SIST EN ISO 12215-7:2021

SLOVENSKI STANDARD
01-februar-2021
Mala plovila - Konstrukcija trupa in dimenzioniranje - 7. del: Določanje
obremenitev za večtrupna plovila in njihove krajevne dimenzije z uporabo ISO
12215-5 (ISO 12215-7:2020)
Small craft - Hull construction and scantlings - Part 7: Determination of loads for
multihulls and of their local scantlings using ISO 12215-5 (ISO 12215-7:2020)
Kleine Wasserfahrzeuge - Rumpfbauweise und Dimensionierung - Teil 7: Bestimmung
der Lasten für Mehrrumpffahrzeuge und ihrer lokalen Dimensionierungen unter
Anwendung der ISO 12215-5 (ISO 12215-7:2020)
Petits navires - Construction de la coque et échantillonnage - Partie 7: Détermination des
charges des multicoques et de leur échantillonnage local en utilisant l'ISO 12215-5 (ISO
12215-7:2020)
Ta slovenski standard je istoveten z: EN ISO 12215-7:2020
ICS:
47.020.10 Ladijski trupi in njihovi Hulls and their structure
konstrukcijski elementi elements
47.080 Čolni Small craft
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 12215-7
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2020
EUROPÄISCHE NORM
ICS 47.080
English Version
Small craft - Hull construction and scantlings - Part 7:
Determination of loads for multihulls and of their local
scantlings using ISO 12215-5 (ISO 12215-7:2020)
Petits navires - Construction de la coque et Kleine Wasserfahrzeuge - Rumpfbauweise und
échantillonnage - Partie 7: Détermination des charges Dimensionierung - Teil 7: Bestimmung der Lasten für
des multicoques et de leur échantillonnage local en Mehrrumpffahrzeuge und ihrer lokalen
utilisant l'ISO 12215-5 (ISO 12215-7:2020) Dimensionierungen unter Anwendung der ISO 12215-
5 (ISO 12215-7:2020)
This European Standard was approved by CEN on 20 July 2019.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 12215-7:2020 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 12215-7:2020) has been prepared by Technical Committee ISO/TC 188 "Small
craft" in collaboration with CCMC.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by May 2021, and conflicting national standards shall be
withdrawn at the latest by May 2021.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 12215-7:2020 has been approved by CEN as EN ISO 12215-7:2020 without any
modification.
INTERNATIONAL ISO
STANDARD 12215-7
First edition
2020-11
Small craft — Hull construction and
scantlings —
Part 7:
Determination of loads for multihulls
and of their local scantlings using
ISO 12215-5
Petits navires — Construction de la coque et échantillonnage —
Partie 7: Détermination des charges des multicoques et de leur
échantillonnage local en utilisant l'ISO 12215-5
Reference number
ISO 12215-7:2020(E)
©
ISO 2020
ISO 12215-7:2020(E)
© ISO 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

ISO 12215-7:2020(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 4
5 Application of this document . 6
5.1 Materials . 6
5.2 Limitations . 6
5.3 Overall procedure for the application of this document . 7
6 Main dimensions, data and areas . 7
6.1 Dimensions and data . 7
6.1.1 General. 7
6.1.2 Bottom deadrise of the hulls βx and chine beam B x of planing multihulls . 7
C
6.1.3 Wet deck bottom . 8
6.1.4 Crossbeams . . 8
6.2 Areas .11
7 Dimensions and pressure for panels and stiffeners under local loads .14
7.1 General .14
7.2 Example of application on multihulls .14
7.2.1 Sections .14
7.2.2 Details on panel assessment and dimensions .16
7.2.3 The constant averaged pressure method .16
7.2.4 Other assessment and dimensioning methods .17
7.2.5 Panels acting as "natural" stiffeners .17
7.3 Other topics on panel or stiffener dimensions .17
8 Local pressure-adjusting factors .17
9 Local design pressures .24
9.1 General .24
9.2 Limits of areas .24
9.3 Tables defining the local design pressures for multihulls .24
9.4 Design pressure for trimaran floats P .27
TRFx
9.4.1 Pressure reduction factors .27
9.4.2 Pressure .27
9.5 Design pressure on watertight bulkheads and integral tanks .27
10 Further treatment of structural elements subject to local loads .27
11 Assessment of multihulls rudders, appendages and their wells .28
12 Multihull global loads .28
12.1 General .28
12.2 Typical structural arrangements .28
12.3 Global load assessment .30
12.3.1 General.30
12.3.2 The simplified method .30
12.3.3 The enhanced method . .31
12.4 Design stresses under global loads .32
12.5 Global load case GLC1: Diagonal load in quartering sea .32
12.6 Global load case GLC 2: Rig loads .33
12.7 Combination of diagonal load GLC 1 and rig load GLC 2 for sailing multihulls .33
