What It's All About?
Excerpted from Ocean Spirit Magazine

Probably no craft suffers from greater misrepresentation or is surrounded by more myths and fallacies than the trailer-sailer. Purist yachtsmen scorn it as a half-breed design while the uninitiated, having picked up all kinds of unfounded information from all kinds of sources, often regard it as the fastest form' of maritime suicide.

Neither of these theories is accurate nor, for that matter, are ninety per cent of other stories that discolour the true picture of what the trailer-sailer is and what it is intended to do.

The only way to really understand what the T-S is all about is to look at it closely in relation to basic yacht design, sailing theory and the adaptation of both which has created this hybrid boat.

The whole trailer- sailer argument centres around the keel, so let's look briefly at the keel and see how it works and why there should be problems with this type of craft.

The Theory

The theory of sailing revolves around two centres of pressure-the pressure of the wind on the sails and the pressure of the water on the keel. Neither can work without the other. If there were no pressure in the sails the boat would not move, and if there were no countering pressure on the keel, the boat would be pushed sideways through the water.

The theoretical point at which the wind pressure operates on the sails is termed the centre of effort, and where the pressure of water acts on the keel is the centre of lateral resistance. It is the balance between the centres of effort and lateral resistance that determines, to a great extent, the boat's performance. Particularly this is the case when the boat is going to windward, for when running before the wind, no lateral resistance is required, and thus the keel is non-effective. This indicates the reasoning behind the shape of the keel, which offers its greatest area, and thus its greatest lateral resistance, when the sideways pressure in the sails is greatest- i.e., when close-hauled.

So it follows that the bigger the keel area and the deeper the keel, the better resistance it offers to the water. Obviously, there comes a point at which the size, weight and friction of a huge keel would create more problems than it would cure, but in theory at any rate, a deep keel is the ideal means of reducing sideways drift or 'leeway' as it is termed.

That's fine for sailing performance. But when the yacht has to be pulled out of the water, the keel becomes one great clumsy nuisance. Bad enough when you just want to run onto a beach, but quite impossible when you want to put the boat on a trailer and take it home. Here exactly the opposite applies, and the ultimate keel for trailering is no keel at all, or at best just a shallow stiffener on which the boat can be landed.

The Practice

A large centre plate which can be raised for trailering and lowered for sailing resolves both problems, and in small sailing dinghies this is the practice used. However, there is another factor involved, for the deep keel of a yacht serves another purpose-that of counteracting the heel of the boat and preventing her from capsizing. Such keels are heavily ballasted with weights of something like 40 or 50 per cent of the total weight of the boat and provide a very strong righting lever when the boat is heeled.

However, it is almost impossible to get anything like good weight into a centreplate. Heavy iron plates are often used, but because of their relatively thin gauge they are never heavy enough. Heavy ballast cannot be secured to these plates or they would not be retractable. Thus the essential righting lever is lost. While some trailer-sailers compromise by having weight low down in the hull, this is still not completely successful as it does not act low enough to create the required righting lever. Which means that given a strong gust of wind, the boat can be capsized, or at least heeled excessively to a point where she will swamp.

The Problem

And this is where the hoodoo of the trailer-sailer lies. Early models would almost certainly capsize if not handled properly, just as a centreboard dinghy will capsize in the same circumstances. Developments in the design of trailer-sailers in recent years have reduced this tendency, however, and it is not common (although still not unheard of) for a T-S to completely capsize and finish upside down. The problem that has not been eliminated, although again it has been greatly reduced, is the tendency for the T-S with its lack of righting lever, to heel excessively, and thus risk swamping.

The Answers

Some of the design methods used to reduce this risk is simply the addition of further ballast in parts of the hull, or by means of bilge keels or patent swing keels which lower a ballast section when the boat is in the water. But even allowing for the possibility of overcoming the lack of ballast to a certain extent, these methods often increase trailering problems because of the added weight or depth of the ballast section.

Increasing the beam of the boat makes her more stable and many trailer-sailer designers have adopted this method either on its own or in conjunction with increased ballast. And there are other systems which rely on the boat rounding up in a squall (not a good practice!) or the use of fancy release gear to free the mainsheet under pressure. But as long as the righting lever is reduced or lacking, there is no way that a boat under sail can be made completely stable, and thus the trailer-sailer buyer must live with the fact that his boat can and will heel to a greater degree than a ballast keel yacht. However, accepting that fact is perhaps the most important aspect of trailer-sailing, for having once accepted it you will take steps to allow for it, realising that like all boats, trailer-sailers have their limitations.

A pilot flying an aircraft with four engines has little fear of engine failure since he has four chances of survival should such a happening occur. The pilot of a single-engined plane, by contrast, knows that if his engine fails, he must put his aircraft-down quickly before she runs out of gliding space. He is therefore aware of this throughout his flying time, and keeps a constant eye out for likely landing places in the event of having to make a forced landing.

So with the trailer-sailer skipper. He knows that his craft may be endangered by a sudden squall unless he is ready for it, and thus sails all the time with this in mind and his eye alert for any such problem. Single-engined aircraft fly hundreds of thousands of kilometres safely, and there is no reason why trailer sailers cannot sail a comparable distance with equal safety provided the person in command knows what he is doing. Most of the rumor and fantasy that has built up around trailer-sailers has been the result of accidents due to 'pilot error', rather than any defect in design or construction of the craft.

The Advantages And Disadvantages

It would be safe to say that the main feature of trailer-sailer design is compromise. Basically, this boat is a compromise between a centre-board dinghy and a keel yacht. As such it inherits many of the advantages of both while also inheriting a few of their disadvantages. And in addition, it has some of its own unique features.

