Know Your Trailer Series

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Part 1 – What is a Boat Trailer?

A boat trailer just what it says, a trailer for carrying a boat. Now I know that’s pretty simplistic, but boat trailers are very different to recreational type garden trailers. Firstly they are going to be dipped into water, mostly saltwater and that’s where the problems start.

When the first boat trailers were built, they were timber, but soon that changed to metal and common in the earliest years of trailer boats were trailers made from steam pipe. I know my dad had one under an 18ft Hartley. We soon moved onto steel box section that was cut and welded to shape. Today trailers are mostly manufactured from a special cut, folded and bent steel sections. Boat trailers are now galvanised to stop the rust, both inside and out and are also available in aluminium.

But it’s not just the frame; it’s also all the running gear that is trailer boat specific, such as lights, brakes, rollers, pads and winches. Most things on a boat trailer are designed for a purpose, to make towing, retrieving and launching your boat that much easier and safer.

Boat trailers come in a variety of sizes from as little as 3m for small dinghies and PWCs to upwards of 10m for the largest trailer boats. Single, tandem or triple axle, it all depends on what size your boat is.

Over the next seven episodes of Knowing Your Trailer, we will be looking at everything from trailer componentry to road rules and what to look for when buying a trailer.


Part 2 – Towbars and Couplings

When you hook your trailer up to your tow vehicle, there are few things to consider. Firstly how heavy is the rig you are towing and is your vehicle rated to tow it. An average 6m-trailer boat is going to weigh around 2200 kgs all up, boat/motor/trailer, package so this means that a 4cyl family car isn’t going to cut it. You need something bigger like an SUV or big six cyl or V8 car,

Moving on up if you are towing a 7m plus boat on the back then you might consider something like an Isuzu D-Max or similar, Most big crew cab utes have a towing capacity of 3500 kgs, which is

plenty. Diesel power is also better in my opinion.
Next, you need to check the way the tow bar is attached to the vehicle. Solid mounting points on the subframe are critical and in the case of larger utes, they are bolted to the chassis. Drilling holes in the boot floor pan is a disaster waiting to happen.

Then there is the tow ball. NZ has a strange system of two standard ball sizes, 1 7/8 and 50mm, plus there are even larger options available. When you hitch the rig up to your tow vehicle, make sure the locking tongue on the coupling engages properly.

Chains are important and you need to make sure you have a quality chain that is bolted (not welded) to the trailer chassis. Certified shackles are also a good insurance.


Part 3 – Winche Poles and Winches

The winch post on your trailer is one of the most important components when you consider it not only stops the boat flying forward, is the winch mounting point and its position has a lot to do with the way the trailer is balanced. Most mounting posts are attached with heavy duty U bolts so you can slide it fore and aft to get the balance of the trailer right. These way manufacturers can make one trailer that will fit a variety of designs and sizes, without compromising the integrity of the trailer.

On top of the post is the winch, which is either manual or electric. In the case of the manual winch, various ratios are available so you can winch on big heavy without having to spend a week at the gym. However, if you are planning on something that weighs over 2500 kgs it is recommended to have an electric winch that will do all the pulling for you. These also come in a variety of sizes with various pulling power and can be operated from a separate battery or off a connection to the vehicle.

While wire was once the only option, winches are now offered with synthetic rope and web straps, so no more metal strands in the hands when you grab the winch wire. Talking of safety chains, again it is important to have solid chains with rated shackles as this is going to be one of the main anchor points for the boat on the trailer.


Part 4 – To Break or not to Break

Boat trailers come with or without brakes. There are two systems available, manual override or electric. Trailer brakes are not required up 750 kg and only recommended from 750-2000 kg. From 2000 – 2500 kg you must have override brakes and from 2500-3500 kgs electric brakes
are mandatory.

The simple system is the manual override brake that is most common on Kiwi trailers. This works on inertia, so when the vehicle is braked the trailer brakes are activated through a hydraulic system. Simple, effective and reasonably fool proof.

However, when you start to tow rigs over 2000kgs, you need to move up to a more serious braking system such as electric over hydraulic, where the system is fully controlled by the braking action of the vehicle.
The most common problem with boat trailers is failed trailer brakes. Because boat trailers are regularly immersed in highly corrosive saltwater, the trailer brakes will corrode and then fail very quickly without regular and constant maintenance. Best preventative maintenance is ushing with fresh water everytime you use the boat.

Irrespective of the type of brake operating system, you need to examine the brake discs and callipers for corrosion. Also, check that the discs are not warped. A warped disc can be a problem because the braking pressure will be irregular, resulting in heat build up on the highway, and possible tyre and wheel bearing failure.

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