Chris Morgan’s letter in the last Bulletin reminded me that other hints have been dropped regarding my writing articles based on my replies to members’ technical queries. Whilst many of the questions are specific to one person’s circumstances of boat, experience, fitness and sailing area, there are many that would form the basis of a regular series of, if not articles, then random jottings. So, subject to the editor’s approval — here goes!

Ballast

Dictionary definition — any heavy material placed in a ship to sink it to such a depth as to give it stability and prevent it from capsizing when in motion.

Why ballast works.

1. In the diagram you will see that the centre of buoyancy moves away from centreline of the boat when it heels. The weight of the ballast remaining on the centreline maintains a downward leverage to resist the heeling supported by the upward pressure of the buoyancy which is now acting from towards the bilge.

2. The extra weight of the hull means that the craft sits lower in the water and that therefore the buoyancy of the bilge is quicker to take effect.

3. The extra weight of the hull adds to its moment of inertia; wind gusts take a little longer to take effect, and the handling of the craft becomes more ‘forgiving’.

Sailing dinghies, regardless of type, are designed to depend to a greater or lesser extent on their crew weight acting to windward in order to hold them upright against the heeling effect of the wind flow over the sails. The more the crew can be depended on — because of their skill, strength to hang overboard, and not least because they only have to exert themselves for the duration of a race — then the lighter the boat can be, the larger the sail area can be, and, within reason, the narrower the beam. The development of lightweight construction methods and the innovative ideas of designers like Uffa Fox have produced, since the 1920s, dinghies that can plane, a feature that is now taken for granted.

It is perhaps unfortunate that the cheapest and easiest dinghies to obtain second-hand are old one-design racing or so called general purpose dinghies. Accordingly, people, notably single handed sailors, often end up with a craft that was intended for a crew of two and/or a boat requiring physical strength and fitness that they don’t possess. The problem mainly arises in sizes of craft above 12’ LOA. One of the DCA guidelines on boat size (viz, one foot of boat for each stone of crew weight) is aimed at the problem. Certain types of heavier, beamier craft of stable shape can be the exception, however. My advice is more often sought-after regarding this racing/GP type of dinghy, and how to turn it into a less tiring beast, than any other subject. I often feel that the easiest and best advice I can give is to sell the b**** (can be either sex). However, it is not really the boat’s fault that it is being used for a purpose for which it was not intended.

There are two obvious solutions — reduce the sail area; add ballast. My belief is that tinkering with a design in this way is not the ideal solution. The craft was designed as a whole ‘concept’; reducing the sail area can make the boat a dull performer, and if one uses fixed ballast on the centreline it can only have an effect if the boat is allowed to heel. This apparent anomaly is explained above. The hull shape of racing dinghies has least water resistance when sailed upright, and only hiking out by the crew can achieve this. However, accepting that no boat is perfect, unlike their owners, what can we do about the inanimate type of ballast?

Position — for obvious reasons, it must be permanently placed as close to amidships as possible, although working craft of yesteryear sometimes had moveable ballast. It must be placed as low as possible: high ballast can add to the heeling effect. For an extreme example of this, think of a weight at the top of the mast! The ballast should also be placed as near the longitudinal centre of buoyancy as possible, thus keeping the ends of the boat light and able to lift to head seas and following seas. Light ends will mean a drier safer boat and also one which is faster.

From the above, one can hopefully deduce that the ideal place for ballast is on the bottom of the centreboard, if one has one, and is the reason that my predecessor John Perry put it there when designing his own cruising dinghy. Alternatively, one can have the whole centreboard of heavy material, commonly galvanized sheet steel. However, usually ballast ends up by being secured close to the sides of the centreboard case and close to the bottom skin or planking of the boat. I accentuate the word ‘secured’ as heavy weights free to move would be an obvious hazard to any craft.

