Should you buy an alloy or a fibreglass boat?

- The rise and rise of small alloy trailerboats
In Australia today, aluminium boats are far and away the most popular. This has come about largely because there are very few fibreglass boats to choose from under 4.8m in length — and the sub 5.0m size range is obviously the high volume end of the trailerboat market.

Of course, there is a reason there are so few small fibreglass boats on offer today. Back in the late 1960s and through the 1970s, during the hey-day of fibreglass trailerboats, there were plenty of small fibreglass boats available. They were neat, durable little rigs too, as evidenced by the number that are still available on the used-boat market and listed on our sites today.

Classics like the Caribbean Comaro and Crestcutter, Haines Hunter 146/445 series, and Cruise Craft Rogue/Rapide, remain highly sought-after on boatsales and Boatpoint.

Sadly, however, when alloy boats burst onto the scene in the late 1960s, with exciting new products from brands like Quintrex, de-Havilland and Brooker, small boat buyers began to switch to aluminium in droves.

The rise and rise of small alloy boats during the 1970s is no surprise really. Pressed aluminium boats are light in weight, strong, durable, easily powered and hardy. They are ideal for small boat fishing applications because they can be dragged over rocks, bumped into a concrete launch ramp, and even dented with minimal damage to the structure of the boat.

Fibreglass boats are also immensely strong (stronger in many ways), but the gelcoat on fibreglass boats is prone to gouging, scratches and cracks caused by sharp or abrasive contact.

When launching and retrieving a fibreglass boat, for example, it is all too easy to deeply gauge the gelcoat and underlying fibreglass laminate simply through contact with a sharp edge on the trailer.

The stem and forefoot of a fibreglass boat, along with the keel and the base of the transom, are particularly vulnerable areas.

Having noted the above, with modern day multi-roller trailers, "missing" the rollers on boat retrieval and scratching the hull is no longer as common a problem... but it still happens.

The upside for fibreglass boats is that they are easy to repair and there are plenty of skilled repairers and shipwrights capable of performing the job. Even replacing structural items such as transoms, floors and stringers is a relatively straight-forward job.

With aluminium boats, when a repair is required, it can be more costly, especially if there is major impact damage — or, worse, damage from electrolysis or galvanic corrosion.

MORE PROS & CONS
- Hull shapes, deadrise angles, displacement, buoyancy, and more stuff
Getting back now to the point in question, should you buy an aluminium boat or a fibreglass boat? Well there are many more pros and cons to this debate than just the question of strength and durability.

For example, as a rule, pressed-aluminium monohulls will be harder riding or more "bangy" than fibreglass boats. There are exceptions, but on a length-for-length basis, a well-designed fibreglass monohull will generally be softer than a well-designed pressed aluminium monohull.

It is all to do with the shape of the hull. Fibreglass hull designers are able to produce a hull in just about any shape they can think of. Conversely, aluminium designers are constrained by how far they can bend or shape a sheet of aluminium. This makes it possible for fibreglass boat designers to produce more sophisticated, usually deeper vee hull shapes that provide a softer ride across the water.

Another factor working against the alloy boat with regard to ride comfort is its light weight. A light boat is great for easy towing, and general man-handling around the launch ramp, but it is a disadvantage out in choppy water.

With small, light boats, hull designers generally have to settle for a shallow or moderate-vee hull shape (8-14 degrees) — otherwise their boats would have far too much buoyancy in the stern, resulting in poor stability.

This isn't true of fibreglass boats. Being heavier and therefore displacing more water, these craft can sustain a much deeper or sharper vee or "deadrise" angle without becoming excessively buoyant. This deeper, more sophisticated vee-hull shape, combined with the extra weight, gives the fibreglass boat (and some heavier plate-alloy monohulls) a much softer ride than a relatively light, pressed alloy craft.

Once you pull the boat out of the water, however, the greater weight of the fibreglass boat then becomes a liability. For example, while most 6.0 m pressed alloy boats can be towed behind a regular family sedan, a big 4WD wagon may be required to haul a similar-sized, but heavier fibreglass boat.

Further, the fibreglass boat may also require a more powerful outboard engine — as well as a two-tonne plus rated trailer with a full (and expensive) electric-hydraulic break-away braking system.

IN A NUTSHELL
- Let's cut to the chase
It should be evident by now that, as a rule, pressed aluminium boats are lighter, hardier, easier to tow, more spacious inside, easy to maintain and require less power than fibreglass boats. However, they are also noisier, harsher riding, and less attractive.

Fibreglass monohulls are the opposite; softer riding, better handling, better looking, and often better finished. They are also heavier, require more care, often a bigger engine, and a more powerful tow vehicle.

In time (like 10-plus years), the timber core material used in the transom and underfloor stringers on many fibreglass boats can be susceptible to rot IF not properly encapsulated with fibreglass or sealed from water ingress. But against that, if not looked after, aluminium boats can suffer from corrosion caused by galvanic action and electrolysis.

PLATE ALLOY
- The best of both worlds?
Plate-aluminium boats fall somewhere between the two extremes of pressed aluminium and fibreglass monohulls. In many ways they have advantages of both types. A good plate alloy monohull will have close to the ride comfort of a good fibreglass boat, matched to the strength, durability and sheer ruggedness of the pressed alloy rig.

However, plate-alloy boats can be as heavy as fibreglass boats, and they can be more expensive because most are custom built — although that in itself can be an advantage with regard to fitting out the boat for your own style of fishing.

THE VERDICT
- Horses for courses
Given all of the above, some conclusions can be drawn with regard to the applications for aluminium and fibreglass boats — monohulls in particular.

For fishing in wide offshore waters, my preference would be for a big fibreglass boat or a plate-alloy boat. Both would provide the degree of handling, ride comfort and performance needed to regularly travel long distances offshore.

A powered catamaran made from aluminium or fibreglass is another good option... but that's a story for another time.

For inshore family boating and fishing applications, pressed-alloy boats have a number of overwhelming advantages including light weight, durability, easy maintenance, low power requirement, and low purchase price.

You can get more good oil and great boating tips with this search for Boating Advice Articles at Boatsales.com.au.

Captions: Alloy Vs Fibreglass
As the photos fall with this story...

PIC 2
The Quintrex Fishabout 4.3m set the standard for light weight, durable aluminium boats when it was launched way back in 1967.

PIC 3
In 2017 there is a full range of Fishabout models in the Quintrex range, including this excellent 570 series runabout with walkthrough windscreen and large rear cockpit.

PIC 7
Plate alloy boats can have the best of both worlds - the comfortable ride of a fibreglass boat combined with the strength and rugged durability of aluminium. Pictured is the Quintrex flagship, the Yellowfin 7600 Southerner Hardtop.

PIC 10
Priced from just $32k, the Formosa 480 Tomahawk Classic is an excellent inshore and nearshore bay fishing alloy boat  - strong, durable, light weight and with a spacious, easy care interior. It is these attributes which make small to medium size alloy boats so popular.