Little Compass RoseCaribbean Compass   November 2004
Fibreglass Boats and Damage Control
by Hugo du Plessis
Are fibreglass boats safe to go to sea? Such a question, daring to cast a doubt about fibreglass boats, will I am sure bring heaps of abuse on my head and indignant denials from every builder, as well as endless reports from owners of fibreglass boats who have crossed oceans, as I have myself, and sailed round the world. So I add hastily, before being burnt at the stake as a heretic (not for the first time! I was the first to dare to suggest that fibreglass boats needed maintenance), that it does not apply to fibreglass boats in general, or indeed to fibreglass as a material. The principle problem is the way most fibreglass cruising boats are designed and built, in particular regarding the difficulty, even the impossibility, of damage control - a very important factor when far from land and help.
My comments are based on 50 years of experience of fibreglass boats as a professional surveyor, builder, charter operator, and owner of over a dozen. I am widely considered to know more about fibreglass boats than most people. My book Fibreglass Boats [Adlard Coles Nautical, ISBN 0-7136-6209-3] has been a standard book on the subject since 1962 and is now in the 15th impression and five languages, frequently revised, updated and rewritten. The latest was in 2002 and I am already working on the next. I was one of those over?enthusiastic pioneers way back in the 195Os and well remember the days when many people could not say anything bad enough about fibreglass and they certainly tried pretty hard. Admittedly in some cases it was justified. Fibreglass boats have been my life's work. So you might think I should be the last person to make such a sweeping condemnation. However I have also had nearly 60 years experience of cruising, including 20 as a liveaboard, and am one of the most senior members of the Royal Cruising Club. Maybe I know a bit about cruising, too.
Not Designed with Damage in Mind

Damage control is an essential feature of big ship design, whether naval or commercial. There are endless rules and regulations. But with yachts, "damage" is not a word in the boatbuilder's vocabulary. Blame the owner's carelessness! No concern of the builder's if the boat sinks. What is insurance for? The surprising thing is that insurers stand for it. Their attitude is to increase premiums for everybody instead of encouraging the design of sensible, safe, easily repaired boats. That is safer policy than risking legal action in this profitably litigious age for suggesting a make of boat is less safe by increasing the premium or refusing insurance.
I sometimes wonder if builders know that boats are meant to leave a snug, safe marina and venture on the sea, a place of storms, rocks and other vessels, mostly of vastly greater size. The sea is a dangerous place, always has been and always will be. Man is a land animal. The sea is not his natural element. Nowadays there has grown up a popular misconception that when you get into trouble, all you have to do is send a Mayday, take to the obligatory "liferaft", which is the limit of the bureaucratic mind, and immediately a lifeboat or helicopter will come dashing to the rescue like the US Cavalry. Gone is the old idea of seamanship and saving yourself and crew by your own efforts. Yet it is still as true as ever that when you leave harbour you are on your own and you and your crew will live or die by your own skill and seamanship. Or as a former Commodore of the Royal Cruising Club once told me "When you go to sea you must be prepared to die like a gentleman".

Sinking has ever been the sailor's great fear. With fibreglass boats there are no seams to leak and no rot or worms or rust to destroy the bottom. So on the face of it, fibreglass boats should be safer to go to sea. Yet there are still many dangers, even in the open ocean, which can sink a boat: containers with sharp steel corners, wreckage, logs, crates with protruding six-inch nails. Boats have been attacked by killer whales and great white sharks, run down by ships and fishing boats, and cannot be detected by a submarine. Structural failure due to overloading a light boat not built to carry the amount of stores and equipment needed to cross an ocean can lead to sudden catastrophe. Failure of some underwater part of the elaborate domestic services now considered so essential is quite common.
There is seldom time to analyse the cause when the boat has a dangerous leak and is sinking. You are out of range of a lifeboat or helicopter, and in any case it would take too long to reach you. The radio is also damaged so a Mayday is impossible. The situation is desperate. The damage has got to be controlled and fast.

Access is Essential
There are many ways to stop a leak given ingenuity and resourcefulness, abilities for which sailors have always been renowned. But above all, survival will depend on access to apply this. That is where the design of fibreglass boats is critical and often dangerously deficient because without access to get at the damaged section of the hull, flooding cannot be controlled and sinking is inevitable.
Given access to the inside face of the hull it may be possible to stuff a sock in the hole or rig pads and shores or whatever ingenuity suggests. But this is not possible with the common one-piece pan moulding forming large parts of the accommodation and which prevents access to the inside of the hull. The crew will be faced with a sinking leak from somewhere unknown, emerging from under the pan moulding, spurting through holes and ducts for wiring and pipes, and probably through splits caused by an impact. How to get at the damage to plug it before the boat sinks is literally a life or death struggle. Builders assume repairs will always be done on land with the boat steady, plenty of time to plan discreet cuts with power tools - power is of course available - good lighting and professional skills, and the certainty of an inflated payment from the insurers.
It will be very, very different for a crew working knee-deep in fast-rising water, by the light of a dim torch, with few tools, seasick, wet, cold and frightened. Ordinary tools like saws and drills - even assuming there are any on board - would be too slow and difficult to use due to the motion. The situation calls for ruthless, brutal butchery. But what with? How many boats carry an axe these days, let alone a prybar or wrecking bar? In any case fibreglass is tough and springy, not at all easy to smash.

