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[Ed: A number of comments inserted in 2023 to the original
article of summer 2014.] A Brief
History of the IOM Class
by Lester Gilbert
To hear Jan Dejmo (SWE) talk, it seems he enjoyed sailing
Marbleheads in the 1970’s and 80’s, and then decided to see what he could do to
improve the situation of radio sailing.
It may be because Jan [was] an architect by profession, but he [had] a
rare gift of seeing the big picture, and then an equally rare gift of not
letting go until he [had] achieved whatever objectives he [decided were]
important in improving the big picture.
Jan [was] an exceptional friend of radio sailing for many years,
alongside his long involvement in full-size boat administration with IYRU and
ISAF. He chaired the working party
which produced the Equipment Rules of Sailing (ERS), being a very significant
change to the Racing Rules of Sailing, and which developed the ISAF standard
class rules format.
Jan joined the IYRU-MYRD (International Yacht Racing Union –
Model Yacht Racing Division, as IRSA was known at that time) as Chairman of the
Technical Committee, and saw the need for a radio sailing class of boat that had
complete and wide-spread international support.
Graham Bantock (GBR) followed Jan as IYRU-MYRD Technical Committee
Chairman when Jan became Vice-Chairman of MYRD in 1994. Together they developed
and in 1988 launched the class rules for the International One Metre we know
today.
There was one over-riding factor which determined the shape
of the original IOM rules: the boat was to be significantly lower in cost than a
Marblehead. So the rules prevented
exotic materials, limited hull design and rig choices, and sought to ensure the
boat could be successfully built by a non-professional builder.
Amongst many benefits, this also provided a boat that was much easier to
transport for international events.
Of the ten or so major design parameters, the rules left only one of those
parameters free, and restricted the remaining nine, as follows:
|
Parameter
|
Restriction
|
|
Hull type
|
Mono-hull
|
|
Sail area
|
No.1 rig
approx. 0.6 m2
|
|
Rig choices
|
3 rigs only,
one-design
|
|
Draft
|
420 mm max
|
|
Ballast ratio
|
62.5% max
(2500 g bulb max)
|
|
Hull length
|
1000 mm
|
|
Displacement
|
4000 g
minimum
|
|
Rig plan
|
Bermuda
sloop, 7/8 fractional rig, No.1
rig aspect ratio approx. 4.8
|
|
Radio control
|
Two channels
|
|
Beam
|
No
restriction
|
A competitive IOM can be built by an averagely competent
model yacht builder on his kitchen table, since the weight limits and materials
limits make home building quite feasible.
And, a competitive boat remains competitive for several years.
This provides very considerable benefits of reduced life-time costs and
maintained resale values. There are
other, more minor, design and build parameters which the class rules also leave
open – fin and rudder planforms, longitudinal rig and foil placements, and hull
rocker profile, for example – and it is these freedoms and characteristics which
have made the class hugely popular and kept it “fresh” for over 25 years.
One serious mistake was made right at the beginning: fins
were allowed to be unrestricted as to materials and dimensions.
Blessed with perfect hindsight, we now know that a competitive IOM must
have a thin fin which inevitably means a fin made of carbon fibre.
Such a fin cannot be easily built on the kitchen table, and has to be
bought from a professional builder.
This mistake was recognized in around 1994, and there were proposals to limit
the fin to a minimum of 10 mm thickness or 10% of chord.
Although these proposals found favour with owners, they were defeated –
there were too many with a vested interest who already had expensive carbon
fins.
Since 1988, due to the popularity of the class, the small
winning margins of well-sailed boats, and intense competition at World,
continental, and national championships, there have been numerous rule
interpretations and rule changes every few years.
While each change generates some heated debate, the intention was always
to keep the boats in the class the same as possible within the spirit of the
rules, and none of the changes have been true “game changers” – the class has
retained a remarkably stable rules base.
Currently [2013], the class has 26 National Class
Associations (NCAs) affiliated to the International Class Association (IOMICA),
though there are undoubtedly IOMs sailing in more than these 26 countries.
The latest count of declared numbers is as follows:
|
IOMs 2013
(from IOMICA Web site)
|
IOMs 1994
(IMYRU)
|
|
Country
|
Registered
|
Certificated
|
Declared
|
|
ARG
|
64
|
49
|
|
|
AUS
|
486
|
482
|
100
|
|
BAR
|
16
|
16
|
|
|
BEL
|
28
|
28
|
|
|
BRA
|
91
|
62
|
50
|
|
CAN
|
108
|
80
|
7
|
|
CHI
|
70
|
35
|
|
|
CRO
|
62
|
62
|
10
|
|
DEN
|
51
|
42
|
5
|
|
ESP
|
136
|
68
|
|
|
FIN
|
|
|
|
|
FRA
|
148
|
148
|
80
|
|
GBR
|
1342
|
1094
|
600
|
|
GER
|
232
|
228
|
40
|
|
IRL
|
61
|
61
|
|
|
ISR
|
15
|
15
|
|
|
ITA
|
87
|
64
|
|
|
MLT
|
13
|
11
|
10
|
|
NED
|
24
|
24
|
|
|
NOR
|
|
|
|
|
NZL
|
159
|
146
|
200
|
|
POR
|
63
|
56
|
15
|
|
RSA
|
60
|
60
|
|
|
SUI
|
28
|
15
|
|
|
SWE
|
154
|
102
|
|
|
TUR
|
30
|
12
|
|
|
USA
|
527
|
284
|
|
|
Total
|
4055
|
3244
|
1017
|
A very large number of IOM designs have been produced, and
this is a (necessarily incomplete and) partial list of 34 of those which have
been seen at international competitions [up to 2013]: 2 Dogs, 3 Dogs, Ace,
Arrival, Britpop, Cheinz, Cockatoo, Fraktal, Gadget, Ikon, Isis, Italiko, Kantun,
Kite, Lintel, Mad Max, Metric Magick, Obsession, Oscar, Pikanto, Psycho, Rage,
Robot, Scharmer, Stealth, Tinto/Red Wine, Tonic, Topiko, Trinity, TS2, V8,
Vektor, Widget, Zig Zag.
It is mainly the unrestricted beam which has driven IOM
design development. Early IOMs had
moderate beams, around 180 mm at the waterline (WL), following the practice of
their time. Then Gary Cameron (AUS)
and Craig Smith (AUS) found the benefits of wider beam with the TS2, and a
number of designs followed with WL beams of around 190 or 200 mm and
visually-imposing maximum deck-level beams up to 300 mm.
Beam progressively moderated for later designs, probably because wide
beam designs were slower in other than top-of-rig conditions, and possibly
because wide-beam designs made it more difficult to keep a well-balanced helm as
wind varied during an event.
Recently, narrow beam boats have dominated, led by the success of Brad Gibson’s
(AUS) Britpop with approximately 160 mm WL beam, 170 mm at deck level.
Acknowledgements
Some of the material for this article has been drawn from
documents originally authored by Jan Dejmo (SWE), Graham Bantock (GBR), Laurent
Chapelot (FRA), and Robert Grubisa (CRO). None
of these documents are easily found in the public domain.
The article has been improved by comments made by Graham Bantock and Bob
Wells (USA).
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