Choosing a canopy for your single- or double-cab bakkie should be easy – just
pick the one that looks best on your vehicle. This may work in dreamland,
but in real life the choice is far more difficult, because the basic design
of
the canopy is determined by the planned use. It really boils down to deciding
whether
you’re = going to be carrying people or goods in the back.
Most canopies are made of a glass fibre composite, ie glass fibre mats impregnated
with a resin. Construction starts by applying a chemical release agent to a
mould, to prevent the material from clinging to it, followed by layers of resin
and fibre. The fibre supplies the tensile strength while the resin spreads
the load, protects the fibre from damage caused by impact and abrasion, and
gives the compressive strength.
Composite canopies can be made without expensive specialised equipment, and
there are a number of fly-by-night outfits that produce canopies, but the quality
will be suspect. The apparent ease of manufacture means that the quality of
the final product depends a great deal on the skill, experience and knowledge
of the people involved. Making a canopy should be left to a specialist, and
one made by a manufacturer well-known in the trade is more likely to be of
good quality than an unknown brand. When buying a bakkie, most vehicle manufacturers
approve certain canopies, and these models would be worth considering. But
don’t necessarily leave the choice of the canopy brand to the vehicle salesman,
because they often get kickbacks from manufacturers, and you may end up with
an unsuitable canopy.
- If you’re seldom going to remove the canopy then the way it is secured
is not very important. If the canopy is bolted down, it will be more secure,
but more time-consuming to remove and refit. If it is secured by quick-release
fasteners it can removed without a spanner, but could also be inadvertently
left partly undone, and could eventually fly off and self-destruct.
- How much does the canopy weigh? A heavy canopy is usually stronger, but
more difficult to fit or remove. A lighter canopy is easier, but will it be
strong enough for your purpose?
- The basic construction – the part you can’t see – depends
on the number of glass fibre layers as well as the quality of the resin. A
quality canopy is constructed from three layers of fibre mat of different
thickness, while a cheaper model will have only two or even one layer. The
resin should be of good quality. Some of the cheaper canopies are constructed
from the cheapest resin.
- Most canopies carry reinforcing strips made from steel or wood, embedded
in the resin. These also prevent drumming. Steel would be stronger, until
it starts to rust, but wood is a better choice because it’s less affected
by the small amount of moisture that gets through.
- The choice of colour needs very careful consideration. Lighter colours can
be mixed into the resin, so a scratch or other light damage can be sanded
away. The disadvantage is that the colour hides any bubbles that may arise
during manufacture, so that they only become obvious later. When the canopy
is white, or colour-impregnated, some manufacturers test for bubbles by lightly
hammering the surface. Darker colours and metallics cannot be mixed into resin,
so the canopy is sprayed after manufacture. Here, any scratches that appear
at a later stage must be sanded down and sprayed over. However, an advantage
is that the canopy can be manufactured using clear resin, so bubbles can be
seen and repaired before spraying.
- The fittings should be rust-proofed, and most quality canopies are fitted
with stainless steel handles and latches. Anything less will not last.
- Most manufacturers offer a range of accessories, and extra interior and
exterior lights are popular. Some manufacturers fit a channel for the cabling
as standard, so you can fit a light at a later stage.
- Should there be a gap between cab and canopy? If the canopy has its own
window just behind the vehicle cab, it makes communication between the canopy
and the cab difficult, but the gap will at least be waterproof. With a canopy
that seals on top of the cab’s roof, communication is easy but after
removing and replacing the canopy you may find a leak at this point. The quality
of the sealing rubber is most important, and it should also be kept clean
because dust can start an abrasive process where the rubber meets the cab.
- If you want to fit a roof-rack, make sure that the canopy is strong enough,
or buy a canopy with a built-in roof-rack.
- Make sure the particular design has been tested to prevent exhaust gases
from entering. Carbon monoxide can make people drowsy or kill them. If ventilation
is needed, the vents should be in a position where they function effectively,
and seal properly. The bakkie’s own tailgate is often the biggest source
of the leak, but a side-exit exhaust pipe extension will help counter the
problem.
- The various layers of material sometimes trap air bubbles that only show
up after the canopy has been in use for some time, so it is important to make
sure the manufacturer will repair such bubbles at his own expense. Warranties
vary from six months to two years, so read the fine print.
- Should the rear door be vertical or horizontal? A vertical one-piece door
is very handy, especially if you carry people, but entails removing the tailgate,
and the resulting entry space is usually too small to accept bulky items.
A horizontal canopy door, one that fits over the vehicle’s tailgate,
has a larger opening, but becomes a real bother if you often open and shut
both tailgates.
that water leaks will be fixed.
- Most canopies are fitted with toughened glass, ie glass that shatters into
tiny fragments when broken, but some of the cheaper canopies may be fitted
with inferior imported glass. An armourplate symbol, or an SABS or E-mark,
is proof that the glass is to a recognised standard.
- Does fitting a canopy affect fuel consumption? In theory, a canopy that
doesn’t increase the frontal area may well improve the drag coefficient,
because an open load area produces a lot of drag. The extra mass of the canopy
affects consumption when you accelerate, so that town driving will increase
your fuel bill marginally.
We tested an Opel Corsa half-ton bakkie, with and without a suitable canopy,
to see for ourselves what difference a canopy makes. Consumption was measured
at a constant 60, 80, 100, 120 and 140 km/h, but we did not find a significant
difference between running with or without a canopy. The roof of this particular
canopy did not protrude above the roof of the cab, and the results seemed to
indicate that the canopy did not change the drag coefficient significantly.
Furthermore, the canopy weighed only 37 kg, so mass played no significant role.
However, we feel certain that a high-roof canopy, or even a normal canopy fitted
to a long wheelbase vehicle, would reduce the total drag at speeds over 120
km/h, and we plan to conduct a test in the future.
