Professional BoatBuilder - February-March 2018

FEBRUARY/MARCH 2018 59

RIG DESIGN: Fractional Update

era—the Concordia Yawl and the Ber-

muda 40—and included a separate

shower, a seaworthy galley, and a cabin

table that did not restrict fore-and-a

passage belowdecks.  ese were to  t

into an easily driven hull that would

require only modest power and an e -

cient rig to provide above-average per-

formance. A scaled-up derivative of

the P-32’s rig was chosen to meet that

latter objective.

About the Author: Jay Paris has worn

many hats: naval architect, oceanogra-

pher, winch designer, writer, and techni-

cal editor. He believes that studying his-

tory provides insights into yacht design

just as it does for many other subjects.

hydrodynamics of the rest of the boat.

 e sail plan for my G-37 (11.3m)

design illustrates the application of

the design methodology of the P-32

to a somewhat larger keel/center-

board yawl. I developed the G-37 in

response to the Cruising Club of

America’s interest in exploring what

aspects of green design would be

applicable to o shore yachts. A green

design is for a given mission, de ned

in terms of accommodation, payload,

and performance to reduce the envi-

ronmental impact of construction

and operation.

The design objectives for what

became the G-37 were basically those

of two classic designs of the CCA rule

reacher, slowing down, and unrolling

the fractional self-tacking jib could we

harden up and make any progress

upwind in a normal fashion.

Later I asked my sailmaker, Win

Fowler of Maine Sailing Partners

(Freeport), about what had happened.

He said that our experience is not

uncommon on high-performance

multihulls. We were reaching faster

than the true wind, which brought the

apparent wind so far ahead that we

couldn’t go to windward.

Petrel’s laudable performance can

be attributed in part to her atypical

fractional rig. This reinforces the

importance of designing a rig in con-

junction with the aerodynamics and

The G-37 (11.3m), the author’s

keel/centerboard yawl design,

has an enlarged version of the

P-32’s fractional rig, with its

roller-ree ng, self-tacking jib at

(^5) ⁄ 7 hoist and a roller-furling
light-air drifter/reacher at^6 ⁄ 7
hoist. The area of the self-
tacking jib is 44% of the main.
The space between the upper
diamonds and the single
lowers allows the high-clewed
over lapping drifter/reacher to
be sheeted in narrower than
the tips of the spreaders. If a
radome is  tted, the mizzen is
not completely freestanding,
because the intermediates
shown on the sail plan are
attached at the radome
mount.
JEP
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