One of the hardest things about the trailer-sailer is to put it in a specific category. That is because some trailer-sailers are in fact big centre boarders, some are small keelers, and some, such as swing keelers, have no comparable design in either the larger or smaller boats. Perhaps the only feature which can in any way categorize the design is the term 'trailer', indicating that this type of craft is portable. The means of trailering it, however, can be wide and varied, hence the different designs used in relation to the keel.

The compromise between keel yacht and centre board dinghy has come about as a result of the demand for sailing craft which can be taken from waterway to waterway without the problem of hazardous passages in open water, and which can be taken to waterways which are completely landlocked or inaccessible from seaward. Initially this demand was relatively small but the advantages of this type of craft have caught the imagination of the public and nowadays it is the most up and coming type of yacht design in Australia and New Zealand. Its popularity has been increased by some of the spin-off advantages, not least of which is the saving in mooring and maintenance costs as a result of keeping the boat out of the water. Mooring, slipping and anti-fouling expenses are eliminated, and the boat can be protected from the ravages of the weather in the garage, or under tarpaulins in the back yard. It can also, of course, be protected from light fingered gentry and others of the waterfront who do not have boating in mind when they creep aboard.

Of course, like any other compromise, there are some disadvantages in the T-S design. It would be a remarkable achievement if any craft were designed without some problems somewhere, and particularly so when the design is intended to cover a range of boating activities or satisfy a great number of different needs.

Probably the best way of looking at this type of boat is to compare the various advantages and disadvantages of the trailer- sailer design with those of a keel yacht of comparable size.



The saving in cost initially is not very great. Although generally speaking, trailer-sailers are somewhat cheaper than comparable keel yachts, that is not always the case, and there is the additional cost of a trailer, which often brings the total outlay up to that of a comparable keel yacht.


This is one area where saving in cost can be considerable. The T-S can be kept under wraps or in a garage, thus reducing the need for maintenance work, particularly where varnish or painting is required. It is more convenient, also, and one is more likely to spend an hour polishing and cleaning if the boat is at home, than when such a job involves getting a dinghy down to the beach and rowing out to the mooring.


Kept on the trailer at home, the T-S costs nothing, unlike the keel boat which is eating its head off on a mooring while it is not in use. This is probably the biggest Cost advantage of this type of boat as mooring fees are not inconsiderable.


Another good cost saving for the trailer-sailer. A boat kept out of water does not require anti-fouling, and like moorings, anti-fouling composition is not cheap.


The greatest physical advantage of the T-S design, it enables you to take your yacht with you on holiday no matter where you go, provided there is water and access. Always check the latter, as even waterways with boat ramps often have difficult car access or ramps that are too shallow for trailer-sailer launching.


Apart from the immediate offering of lots of stowage room for holiday gear in the boat, if need be she can be utilized as temporary accommodation both on the trailer and in the water. This is a common practice in Europe where T-S's vie for space in caravan parks.


Another good physical advantage of the shallow draft design. You can run your boat up on a beach without risk of damage to the keel and thus eliminate the keel boat hassle of having to tow a dinghy everywhere if you want to get ashore. Indeed, while requiring the added expense of a trailer, at least the T-S eliminates the cost of a dinghy!



This is without doubt the principal disadvantage in the trailer-sailer design. Although different types of craft may approach the problem differently, the fact remains that without the deep keel, a T-S can never be as stable as a keel yacht. To what degree this instability affects the boat and her sailing ability varies from model to model.


Not a very great disadvantage, but there is no denying that getting sailing on a T-S involves more hassle than on a keel boat. Where in the latter case you just slip the mooring and go, with the trailer-sailer there are all the problems of trailering, launching, rigging the mast, parking the trailer and so on. Of course, these have to be weighed against the saving in the cost of moorings, and the ability to launch and sail where you wish.


As a general rule, interior accommodation is usually more limited in trailer-sailers than in keel yachts, due mainly to their design needs for trailering, and intrusion of the centreplate housing.


The question that arises out of all this, of course, is whether the advantages outweigh the disadvantages. And the answer, obviously, depends on the individual boat and the individual buyer, and also on the sort of work he intends the boat to do. If your plans involve only quiet water sailing in sheltered areas then the disadvantages virtually do not apply, and the advantages of the design are considerable. By contrast, if you aim to sail offshore or in any sort of open sea areas, then the lack of stability overrides most of the advantages. For the most part it is probably safe to say that the average trailer-sailer man has family holidays in mind with perhaps the odd bit of club racing. In this case there is much to be said for the design provided, of course, its limitations are kept in mind. This sort of sailing usually involves both sheltered and open waters, although not usually open sea. So both the advantages and the disadvantages have a place, but without doubt the advantages have the edge.

Naturally, it is not easy to make comparisons when there are so many different styles of trailer-sailers. Where a centre-boarder may offer decided advantages, a swing or bilge keeler may not be suitable. However, in order to offer some guidance to the would-be T-S buyer, some standard must be set. For the following guide to the features of keel and T-S boats an average comparable craft of each design is used. This means that the descriptions are broad and some variation may occur in special cases or with special craft. But as a general all-round comparison, the table will give some indication of the advantages and disadvantages of trailerable as opposed to keel yachts.

Trailer Sailer
Keel Yacht
Shallow Lake
Deep Lake
Wind Strenghts
Gale Force
Performance Racing
Club Racing
Day sailing
Family Holiday
Extended Cruising Limited Good