Read and studied the user manual for the brand of epoxy being used.
Agree to build and paddle the Point Bennett at their own risk.
Rough Cutting the Panels
Cut from 4 sheets of 8 foot (actually 8', 2
1/2") by 4 foot marine grade 4 mm Okoume plywood:
8 pieces that are 11 inches wide and 8 feet (use the full 8',
2 1/2") long. Four of these pieces are for the side panels and
4 for the bottom
panels.
These
pieces will use up the first and second sheets of plywood.
2 pieces that are 12 inches wide and exactly 6 feet and 3 inches
long. Lengthwise (6 feet and 3 inches long), the center panels are
a final cut, not a rough cut, so these final cuts should be made
cleanly at right angles. Each piece needs one straight edge lengthwise,
so cut them out at the 2 long straight edges of the 8 foot by 4 foot
plywood. Mark them as the center panels for the deck.
1 piece that is 22 inches wide and 7 feet long. Mark it as the
stern panel for the deck. This piece and the 2 pieces from number
2 above
will use up the third sheet of plywood.
1 piece that is 17 inches wide and 5 feet and 6 inches long. Mark
it as the bow panel for the deck.
2 pieces that are 11 inches wide, and 2 feet and 6 inches long.
Mark these 2 pieces as the bow end of the side panels. These 2 pieces
and the piece from
number 4 above will use the forth sheet of plywood and leave enough
extra for the cockpit coaming lip and bulkheads.
Joining the Rough Panels
Use butt or scarf joints to join the rough panels. There is enough
extra length in the rough panels for either type of joint. I recommend
scarf joints in the hull and butt joints in the deck.
For each of the 2 bottom hull panels, join 2 of the 11 inch by
8 foot (actually 8', 2
1/2") panels end to end.
For each of the 2 side hull panels, join 2 of the 11 inch by 8
foot panels and one of the 11 inch by 2 foot and 6 inch panels end
to end.
On the deck don’t join the 2 center deck panels side by side.
The 2 center panels are positioned together but not
joined
so that the center deck can be raised into a peaked deck. Join the
bow deck panel to one end of center deck panels and the stern deck
panel to the other
end. Be sure the bow and stern deck panels are centered on the ends
of the center deck panels.
From left to right, the deck, 2 bottom panels,
and 2 side panels. The weights are being used to hold down the backing
plates for butt joints while the epoxy hardens. Scarf joints can be
used too.
Lofting the panels
The lofting numbers for the panels are easy to understand. From a
starting point on a panel, the numbers tell you how far to go to the
right, and
then from there, how far to go up or down for each point. For example,
one of the lines for lofting the bottom hull panels reads, “At
5 feet and 1 13/16 inches to the right the keel is up 1/8 inches and
the chine is up 8 11/32 inches.”
Important! Some of the panels are measured bow to stern, and others,
stern to bow. Be sure to check the direction being measured, especially
with
the bottom panels, and mark the bow and stern on the panels to prevent
installing them backwards.
Make sure the lines are fair, meaning the curves are smooth and without
bulges or hallows. Being off by as little as 1/32 of an inch can cause
a noticeably unfair line.
Try your best to keep the keel line in the bottom hull panels as
accurate and fair as possible. Because the bottom panels meet at a
shallow angle, any unfairness
is compounded here, resulting in bulges or hallows along the keel line.
It is difficult to get the keel line of the bottom hull
panels perfectly fair, but don’t worry, because I will tell you
how to compensate for any unfairness later.
A batten being used to loft the deck.
Side Panels
Measure bow to stern with the chine on the bottom and the sheer on
top.
At 0 inches to the right there is no chine yet and the sheer starts
(bow) up 9 19/32 inches.
At 1 foot and 3/8 inches to the right there is no chine yet and
the sheer is up 8 13/16 inches.
At 1 foot and 3 15/32 inches to the right the chine starts up 21/32
inches and skip sheer.
