A few years ago I started sketching possible designs for a cruising dinghy to replace my small Mirror. The new boat was to be about 15' long, this being the largest which could be constructed in a normal sized domestic garage. My first ideas were strongly influenced by Eric Coleman’s innovative Roamer design which, at that time, had recently been introduced. The main difference between my sketches and the Roamer was that I proposed to concentrate the whole of the ballast at the bottom of a retractable keel, rather than use a combination of internal ballast and a steel centreplate. I considered that the better righting moment due to the lower centre of gravity of the retractable keel would allow me to avoid the need for raised buoyant ‘castles’, as used on the Roamer, and so save windage and produce a more conventional looking boat. An argument sometimes used against having retractable ballast is that it is only fully effective when lowered, but this has not caused me undue concern since a heavy keel tends to be left down most of the time that the boat is sailing, and the occasions when it would be raised are not generally those when a capsize would have serious consequences.

My second design also included a retractable ballast keel, but differed from the first, and from the Roamer, in that it featured a self-draining cockpit which required a different positioning of the buoyancy tanks, and hence a different internal layout. To make a dinghy self draining it is necessary to ensure that the floor inside is above the level of water outside, and to seal off the space under the floor to form a large buoyancy tank or, preferably, a series of separate buoyancy tanks.

Having placed such a large volume of buoyancy low down in the hull, it is then necessary to reconsider the stability characteristics, since this buoyancy is likely to be close to the centre of gravity of the boat, so that it produces little righting moment when the boat is capsized. To overcome this, I combined the buoyancy under the floor with buoyancy tanks extending to deck level on each side of the cockpit, and for good measure I also included buoyancy tanks at the bow and stern. Each of the buoyancy tanks alongside the cockpit is alone capable of supporting a large part of the weight of the laden boat. The stern buoyancy tank was intended mainly to provide essential dry storage: it is hardly necessary for stability since even at 90° of heel it is only just immersed.

Comparing the stability of this second design with that of the first showed that for angles of heel of around 60° the second design, with the wide spacing of the buoyancy tanks at the sides of the cockpit, would have better righting moment than the first boat, and so would have a good chance of recovering from an imminent capsize situation before the angle of heel became so extreme that the crew and loose equipment would be likely to be lost overboard. However, if both designs were to be capsized at extreme angles of heel, the first design with its buoyancy concentrated at the ends would start to show a superior righting moment as the heel approached 90°, particularly if raised ‘castles’ were used: and at angles beyond about 110° the second design tends to become stable in an inverted position.

To summarise, the advantages of the end buoyancy arrangements are:

A positive righting moment is available to recover from a capsize to 90° or more, even with only a relatively small weight of ballast.

The shape of the buoyancy tanks is such that they can readily be made internally accessible for maintenance and for use as storage compartments.

The cockpit floor can, if desired, be at a low level which would give a deep cockpit offering a sense of security. A deep cockpit is not, however, necessarily more comfortable than a shallow one, especially at large angles of heel.

The construction is generally simpler and can probably be made lighter.

Against these advantages the self-draining design offered the following:

Provided that an adequately sized cockpit drain was fitted, it would be unaffected by shipping any amount of water.

As discussed above, it has a rather better chance of avoiding capsize, and after self-righting it would rapidly self-drain and could continue sailing almost immediately.

Having buoyancy widely distributed throughout the hull, it would have a better chance of surviving a serious collision or grounding.

It could be left on a mooring for long periods without collecting rainwater.

It would be an easier boat to keep clean since mud, and sand could be flushed out through the cockpit drain with buckets of water.

The advantages of these two types seem to be fairly finely balanced, but I chose to build the self-draining type. I was, however, concerned that the widely spaced buoyancy tanks alongside the cockpit would give considerable stability in a fully inverted position, and to counteract this I built in a water duct leading from an inlet close under the centre of the foredeck, to one of the buoyancy tanks, together with a gravity operated air vent which would allow air to escape from this tank when the boat was inverted. The idea is that with the boat upside down, one of the side tanks would fill with water until the stability would be sufficiently reduced for the keel weight, possibly assisted by wave and crew action, to right the boat. I would readily agree that this is a last ditch measure and I have not actually tried it out.

