Basic towing checklist

Among them are quick release tow balls that are easy to change and others where the ball diameter can be set to either standard. Many modern trailer couplings fit either standard; simply turn the release handle around to change the setting.

TOWING A TRAILER BOAT – LEGALLY

Trailer boats give you the freedom to go boating just about anywhere: as long as you can find somewhere to launch and retrieve you can explore rivers, lakes, bays and inlets as well as the open ocean.

This ability is the main reason they are so popular, but as the weight, length and beam of trailer boats increase, so does the muscle power needed to launch and retrieve them. A small boat is easy for one person to handle at the ramp, but larger boats may require additional hands.

If you’ve never towed a boat on a trailer before, you’ll need to take it easy to start with. First, make sure your vehicle is up to the task. New Zealand Transport Agency guidelines stipulate that the laden weight of an unbraked trailer should not exceed threequarters of the unladen weight of the towing vehicle.

Start by determining the ‘dry weight’ of your boat and trailer. That’s the weight of the boat, less fuel and gear. The manufacturer may be able to supply these figures, or run the rig over a weighbridge. Make sure when you’re assessing your vehicle’s towing capacity you add a couple of hundred kilos to the dry weight of the boat and trailer to account for those extras.

It’s even more critical for owners of large trailer boats to ensure their tow vehicle is legally able to tow the boat and trailer combination, especially if the trailer’s gross laden weight is approaching the upper limit of 3,500kg.

There are quite a few vehicles with 3.5 tonnes (braked trailer) as their maximum towing weight, including several popular utilities (see list). But this figure can be misleading. If driving with a Class 1

• Coupling hitch and tow ball are of the same size • Coupling and safety chains are safely secured to

tow bar of tow vehicle • All fasteners are properly tightened • Boat is securely tied down to trailer (winch line is

not a tie down) • Wheel nuts are properly tightened • Wheel bearings are properly adjusted and

maintained • Load is within maximum load carrying capacity • Tyres are properly inflated • All trailer lighting is working properly • Trailer brakes are properly adjusted and working. Be sure to check requirements regarding brakes and any additional equipment that may be required.

car licence, the gross combined mass (GCM) of the trailer and tow vehicle must not exceed six tonnes.

Most vehicle manufacturers supply a maximum towing capacity for vehicles. They also display the vehicle’s gross vehicle mass (GVM), which includes its maximum payload. For instance, a vehicle may have a kerb (tare) weight of 2,000kg and a GVM of 3,000kg. That leaves 1,000kg for payload, but that’s quickly soaked up by modifications such as roof racks, bull bars, winches, storage systems and tool boxes – even before loading your fishing gear and supplies.

How much weight you can actually tow depends on the combined weight of the tow vehicle and the trailer it’s towing (gross combined mass, or GCM). Typically a utility vehicle will

only be able to tow its maximum braked trailer weight with a light load, or it will exceed its design limits for weight.

For example, let’s take the popular Ford Ranger (or Mazda BT50) utility with a 3,500kg braked trailer tow rating and say we want to tow 3,500kg. Subtract 3,500kg from the maximum GCM of 6,000kg and 2,500kg is the maximum the Ranger can weigh if towing 3,500kg.

As the Ranger’s tare (kerb) weight is 2,200kg, 2,500kg less 2,200kg leaves just 300kg for payload. Four people at 75kg each is already 300kg without any gear. The Ranger’s kerb weight wouldn’t even include a tow bar.

If the Ranger is at its GVM legal limit (3200kg) – which wouldn’t be too unusual when setting off on a fishing expedition – then the equation looks like this: 6,000kg minus 3,200kg means a tow capacity of 2,800kg, which is the maximum the trailer can weigh.

Bottom line is if you work off the GCM, then you can only tow 3,500kg in a Ranger if you have no more than 300kg of load on the truck, or if the truck is at GVM, you can tow no more than 2,800kg.

There’s more. Axle loads also need to be taken into account and these are affected by the load transferred to the tow vehicle as down force on the tow ball. Most manufacturers give a maximum allowable down force at the tow ball, which may be less than 10 percent of aggregate trailer mass (ATM) often given as a rough guide for tongue weight, which for a trailer of 3,500kg is 350kg. The correct amount of down force may well be greater than the allowed amount for the vehicle.

CHOOSING A TRAILER

While there’s no official Trailer Manufacturers Association in New Zealand, it is preferable to buy a locally-manufactured trailer of a well-known brand. All trailers in New Zealand are required to meet current warrant of fitness standards as laid down by the New Zealand Transport Agency. It should be remembered that boat trailers are required to operate under very tough conditions, so a ready supply of spare parts is a very important consideration, something which can become a problem if the trailer has been manufactured outside New Zealand.

Most New Zealand-manufactured trailer boats are sold on good quality trailers from reputable makers. B