At 2 foot and 23/32 inches to the right the chine is up 1/4 inch
and the sheer is up 8 1/4 inches.
At 3 feet and 1 3/32 inches to the right the chine is up 0 inches
and the sheer is up 7 31/32 inches.
At 4 feet and 1 15/32 inches to the right the chine is up 0 inches
and the sheer is up 7 25/32 inches.
At 5 feet and 1 13/16 inches to the right the chine is up 1/16
inch and the sheer is up 7 25/32 inches.
At 6 feet and 2 3/16 inches to the right the chine is up 7/32 inches
and the sheer is up 7 29/32 inches.
At 7 feet and 2 9/16 inches to the right the chine is up 3/8 inches
and the sheer is up 8 1/16 inches.
At 8 feet and 2 29/32 inches to the right the chine is up 19/32
inches and the sheer is up 8 1/8 inches.
At 9 feet and 3 9/32 inches to the right the the chine is up 3/4
inches and sheer is up 8 1/8 inches.
At 10 feet and 3 21/32 inches to the right the chine is up 29/32
inches and the sheer is up 8 1/8 inches.
At 11 feet and 4 inches to the right the chine is up 1 3/32 inches
and the sheer is up 8 1/16 inches.
At 12 feet and 4 3/8 inches to the right the chine is up 1 9/32
inches and the sheer is up 8 inches.
At 13 feet and 4 3/4 inches to the right the chine is up 1 7/16
inches and the sheer is up 7 29/32 inches.
At 14 feet and 5 3/32 inches to the right the chine is up 1 11/16
inches and the sheer is up 7 27/32 inches.
At 15 feet and 5 15/32 inches to the right the chine is up 1 15/16
inches and the sheer is up 7 7/8 inches.
At 16 feet and 5 27/32 inches to the right chine is up 2 3/8 inches
and the sheer is up 8 1/4 inches.
At 17 feet and 3 5/16 inches to the right the chine ends up 2 29/32
inches and skip the sheer.
At 17 feet and 6 7/32 inches to the right there is no chine and
the sheer is up 9 1/32 inches.
At 18 feet and 1 11/16 inches to the right there is no chine and
the sheer ends (stern) up 9 19/32 inches.
Bottom Panels
Measure stern to bow with the keel on the bottom and the chine on
top.
At 0 feet to the right skip the keel and the chine starts (stern)
up 2 5/8 inches. Be sure to mark this end as the stern.
At 4 9/16 inches to the right the keel starts up 1/8 inches and
skip the chine.
At 1 foot and 3/8 inches to the right the keel is up 7/32 inches
and the chine is up 3 11/32 inches.
At 2 feet and 23/32 inches to the right the keel is up 7/32 inches
and the chine is up 4 9/16 inches.
At 3 feet and 1 3/32 inches to the right the keel is up 3/16 inches
and the chine is up 6 inches.
At 4 feet and 1 15/32 to the right the keel is up 5/32 inches and
the chine is up 7 9/32 inches.
At 5 feet and 1 13/16 inches to the right the keel is up 1/8 inches
and the chine is up 8 11/32 inches.
At 6 feet and 2 3/16 inches to the right the keel is up 3/32 inches
and the chine is up 9 3/32 inches.
At 7 feet and 2 9/16 inches to the right the keel is up 1/16 inches
and the chine is up 9 9/32 inches.
At 8 feet and 2 29/32 inches to the right the keel is up 1/16 inches
and the chine is up 9 3/32 inches.
At 9 feet and 3 9/32 inches to the right the keel is up 1/16 inches
and the chine is up 8 5/8 inches.
At 10 feet and 3 21/32 inches to the right the keel is up 1/16
inches and the chine is up 7 27/32 inches.
At 11 feet and 4 inches to the right the keel is up 1/16 inches
and the chine is up 6 27/32 inches.