That is why I question whether many fibreglass boats are safe to go to sea. It is a question of design and access. This problem seems to have escaped the notice of all classification societies and authorities interested in safety. The bureaucratic attitude is to list safety equipment which must be carried for when the boat sinks. Do they not realise that the boat would be safer if it did not sink - if it could be kept afloat?
Accommodation, whether made in separate pieces or a large one-piece pan moulding, must allow full and easy access to all of the inside of the hull. Lockers should be cut out, not formed integrally with the moulding. Linings should be easy to tear away. There should be no closed compartments. All parts of the bilges should be accessible.
Wooden accommodation should also provide easy access. Modern practice is to glue not screw, yet even if wooden accomodation has to be destroyed it is much easier to repair than an elaborate fibreglass moulding.
Lockers, of course, are meant to contain things and - as I know from trying to survey bluewater liveaboard cruising yachts, as well as living on one for 20 years - are invariably stuffed full. There is never enough stowage space. Yet it is surprising how quickly a locker can be emptied in an emergency and no one is worrying about the clean contents getting wet and dirty.

Stopping the Flood
The first essential is to stop or reduce the inflow of water so that the danger of immediate sinking is averted and there is time to contrive something better. There are various ingenious devices such as a sort of folding umbrella, but damage can take so many forms it is impossible to generalise about best methods or materials. There are, however, certain basic principles. The first is that the water will be coming in under pressure and will wash away anything not well supported or strong enough, and in particular anything that relies on bonding or takes time to set. An external repair, if strong enough to avoid being sucked in, will at least contain the pressure. A polythene bag would do, but probably needs something to strengthen it. Old waterproof trousers have also been suggested. To attach an external repair, it is likely to need somebody going overboard and that can be dangerous if it is rough (as the ocean usually is) and cold. Exhaustion and hypothermia have sunk as many boats as hull damage.
Damage to a fibreglass hull will rarely be a neat hole as is usually assumed in theory; it is nearly always a split with jagged sides. This makes it more difficult to stuff in a sock, or push through an umbrella-type leak stopper. As a rule, only repeated impact, such as pounding on a rock, will produce the multiple cracks to form a hole. That is unlikely at sea where any impact will be a single wallop.
Once the flow of water has been controlled, a stronger repair can be contrived. Forget the fibreglass repair kit you were persuaded to buy. It will not stick to a wet surface. That is for when ashore. Some epoxies and putties will set underwater, but that does not mean that they will bond. Water has to be displaced from the surface and very few adhesives can do that. All take time to set and that is too long.
The old seaman's collision mat using a sail will take time to rig. Also there are practical difficulties. How do you rig a collision mat on a keel boat? A sail needs something to hold it tight against the hull, otherwise it will just act as a scoop. A mattress or foam plastic is better.

Making a Boat Unsinkable
Fibreglass does not float, an early objection - but the same was said of the first iron ships. If flooded, few wooden yachts with ballast and an engine will float either. So making a boat unsinkable is a problem to be tackled at the design stage. The structural requirements would make it very difficult to achieve later. There are two fundamental principles:
1) Even the lightest buoyancy material, air, requires space: for one ton of buoyancy you need one cubic metre (roughly 35 cubic feet) of air - the equivalent volume of five big oil drums. For the average 35- to 40-foot ocean cruiser weighing ten tons, there would have to be room for the equivalent of 50 oil drums! Moreover the paper displacement figure is just for the bare boat. To this must be added the two or three tons of stores, equipment and possessions - and for any ocean cruiser we really are talking about tons, and probably underestimating. The more stores and equipment, all absolutely essential, the less room for buoyancy, and conversely the more buoyancy the less room for essentials. There has to be room to work the boat and live in reasonable comfort when in harbour where the boat will spend a lot more time than at sea. Therefore the sheer space required for using trapped air as a buoyancy material rules out anything except emergency air bags, and once those are operated, on purpose or accidentally, the boat becomes unliveable and "unsailable".
2) It is not sufficient just to keep the boat afloat, decks awash. Sheer survival requires a degree of shelter, habitability and perhaps "sailability". The widow maker is exposure and hypothermia. This means the boat must float high enough for the crew to remain reasonably dry, sheltered from wind and water, able to cook, and have electrical power to operate a radio and lights. Perhaps also to run an engine, especially if a power boat, and ideally to sail after a fashion. Morale too is very important. It is far better to stick with the boat, if possible, than take to a "liferaft". However in practical terms this amount of buoyancy is almost impossible to achieve with a ballasted, well-equipped cruising monohull, although feasible with a catamaran.

