Professional BoatBuilder - April-May 2018

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