At 12 feet and 4 3/8 inches to the right the keel is up 1/16 inches
and the chine is up 5 19/32 inches.
At 13 feet and 4 3/4 inches to the right the keel is up 1/16 inches
and the chine is up 4 13/32 inches.
At 14 feet and 5 3/32 inches to the right the keel is up 1/16 inches
and the chine is up 3 13/32 inches.
At 15 feet and 5 15/32 inches to the right skip the keel and the
chine is up 2 7/8 inches.
At 15 feet and 6 7/16 inches to the right the keel ends up 0 inches
and skip the chine.
At 15 feet and 11 27/32 inches to the right skip the keel and the
chine ends (bow) up 2 7/8 inches. Be sure to mark this end as the bow.
Deck Panel
Measure stern to bow, beginning on the stern panel and centered exactly
6 feet and 11 inches behind where the center panels meet the stern
panel.
At 0 feet to the right (stern) go up and down 0 inches.
At 1 foot and 3/8 inches to the right go up and down 2 1/16 inches.
At 2 feet 23/32 inches to the right go up and down 4 1/16 inches.
At 3 feet and 1 3/32 inchesto the right go up and down 5 7/8 inches.
At 4 feet and 1 15/32 inches to the right go up and down 7 15/32
inches.
At 5 feet and 1 13/16 inches to the right go up and down 8 13/16
inches.
At 6 feet and 2 3/16 inches to the right go up and down 9 27/32
inches.
At 7 feet and 2 9/16 inches to the right go up and down 10 1/2
inches.
At 8 feet and 2 29/32 inches to the right go up and down 10 3/4
inches.
At 9 feet and 3 9/32 inches to the right go up and down 10 9/16
inches.
At 10 feet and 3 21/32 inches to the right go up and down 10 1/32
inches.
At 11 feet and 4 inches to the right go up and down 9 5/32 inches.
At 12 feet and 4 3/8 inches to the right go up and down 8 1/16
inches.
At 13 feet and 4 3/4 inches to the right go up and down 6 13/16
inches.
At 14 feet and 5 3/32 inches to the right go up and down 5 13/32
inches.
At 15 feet and 5 15/32 to the right go up and down 3 7/8 inches.
At 16 feet and 5 27/32 inches to the right go up and down 2 5/16
inches.
At 18 feet (bow) go up and down 0 inches.
Paddler/Cockpit Location
In the proper paddling position (sitting straight up or slightly
forward), the paddler’s lower back must be exactly 7 feet and
3 inches forward of the stern. Any variation in the location of the
paddler will alter the intended performance of the kayak. Generally,
it is best to have 4 inches between the paddler's lower back and the
back of the cockpit. As a result, I recommend that the back of the
cockpit be 6 feet and 11 inches forward of the stern.
Stations
Stations are absolutely necessary to help shape the hull. Using the
lofting numbers, draw and cut out the stations from 1/2 inch hardwood
plywood. Lofting the stations is similar to the panels, but with the
stations the measuring begins at the keel, and then you are told how
far to go up and to each side for the chine and sheer. When drawing
the stations, be sure to include a vertical center line to help with
checking the alignment of the hull.
Station #1: From the keel, the chine is up 2 3/8 inches and left
and right 3 11/32 inches, and the sheer is up 9 29/32 inches and
left and right 5 13/32 inches.
Station #2: From the keel, the chine is up 1 7/8 inches and left
and right 7 11/32 inches, and the sheer is up 9 9/32 inches and left
and right 9 5/32 inches.
Station #3: From the keel, the chine is up 1 13/32 inches and left
and right 9 3/32 inches, and the sheer is up 8 7/16 inches and left
and right 10 3/4 inches.
Station #4: From the keel, the chine is up 1 19/32 inches and left
and right 7 9/32 inches, and the sheer is up 7 29/32 inches and left
and right 8 13/16 inches.
