Installing the Decking
With the strongbacks and clamp installed, a light sanding of the epoxy coated
interior, and planing the sheer clamps level with the plywood sides using a
hand planer it was almost time to begin decking. The last thing to do before
attaching decking was to pour the flotation foam. Using two-part polyurethane
foam I mixed and poured it into the front flotation compartment. Marine grade
electrical wire for the bow light was run into this compartment and the bow eye
was installed prior to pouring the foam. The plans call for foam flotation on
each side of motor well in the very rear of the boat. The compartments to the
side of the motor well are divided into two parts. The rearmost is flotation and
the forward area is storage. Not wanting to lose storage area I elected to use the
flotation compartments for dry storage. Not wanting to lose flotation I installed
water tight deck hatches. I used circular, water-tight hatches that have a six inch
diameter opening. The lids to the hatches screw in. I never leave the hatches
open. They are closed immediately after storing or retrieving any item. These
sealed air flotation compartments passed the inspection required to register the boat.
In the future I may add flotation under the floorboard for an extra margin of safety.
The blueprints do not contain lofting points for the decking, rather the
hull of the boat serves as a template. The first step was to determine how the
decking would be cut from two sheets of plywood plus a little scrap. After taking
some measurements it was determined that the decking would consist of five
pieces: two rear pieces that covered the sides of the motor well forward to the
first set of knees(closest to the front of the cockpit), two center pieces that
covered from the first set of knees to the floatation compartment, and a single
piece that covered the flotation compartment.
Before I cut into my remaining expensive marine ply I used 1/8" Luan to rough
out decking templates. Using the boat as a template I traced one of the rear
decking pieces onto the Luan. I allowed excess of an inch or more when I traced
it. I measured the shape and determined I could get two rear deck pieces from
one piece of plywood. I then cut out the template and laid it on the Okoume and
verified that both pieces could be obtained from one sheet. The process was
repeated for the center deck pieces. Let me emphasize here that there is no need
to worry about exact cuts at this point. All that is being done is roughing out
the pieces. The boat will eventually be a guide for making finishing cuts.
The next step was to bend the decking pieces into place, countersink all
screw holes, mark and make the necessary cuts so that all decking pieces fit
together. Pre-drilling, testing, and finalizing the fit is strongly recommended
before you try and epoxy everything into place. Bending the plywood to the
curvature of the boat in the storage/flotation area proved to be tricky. My first
attempt failed and it took Jeff Smith's woodworking knowledge to bail me out in the
following manner. The two center decking pieces were temporarily butt joined with
a 6" wide 3/8" piece of scrap Okoume plywood. The butt joint was formed by screwing
the 6" piece onto the backside of the center decking pieces. This created 3" of
overlap on each deck piece that was later permanently epoxied into place. With the
two center decking pieces joined they were bent into place. Bending was accomplished
with the use of large clamps and Mahogany boards that served as straps. The boat was
moved back on the cradle so that the clamps could hook on to it.
With the center decking pieces clamped into place I drilled the counter-sink
holes in the decking and clamps/strongbacks. Drilling the holes in the clamps
took some care. If a hole was drilled too close to the outside of the clamp the
screw would be visible in the clamp's groove. If a hole was drilled too close
to the inside I risked sinking the screw in the plywood instead of the strong
Mahogany. Jeff showed me a slick way of drilling the holes consistently in the
right place. With a piece of scrap 3/8" plywood he cut what resembled a tuning
fork. One of the legs of the "tuning fork" was longer by the distance from the
outside edge of the clamp to where the hole needed to be drilled. The distance
between the legs of the tuning fork was 1/2", just large enough to fit over the
protruding plywood decking. Using the tuning fork I simply put the shorter leg
against the clamp and marked with a pencil the end of the longer leg on the
decking. Marks were made every 6". After every couple of marks I would drill
the counter-sink holes and screw in a temporary fastener (sheet rock screw).
By fastening a little bit at a time I was "spreading out" the decking.
