Technical

Controlling weight aboard

Create a notification for "Technical"

It’s always the same old story: when you are equipping and provisioning your boat, following the exhaustive and essential list of provisions and various equipment to the letter, you can’t bring yourself to get out the scales. Weighing everything you are preparing to embark aboard – no thanks! Very few of us would be inclined to leave on the quay a few nice Burgundies, the tins of ‘confit de canard’ from Castelnaudary, the full Rhythm and Blues of the glorious 30s CD box set, or even the batteries for the electric bicycles and Aunt Lucie's bottle of vintage calvados. Of course you would delight the first person hanging around the pontoons watching you mockingly, keeping an eye on everything you can't get into your lockers and cupboards. Actually, you wouldn’t envisage for a moment dismantling the recently installed cool box or air conditioning system and taking it back to the chandlers in exchange for a box of spare blocks which in any case weighs the same. No, envisaging the pastis without ice cubes, or warm beer, is honestly not compatible with a successful cruise. Yet once everything has been embarked, you are close to, or have even exceeded, the recommended laden displacement. Then you ask yourself the inevitable question – am I safe with all this epicurean paraphernalia aboard? According to the most well-known architects, if you limit the excess weight to 15%, the consequences are less catastrophic aboard our modern multihulls, whose sections are quite beamy, and whose freeboard is greater than on the older models. The margin is still quite large before the risk of digging in the bows. Rather you will suffer from mediocre maneuverability which can lead to missed tacks, poor agility in choppy seas, hard work for the autopilot due to poor balance, or again premature wear of the structure and the parts taking care of the transmission of the power of your sails. Which is quite a lot… But the excess weight produces above all very poor performance in light weather, obliging you to start the engine(s) more often. And more diesel embarked means even more additional weight, with the risk of exceeding the + 15% limit definitively. Our new way of sailing leads us to demand more comfort – to the detriment of performance, of respect for the environment and perhaps even of active safety… So what are the (right) questions to ask oneself, to reach an acceptable compromise? 

If you are not yet owner of your own multihull

A quick analysis of your ‘comfort’ cursor is necessary, before deciding on the model which will suit you. If you can’t do without a dishwasher, a washing machine, the XXL-sized freezer, a TV screen in every cabin, as well as a bound copy of the complete works of William Shakespeare – not to mention the dive bottles and their compressor, it would be best to count on a boat of over 50 feet. Because the good news is that the waterline length can limit the problem - the bigger the boat, the bigger the useful load that it can accept. A simple formula to remember? The coefficient of finesse. The explanation from Christophe Barreau, the architect of the TSs from Marsaudon Composites and some of the Outremers in the new range, two lines where the displacement is an essential element in the design: “we obtain this value by dividing the waterline length in meters by the cube root of the unladen displacement in tonnes.” To understand better, let’s take some practical examples. The Lagoon 46, 14 m and 16.6 tonnes, will have a coefficient of 5.45, and an Outremer 45, 14.6 m and 8.7 t, will have a coefficient of 7.11. For comparison, Macif, second in the Route du Rhum, has a coefficient of 14 or 15. It is obvious that bigger floats are going to be able to absorb more useful load, but everything depends on the multihull’s design, Marc Van Peteghem points out: “between an ultra-comfortable and an ultra-fast boat, everything is about compromise.” As proof, let’s look at the difference in useful load between an Outremer 45 and a 15.24 m TS 5. Whilst they have a coefficient which is quite similar – 7.11 and 7.443 respectively – the first will be able to load 3 tonnes, whilst the second, which is longer, but has narrower sections, can only embark 2.4 t. Let’s also explain what we mean by unladen displacement. In principle, it is calculated with nothing full and no equipment, but also in its basic configuration, without any options. Consequently it is not surprising that certain builders are always trying to save weight in the structure, mainly by using sandwich construction. This is made possible thanks to the experience acquired in building, and allows some leeway for the equipment that will naturally find its way aboard. On sporty and luxurious boats, carbon even appears in the accommodation. It is no longer rare to see armchairs, chart tables, and even toilets in this material, which until now was reserved for the rig or the appendages. The more the boat is lightened, with headlinings, furniture and doors in composites, the more weight is available for a microwave or an ice-maker. More powerful and of course lighter lithium batteries accompany this approach. By saving some precious pounds everywhere, the builders have succeeded in fitting domestic appliances worthy of an apartment into a 40-footer.

