Professional BoatBuilder - April-May 2018

(Ann) #1
APRIL/MAY 2018 55

DESIGN BRIEF: Dive Tender 14


My speci ed scantlings for Doug-
las- r marine plywood construction
are intended for heavy-duty service.
For a tender to my motorsailer, I may
reduce scantling sizes, employ a
lighter, thinner, stronger plywood (like
okoume or meranti), and minimize
fabric/epoxy covering, which adds
substantial weight.
A er cutting out the design stations/
bulkheads, they are set up on a simple
strongback made from three sawhorses
with 2x4 girders and 1x2 stanchions.
Longitudinal components made from
2x4, 1x4, and 1x2 stock are sprung into
place over notches in the bulkheads.
Plywood skins are epoxy-glued and
stapled over the frame. Basic construc-
tion should take about 40 hours;  n-
ishing time will depend on the degree
of perfection desired. A watertight
inspection plate will be located over
the deepest part of the hull, forward
of the helm pedestal. Steering and con-
trol cables will run down through the
pedestal, exit to starboard close above
the deck, lead into the starboard seat
locker, thus exiting to reach the out-
board motor. Running the cables below
deck might be more elegant but would
compromise the boat’s essential water-
tight integrity.
To beach the Dive Tender 14, I
designed a simple roller assembly,
which can be inserted into the out-
board motor slot from the stern. With
two people grabbing the bow handles,
the boat may be easily brought up
onto the beach.
I hope to build the prototype in the
winter of 2017–18 and will perform
initial sea trials in South Florida’s
Indian River.  e real trials will have
to wait until I make my next extended
cruise in the Bahamas.

About the Author: Reuel B. Parker is a
yacht designer, shipwright, author, and
cruising sailor. Dividing his time between
Maine, South Florida, and the Baha-
mas, he does business as Parker Marine
Enterprises, and is a frequent contribu-
tor to Professional BoatBuilder. Yo u c a n
read his blog at http://www.woodenboat.com/
whiskey-plank.

kg) dry weight, bringing total boat
weight to 350 lbs (158.8 kg) or a little
more, depending on how much fuel is
carried.
To minimize weight, I speci ed
pine for solid wood components—
chine logs, sheer clamps, deck and
hull stringers, and cleats—mostly
made from 1x2 nominal stock. Small
 llets joining hull-to-deck joints will
be made from epoxy, expanded silica,
and microballoons. For  otation, the
hull and deck must form a hollow,
airtight structure that can safely
become partially submerged when
exceeding carrying capacity.
I dra ed full-size construction sec-
tions for every design station, obviat-
ing the necessity for o sets or lo ing.
Full plans will include these drawings
(15 pages total), which are traced
directly onto plywood bulkheads with
a pattern wheel. Below is the con-
struction section for design station/
bulkhead #3. Fasteners will primarily
consist of pneumatically driven ¼"
crown staples. Bulkhead #3 will be
made from^1 ⁄ 2 " plywood to strengthen
the outboard-motor bracket. All other
bulkheads will be^3 ⁄ 8 " plywood.

helm seat I designed an enlarged, cush-
ioned bicycle saddle with back sup-
port.  is will provide a secure seat for
tight cornering at speed and for punch-
ing into head seas. A built-in or carry-
on cooler may be placed in front of the
helm station, providing an additional
passenger seat, although four people
aboard will likely exceed carrying
capacity.

I


computed weights for all materials,
including wood (mostly Douglas-
 r marine plywood), epoxy, Xynole-
polyester fabric, paint, and hardware.
I came up with a dry weight of 250 lbs
(113.4 kg), which may be reduced by
using lighter-weight, thinner plywood
such as okoume. A 9.9-hp 4-stroke
outboard weighs about 90 lbs (40.8

S
T
T

1

3A 1A

(^23)
2A
LWL
Base
Top of transom
To p of bulkhead
Sides:^5 / 8 " ply
Deck:^3 / 8 " ply
Fillets
1x2 sheer clamp
1x4
stiffener 1x2 stringers 1x2
2x4 chine log
keel plank
Soft
rubrail
Sides
¼" ply
Seat lid:^3 / 8 " ply Piano hinge
OB well side
(^5) / 8 " ply
Bench seats P & S
Seat face: ¼" ply
Bottom planking:^3 / 8 " ply
Fillets both sides
¼" ply
½" ply bulkhead
(^5) / 8 " ply
gusset
A cross section at bulkhead #3 reveals the structure of the hull in way of the narrow,
partial, high transom, which serves as the outboard mount, well forward of the broad,
low, open transom at the stern. Plywood is marine-grade Douglas- r, and solid-wood
components are pine. The entire boat is sheathed in epoxy and Xynole fabric.
DesignBrief172-EDFinal.indd 55 2/22/18 10:38 AM

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