Fiberglassing the Hull
With all the joints filleted it was time to flip the boat over and work on the hull.
Flipping the boat over was a three man job. The cradle was put aside for the time being while
the boat rested upside down on two saw horses.
The first task was to remove the wire stitches. Even though the wires were encapsulated
in epoxy removing them wasn't difficult. Essentially all that was required to remove them
was heat and leverage. The first step was to untwist the wires. Next, using a small propane
torch the ends of the wires were heated until they were glowing red hot. The heat is conducted
along the wire into the area sealed in epoxy and brings the epoxy to its melting point. When
this occurs the wire may be pulled out with pliers. The melted epoxy actually serves as a
lubricant easing the removal. A block of wood is useful for leverage and to protect the
plywood from getting marred. Occasionally a wire end would break while pulling on it. When
this happened I would apply more heat and pull on the remaining wire end. After about three
hours every single wire was extracted.
With the stitches removed it was time for final preparations before fiberglass sheathing
the hull. Using a block plane the side pieces were planed at the chine. Wire holes and
the joint down the keel were filled with epoxy which was allowed to cure. All edges were
then radiused. Fiberglass loses its strength when it makes an abrupt change in direction.
Corners should always be rounded to maintain strength. The chines were hand sanded to
round-off the edges. The keel was sanded similarly. Edges formed by the transom and the
motor well were rounded-off first with a router using a 3/8" radius roundover bit with a
bearing guide, and then finished by hand with sandpaper.
Sheathing the hull with fiberglass cloth turned out to be one of the easiest steps
in the whole boat building process. The entire hull was glassed in less than four hours,
from start to finish.
With all the corners radiused the next step was to prepare the cloth. I used 50" wide
6 ounce fiberglass cloth. This was the recommended width and weight. Other options could
be used if hunting circumstances warrant it (e.g. thick ice, rocks). The first step was to
pre-cut the needed sections of cloth. There were a total of eight pieces needed. These
- Port bottom and side of the hull
- Starboard bottom and side of the hull
- Port transom
- Starboard transom
- Port motor well longitudinal
- Starboard motor
- Motor bracket doubler
- Bow bulkhead
Pieces 1 and 2 were cut oversized to allow 4 inches of overlap on both sides of the
keel and several inches to hang below the sides. The remaining pieces were also cut
oversized. A double layer of cloth at the joints increases strength and abrasion
The cut pieces were set aside for the moment. Using the Makita sander I lightly went
over the entire hull with 80 grit paper. Next I mixed up a batch of epoxy and painted
all the joints. This served two purposes. First it allows the exposed end-grain to soak
up a little extra epoxy to seal it off. Second, the epoxy helps hold the cloth in place
initially as you place it over the hull allowing you to spread out wrinkles or gathers.
Next the Port bottom and side cloth piece was placed into position and smoothed out.
At this point having an assistant is a huge help. I gave my father-in-law a crash course
in mixing epoxy. He mixed up batch after batch while I worked it in the cloth. Epoxy
mixing for this step is a little different than during the filleting process. Larger
batches are mixed and used quickly. It is preferable to use mostly fast cure
hardener because there is very little heat build-up once the epoxy is
spread over the hull. Thermal build-up does not occur so if slow cure hardener is used
you could be in for a long wait for the epoxy to harden. I worked with 15 ounce batches
that were four ounces fast cure, one ounce slow cure, and of course, ten ounces resin.
Starting at the highest point in the middle I poured pure epoxy onto the cloth. With an
auto body squeegee the epoxy was spread down and away. I used a figure eight motion with
the squeegee to spread and move the epoxy over dry cloth. I worked my way from the middle
of the boat towards the stern and the bow. This allowed the cloth a place to stretch and
work out wrinkles. With the squeegee I applied enough pressure to squeeze out excess
epoxy. Too much epoxy can cause the cloth to float up off the wood which greatly increases
the chance for delaminating. The cloth appears clear, yet dull, and the weave is visible
when it is wet out properly. The sides of the boat were wet out by pouring epoxy close
to the chine and then working the epoxy over the chine and down the sides with the squeegee.
The same procedure was repeated with Starboard bottom and side piece.
The remaining pieces were placed into position. Because they are nearly vertical it was
not possible to pour epoxy on them without spilling. Instead a chip brush and foam roller
was used to spread the epoxy. The squeegee was used to remove excess epoxy. Because they
were cut oversized the edges of these pieces overlapped with the bottom and side pieces.
Perfectly straight edges of the overlaps was not an issue since I would be applying several
more layers of epoxy and taping all the seams, thus covering the overlaps.
After the epoxy had cured for several hours I used a utility knife to cut the overhanging
cloth. It is amazing how easy epoxy saturated cloth is to cut if you catch it at the
right time. If you try and cut it too early you risk peeling it off the wood. If you wait
too late it is tough to cut with a knife and will have to be sanded. A dirty and
time consuming process. When you time it just right it takes no more than ten minutes
to trim away all the excess.
The epoxy was given a day to cure. The next step was to fiberglass tape all the joints
and re-coat the entire hull with epoxy. Using the Makita sander/polisher I lightly sanded
the entire hull. All corners and edges were sanded by hand to avoid cutting through the
cloth with the sander/polisher. I then pre-cut fiberglass tape for the chines, keel,
bow bulkhead, transom, longitudinals, and motor bracket. Two layers of tape were used
on the transom and motor well components. With epoxy and a chip brush the fiberglass tape
was wet into place. Another layer of epoxy was then rolled onto the entire hull with a
After another day of curing the hull was lightly sanded again. The protruding tape edges
were feathered by moving the sander/polisher across the tape edges from the low side to the
high side with minimal pressure. All corners and edges were hand sanded to prevent cutting
through the tape. A final coat of epoxy was applied to the hull. After a day of curing the
hull was lightly sanded again, as before.
Final inspection of the hull was very pleasing -- no lumps, bumps, or seams. My first
attempt at fiberglass sheathing was a huge success. At the outset of the project I thought
the sheathing might be one of the hardest steps. It turned out to be one of the easiest.
I was now ready to install the keelsons.