Station #5: From the keel, the chine is up 1 7/8 inches and left
and right 4 1/4 inches, and the sheer is up 7 23/32 inches and left
and right 5 7/8 inches.
Cutting and planing the panels
Before cutting the 2 side and 2 bottom hull panels, attach the pairs
to each other so that the work can be reduced by half and the pairs
are better matched. The pairs can be attached with nails, screws, or
staples.
Use a jigsaw to cut just outside the lines, and then use a plane to
go down to the line. Along the last 12 inches at the bow and stern
tips of the deck, leave
about 1/8 of an inch of extra wood around the lofted lines so that
fine trimming can be done later to better match the deck to the hull.
Check the lines on panels for fairness. If they are not fair, don’t
be afraid to use the plane a little to make them fair.
Again, try your best to keep the keel line in the bottom hull panels
as accurate and fair as possible. Because the bottom panels meet at
a
shallow angle, any unfairness
is compounded here, resulting in bulges or hallows along the keel line.
It is difficult to get the keel line of the bottom hull panels perfectly
fair, but don’t
worry, because I will tell you how to compensate for any unfairness
later.
Before detaching the pairs of bottom and side panels, drill some of
the holes for the wires. Drilling the holes through the pairs will allow
the holes to match evenly on each side of the stems and along the keel.
Also, it is easier to drill the chine holes on the bottom panels now
rather than when the hull is assembled. However, some of the drilling
will have to wait until the hull is assembled. Drill the holes around
the entire perimeter of the bottom panels and only along the stems of
the side panels.
Detach the pairs of bottom and side panels.
Assembling the Hull
With the inside of the bottom panels facing each other flat, use 18
gauge copper wire to first snugly attach the bow and stern stems. Loosely
wire the keel so that there enough slack to pull the chines apart. Pull
the chines of the bottom panels apart to get the approximate shape of
the finished hull. Use duct tape to help hold down the chines. Use scraps
of wood to evenly support the bottom panels as necessary.
The bottom panels wired together.
With the inside of the side panels facing each other, snugly wire
the bow and stern stems. Place the side panels on top of the bottom
panels.
Line up the bow edge of the side panels with the bow edge of the bottom
panels. It is easy to mix up the bow and stern ends of the bottom
panels, so check where you marked the bow and stern to make sure
the bottom panels are not installed backwards. From the bow, drill
holes
along
the chine
of the
side panels
near the bow
to
match
the
holes
already
drilled
along
the
chine
of
the bottom panels. As you drill a hole, wire it, alternating the sides
of
the hull to keep the wiring even as you go along.
The side panels wired to the bottom panels at
the bow.
Each station
is installed after the chines are wired about one foot past the station
location.
Install
the
stations
in their
numerical
order, meaning station #1 first and
#5
last. From the bow of the hull, station #1 is 3 feet and 7 9/32 inches
back, station #2 is 6 feet and 8 3/8 inches back, station #3 is 9 feet
and 9 15/32 inches back, station #4 is 12 feet and 10 9/16 inches back,
and station #5 is 14 feet and 11 9/32 inches back.
Stations helping to shape the hull.
The stations should fit
pretty good, but if necessary, trim the sides of the stations so that
they fit inside the
side panels
of
the
hull. It is
better to trim more than is necessary than not enough, because not
enough
trimming
will cause a bulge and gap at the chines. Don’t make
any changes to the angle of the bottom V on the stations, because the
bottom
panels
must be pushed to match them and give the hull its intended shape.
Secure the stations in place by stapling them with a staple gun through
the hull, from the outside, both on the bottom and side panels. Make
sure
that
the bottom panels
are snug against the stations to insure that the hull will be in
the proper shape. Also make sure that the center line drawn on the
stations
is lined up with the keel line.
Because station #5 has the most twisting of the bottom panels, staples
will not hold it very long. As result, at this station it is necessary
to use a small screw on each of the bottom panels to help hold these
panels snugly against the station. Pre-drill the screw holes.