Sadlers', for example, have built unsinkable boats by use of double skinned, foam-injected hulls, but even so still have to steal essential storage space. Both skins are fairly light construction and do not allow for the tons of extra weight essential for ocean cruising. Double skinned hulls like this and foam-filled spaces can only be done while the boat is being moulded, and are therefore design features. It is claimed that damage is limited with this type of construction. This may be so with minor damage. But the foam filling must be weak, or it becomes too heavy, and would not prevent a serious impact from damaging the inner skin too. Foamed compartments can become waterlogged and are then almost impossible to dry. Even closed-cell foam will disintegrate when wet, and then flotation is lost.
Aiming at unsinkability, ships have watertight doors and bulkheads. This is not practicable on a yacht. The interference with habitability would be unacceptable on anything but the most dedicated, large, ocean-going racer. The average yacht bulkhead is not strong enough; the sheer pressure of, say, a forecabin full of water would be formidable, even without surging. Most bulkheads, being designed for inward compression only, are secured by weak angles, sometimes  none at all, and would be torn adrift. Possibly the hull or deck would burst too. The weight would also affect the stability.

Well meaning bureaucrats specify collision bulkheads. Sadly they know little about boats and their thinking is based on fast, wide-fronted cars on narrow roads where head-on collisions are the rule. With boats, free to move in any direction, head-on collisions between two pointed end shapes are very unusual, rather like two spears meeting in mid-air. Most impacts are glancing blows and if between two boats, the victim is usually hit on the forward topsides or amidships where it is weak. The victim sinks and the attacker, with its strong stem taking the impact, escapes relatively unscathed. Even a hard-sailed dinghy can sink a much larger boat. Because it interferes with the accommodation, a collision bulkhead is usually placed well forward. With the usual overhang this is above the waterline and is therefore just a token, the collision bulkhead commonly being the aft end of the chain locker. Most boats have an overhang forward and fast power boats in particular sail with a pronounced bows-high trim so that any impact with rocks or debris will be well aft of any collision bulkhead. In all my years as a surveyor I remember only one case of a dangerous leak due to impact on the waterline. This was when a Moody hit a heavy mooring buoy, and it was well aft of the mandatory collision bulkhead. I have seen a few crumpled bows from hitting dock walls or lock gates, most often just resulting in bent pulpits. But I have seen plenty of underwater damage from rocks. Because any dangerous impact will be at or below the waterline, it makes more sense to have a double bottom.

The Watertight Lockers Option
One idea seldom mentioned, and more in the way of damage control than unsinkability, is to have numerous small watertight compartments. This is copying ship practice, where each watertight section is small enough that flooding it does not affect the integrity of the ship. However, on a yacht it is not practicable to divide the boat with watertight bulkheads, and even if it was, the spaces would much too large. But almost every cruising boat has dozens of lockers which could be made watertight fairly easily. This is not the same as filling them with buoyancy, as is done with "unsinkable" boats. By making the lockers watertight and fitting watertight lids, such as large dinghy hatches, they would provide some limited buoyancy yet still remain useable, just as a ship cannot afford to lose the payload of a hold.
As well as providing buoyancy, making lockers watertight would have the even more important function of containing a serious leak. With good planning the boat could virtually have a double skin over the entire underwater area. (If a pan moulding was used it would need to be stronger and better attached than usual because, being considered just accommodation, most are lightly moulded and weakly bonded. They generally break away and split if the hull is damaged.) One or more such watertight lockers could flood without unduly affecting stability and, most important, would prevent the rest of the boat filling and sinking. Essential systems like batteries and engines could be in their own watertight compartments so that the boat remains operational.

Another important factor is that having many small, watertight compartments would prevent surging, which alone can cause damage and seriously upset the stability of a flooded boat, even if nominally unsinkable. Moreover, a lot of this work could be retrospective and done in preparation for an ocean cruise.
Buoyancy and unsinkability sound like nice safety features. But do your sums. Work out the weight of the boat - plus everything you have or intend to stuff inside it. To be on the safe side double this at least; it is invariably underestimated. On the first haul-out after an Atlantic crossing every crew finds they have to raise the waterline several inches! On my 31-foot-waterline boat the rate of waterline change is roughly two inches per ton, a fairly typical figure.

So is it safe to go to sea in a fibreglass boat? Well thousands of us do. But they could be designed and built to be a lot safer. The trouble is that builders do not go to sea often enough - they certainly do not have the time for long-term liveaboard ocean cruising - and some have one-track minds based on racing. Speed sells boats, and to many designers the idea that anyone may not want to go racing is unthinkable. Production is dominated by convenience more than practical seaworthiness. Moreover, whatever the designer may say or the owner want, the last word in boatbuilding today is that of the company accountant.
Hull shape is also important. A long keel boat will ride over an obstruction and the slack bilges will tend to slide past. They are also more strongly built. The modern straight stem, flat-bottomed, fin keel, lightly built boat is more vulnerable to impact. And, with no proper bilges, if flooded the water will rise to a critical level much faster and the weight will soon have a critical effect on stability.
Damage control should begin on the drawing board.


Copyright© 2004 Compass Publishing