12.8 Global load case GLC 3: Asymmetric broaching loads in sailing multihulls .33
ISO 12215-7:2020(E)
12.9 Global load case GLC 4: Longitudinal broaching/pitchpoling .34
12.9.1 General.34
12.9.2 Full method of analysis of the buoyancy load when the craft pitchpoles .35
12.10 Global load case GLC 5: Longitudinal force on one hull .36
12.10.1 General.36
12.10.2 Longitudinal force .36
12.11 Global load case GLC 6: Bending of crossbeams connecting hulls for motor catamarans. .37
13 Structural arrangement for supporting global loads .38
14 Multihulls used as commercial craft and workboats .38
15 Information to be included in the owner's manual .38
15.1 General .38
15.2 Respect of maximum loaded displacement .38
15.3 Operational guidance .38
15.4 Information to take care of sandwich plating .38
15.5 Information required by Annex J of ISO 12215-5:2019 - for commercial craft and
workboat .38
Annex A (informative) Application sheet of ISO 12215-7 .39
Annex B (informative) "Established practice" recommendations for global loads
assessment using FEM methods and reporting .41
Annex C (informative) "Established practice" details .43
Annex D (informative) Technical background and example of torsional moment analysis
with differential deflection of crossbeams .51
Bibliography .58
iv © ISO 2020 – All rights reserved

ISO 12215-7:2020(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 188, Small craft.
A list of all parts in the ISO 12215 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
ISO 12215-7:2020(E)
Introduction
The reason underlying the preparation of this document is that standards and recommended
practices for loads on the hull and the dimensioning of small craft differ considerably, thus limiting the
general worldwide acceptability of boat scantlings. This document has been set towards the minimal
requirements of the current practice.
The dimensioning according to this document is regarded as reflecting current practice, provided
the craft is correctly handled in the sense of good seamanship and operated at a speed appropriate
to the prevailing sea state in a safe and responsible manner, having due cognisance of the prevailing
conditions.
Implementation of this document allows to achieve an overall structural strength that ensures the
watertight and weathertight integrity of the craft. This document is intended to be a tool to determine
the scantlings of a craft as per minimal requirements. It is not intended to be a structural design
procedure.
The mechanical property data supplied as default values in this document make no explicit allowance
for deterioration in service nor provide any guarantee that these values can be obtained for any
particular craft.
Like the other parts of ISO 12215, this document was developed to assess the structure of recreational
craft up to 24 m L , but it can also be used, where relevant, for non-recreational craft, workboats or
H
yachts with an IMO load line length of up to 24 m, with the necessary critical mind.
vi © ISO 2020 – All rights reserved

INTERNATIONAL STANDARD ISO 12215-7:2020(E)
Small craft — Hull construction and scantlings —
Part 7:
Determination of loads for multihulls and of their local
scantlings using ISO 12215-5
1 Scope
This document defines the dimensions, local design pressures and global loads acting on multihull
craft with a hull length (L ) or load line length of up to 24 m (see Note). It considers all parts of the
H
craft that are assumed watertight or weathertight when assessing stability, freeboard and buoyancy in
accordance with ISO 12217 (all parts). Scantlings corresponding to the local design pressures are then
assessed using ISO 12215-5.
NOTE The load line length is defined in the OMI "International Load Lines Convention 1966/2005", it can
be smaller than L for craft with overhangs. This length also sets up at 24 m the lower limit of several IMO
H
conventions.
This document is applicable to multihulls built from the same materials as in ISO 12215-5, in intact
condition, and of the two following types:
— recreational craft, including recreational charter vessels;
— commercial craft and workboats.
It is not applicable to multihull racing craft designed only for professional racing.
This document is applicable to the structures supporting windows, portlights, hatches, deadlights
and doors.
For the complete scantlings of the craft, this document is intended to be used in conjunction with
ISO 12215-8 for rudders, ISO 12215-9 for appendages of sailing craft and ISO 12215-10 for rig loads and
rig attachment in sailing craft. ISO 12215-6 can be used for additional details.
