to go about in both directions and this was achieved with no problem whatsoever. Also, there was no detectable difference in helm balance from one tack to the other. A feeling of delight began to sweep over me. As I explored other points of sail on the (F2?) wind, I found Geese to be perfectly well behaved and swift. What a relief!

My daughter came along as passenger for some of the time. Her 8 stone did not appear to make much difference to the performance although, of course, progress must have been a slower. I sailed after several conventional dinghies and we seemed to be faster. This was not one of my main aims but was of course a pleasant surprise! Nobody seeks to sail slowly in normal circumstances, do they?

However, by now I was feeling much too pleased with myself and was about to take a fall. I was sailing alone at this point. In the boat’s current trim, the outrigger was displacing less than 40 lbs. I knew that I needed 50 lbs to balance my weight on the port gunwale Now you’re getting ahead of me! Having sailed light dinghies, I was used to sitting well out on the backs of my knees at this sort of speed. I was on port tack and had to take avoiding action from another boat. I steered up-wind too rapidly and — back winded — tipped myself ‘in’ backwards!

I allowed myself to slide out of the boat to avoid inverting it. Mercifully, by the time I surfaced, Geese was righting herself and I was scooped up by the side deck. It was all over in a flash. The only water in the boat was from my saturated clothes. I sailed back to get changed and as it was now about 5 o’clock, this seemed a good point to pack up for the day. I couldn’t wait to sail again so took a mid-week holiday to visit Rutland Water while the weather held out. I estimate that the wind was up to F4. Most boats, including small cruisers, had a reef in for comfort. If I had had a reefing arrangement I would have used it but this was to be a later modification.

Single handed again, I set off on a starboard beat. The water was darkened by the wind coming across it and there were some slamming gusts coming around a headland that I thought best to spill from the sail. I didn’t want to break anything just yet. Once clear of the headland, the wind was more constant and I began to entertain myself by hanging onto the sheet to ‘fly’ the ama. I played the sheet to keep the ama flying as long as possible and then land it gently. This is not very seamanlike but is great fun! I estimated our speed to be about the same as the Solo or Streaker that I used to own.

If I bore away to a close reach, the speed increased to multihull style! Each wave caused a shower of spray to leap the length of the boat (except the bucketful that hit me!). I found I could ease the sheet and slow down if necessary but continued on full song.

On going about at the far side of the reservoir, I was broad reaching back the other way. Geese set off like a rocket! I was mindful of the dipping I took on the previous trip and since my weight didn’t seem to be required on the side deck, I crouched on the floor to be ready for any mishap, though none came. We hissed along as if on rails. Watching the ama take the strain, piercing the water semi-submerged, was exhilarating. I laughed out loud all the way back. Luckily there was no one around to call the nice men in white coats! The 5 hour sail around Rutland continued in much the same way and I became more comfortable with the handling of the boat.

After the first outing, I had moved the mast back 1½” to try to remove a tendency of lee-helm. It is acceptably neutral now but if I ever have a new sail made I will increase the roach to add a little more weather helm. I am currently fitting a hatch to the ama so that I can add 11 lbs of ballast inside. This will increase the port going stability by more than 25% and should be enough to keep me upright.

In conclusion, my initial enthusiasm has been for the gratifying speed under sail. However, I am still confident that Geese will provide the basis for a good cruiser. Of course, I still need to prove her capabilities when fully laden and in waves. I look forward to being able to provide some feed-back next year.

The future of dinghy cruising?