After the center decking pieces were temporarily fastened I climbed in the
boat and marked the bottom of the decking along the flotation bulkhead,
the storage bulkhead (cockpit side), and the knees (forward side). The objective
of marking the decking was to ensure that all the decking pieces would fit
together and that all decking joints would be centered over a bulkhead or knee,
thereby creating a strong butt-joint. I then removed the screws and unclamped
the center decking pieces. The lines just made were to
serve as cutting guides so that all the decking pieces would fit together. With
the flotation bulkhead line I measured 3/8" (half the thickness of the 3/4"
bulkheads) forward and drew a parallel line. In all honesty that is what I meant
to do. In actuality I made a mistake and marked behind the original line. This
made the center decking piece 3/4" too short and I wound up having to install blocks
on the flotation bulkhead in the storage area to support the decking. Oops. Next, I
measured 3/8" back from my line drawn on the forward side of the knee and drew a
parallel line. I scratched out the original lines to make certain I cut the correct
ones. Using my jigsaw I cut along the lines.
This entire process of bending the decking into place, drilling, screwing in
temporary fasteners, marking joint lines, removing the temporary fasteners, moving
the joint lines, and cutting was repeated for the rear deck pieces, and the front
deck piece. Upon completion it was time to epoxy and fasten the decking.
The first decking piece installed was the center piece. The two center pieces
were butt-joined with the 6" piece of 3/8" just prior to installing. Epoxy mixed
to the consistency of ketchup was used to bond the three pieces together. Screws
were used to temporarily hold everything together. The clamp and bulkhead tops
received a coat of pure epoxy and then a coat thickened to the consistency of ketchup
as did the decking. The center piece was then clamped into place and #8 1 1/4" silicon
bronze Frearson head screws were installed in each of the pre-drilled holes. Plastic
sheeting was used under the Mahogany straps to keep excess epoxy from laminating them
to the deck accidentally.
The same process was repeated for the rear decking pieces and the front deck
The next step was quite possibly, no make that definitely, the worst step
in the entire boat building process. In fact it was the only step I did
not enjoy. I am referring to filleting the underside of the deck. The
deck fillet joints are much smaller than the hull joints but were ten
times more difficult. The reason being that you are applying epoxy
upside down. Instead of gravity working the epoxy into the joint the
epoxy wants to fall away from the joint and into your face, hair, etc..
The absolutely worst deck joints are those in the storage area. Imagine
filleting joints upside down on your head in a suitcase!!
As with the hull joints the deck joints were painted with pure epoxy and
then peanut butter was filleted with an autobody squeegee. The amount
of epoxy used is much less. The idea here is to create a small radius with
the epoxy to relieve stresses. The only deck joints that I taped were the
knees. This was done because a Black Brant owner told me that after eight
years of usage one of those joints delaminated. He also said repairing that
joint was the only maintenance he ever had to perform. If I ever build another
I will flip to boat upside down before I fillet the deck joints.
After the epoxy cured the clamps were removed. A small batch of peanut butter
was made and the screw holes were filled. After curing they were sanded flush.
The next step was to make the final decking cuts and route the edges. Using
a jigsaw I cut the excess decking around the perimeter of the boat to within
1/4" of the bow/clamp/transom/longitudinals. Using my router and a 3/8" radius
round-over bit with a bearing guide I went around the entire perimeter of the
The last step in the decking installation process was to cut the interior
edge of the cockpit decking, nice and curved. To do this I made a guide out
of scrap plywood. The guide was shaped like an isosceles triangle and had
two bolts at the bottom apexes to act as guides when sliding along the sheer
clamp. The distance from the tip to a line drawn between the two bolts was
15 1/2", the width of the knees plus one inch to account for the clamp.
In hindsight I wish I had made my decking a couple inches wider. Using the
guide I slid it along the sheer clamp and marked the cockpit decking with a
pencil. This created a curve parallel to the side of the boat. I then used
my jigsaw and cut along the line. The decking was now ready for installation
of cockpit coaming.