How to select a trailer boat part 1

How to select a trailer boat part 1

Hull Basics

As has been widely quoted, “All boats are compromises.” Design one aspect of a boat to fulfil a certain need and you may well adversely affect other functions. The trick is to figure out your boating/fishing priorities and choose a rig with those design features that are most important for you, tempered by practical considerations like safety, affordability, performance, tow-ability, glass/alloy preference, and others.

While I have found the following concepts generally true, I have also had some big surprises from boats which perform quite unlike their designs would suggest.


While I appreciate a good-looking hull, I will always prioritise function over form. For example, one day I was watching a mate back his brandnew aluminium pontoon boat into his driveway. Its large, blunt, sealed pontoons looked like they would provide a huge amount of positive buoyancy but were a long way from being aesthetically pleasing.

My mate’s wife came out of the house to view the new arrival and, seeking an ally in what looked to be an ongoing disagreement over the choice of boat, said to me, “Sam, don’t you think that’s just the ugliest boat you’ve seen?” My reply was: “It may not be pretty, but it could save your husband’s life one day.” There was no answer to that one.

So, one particularly important aspect of a boat’s design, to me, is a decent amount of reserve buoyancy (buoyancy over and above rig weight), held in a number of separate sealed or foam-filled chambers. The rig should float if swamped, preferably upright, with enough buoyancy left over to support the crew and all the equipment aboard.


Another important aspect of a boat design is stability. That is, how stable the boat is in the water – the degree to which it will take on a list when the load is moved off the centre-line. A boat which takes on an uncomfortable list when several of the crew move to one gunwale is said to be ‘tender’. In extreme cases when the list becomes strong, any unsecured load may slide to the ‘low’ side, which can cause a capsize.

Good stability is a valuable aspect in a boat, especially when the crew is standing up and moving around, one side is loaded (such as when trying to pull a net or pot), or when a number of people move to one side to deal with a big fish. Some types of boats are inherently stable, particularly pontoon boats and catamarans, which also have excellent load-carrying ability and high levels of reserve buoyancy. In New Zealand, pontoon boats seem to be the more popular of these two types.

The inherent stability of monohulls can be affected by their deadrise (the ‘V’ of the hull, usually measured at the transom). In general, the shallower the ‘V’ the more stable the hull, but the harder it rides. Deep-V hulls (with a deadrise of, say 18 to 21 degrees) tend to ride softly, but are less stable at rest.

Stability in monohulls can be improved by design features including self-flooding ballast tanks along the keel; wide and/or down-turned chines (the line where the side and bottom meet); a low centre of gravity; incorporating a keel; and under-hull strakes. All of these aspects in various combinations, will also affect the ride the boat will deliver.


Commercially-built trailer boats are almost exclusively made from two materials these days: fibreglass or aluminium. I can’t think of any manufacturers using wood for this class of boat any more, and now that Mac Boats has bought Smartwave Boats, as far as I know, there is only a single manufacturer of rotationally-moulded plastic hulls in New Zealand.

Of the two main materials, each has its fans – a little like Ford vs Holden, or Pepsi vs Coke. Each material has advantages and disadvantages. Fibreglass (technically Glass-Reinforced Polyester – GRP) is said by its supporters to be better-looking, quieter and softer riding, while metal-heads reckon aluminium is lighter, harder wearing, and that a well-made ‘tinny’ can also look good and ride well.

I was brought up on a series of wooden boats: a couple of lap-strake hulls, several ply boats, and one glass-over-ply that I assisted my dad to build. These were followed by a several fibreglass Sea Nymph hulls and a home-built fibreglass dinghy. Since then, my personal boats have been glass, aluminium, aluminium, rotationally moulded plastic, and my current craft is another aluminium vessel.

I will fish off anything that floats, and you can see from the mix of materials just listed, I don’t really have an axe to grind regarding hull material. However, as a fisherman who likes to customise his boats for fishing, I do find aluminium simpler to work with and at a commercial level, the same is true for manufacturers.

Aluminium boats can be easily customised by cutting and welding, so one-off items are easily fabricated without having to spend a whole heap of money and time making new moulds. This makes it easier to build a hull to a customer’s requirements if they have specialist fishing needs.

