July 2010 65
AMA Plans Service Showcase
The final
Sopwith of
WW I is an
FAC charmer
Sopwith Dolphin
THAT’S NOT AN optical illusion; the
wings of this almost-famous British fighter
are negatively staggered. The scare,
though, is that short-nose biplanes are
notoriously challenging to balance—and
with the lower wing located forward, the
correct CG is even harder to obtain.
Bill Noonan got creative on that front
and devised an aerodynamic solution to the
issue; his Dolphin uses two airfoils.
The high-lift version went to the top,
and the bottom wing uses a symmetrical
airfoil that provided less lift. This allowed
the CG to be farther aft, permitting the
short nose to have a better ballast effect
against the long rubber motor that the
design required.
Today’s rubber braiding technique
enables the Dolphin to be balanced even
more easily. Braiding allows a motor to be
shorter for a given power requirement.
Although the wings’ area does add
significant drag, the Parasol effect of the
airfoil treatment helps the model perform in
windy conditions. Another bonus of Bill’s
design is that the wings can be removed in
pairs from the fuselage. At a scale of 3/4
inch = 1 foot, this is a substantial airplane.
The motor upthrust is purposeful.
(Downthrust is more typical.)
The Sopwith Dolphin was featured in a
construction article that was published in
the June 1981 MA. It’s AMA Plans Service
listing 335A and is available for $6 plus
shipping and handling. See page 167 or go
to www.modelaircraft.org/plans.aspx for
ordering information. MA
07sig3x.QXD_00MSTRPG.QXD 5/25/10 2:59 PM Page 65
Edition: Model Aviation - 2010/07
Page Numbers: 65