Throughout this document, unless otherwise specified, dimensions are in (m), areas in (m ), masses
2 2
in (kg), forces in (N), moments in (Nm), Pressures in (kN/m ) (1 kN/m = 1 kPa), stresses and elastic
2 2
modulus in (N/mm ) (1 N/mm = 1 MPa).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 8666:2020, Small craft — Principal data
ISO 12215-5:2019, Small craft — Hull construction and scantlings — Part 5: Design pressures for monohulls,
design stress, scantlings determination
ISO 12215-8:2009, Small craft — Hull construction and scantlings — Part 8: Rudders
ISO 12215-9:2012, Small craft — Hull construction and scantlings — Part 9: Sailing craft appendages
ISO 12215-10:2020, Small craft — Hull construction and scantlings — Part 10: Rig loads and rig
attachments in sailing craft
ISO 12215-7:2020(E)
ISO 12217-1:2015, Small craft — Stability and buoyancy assessment and categorization — Part 1: Non-
sailing boats of hull length greater than or equal to 6 m
ISO 12217-2:2015, Small craft — Stability and buoyancy assessment and categorization — Part 2: Sailing
boats of hull length greater than or equal to 6 m
ISO 12217-3:2015, Small craft — Stability and buoyancy assessment and categorization — Part 3: Boats of
hull length less than 6 m
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
multihull
craft with two or more hulls with a connecting wet deck (3.8)/crossbeams above the loaded waterline,
as opposed to a tunnel boat or scow
Note 1 to entry: See Clause 6 and Figure 2 for the main dimensions of a multihull.
3.2
design categories
description of the sea and wind conditions for which a craft is assessed to be suitable
Note 1 to entry: The design categories are defined in ISO 12217 (all parts).
Note 2 to entry: The definitions of the design categories are in line with the European Recreational Craft Directive
2013/53/EU.
[SOURCE: ISO 12215-5:2019, 3.1.]
3.3
loaded displacement
m
LDC
mass of water displaced by the craft, including all appendages, when in fully loaded ready for use
condition
Note 1 to entry: The fully loaded ready for use condition is further defined in ISO 8666.
[SOURCE: ISO 12215-5:2019, 3.2.]
3.4
mass in minimum operating conditions
m
OC
mass of the craft in minimum operating condition
Note 1 to entry: The minimum operating condition is further defined in ISO 8666.
3.5
sailing craft
craft for which the primary means of propulsion is wind power
Note 1 to entry: It is further defined in ISO 8666.
Note 2 to entry: In this document, non-sailing craft are considered as motor craft.
2 © ISO 2020 – All rights reserved

ISO 12215-7:2020(E)
[SOURCE: ISO 12215-5:2019, 3.3.]
3.6
beam of hull
B
H
beam across the outer hulls
Note 1 to entry: The measurement of the beam of hulls is specified in ISO 8666.
3.7
chine beam
B
C
beam at chine of planing hulls
Note 1 to entry: It is further characterized in 6.1.2.
3.8
wet deck
underside area of the structure connecting hulls with an area greater than 5 % L B
H H
Note 1 to entry: Some multihulls (3.1) have no wet deck but just crossbeams. i.e. connecting beams.
3.9
craft speed
V
for motor craft, maximum speed in calm water and m condition that is declared by the manufacturer,
LDC
expressed in knots
[SOURCE: ISO 12215-5:2019, 3.6.]
3.10
displacement craft
motor craft whose speed is such that VL<5
WL
[SOURCE: ISO 12215-5:2019, 3.7, modified - the definition is reworded.]
3.11
displacement mode
mode of running of a motor craft in the sea such that its mass is mainly supported by buoyancy forces
Note 1 to entry: This is the case where the actual speed in a seaway in m condition is such that its speed/
LDC
length ratio makes the craft behave as a displacement craft (3.10).
[SOURCE: ISO 12215-5:2019, 3.8, modified - in the definition, "craft" is replaced with "motor craft".]
3.12
planing craft
motor craft whose speed is such that VL≥5
WL
Note 1 to entry: This speed/length ratio limit has been arbitrarily set up in this document, but it can vary from
one craft to another according to hull shape and other parameters.
[SOURCE: ISO 12215-5:2019, 3.9, modified - the definition is reworded.]
3.13
planing mode
mode of running of a motor craft in the sea such that a significantly part of its mass is supported by
forces coming from dynamic lift due to speed in the water
Note 1 to entry: A planing craft (3.12) in calm water runs in planing mode, but it can be obliged to significantly
reduce its speed when the sea gets worse, running in that case in displacement mode (3.11).