Don’t
fasten the screws all the way down, because it will be necessary to
leave
these
screws
in
position until after the first layer of fiberglass is epoxied over
the bottom of the hull. Leaving the screws about ¼ of an inch
out from the bottom panels will allow you to fiberglass around them
and
then remove them after the epoxy has hardened.
The screws used to hold station #5 until after
the first layer of fiberglass hardens on the outside of the hull. Note
that in this photo the first layer of fiberglass is on the hull, which
is a later step.
At the stem of the stern, the bottom panels extend about 1/2 inch
beyond the side panels. In other words, when the bottom and side panels
match perfectly at the bow, the bottom panels will stick out about
1/2 inch past the side panels at the stern. The reason for the extra
1/2 each is to allow for trimming to precisely match the bottom and
side panel stems at the stern.
Now is the time to trim this extra 1/2 inch off the stern end of the
bottom panels. To avoid over cutting, it is better to not quite cut
enough off and then file it down the rest of the way. Remove wires
as necessary as you cut, and where the wires have been removed, use
spring clamps to hold the bottom panel stems together. Once the trimming
is complete, drill new holes and re-wire the the panels at the stem.
Now comes the most critical part of plywood kayak construction. It
is extremely important to sight down the chines, and especially the
keel, to make sure that the lines are fair or straight. Look for hollows,
bulges and hooks, especially in the keel. Now is the best time for
any adjustments to correct
the lines. If the lines are not correct, first check to see that
the
panel edges are even against each other. Then tighten the stitches
in the area of bulges and loosen the stitches in the area of hallows.
Small wedges of wood in the seam help
to remove larger hallows. It is OK to have small gaps between the panels
to avoid
hallows.
Any
gaps
can be well reinforced later with fiberglass.
Also, make sure that the kayak is not twisted. Sight along the vertical
lines on the stations and the bow and stern stems to make sure they
line up. If necessary, twist the hull to get them straight. Also, it
is critical to make sure that the keel is straight, especially near
the bow and stern. If
necessary, loosen some wires, push and pull the panels until straight,
and then retighten the wires.
Use a syringe to apply a small amount unthickened epoxy to all of the
seams. This step is not for filleting. Instead, it is for securing the
hull panels together so that the wires can be pulled out and the outside
of the hull can be reinforced with fiberglass while the stations are
still holding the shape of the hull. Also, use a bead of wood glue to
secure the edges of the stations to the panels, so that the staples
(not the screws at station #5) can be removed soon. Don’t use
a lot of glue on the stations, because they will have to be removed
later.
After the epoxy in the seams has hardened,
carefully pull out the wires, which are not necessary now that the
seams are epoxied. With the wires removed, it is easier to sight along
the seams to check again that the lines are fair or straight. If a
line is bothering you, use a razor knife to cut through the epoxy in
the
seam
and rework it. This is your last chance to make any changes. Once you
are satisfied with the lines, fill the outside seams with thickened
epoxy, and after it has hardened, file and sand the outsides seams
smooth.
Reinforce the outside of the hull with fiberglass as desired. After
the epoxy has hardened in the first layer of fiberglass, it is safe
to remove the screws on the bottom panels at station #5. Fill the screw
holes with thickened epoxy. Try to avoid getting the thickened epoxy
all of the way down into the station to make removing the station easier
later. Add additional layers of fiberglass as desired.
Leave the stations in place to help keep the shape of the hull while
you assemble the deck.
Assembling the Deck
From scrap plywood, make a template for a cockpit that is the size
and shape as desired. The template is used for the marking the inside
line of the cockpit on the deck, and later the cockpit coaming spacer
and lip.
My cockpit template.