Having decided on the general layout of the boat, I proceeded to finalize the shape of the hull. I did this with the aid of a computer program which calculated the shapes of all the curves as lists of dimensions, so replacing the traditional drawing spline held down by lead weights on the drawing board. I still had to do some drawings, but these did not have to be very accurate since the table of offsets and the shapes of many of the plywood parts were read directly from the computer printout, rather than being scaled from drawings. This was several years ago, and if I was to tackle the same job today with the use of a more modern computer, linked to an automatic drawing machine, I would be tempted to arrange for the computer to produce at least the line drawings, rather than simply a printout of dimensions.

Before starting construction, I made a tenth scale model of the boat out of plasticard (a modelling material convenient for modelling chined boats and available from model railway shops), and this did help to check that the appearance was as expected, and by floating it in a basin I was able to do some stability measurements. With modern computer facilities the stability characteristics could be accurately calculated, but writing computer programs is likely to take longer than making simple models, as most people who have tried will confirm.

The form chosen for the hull was fairly narrow, 5’6” beam, and with a soft turn to the bilges it is more like a typical small keel boat than most un-ballasted dinghies. I considered that this form would give a righting moment which, although initially low, would rise steadily and predictably until a large angle of heel was reached, so that although the boat would frequently be well heeled, the risk of a disastrous capsize would be minimized. Generally this has proved to be the case and also the boat is well balanced and easy to steer when well heeled, but the disadvantage is the relative lack of initial stability which allows the boat to roll more than I would like when at anchor, and worries potential crew members when they first come aboard.

Double chined plywood construction was adopted, and a very useful feature is that aft of the mast position the bottom panels blend from a vee section into a flat region, and two deep rubbing strips on each side of this flat region allow the boat to sit level when it dries out on hard ground. This makes it more comfortable when dried out for the night, and simplifies the chocks needed to support it on its trailer. On hard ground the rubbing strips lift the centreboard slot clear of the ground level and this does seem to help prevent stones getting into the centreboard case.

The buoyancy spaces are divided up into twelve separate watertight compartments, and most of those compartments which are below the waterline are filled with polyurethane foam. In the event of a collision with a ship I would hope that the pieces of boat left afloat might be large enough to act as a life raft. A large volume of foam buoyancy is quite heavy so if it is low down in the hull it is useful ballast as well as buoyancy.

Heavy retractable keels are usually made to retract vertically, but I chose a pivoting arrangement since in an open boat it is not easy to accommodate the height of a vertically retracted keel, and also a pivoted keel is more suitable for a boat which is to be frequently sailed in shallow waters. A disadvantage of the pivoted keel is that a ballast bulb is not practicable, so the keel must be fairly thick to accommodate a useful quantity of ballast, and this leads to a wide trunking holding a lot of water which sloshes about violently when sailing fast. In a future design I think that it would be feasible to construct the trunking with a weighted flap folding down from the trailing edge of the keel. The alternative of flexible flaps as on racing dinghies might not be practicable because of the width of the trunking. The side forces between the upper part of a pivoted keel and the casing can be large when the boat is sailing, and to reduce these forces I made over a third of the length of the keel to extend beyond the pivot point. The lifting cable is attached to the top of the extended part of the keel so as to have a good lever arm and to keep all the mechanism and cable above the water line. The cable is led to a stainless steel ratchet winch which is quick acting, but one must try not to let go of the handle when the ratchet is disengaged to lower the keel. Winches with an automatic brake are now available but not, as far as I know, in non-ferrous material. The forward end of the centreboard casing is extended up to house the keel mechanism, support the aft end of the foredeck and take the downward thrust from the deck-stepped mast. Nylon rollers built into the upper part of the keel were intended to reduce friction and wear between the keel and the fibreglass lined casing, but PTFE pads would probably have been simpler and equally effective. The keel, which is of aerofoil cross section, consists of a lower part of solid lead and an upper part of timber, the two being joined and encapsulated by a substantial fibreglass sheath. The weight of ballast in the keel was originally intended to be about 170 lbs, and because this weight is close to the tip of the keel it would, in the event of a capsize, provide a greater righting moment than would the crew of a capsized racing dinghy standing at the root of the centreboard or pulling down on the weather jib sheet as is the usual practice. However, when the completed hull was weighed it was found to be somewhat heavier than expected and at this stage the keel was the only part which was unfinished and which could be lightened. Accordingly some lead was removed from the keel, but the boat is still self-righting from 90° of heel, as has been verified by a test in a marina. The reduction made to the ballast must, however, have reduced the margin of righting moment available to overcome the windage of the side of the hull and the effect of shifting cargo and falling crew members.