ISO 12215-7:2020(E)
[SOURCE: ISO 12215-5:2019, 3.10, modified - the definition slightly reworded and "craft" replaced with
"motor craft".]
3.14
non-walking area
area of the craft comprising those areas defined in the owner's manual as being both outside of the
working deck and where people are not liable to stand or walk in normal or emergency operation, and
those of the working deck of a multihull (3.1) with an inclination of more than 25° against the horizontal
in the longitudinal and transverse directions
Note 1 to entry: All other areas of the working deck, cockpit bottom and superstructures are deemed to be
walking areas.
4 Symbols
Unless specifically otherwise defined, the symbols shown in Table 1 are used in this document. The
symbols are shown by group type and in alphabetical order.
Unless otherwise specified, all dimensions, measured in m condition, are according to ISO 12217.
LDC
Table 1 — Symbols, dimensions, factors, parameters
Reference/
Symbol Unit Designation/Meaning of symbol Clause
concerned
General dimensions and data
6.1, Fig 2 &
B m Beam between hulls as defined in Table 4
BH
Annex D
6.1.1, Fig 1 &
B m Chine beam at 0,4 L from the origin used for k and P
C WL DYNM1 BMUP BASE
Table 7
6.1, 12.5 &
B m Beam between centres of buoyancy
CB
Fig 2
B m Beam between upper shrouds chainplates Annex B
CP
B m Beam at the inside of wet deck/beam connection with hulls at section x 6.1.3 & Fig 2
WDx
B m Beam of hull according to 3.6 6.1 & Fig 2
H
B m Beam at overhang root, n = F(fwd) M(mid), A(Aft), and i = H(Hull), F(Float) Table 11, Fig 9
nOHi
L m Length of overhang, n = F(fwd) M(mid), A(Aft), and i = H(Hull), F(Float) Table 11, Fig 9
nOHi
D m Depth of hull at overhang root Table 11, Fig 9
ROH
D Design Waterline plan or section 6.1.3, Figure 2
WL
h m Height of mid panel of cockpit side or stiffener below overflow level Table 5 it. 10
SIDEx
H m Height of mid panel or stiffener above the lesser of Z or Z Table 5 it. 10
SUPx SDTMx SDAMx
L m Length of crossbeam i Table 11, Fig 9
C i
L m Length between main beams centre of inertia Annex B & C
BB
L m Length of hull 1
H
L m Length of a trimaran float 9.4 & Fig 9
FLOAT
L m Length of waterline Fig 2
WL
m kg Mass of craft in fully loaded condition 3.3, 9
LDC
m kg Mass in minimum operating condition 3.4, 11
MO
T m Max canoe body draught (see Figure 2) Fig 2, 9.3
C
V Knots Craft maximum speed in m condition 3.9, Table 5 it. 2
LDC
Panels, stiffeners and local dimensions and data
A m Panel or stiffener supported area Table 5 it. 9
D
4 © ISO 2020 – All rights reserved

ISO 12215-7:2020(E)
Table 1 (continued)
Reference/
Symbol Unit Designation/Meaning of symbol Clause
concerned
b mm Small unsupported dimension of panel plating Table 5 it. 9
l mm Large unsupported dimension of panel plating Table 5 it. 9
s mm Stiffener spacing (small unsupported dimension of stiffener) Table 5 it. 9
Stiffener length: long unsupported dimension of stiffener (frame/
l mm Table 5 it. 9
u
stringer)
Q Point at section x where the pressure is assessed Figures 2 & 3
x
T m Local canoe body draught at section x (see Figure 2) Fig 2
x
x m Distance of a section x from aft of L Fig 2, 9.3
WL
Z m Height of point Q above D at section x Fig 2, 9.3
Qx X WL
Z m Height of local canoe body above D at section x (usually <0) Fig 2, 9.3
Tx WL
Z m Height of local hard chine above D at section x for planing craft Fig 2, 9.3
Cx WL
Z m Height of actual side/deck limit for trimaran float at section x Fig 2, Table 4
SDAFx
Z m Height above D of the theoretical side/deck limit at section x Fig 2, Table 3
SDTMx WL
Z m Height above D of the actual side/deck limit at section x Fig 2, Table 3
SDAMx WL
Z m Height above D of the theoretical wet deck height at section x Fig 2, 9.3
WDTx WL
Z m Height above D of the actual height of wet deck at section x Fig 2, 9.3
WDAx WL
α , α , Degree Longitudinal and transverse angle of superstructure at section x Fig 2, Table 5
LSx TSx
α Longitudinal slope angle against horizontal of wet deck or deck/cross-
LWDx
Degree Fig 8, Table 5 it 9
α beam at section x
LDx,
β Degree Deadrise at section x, of planing craft, not to be taken <30° nor >60° Fig 2, 9.3
x
β Degree Deadrise of planing craft at section x/L = 0,4, Fig 2, 9.3
0,4 WL
Calculation data, factors, etc.
