Thursday, July 7, 2011


Trailer types:

Simple single axle boat trailer

 Single axle:

This is the smallest type of boat trailer, Usually made for carrying small pleasure craft under 15 ft. This trailer makes boat ownership easier for more people. 

Double Axle:
A double axle trailer is for Larger boats. Four wheels means that the larger weight of the boat is spread onto a larger surface area. Double axle trailers usually contain a braking system as there is more weight extra breaking power is necessary.

Triple axle:

This type of trailer is only for the largest of boats. Boats larger than this usually cannot be taken in and out of the water. This type of trailer is uncommon in New Zealand.

Trailer design:
A frame design:

An A frame boat trailer is the simplest type of boat trailer, however it is a strong and easy to fabricate design. 

A simple trailer for a sailboat

Draw bar:

A draw bar type trailer, utilises a simple frame design and a draw bar. This is a moving attachment to a trailer which allows a better turning ability. 

Trailers are often personalised to individual boats, this is because of different hull shapes and different sized boats.

Bunk Type trailer:

A bunk type trailer is a trailer with a solid skid for the boat to rest on.

Roller type trailer:

A roller type trailer has rollers that allow a boat to easily be retrieved from the water, this also reduces the damage to the bottom of the hull. the rollers are prone to corrosion as water can become stagnant.
A tandem roller type trailer

Trailer materials:
Trailers are made of highly corrosion resistant materials, as they have to be submerged into salt water constantly. Usually stainless steel or mild steel with galvanising layer to protect it. Galvanisation is the process of protecting metal from corrosion by bonding a layer of metal over the original metal. 
Aluminium is also used as trailer material as it is light and is resistant to corrosion.

  • If you own a boat you can tow a trailer that can be 2.5m wide, up to 4.25m high when the boat is sitting on the trailer, and 11.5m long, assuming that the car plus the boat doesn't exceed 20m which is the limit.
  • When you load your trailer the I deal position is to have the weight is so about 10% of the weight is taken on the tow ball and the rest supported and distributed over the single/tandem axles of the trailer. If there is to much weight on the tow ball the trailer coupling will not be parallel to the ground therefore the car will be hard to steer (and good luck pulling your boat up a steep launch ramp if the car is front wheel drive). If the load is to far to the back of the trailer  it will have the tendency to fish tail around at certain speeds.
  • Another thing to consider is what gear you have in the boat, “is it heavy” if so where is the weight adding to the load.
  • The tongue of the trailer is also very important – the A-frame design has the coupling of the trailer where the apex of the frame meets.
  • The draw bar style has a strut running through the apex of the A - frame which extends out further and is attached to the tow bar by a coupling.
Trailer Weight Estimates
This chart relates to single axle trailers only
1000 lbs.115'4"62"295 lbs.
1500 lbs.115'4"62"305 lbs.
2000 lbs.117'2"88"492 lbs.
2450 lbs.118'2"96"522 lbs.
2999 lbs.118'2"96"625 lbs.
3500 lbs.119'8"96"677 lbs.
5000 lbs.120'8"96"933 lbs.
7000 lbs.127'9"96"1512 lbs.

Suspension types:

Boat trailers can utilise a number of suspension types. Leaf type springs on boat trailers are quite common as they can deal with the weight of heavy boats. Leaf type suspension is susceptible to corrosion though as water can get caught in the crevices between suspension leaves.

Another type of suspension is the strut type, this is a sealed unit so it does not suffer the same problems with corrosion however the strut type cannot support as much weight as the leaf type, so is  used on small single axle trailers.

Wheels and tyres:

The wheels on a boat trailer suffer from corrosion as they are submerged when the boat is being loaded. salt can build up and crystallise in the crevices on the wheel and tyre. Salt can also degrade the rubber in the tyre.


Boat trailers that haul a large boat must have a braking system. The weight of a large boat is too much for the towing car to safely control. they are controlled in conjunction with the towing vehicles brakes. These also suffer from corrosion as salt water degrades them.

These brakes are also activated by a cable much like a hand brake when the boat trailer is stationary.

Hubs and stubs:

Wheel hubs are usually galvanised to protect them from corrosion, wheel stubs can seize if crevice corrosion takes hold. so are protected with galvanisation.


The lights on a boat trailer are connected to the towing vehicle by a wire, brake lights and indicators are controlled in conjunction with the towing vehicles lights, as a long trailer could obscure the vehicles lights.
the electrical coupling is waterproof to prevent failures. 


simple coupling and electrical connection.


A winch on a boat trailer is used to haul the boat in from the water. on small craft a hand winch can be operated, but for larger craft a high torque electric winch is required.

A hand operated winch

an electric winch

An extreme case of moving a boat by trailer.


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