The ballast in this boat was intended only as a self righting device; it was never expected that it would make much contribution to stability at normal sailing angles of heel. Generally in a small boat the crew forms quite a large part of the total weight, and so it is logical to make full use of this weight as movable ballast by providing comfortable side decks so that the crew can use their weight effectively for long periods. In my boat I have avoided any seating other than the side decks and a removable rowing thwart so as to leave the cockpit as spacious as possible. In light winds the crew can either sit on opposite side decks, on the thwart or on the floor, the latter being the most comfortable.

To increase sail carrying ability to beyond that which the crew weight can provide, one could design the hull with an increased waterline beam to raise the metacentric height. However, the extra wetted surface and more distorted underwater shape of a wide boat would more or less eliminate any speed advantage made possible by the larger sail area. This explains why the International 10m² Canoe is about the fastest of all small sailing craft around a triangular course (a sailboard, which is also narrow, can be faster on a broad reach), and a sailing canoe fitted with the minimum weight of deep ballast keel to make it self righting could be an effective cruising dinghy, as was demonstrated by Uffa Fox when he sailed to Brittany in such a craft. This is not to deny that wide boats do have a great advantage as cruising dinghies in that their initial stability offers a safer working platform and much more comfort at anchor.

It must be noted that these brief and perhaps over simplified comments apply only to dinghy sized boats; for larger boats the crew can usually provide only a small part of the moment required to support the sails and it is therefore necessary to increase beam and/or ballast to achieve a good performance, the trend these days being to go for extra beam rather than extra ballast, although there are exceptions.

The rig of my boat is gunter, but with provision to stow away the gunter yard and attached mainsail and to then set a much smaller, heavier weight Bermudan mainsail in strong winds. This arrangement is intended to allow a large sail area for light winds without the penalty of the excess weight and windage on an unused length of spar aloft when under shortened canvas. To make the arrangement work it is necessary to design the boat with storage for a spar which is only 3’ shorter than the hull, and this was achieved by building a watertight tunnel into the forward buoyancy tanks. It would not be feasible to adapt most existing boats in this way.

The mast, which is of aluminium, is free to rotate in a socket on the foredeck and this allows the mast and gaff to line up with the wind which should, hopefully, improve the airflow over the mainsail. Also, because the mast and gaff rotate together, the gaff does not have to rotate around the mast, so it is possible to avoid the use of gaff jaws which might perhaps damage an alloy mast and would dictate a circular section extrusion. Instead of gaff jaws a specially made slider, which runs in the luff groove in the mast extrusion, is used to connect the lower end of the gaff to the mast. The same luff groove also carries the sail slides fitted on the luff of the small Bermudan mainsail, and on the lower part of the luff of the gunter mainsail. To avoid the mast rotating through an excessive angle, the kicking strap is led from the boom to a strong arm projecting slightly further from the back of the mast than does the gooseneck vertical pivot axis. This gives an angle of rotation of the mast about 20° greater than that of the boom, although when the boom is well out, the angle of the mast, gaff and boom are all limited by contact with the shrouds, which are attached to the front of the mast near the top.

To make the mast buoyant it is plugged at top and bottom, and external halyards are used. The main halyard is attached to the gaff by passing it through a rope strop tied through a hole in the gaff, and then hooking the looped end of the halyard over a plastic hook on the front of the gaff below the strop. By making the strop fairly tight around the gaff, the gaff can be hoisted right up so that it is almost in contact with the mast, which would not be possible with conventional fittings between the halyard and gaff. With the gaff hoisted into this position and with a tapered lower end to the gaff, the cut of the gunter sail can be the same as for a Bermudan sail. The strops and hooks on the gaff are duplicated so that the sail can be slab reefed, and the small Bermudan mainsail can also be slab reefed, giving four alternative mainsail areas. It is necessary to lower the sail to reef, but I would do this anyway, especially if single-handed. Another detail is the use of plastic reefing pegs to attach the foot of both mainsails to the boom. I find these more convenient than a bolt rope in a groove and they double as reefing ties.