k 1 Area pressure distribution factor Table 5 it. 9
AR
k 1 Wet deck transverse pressure distribution factor Table 5 it. 6
BWD
k 1 Design category factor Table 5 it. 1
DC
k 1 Deadrise pressure reduction factor for planing multihulls in planing mode Table 5 it. 8
DRx
k g’s Dynamic load factor for multihulls, see Figure 4 Table 5 it. 2
DYNM
k 1 Deck longitudinal pressure distribution factor for multihulls Table 5, Fig 4
LDMx
k 1 Side longitudinal pressure distribution factor for multihulls Table 5, Fig 3
LMx
k 1 Side longitudinal pressure distribution factor for trimaran float 9.4.1
LMTx
k 1 Deck longitudinal pressure distribution factor for trimaran float 9.4.1
DLMTx
k 1 Wet deck longitudinal pressure distribution factor Table 5, Fig 5
LWDx
k 1 Superstructure/deckhouse pressure distribution factor for multihulls Table 5 it. 10
SUPx
k 1 Slope factor respectively k or k for deck and wet deck, see Figure 8 Table 5 it. 11
Sx SDx SDx
k 1 Vertical pressure correction for deck where Z < Z Table 6 it. 1
ZDMx SDAMx SDTMx
Inner side/bottom vertical pressure correction factor in way of wet deck
k 1 Table 6 it. 3
ZMIx
for sail and displacement multihulls
Outer and inner side/bottom vertical pressure correction factor clear of
k 1 Table 6 it. 2
ZMOx
wet deck for sail and displacement multihulls
Inner side/bottom vertical pressure correction factor in way of wet deck
k 1 Table 7 it. 3
ZPMIx
for planing multihulls in planing mode
Outer and inner side/bottom vertical pressure correction factor clear of
k 1 Table 7 it. 2
ZPMOx
wet deck for planing multihulls in planing mode
k 1 Wet deck vertical pressure correction factor Table 5 it. 7
ZWDx
ISO 12215-7:2020(E)
Table 1 (continued)
Reference/
Symbol Unit Designation/Meaning of symbol Clause
concerned
Design pressures for sailing and displacement motor multihulls
Base pressure for sailing and displacement catamarans and trimarans
P kN/m Table 6 it. 1
BMU BASE
central hull
P kN/m Design pressure at lowest point of section x Table 6 it. 1
BMUx
P kN/m Design wet deck/crossbeam bottom design pressure at section x Table 6 it. 1
WDx
P kN/m Base design pressure for deck and cockpit bottom Table 6 it. 1
DMU BASE
P kN/m Design pressure for deck and cockpit bottom at section x Table 6 it. 1
DMUx
P kN/m Inner design pressure in way of wet deck/crossbeam at section x Table 6 it. 3
HMUIx
P kN/m Outer and inner design pressure clear of wet deck/crossbeam at section x Table 6 it. 2
HMUOx
P kN/m Superstructure and cockpit side design pressure at section x Table 6 it. 4
SUPMx
Design pressures for planing multihulls in planing mode
P
BMUP 2
kN/m Base bottom design pressure for planing multihulls in planing mode Table 7 it. 1
BASE
Inner design pressure in way of wet deck/crossbeam for planing multihulls
P kN/m Table 7 it. 1
HMUIPx
in planing mode at section x
Outer and inner design pressure for planing multihulls in planing mode
P kN/m Table 7 it. 2
HMUOPx
clear of wet deck/crossbeam at section x
Design pressures for trimaran floats
P kN/m Base bottom pressure for trimaran float (same as for central hull) Table 8
TRF BASE
P kN/m Bottom/side design pressure for trimaran floats at section x Table 8
TRFx
Stresses, shear forces and moments
σ , τ N/mm Design stress for global loads Table 12
d d
q N/mm Shear flow such as τ = q/t Tables C.1, C.3
M Nm, kNm Bending moment, design or ultimate Annex D
B
M Nm, kNm Torsional moment, design or ultimate Table 14
T
F N, kN Force, shear force Tables 14, 15
5 Application of this document
5.1 Materials
The materials considered in this document are the main modern building materials listed in Clause 1
and Table 17 of ISO 12215-5:2019. This document may be used with other materials, including new fibres
and resins, provided that they show similar cohesion, durability, resistance to marine environment and
elongation at break as the ones quoted in Table 17 of ISO 12215-5:2019.