You already own your multihull

There are many solutions and tips for saving weight, or distributing it better. Of course the smaller the boat, the more inventive you have to be. With the accessibility of carbon, the rig and the fittings can also be a source of weight savings. Be careful in this area with ‘false friends’; the new 3D single point sheet trimming systems for example require heavy structural reinforcements which are not necessarily advantageous compared to a track, which takes the forces in a more linear fashion. Preferring to repaint the deck, rather than falling for teak can prove to be a judicious choice, and can save quite a bit of badly-positioned weight. There is also no point in fitting a hot water tank which is too voluminous. As the temperature is very high, a 30-liter (8US gal.) tank is amply sufficient for having a hot shower. If you opt for a bigger model, remember that the tank always remains full. Likewise, there are now some shower sprays on the market which allow you to use up to ten times less water. Very good ventilation, with a few well-positioned dorade boxes and mushroom vents fore and aft can help you resist the latest special offer on air conditioning equipment. Finally, many doors and locker fronts can be replaced by flexible closures or curtains, and the drawers by cloth bags. In the galley, if you are leaving for a long time, it can be worthwhile looking at what exists in freeze-dried products, to replace the heavy cans of food. In fact weight can be saved everywhere aboard, and it is the sum of these small savings that makes the difference.

The solely useful load

The exercise will consist of reflecting on the mass of each piece of equipment, and studying what lighter alternative could replace it. A more radical choice: don’t embark this equipment according to your priorities, but also according to the availability of certain parts and accessories on your route. A list of the references of spare parts, with the addresses of where to find them, as well as the assistance of a person locally who could send you the parcels quickly according to your planned itinerary is without a doubt wiser than filling the forward part of the hull with a clutter of parts which in any case will never be the ones that break… Similarly, there is no point in fitting an XXL-sized refrigerator if you have decided to cruise in cold waters, where food can be stored under the floors below the waterline. Because this useful load, whose capacity has increased by 30 to 50% over the last three decades - we have gone from 2 to 3 tonnes for 45-foot boats - has reached its limits nowadays with the ever-increasing need for comfort. Resist the temptation to push the cursor to its maximum, and above all take care with the load distribution – it plays an important role in your multihull's handling. There are two rules to be respected, Jean-Pierre Fréry from Chemins d’Oceans reminds us:  “put the weight as low down as possible in the boat and avoid loading the forepeaks, so as to keep the rudders in the water, for good control, especially if the boat planes." Chemins d’Oceans has prepared a Lagoon 400 S2 for a circumnavigation via the Great Capes. Although the essential part of the preparation is concerned with safety, the weight distribution has also been taken seriously. “The idea is above all to sail with a minimum amount of weight forward of the mast bulkhead. We have even done away with the traditional anchoring equipment and fitted a 16 kg (35 lb) Fortress anchor and 60 m (200’) of weighted line (having personally tested it, it works very well). A removable bowsprit, adjustable in 2D was preferred to a thick beam.”

Afterwards, to save weight on the scales, everything is about common sense. Numerous attitudes when cruising allow you to avoid weighing down the boat. In first place, and to avoid extra weight in diesel and the use of a heavy, thirsty generator, 1,000 watts of solar panels and two wind generators supply a 1,080 Ah battery bank. A 3,000 watt inverter can supply 220V at a sufficient rate. The same practical philosophy applies for Olivier Mesnier, our ocean-going admiral, who takes a small, light, portable generator, and adopts a similar fresh water strategy:  “so as never to drag around full water tanks, we fitted a fairly powerful watermaker, 63 l/h, and we often use it when under engine.” In two or three hours, which is often the case daily, you have enough for your needs.

You don’t want to do without the assistance of automated winches and roller furlers? Hydraulics can be worth serious study. Nowadays, the units are small and compact. And the motors of the accessories are much lighter and less bulky than their electric counterparts. Not to mention that they are much less energy-hungry – with less weight in the battery bank as a bonus.

If you want to retain your boat’s agility and enjoy its sailing qualities, don’t hesitate to treat yourself in your chandlers: many new products have the required lightness qualities, for example textile fenders, or furlers which will be perfect for lightening the bows of small boats.

Share this article