At this point, I should digress about the ‘flip side’ of ballast. If replacing a wooden centreboard with a steel one, one should ensure that the pivot pin area is strong enough: actually I fancy that the most strain comes from resisting leeway, but the extra weight still has to be supported. It also has to have a tackle or small winch to haul it up. Invariably the plate will be thinner than the board, although there is no point in a thin plate as, apart from the danger of its bending, it would not have much weight. In order to prevent the plate from banging from side to side — we used to call it ‘bonking’ — one can fill the space with sheets of Formica. This can be attached to the inside of the case (difficult; in the form of large washers around the pivot, may not be large enough to give a reasonable bearing service) or glued to the sides of the plate where it is inside the case. I have found this latter solution to work well but epoxy glue does not work, at least for me, and contact adhesive such as Thixofix or Evostick has been satisfactory. The most important consideration is that, as ballast is weight, extra buoyancy may have to be provided if you want your dinghy to float when swamped, unless you use water as ballast. This is easily ascertained by swamping your dinghy and having an extra person of the weight of the proposed ballast stand in it. Bear in mind that the open part of the top of the centreboard case should remain above water if you want to be able to bale out the boat, or check that you can seal it off effectively by stuffing in rags etc. A frightened crew with a large bucket can make up for some seepage!

Ballast material — this can, of course, be almost anything, but usually the choice comes down to water, sand, gravel or lead. To my mind, the best is lead, as it is the heaviest for the volume of space it takes up; it is, however, undoubtedly the most expensive. Water sounds attractive, as it does not detract from the buoyancy of the hull in theory: it does take up a lot of space nevertheless, and if it stands above the waterlevel in its containers in the swamped dinghy, does reduce the effective buoyancy. As dinghies can vary in their response to ballast, it makes sense to have a trial with water ballast in old plastic containers before planning any more expensive and time consuming alterations.

Reinforcement of the bottom of the hull will certainly be necessary if you use the concentrated weight of lead, less certainly if you use flat bags of gravel or sand. These latter are less easy to ‘secure’, but are less likely to shift at normal sailing angles. You can, of course, throw them overboard, or lose them, with less effect on the purse. When using lead one should always try to ensure that one side of your ‘pig’ lodges on the hog (inner keel) in a timber boat. This is the part of the boat best able to carry the weight. If the other side bears on a stringer or frame member or rib you are lucky, but much more likely you will have to glue, fasten or glass in a part rib or stringer to spread the load across the bottom planking or skin. Securing lead can usually be accomplished with a little ingenuity. Lengths of stainless steel shroud plate are useful as they can be easily bent to shape in a vice.

How much ballast? — theoretically the more the merrier, but bearing in mind that the boat should still float, the following is a rough guide based on overall length. One thing is certain — half the minimum shown would have little effect.

12’ 100 to 140 lbs 14’ 120 to 180 lbs 16’ 160 to 220 lbs

Trailing — if you are not sure of the strength of the hull where the ballast is stowed, it is better to make some or all of the ballast removable. There is a great deal of difference in the ability of the hull to resist this type of stress when not supported by the water.

Making pigs of ballast — the traditional way is to cast them in moulds from molten metal. If, like me, you find heating a quantity of lead a hazardous occupation, then you can build them cold from roofing lead, which comes in rolls in various thicknesses and widths. Cut as many leaves of the required size as necessary to get the required depth, clamp them together and drill them, slowly and using lubricant, for the holes for the bolts which will hold it all together. Use stainless bolts, nuts and penny washers. When lugging them in and out the boat, you can call them Peter’s pigs, or something like that! If you make them removable, keep them small — 28 lb is big enough.

Data and Diagrams

Weight of a cubic foot in pounds:

Alcohol (it’s an idea) 50 Common brick 120 Lead 710 Hard coal 47 Iron 450 Softwood 25+ Water 63 Hardwood 40+ Concrete 140+

1 gallon (0.16 cubic feet) of water weighs about 10 lb. A slab of lead 10” x 8” x 1” thick weighs about 33 lb.