Generally I have found this rig to be successful, and the short mast compared to an equivalent Bermudan rig is an advantage on inland waterways and when trailing. The only problem I have experienced is that in strong winds when the sails are reefed, or the small mainsail is used, the middle part of the mast bends slightly backwards rather than forwards, and this increases the flow or camber in the sail, which is undesirable in these conditions. I do not think this is because the rig is a gunter, it is probably simply due to the rig being rather large for only one pair of shrouds. I am considering the use of spreaders and/or lower shrouds to give support to the middle of the mast, as is normal on all but the smallest of Bermudan rigged dinghies, but if I do get around to making this modification I will find it more awkward to get the mast up and down when going under bridges.

Changing to a smaller jib in a rising wind is one of the most difficult operations to carry out in a dinghy, particularly if the boat has a foredeck and one is single-handed. I have experimented with a wire running forward from the cockpit to a sheave at the stem head. This allowed the three corners of the jib to be shackled on while working in the cockpit, and the tack could then be moved out to the stem before hoisting the peak. The disadvantage was that the jib had to be set flying, which proved to be unsatisfactory. I have now discovered that in strong winds my boat is well balanced with just the small mainsail, so my intention in future is to sail with the small mainsail only, as soon as the wind threatens to become too strong for the working jib. If the boat could not be managed without a jib, I would have had to consider a roller-reefing jib, although I have doubts about their efficiency as a substitute for a storm jib. These doubts may be unfounded; I have never sailed with a roller jib. A possible alternative to a roller jib might be a ‘running forestay’, which would be additional to the normal forestay and would be led to a Highfield lever in a similar manner to a running backstay. This would allow the jib to be hanked on while in the cockpit, and to remain under control while being hoisted.

I have noticed when sailing Wayfarer dinghies that the further aft one sits, the less one gets soaked by spray. This was one reason why I positioned the small cockpit in my boat well aft behind a long foredeck. This positioning of the cockpit also suits the hull shape which, following modern trends, has the maximum beam and the centre of buoyancy well aft. The cockpit is under 6’ long, but being uncluttered with unnecessary furniture it has adequate space for two or three persons. The flat floor continues under the foredeck to give full berth length for sleeping. A single thwart spans the cockpit, but is removable for sleeping. A gimballed compass is mounted under a removable panel in the centre of this thwart. Gimballing only about a fore and aft axis has proved to be satisfactory. At the forward end of the cockpit the top of the centreboard case projects about 3” above the floor, but although I originally thought that this would be an obstruction, it does in fact provide a useful foot rail for the crew. At the aft end of the cockpit the floor is flat right across and, despite the use of non-slip finish, I found it necessary to fit toe-straps for the helmsman; but a solid foot rail might be better. Because the cockpit is wide and deep it is completely self-draining only when the boat is level. However, the water drains from the cockpit into a transverse 'gutter' fitted with a special oversize self-bailer, and the suction which this creates minimises the quantity of water which can collect at the lee side of the cockpit when the boat is heeled. The self-bailer is operated through a linkage from a small lever in the centre of the cockpit, so that it can be kept closed when not required.

A large compartment aft of the cockpit provides dry storage space and contains the outboard engine, together with all bedding and clothing. A shelf inside this compartment holds small items such as the radio set, and prevents them falling into inaccessible places. It is a pity that the engine has to be kept in the same locker as clothing, but it is an item which must be kept dry if it is to be fully reliable. The hatch on the aft compartment is arranged to slide fore and aft like a yacht’s companionway hatch, but it can also be clamped down onto a soft rubber-to-stainless steel seal using two overcentre clamps.

Under the foredeck is a ‘galley’ area to port, and stowage for inflatable dinghy, anchors and sails to starboard. Food and cooking utensils are kept in two plastic racks which slide out from under the foredeck, and fresh water is pumped from a 9 gal. tank under the cockpit floor. This tank was actually a tentative approach to water ballast, but is not really large enough for this purpose. It does, however, allow sailing for several days without bothering to collect water.

