a kayak: Hull
This is a foto-documentary about my handicrafts and experiences,
separated into 3 sections. It is not meant to be a complete
instruction replacing a reference book, but I hope it’ll
give you a clear overview. The order of things is, more or
The plywood boards are usually too short. To get them sufficiently
long, they need to be extended by glueing boards together.
For doing that, the edges are bevelled to enlarge the area
of overlap. A ratio of the bevel of 1:10 (4 mm thickness of
board : 40 mm slope length) is common, 1:5 has worked fine
for me. For this purpose, a belt grinder is very useful.
On the pictures you see 4 boards on top of each other, the
edges spaced at 20 mm in a step-like fashion. Hold the belt
grinder in an acute angle and grind the steps down until a
smooth slope is achieved, exposing the individual layers of
the plywood (lower picture). Afterwards, the boards are glued
TIP: my boards
have a manufacturer print on one side, hence it’s important
to watch the orientation of inside and outside.
panels & cut
Draw the shape of the panels onto
the extended boards. In doing so, watch the straight alignment
of the parts (taut string as a guide), paper easily warps
over a length of 5 m.The mirro-like left and right panels
can be cut together, place the boards accordingly.
boards well with clamps against slipping. A jig saw cuts while
lifting, hence the plywood get torn a bit on the upper surface.
Therefore place the good face down, and cut with someseam
allowance. Afterwards, sand the edges smooth
the panels & align the hull
To do that, drill holes into the panels: in pairs close to
the edges at a distance of about 30-50 cm, closer near bow
and aft. Place the panels into the mounts and align them with
the help of the construction aids. Tie the panels together
loosly, either with cable ties or copper wire. And
already it looks like a boat!
Align the boat, make sure the panels butt evenly at the edges.
Tighten cable ties. Fix panels in place with tape to stop
them from slipping. The seams and the keel must not be wavy
– reason for that: a couple of mm inexact cutting and
uneven tightening of the ties, resp. Rather fill in a little
On the large picture the inner construction aids and outher
mounts stabilizing the panels are clearly visible. The little
picture shows the cable ties, which give the hull the appearance
of a hedgehog. The hull is still very wobbly.
up inner seams & and laminate with fibre glas band
Lay the inner side seams with 25 mm fibre glass band and
the keel with 50 mm. Laminate with epoxy resin.
After curing, cut the ties on the outside.You can laminate
either over the cable ties, or just the sections in between.
The first option is faster, but doesn’t look so professionally.
epoxy & fillet
The runny epoxy resin can be thickened with cotton fluffs,
hollow micro-balls or grinding dust (from the belt grinder)
With this stuff seams, or more generally two parts adjoining
at an angle, can be glued in a very stable fasion. To do so,
the inner side of the angle is filled with the thickened epoxy,
a so-called fillet.
It should form a nice smooth concave curve.
The bulkheads close off the cockpit from the compartments.
Their distance is adjusted to the length of the paddlers legs.
Install the bulkheads well with ambient thickened epoxy,
you may re-enforce the fillets with fibre glass band.
For the forward bulkhead I have used thicker birch plywood,
because it has to take the pressure of the feet (stem block).
In the rear, the 4 mm plywood used for the hull I decided
to be sufficient.
Glass cockpit & bulkheads
The cockpit area and the sides bulkhead facing inwards into
the cockpit are more exposed to wear and tear, and therefore
should be re-enfored. These areas are glassed with fibre glass
The front and rear sections of the hull, i.e. the area of
the compartments, are varnished only.
Fill outside seams & sand
The hull gains enormously in stability by filling in the
outer seams with thickened epoxy. Also, the cable tie holes
Afterwards, smooth and round off the plywood edges along
the seams, because the fibre cloth doesn not lay well along
Skeg & Skegbox
After quite some brain gymnastics a skeg and its housing
was constructed, see drawing. The skeg is approx. 30 cm long,
plywood and covered with fibre cloth. The wire, 4 mm, is firmly
glued into the skeg.
The left picture shows the hull from below. The skegbox is
inserted through and glued into a large opening cut into the
hull. It is stabilized from the inside with generous fillets.
or varnish well all sides of the box which are exposed to
the water to avoid deterioration. Later, access to the box
is rather difficult.
wire guide from box to cockpit
A plastic tube runs
from the box below the (future) deck to the rear bulkhead,
through the bulkhead and up to about the area where the thigh
sits later, on the chocolate side of the paddler.
The tube, here glued in with grinding dust-epoxy, should
have as little bends as possible to avoid friction of the
wire. More about the skeg-system on the page Finish.
strips bow and aft
Bow and aft as well as the keel suffer from wear and tear.
Here are additional xxx useful. Ash, planed to a thin veneer,
bends well around the curvatures.
For the keel, an additional keel strip of 5 mm wide glass
band might be a good idea, laid over the whole length of the
& glass outer side
Sand the timber, dust well. Place glass cloth (163 g/m2)
diagonally to the fibre direction over the hull. This way,
the cloth can adjust well to the shape of the hull, and you
get better use of the width of the fabric.Glass
After curing, cut the extra bits and sand. Watch out, don’t
sand into the glass fibre.
Hull is ready !!
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