Because of the cost of developing specialist hull moulds for fibreglass boats, many of them (but not all) are designed to be all-rounders/family boats, to maximise their market appeal, while the majority of hard-core fish-and-dive machines tend to be aluminium because they are easily altered to meet specialist needs and perceived to better withstand the wear and tear associated with fishing.

There are many excellent local manufacturers working in each material, so take your pick.


Having recently passed my 60th year, with accompanying creaks and groans, the day is long gone when I want to go racing, bouncing and banging across the sea at high speed. These days I value a boat that rides softly, smoothly and dryly at a reasonable speed. In other words, give me comfort over adrenalin any day!

The way a boat rides can be affected by a combination of the hull design, engine and propeller set up, rig balance (including fuel tank and engine placement), how you drive and trim the boat, and the sea conditions at the time. I have already mentioned some of the hull design factors that affect ride in the previous ‘stability’ section.

Other aspects include hull weight, the fineness of the hull entry and how full it is in the ‘shoulders’.

As I said earlier, changing one aspect of a hull design can affect another. I have seen hulls built with a fine entry and a deep-vee with the idea that they will slice through the water nicely and give a good ride. Unfortunately, this meant the planing surface was reduced and the boat struggled to get up on plane. This issue, in turn, was corrected by the addition of a series of planing strakes to the bottom to provide more ‘lift’ but this made the hull pound! Back to square one!

It does take a little while to learn to get the most out of any boat – the mix of trim and speed that is best suited to the sea conditions. This can include the use of engine trim, trim tabs, and even computerised boattrim systems, but there is no substitute for spending time on the water in a range of conditions to get a real feel for a boat.

Don’t worry if a rig doesn’t impress initially – things will often improve as you get the hang of handling a particular boat. For example, on one boat, trimming the bow down so its fine entry does a better job of cutting through the sea may make it ride more softly. On another design with heavier shoulders, trimming the bow down could result in bow drag and bow-steer and you may need to trim the bow up to get decent performance.

The configuration

Moving past the basic hull design, there are a range of deck and superstructure configurations that should be considered. Hardtops (open-back or enclosed), cuddy cabins, centre consoles, centre cabins, side consoles and dories (open boats) are some of them.

The choice is usually governed by the size of the boat and its intended purpose. By this I mean that a certain hull size is needed to support a hardtop to avoid making the boat top-heavy and unstable (about 6-6.5m minimum for a monohull; pontoon or cat hulls with their extra stability can be a little smaller). Enclosed hardtop designs eat up a bit more cockpit space than open-backed designs, so the hull needs to be longer in the first place, say 6.5m-plus.

Given the weather extremes experienced in NZ waters (harsh UVs in the summer with rain and cold winds almost any time) it is no surprise that hardtops are such a popular configuration in boats of 6m and longer.

Cuddy cabins (runabout/windscreen types) offer some protection to their crews and a whole lot less windage, weight and expense than a hardtop. These are often fitted with canopies (ragtops) which may or may not incorporate a rocket launcher. Canopies can fold down for easier shed storage and less windage when towing, but sometimes leak in heavy weather and visibility may be reduced.

Another configuration that has recently gained popularity with the advent of fishing techniques that involve drift fishing and lure casting (poppers, stick-baits, soft-baits, saltwater and freshwater fly, jigging etc) is the centre-console.

Centre-consoles open up a heap of fishing space in the bow and around the sides, allow anglers to easily follow hooked fish right around the boat and make anchoring access easier.

The downsides include reduced shelter for the crew and the boat’s centre of balance is shifted aft, so the positioning of things like batteries and fuel tank/s may need to be adjusted to address this.

Variations of the centre-console include the side-console and the centre-cabin. Like a hardtop, the centre-cabin layout works best on a larger hull for the same reasons. Like centreconsoles, centre-cabin boats retain walking access around the sides.

Centre consoles seem to be at their best in warmer, more sheltered east-coast waters of northern New Zealand, or when jigging or flyfishing in lakes.


   This article is reproduced with permission of   
New Zealand Fishing News

April 2018 - Sam Mossman
Re-publishing elsewhere is prohibited

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