The oars are over 9' long and, together with the slim hull form, this makes rowing reasonably easy so, in principle at least, the motor is used only for long distances in flat calms or on inland waterways. The sides of the cockpit are straight in a fore and aft direction and this allows the long oars to be stowed on brackets on the sides of the cockpit, with the blades forward under the foredeck. The provision of convenient stowage for oars is a point to be considered early on in the design of any cruising dinghy.

At night a simple ridge tent is fitted over the boom and covers the cockpit and also the hatch into the aft compartment. The tent is as small as possible to make it easier to handle in a high wind. The material is heavy PVC which certainly produces considerable condensation, but at least does not leak or rot. The colour is blue, but I think that a warmer colour such as brown or red would be nicer on a cold grey morning. The sides of the tent wrap over the gunwales and are secured by ropes passing back through Tufnol reinforced slots through the teak rubbing strake to cleats inside the boat. This avoids vulnerable attachment points on the outside of the hull, and the slots in the rubbing strake are also useful for securing fenders.

The rudder and rudder fittings are extra strong; we did have one of our club-owned Wayfarers break its rudder at sea, and I have heard of this happening to other Wayfarers. Fortunately our Wayfarer was able to drift back downwind to the shelter of the Blackwater. I tried to make the stock of the rudder even stronger than the pivoting blade so that if anything did break, it would be the blade, which would be relatively easily replaced, and it would perhaps be feasible to carry a spare, possibly shorter, blade on board. A tiller line is permanently rigged and runs around the inside of the cockpit. This line can be clipped to a hook on the tiller, either to hold the tiller at a fixed angle or to allow steering from any position in the cockpit. With the tiller fixed the boat will self-steer on almost any course in light winds. I remember once sailing from Clacton through the Raysand Channel and into the mouth of the Crouch without adjusting the helm. I suspect that more dinghies would be capable of self-steering if they had larger rudders.

This boat has now been in use for several seasons and has made a cruise of one to two weeks each summer, as well as week-end sailing in company with our club-owned Wayfarers. The annual cruises have

included four cross channel passages, the longest of which was about 80 miles, this being completed in about 20 hours, sailing with a light beam wind, which I would consider to be ideal conditions. Inevitably, I frequently find myself trying to race our club’s Wayfarers, and usually losing, which is only to be expected since the Wayfarer is longer, wider and much lighter than my boat. Surprisingly, in very light winds I can just about keep up with, or even overtake, the Wayfarers, possibly because I have marginally less wetted surface per sq. ft. of sail. In stronger winds the Wayfarer becomes progressively faster since its wide beam at deck level allows the crew to sit out more, and its light weight gives it less drag and a chance of planing. I would like to think that there must come a point at which the Wayfarer would have to lower sail to avoid the danger of swamping or capsizing, and I could catch up again but, perhaps fortunately, this has never occurred.

If I were to build another cruising boat of this size I would seriously consider a miniaturised cabin boat designed to give the crew some shelter from the weather while at sea. The recently proven ability of cabin boats under 10’ long to cross the Atlantic must have impressed many dinghy cruising enthusiasts, despite suggestions that these voyages incurred excessive risk. However, if I did choose an open boat again I would make little change to my present design, apart from trying harder to save weight in the hull structure. Following the advice of writers in the DCA Bulletin and elsewhere, I made the hull of my boat stronger than would be normal for a racing boat, and I also sheathed it all over with fibreglass which gives a durable, low maintenance surface, but does add weight. I would now question whether the construction of a cruising dinghy needs to be any heavier than that of the racing dinghies. Most DCA members seem to take care in maintaining their boats, so durability need not an overwhelming consideration, and should one suffer a collision with an immovable object, the impact would be greater with a heavy boat, possibly resulting in damage as equally expensive as with a light boat. A light boat will have a better performance under almost all conditions, sailing or rowing, and will be easier and safer to road trail and to handle ashore. If sheer weight is a help in extreme rough weather conditions, as is often suggested, then perhaps this weight could best be provided by seawater ballast which could be jettisoned when it is not required.