Choosing Your Boat Trailer
The parts of a boat trailer were covered in detail in our boat trailer parts section, the maintenance of trailers being covered on our maintaining your boat trailer page. This section covers the issue of choosing the right trailer for the job.
What Size Boat Trailer Do You Need?
The size of the trailer is very much connected to the physical size of the boat (you don't want it hang over the back too much - see trailer weight distribution) you wish to transport and more importantly to the boat's weight (the weight of the boat includes the engine and fuel). To help here, all trailers have their Maximum Weight (including the boat etc) stamped on them (normally on the manufacturers plate located near the trailer coupling). It is important that you don't choose a trailer that is just too lightweight for the job in hand. The rule is basically that the boats weight + unladen trailer weight must not exceed the maximum laden weight of the trailer.
If you choose a trailer that is designed for a lighter boat, you will stress the trailer components too much, resulting in their wearing out very quickly indeed, thus risking failure when towing, with all that that entails.
On the other hand, if you purchase a trailer designed for a heavier boat, then you run the risk of your boat being bounced around on the trailer, something that could cause a lot of damage.
You should also bear in mind the towing capacity of the towing vehicle, as whilst there is no UK law covering trailers that have n laden weight of less than 3500kg, the maximum trailer weight (as quoted by the vehicle manufacturer) should not be exceeded. In some cases you might only be quoted the gross train weight (the laden weight of the trailer plus the laden weight of the towing vehicle) and again this should not be exceeded. If you break either of these 'rules' and an accident occurs, you may well find that the courts and your insurance company take a dim view.
Finally, it is important that the overall length of the towing rig is less than 18.35m (18m + a small overhang).
Towing and The Law
On the matter of towing and the law, it is worth remembering that if you passed your driving test after January 1997 that you must pass an additional test in order to prove that you are safe to tow any trailer which weighs more than 750kg.
There are a number of companies that offer assistance in obtaining the relevant training for this test, some of which are listed below:-
The great advantage of galvanized steel trailers is their resistance to corrosion. Painted steel or powder coated steel has far less resistance and tend to rust from the inside out – as only the outer shell is protected.
With steel trailers the running gear can be either bolted or welded to the frame. The ability to move the axle(s) forward or back is a consideration if you want to be able to increase or decrease the nose (the downwards pressure on the hitch) weight, this being achieved by moving the axle back (to increase) or forward (to decrease). It goes without saying that this adjustment can only really be done where the running gear is bolted to the trailer's body.
The standard in boat trailer suspension was once to have a solid axle mounted on multi leaf springs. Over recent years the trend has moved towards single leaf springs and torsion axle suspensions. The big reason for the move away from multi leaf springs is that they (especially when used in saltwater) tend to rust together. This creates a ride as if there was no suspension at all, with all the potential damage to your boat that this could bring. Thus a single leaf suspension system will maintains it's flex, even when used in saltwater, the downside being that there is more bounce when used with heavier boats.
Torsion axles are too used as they don't rust, two sets of rubber-cushioned axle assemblies being used inside the axle housing, one set per wheel. Also torsion axle systems are more stable because they sit lower to the road surface, and thus provide both fully independent suspension and have more dampening, thus providing an improved ride.
Number of Trailer Axles
If you can get away with having a single axle trailer, all the better. Single axle trailers are much easier to manoeuvre by hand and cost less to buy and to maintain. Single axle trailers can generally accommodate boats up to up to 21 feet.
The next step up is to have a tandem axle trailer. These are designed to carry heavier boats, the trailers are wider and equipped with larger tyres. Tandem axle trailers provide for smoother rides, especially on rough roads, but this smoothness comes with a higher price tag and maintenance costs, and less 'by hand' manoeuverability too. Tandem axles are preferred for boats over 20 feet long.
Your trailer will require brakes if you exceed 750kgs gross load (trailer weight and max. load combined) The need for brakes is also connected to the type of towing vehicle (and it's weight), the weight that can be pulled when the trailer has no brakes being far less than that for a braked trailer. Brake systems on boat trailers are generally of the hydraulic surge or overrun type, since the electric systems, sometimes used on land-bound trailers (especially in the USA) don't do well in water. Hydraulic surge or overrun systems rely on the pushing force of the trailer against the tow vehicle to activate the brakes, the greater this force, the greater the braking effort. The system is completely independent of the tow vehicle's braking system and involves a minimum of moving parts and importantly is ideally suited for boat trailers that are often placed in water.
Wheels and Tyres
Always use tyres that have been designed for trailer use, as these are different from car tyres. Make sure that the tyre on your trailer is designed to cope with long periods where it will not be used and ones that can withstand the effects of ultraviolet light from the sun too. Also make sure that the load rating of the tyre is compatible with the weights being supported.
Hull Supports - the Trailer Bunk
Boat trailers use so called bunks, rollers, or a combination of the two to support the boat's hull. Bunks are in most instances wooden planks (often carpeted) mounted on fixed or adjustable upright brackets. These should closely match the shape of the hull and it is therefore important to check the positions of the bunk supports before every journey, this to make sure that the planks haven't shifted out of position.
In order to support the boat in the correct way, the bunks should be positioned to provide support across the transom and along the forward part of the keep. The bow stop should also be adjusted so the bunks protrude an inch or so behind the transom. You should never choose a trailer where the hull hangs over the end and this will eventually cause hull deformities.
On the other hand 'roller trailers' use rollers on articulated arms. These have the advantage over bunks as they in effect self adjust and thus distribute the weight equally over each roller. Roller trailer have a strong, self-centering effect when loading, particularly in high crosswinds or in strong water currents, plus you can also both launch and load in shallower water than with a bunk trailer.
Choosing a Trailer
As you can see, there are quite a few variables to consider when choosing the right trailer, plus the following factors also need to be born in mind..
The Right Style
Do you choose a "bunk" trailers or a "roller" trailer? What is the best for you will depend on your boat and your projected use. To assist here, it is generally accepted that a riveted aluminum boat hull is best supported on a bunk trailer, so as to avoid "point" loading on their thin hulls. On the other hand, well constructed, deep-V, fiberglass and welded aluminum boats are just as happy on roller trailers.
The sort of launch conditions will also affect your choice as bunk style trailers require deeper water to launch and load than roller trailers.
The Right Match for You
The biggest issue is the proper matching of trailer to boat. What will your boat weigh? How much more weight will be added by fuel, water and personal items? All these have to be taken into consideration when choosing your trailer, too light a trailer will result in damage to trailer, while too heavy a trailer could result in your boat bouncing about and that could cause a lot of damage too. Also always remember to check that your towing vehicle can cope with the fully laden trailer.
Weight distribution is another issue, as in all cases the proper hitch weight should be in the region of 5-10% of the total loaded weight of the trailer. Too light a weight will could result in "fish-tailing" (swaying from side to side), too much weight potentially damaging the towing vehicle.
With trailers that have the running gear bolted to the chassis it is easy to adjust the hitch weight, the axle or axles being moved backwards or forwards as required, thus this is another reason to carefully consider which type of trailer you buy.
Let SBS Boat Trailers Sort any Confusion
At SBS boats we can help you choose the prefect trailer (or refurbish your current boat trailer), so contact us today and together we can select the right trailer for your unique needs.
Some of the boats and boat suppliers our trailers are used for today:-