Boat Building Materials
Here at BNJ Marine Ltd. we concentrate our efforts on Custom Welded
Aluminum Boat Building. We believe that if you consider all the
boat-building materials, and seek knowledge about boat building
you will seriously consider building your boat of welded aluminum
in preference to building with other materials. This is simply because
aluminum boats have so many positive aspects that it's difficult
not to make aluminum your material of choice.
It is important in any discussion of boat building materials to
talk a little about hull form. Any boat hull that is to be constructed
from sheet material, plywood, aluminum, and steel, are for the most
part restricted to developable surfaces. A developable surface can
consist of flat areas, sections of cylinders, sections of cones,
or a combination of flats, cylinders, and cones. Non-developable
surfaces conversely are shapes that consist of compound curvature.
Fibreglass boats, wood planked boats and Ferro cement boats are
examples of boat building that can be done with non-developable
surfaces. These non-developable surfaces are difficult to imitate
in metal and are very labor intensive.
From a BNJ Marine Ltd. point of view, using our advanced 3D design
and an eye for fine lines we can produce very attractive hulls and
outboard profiles. Using fully developable surfaces for welded-aluminum
boats are indeed possible and cost effective. Though BNJ Marine
Ltd. has not yet had occasion to develop a sailing mono hull. It
would be our intention that very acceptable results can be achieved,
either with single chine or radius chine development in aluminum.
Custom Welded Aluminum Boat building is our choice. However it would
be irresponsible not to mention some of the other fine materials
used today. See below each item in brief.
It is our purpose, below, to briefly cover some of the advantages
and disadvantages of common boat building materials for your comparison.
It is not our intention to offer complete information on these subjects.
Each of these materials may include several building methods that
are studies on their own.
Custom Aluminum Boat Building
There are basically two main methods of building boats with aluminum,
the pull up method and the jigged or frame and skin method. In the
pull up method the hull is built first with all framing hand fit
to the hull after the hull construction is complete. In the jigged
method jigs are built before the boat is started, to control the
hull and framing. BNJ Marine Ltd. has developed a third method of
aluminum boat building. Using our 3D modeling advantage, we combine
the best of both methods, which we like to call self-jigging.
One primary advantage of aluminum is its high strength-to-weight
ratio, a comparison of dead weight of the material to its mechanical
properties. In simplest terms, the higher the strength-to-weight
ratio of the hull material, the lighter the boat can be constructed
while maintaining a given level of strength. An equivalent hull
constructed from a material with a lower strength-to-weight ratio
will be heavier.
For a planing hull the lighter the boat the less horsepower required
and better the efficiency.
With mono-hull sail boats this equates to a higher percentage of
ballast in the keel, resulting in a stiffer boat that can carry
In addition to lightweight and high strength, aluminum is also
much more impact-resistant than steel or fibreglass. Aluminum is
very ductile; it will stretch up to 12 percent before rupturing-about
three times the elasticity of ship steel-in the working-stress range
Aluminum does not need painting. It's nearly impervious to seawater
corrosion; it isn't affected by ultra-violet light; it doesn't rot
or attract worms; and it doesn't rust. The time and cost savings,
realized with a boat that doesn't require routine hull maintenance
to protect it from the environment, are significant. It is very
easy for the novice to inspect and see good welding practice and
that the material is consistent.
BNJ Marine Ltd. is happy to offer prototype designs in any of the
fine boat building materials, however we only offer building services
Click for important information on aluminum building issues,Galvanic
Custom Ferro Cement Boat Building
Ferro cement is a technical term, not to be confused with ordinary
reinforced concrete. It might be defined as a composite material
consisting of a mix made from hydraulic cement mortar and a number
of layers of continuous steel mesh reinforcement distributed throughout
Disadvantages: its weight and poor impact resistance.
Advantage: possibility of building non-developable surfaces and
one of the cheapest and easiest forms of construction available
to the amateur builder.
Custom Fibreglass Boat Building
Polyester resin, vinyl esters and epoxy resin and other composites.
In the marine industry, liquid plastics, namely epoxies, polyesters,
and vinyl esters are used to saturate (wet out) the fibres of wood,
glass, Kevlar, or carbon to form a fibre reinforced plastic (FRP).
There are many methods of fibreglass lay up, c-flex, single skin,
or sandwich. See disclaimer above.
Epoxy resin is known in the marine industry for its incredible toughness
and bonding strength.
Vinyl ester resins are stronger than polyester resins and cheaper
than epoxy resins. Vinyl ester resins utilize a polyester resin
type of cross-linking molecules in the bonding process. Vinyl ester
is a hybrid form of polyester resin, which has been toughened with
epoxy molecules within the main molecular structure.
Polyester resin is the cheapest resin available in the marine
industry and offers the poorest adhesion, has the highest water
absorption, highest shrinkage, and high VOC's. Polyester resin is
only compatible with fibreglass fibres and is best suited to building
things that are not weight sensitive.
Disadvantage: deterioration in sunlight, are subject to cracking
and chipping damage and very expensive moulds are required thus,
reducing custom build possibilities. It is very difficult for the
novice to tell good lay up practice from bad. See article (click).
Advantage: complicated non-developable surfaces are possible.
Custom Steel Boat Building
Steel is an excellent boat building material, proven in use worldwide.
Steel also requires developable surfaces when boat building.
Disadvantage: weight, added build consideration for rust prevention,
and special tools required for cutting and shaping.
Advantage: very strong, less expensive than aluminum and is easy
to repair any where in the world.
Custom Wood Boat Building
Wooden boat building is a large subject. For our purpose we will
break it down to sheet material or plank material. Sheet material,
like aluminum and steel, has the requirement of working with developable
Also of note is that modern wood boat building has muddied a little,
it is some times hard to distinguish what is a wooden boat and what
is a fibreglass boat. This is because of the use of epoxy resin
in most wooden boat building today.
Disadvantage: increased maintenance required keeping finished boat
in good shape, possibility of rot. Use of epoxy resin during construction
will increase cost but will reduce possibility of rot considerably.
Advantages: plank (carvel, lap strake, strip planking) very nice
complex shapes are possible. Amateur builders requiring considerable
skill levels can do wooden boat building.
Perry Baskier, President
We'll build you the best boat you ever had.
Here at BNJ Marine Ltd. we believe neatness counts.