Use the cockpit template to draw the inside line for the cockpit on
the deck. When positioning the cockpit on the deck, it is important
to keep in mind that in the proper paddling position (sitting straight
up or slightly forward), the paddler’s lower back must be exactly
7 feet and 3 inches forward of the stern. Any variation
in the location
of the paddler will change the intended performance of the kayak. Generally,
it is best to have 4 inches between the paddler's lower back and the
back of the cockpit. As a result, I recommend that the back of the
cockpit be 6 feet and 11 inches forward of the stern.
Cut just inside the cockpit line on the deck to allow for trimming
down to the cockpit coaming when it is attached later. You may also
want to leave thigh braces when cutting the cockpit on the deck.
The deck area on the center panels in front of the cockpit is peaked.
This peak is formed by pulling up the center of the 2 center panels
at the front of the cockpit and filling the gap formed in the peaked
deck with a strip of 4 mm plywood that is trimmed to fit.
The peaked deck.
The assembly of the deck peak can be done on a flat surface or on
the hull. If the assembly is done on the floor, place pieces of scrap
wood under parts of the deck to roughly follow the curve of the sheer
in the hull. For a depth of 12¼ inches
at the front of the cockpit, a finished 2x4 inch block of wood (3 3/8
inches
wide) on edge is used to raise the center of the center panels at the
front of the cockpit. Place weights on the deck as needed to prevent
distortion of the deck. Trim a piece of plywood to fit in the gap caused
by the peak in the deck. Epoxy this trimmed piece in the deck. Once
the epoxy has hardened, reinforce the topside of the peak with fiberglass
tape. Then turn the deck upside down and reinforce the underside of
the peak with fiberglass tape.
Now is also the time for reinforcing the underside of the deck with
fiberglass as desired. Before doing so, use scraps wood to allow the
sheer of the deck to curve approximately as it would on the hull.
Completing the Inside of the Hull
Use a hammer to tap the stations loose.
Fillet the inside hull seams and reinforce the inside of the hull with
fiberglass.
Attaching the Deck to the Hull
Place the deck on the hull, and make sure that the deck is centered
on the hull. Beginning at the bow and alternating sides, drill holes
through the hull and deck as close to the sheer as possible and wire
the deck to the hull.
Using thickened epoxy, fill the outside of the sheer seams to glue
the deck to the hull. Pull out the wires after the epoxy has hardened
but is not fully cured. Use more thickened epoxy to fill the voids
where the wires where removed. Then file and sand the sheer smooth
and fair with the hull and deck. Cover the outside sheer with fiberglass
tape or the fiberglass cloth used to reinforce the deck.
Fillet the inside sheer seams and reinforce them with 2 inch fiberglass
tape. To make applying the tape easier, cut the hatch holes so you
can reach through them. The tape doesn't need to be applied all the
way to the ends. As far as you can reach is good enough. Roll up the
length of tape you need, and soak it is a plastic cup of epoxy to wet
it out. Remove the excess epoxy by drawing the tape between two fingers.
Roll up the tape again and then unroll along the inside seam.
Using sheer clamps to attach the deck to the hull doesn't work for
this design, because they prevent the top of the side panels from being
flexible enough to match the outline shape of the deck.
The Cockpit
The coaming spacer is cut from ¾ inch, 5 layer, hardwood plywood,
and the coaming lip is cut from the 4 mm plywood. Use your cockpit template
to draw the inside lines for the spacer and lip. The spacer should be
about ¾ inches wide, and the lip should be about 1 ¾ inches
wide. Cut the spacer and lip so that they are one piece each, with a
thin cut down the front center of each to allow for the peaked deck.
Epoxy the spacer to the deck, using clamps to hold it down until the
epoxy has cured. Then epoxy the lip to the spacer, using clamps to hold
the lip down until the epoxy has cured.
Note the gap in the front of the coaming. It will
be filled in a later step.
Fill the gap at the front of the spacer and lip with a trimmed to fit
piece of ¾ inch hardwood plywood and several trimmed layers of
4 mm plywood, which allow for rounding off the top of the lip at the
front of the coaming.
