Homebuilt
pontoon boat / double-hull kayak
made from
PVC Pipe, foam
insulation and vinyl siding.
Design goals (not
necessarily in order):
Cheap, simple and
fast to build
Stable, safe, easy to re-mount from the water
Zero or near zero maintenance
Better hydrodynamics than 1-2 person pontoon bass boats on market
Propel with paddle, electric (12v) or gas
Able to evolve -- easy to modify in future
Design basics:
Dual hull kayak with deck between hulls
Frame - PVC pipe, 3 inch diameter
Floatation - pontoons made of 2 inch insulating foam cut to shape and
stacked
Deck - 4x8 ft x 1/2 inch exterior plywood (heavy, but cheap)
Length = 10 - 11 feet
Width = 4 feet
Propulsion - double paddle, 12v trolling motor or small gas outboard
Drew rough plans modified
over several months for strength and construction simplicity.
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Cut 3 inch PVC pipe
to size with power mitre saw. Fitted and glued pieces flat on concrete
driveway for reasonably decent alignment.
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Bow and stern crosspieces
were glued to elbows flat on driveway and allowed to dry completely before
joining them to pontoon frames. This insured that all vertical pipes would
be acceptably close to square (90 deg from horizontal). Vertical pipes
are spaced to allow 3 on each side to catch 8 ft long deck.
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Deck holes were cut
extra large to allow easy fitting and plenty of wiggle room for alignment
later. Plan is to fill gaps between deck and PVC pipes with epoxy / glass
/ putty once deck is installed and aligned.
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Cut cardboard templates
from discarded boxes and assembled them with hot glue. (Note: hot glue
is HOT not warm; on skin, think arts-and-crafts napalm.) Templates were
made 11.5 inches wide to allow four pieces to be cut from 48 inch wide
sheet, since some foam is lost to soldering gun.
Pattern was transferred to foam sheet by tracing template with felt tip
marker.
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Pontoon
layers were cut from sheets of foam insulation using an old yard sale
soldering gun. This was slow, tedious work as soldering gun didn't seem
to get very hot.
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Stacked
cut foam pieces in place after applying silicon caulk to surfaces of each
layer to help keep them in place. Filled space in oversized holes around
each vertical pipe with spray foam. Strapped layers together with strips
of fiberglass epoxied in place (note brown vertical stripes). Cut excess
spray foam around vertical pipes flush to surface after it dried.
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Made
deck from 4x8 ft sheet of 1/2 inch exterior plywood painted with white
roof paint (water resistant, UV resistant, cheaper than house paint).
Reinforced it with aluminum box tube bolted to plywood with 1/4-20 galvanized
bolts.
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Put deck
in place and completed pipe frame. Sanded paint from bottom of deck where
it contacted foam pontoons and applied epoxy resin to contact area. Filled
holes in plywood around vertical pipes with epoxy resin mixed with cooking
flour to form thick paste, then applied several layers of fiberglass strips
soaked with resin.
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Detail
of fiberglass & resin collar around vertical posts through deck.
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Used
sheet metal snips to cut plastic (vinyl, PVC?) siding to approximate shape
of pontoon points. (circular saw, bandsaw or jigsaw might've worked better,
since snips didn't steer well in this material.) Ragged edge is ok, as
fiberglass tape / epoxy will cover flaws.
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Good
new is, just happen to have a stack of scavenged "slightly used"
plastic (vinyl / PVC?) siding. Bad new is, the edges of the layers of
foam making up the pontoons are too rough / uneven to allow the epoxy
resin to form a good bond to the siding. Need something that'll adhere
well to both the foam and the siding, that won't drip or run, and that
will easily fill gaps between the uneven foam and the smooth siding.
Looked into construction adhesives (Liquid Nails) and glue specifically
sold for foam (PL Foamboard Adhesive) but both carried warnings against
immersion in water. Checked out the roofing department of Home Depot and
found a few adhesives that claimed to be waterproof, but they all said
not for use on foam or plastic.
The closest
thing to a foam / plastic safe waterproof adhesive seems to be silicone
caulk. Not sure if it'll work, but applied lots of caulk to inside face
of siding then tacked them in place with nails and bits of wire (that's
what all those holes are for) until caulk cured.
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Applied
strips of fiberglass with epoxy resin to seal joints between pieces of
siding. Added additional layers of fiberglass & resin, averaging 3-4
layers for most joints, more where abrasion from launching and landings
might be an issue.
Note:
used epoxy, not Bondo, as Bondo melts fooam.
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Added
PVC molding to joints in areas where abrasion seemed likely.
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This
is during the process of glassing all the joints. Also applied lots of
"putty" made from resin and cooking flour.
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Bottom
view of the completed pontoon boat. Repainted top & bottom of deck
with white roof coating. Painted pontoons with roof coating too, mostly
for cosmetics, as epoxy resin had turned brown for some reason.
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Bon
voyage!
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