5.2 Limitations
The shape of multihulls entails that significant deflexions are observed without rupture of structural
elements. In contrast, non-structural elements (i.e. accommodations) are sometimes stiffer, but not
necessarily stronger, than the structural elements and can suffer from this difference of behaviour.
This is not considered in this document provided the structural elements are strong enough. The
strength and arrangements of non-structural elements are left to the responsibility and experience of
the manufacturer.
On multihulls, the value of the loaded displacement m has a greater influence on the loads than for
LDC
monohulls. Exceeding the m value can cause significant load increase which can transform a craft
LDC
6 © ISO 2020 – All rights reserved

ISO 12215-7:2020(E)
meeting the requirements of this document into a non-conform craft, for example a lower wet deck
clearance induces a much greater pressure. Overloading shall therefore be avoided, and a caution
information shall be included in the owner's manual, see 15.2.
5.3 Overall procedure for the application of this document
Table 2 describes, by steps, the overall procedure of this document for scantlings determination.
Table 2 — Overall procedure for scantlings determination
Step N° Subject Clause N°
1 Main dimensions, data and areas 6
2 Dimensions of panels and stiffeners under local loads 7
3 Local pressure adjustment factors 8
4 Local design pressures 9
5 Further analysis of structural elements subject to local loads 10
6 Multihull rudders, appendages and their wells 11
7 Multihull global loads 12
8 Structural arrangements for supporting global loads 13
9 Multihulls used as commercial craft and workboats 14
10 Information to be included in the owner’s manual 15
6 Main dimensions, data and areas
6.1 Dimensions and data
6.1.1 General
The dimensions are usually the same as in ISO 12215-5:2019, many of them being as defined in ISO 8666,
see Table 1 and Figures 1 and 2. The figures show sections at any longitudinal coordinate x, measured
from aft of D and some values like B , B , etc. shall be taken as the average values of B , B ,
WL WD BH WDx BHx
etc. For clarification, data that vary with length x are followed by index x.
6.1.2 Bottom deadrise of the hulls βx and chine beam B x of planing multihulls
C
Figure 1 explains local chine beam B and deadrise determination for planing craft at any section x:
Cx
— where the bottom hulls sections of planing multihulls are approximately straight lines, the deadrise
is the actual deadrise β [see Figures 1 a), b) and d) and at right part of Figure 2 c)], and
x
— where the bottom has round bilges, the deadrise β shall be measured as the angle between lowest
x
point of the hull bottom (hull centreline) and the point where the bottom is tangent to a line angled
50° from horizontal [see Figure 1 c) and at right part of Figure 2 c)].
For planing multihulls that reach speeds allowing them to progress in planing mode (3.13), the chine
beam B and corresponding deadrise angle β , measured at x = 0,4 L from their aft end, are used for
C 0,4 WL
the determination of k and bottom pressure of planing multihulls P .
DYNM1 BMU BASE
Where the bottom of a planing catamaran is not symmetrical, as in Figure 2 g), the bottom has an angle
β on the outer side and β on the inner side. In the inner side, the deadrise factor k defined in item 8
xo xi DR
of Table 5 lowers significantly the design pressure.
ISO 12215-7:2020(E)
a) b) c) d)
Figure 1 — Measurement of chine beam B and deadrise angle β
Cx x
6.1.3 Wet deck bottom
See definitions of wet deck in Table 4.
For catamarans: the actual local height of the wet deck Z at section x is its height above D see
WDAx WL,
Figure 2 b). Where the wet deck bottom height is not constant, it shall be taken as the average height of
80 % of its width inside the limits of its connection with the hull plating B . Where there are parts
BWDx
with a width greater than 0,33 B and with a height differing by more than 10 % from Z , each of
WDx WDAx
these panels shall be assessed as a specific panel. B is the beam of the wet deck, averaged if variable,
WDx
inside the angle or fairing/connection with the hulls, it is used for the calculation of k in item 6 of
BWD
Table 5.
Where different from horizontal, the angles of the wet deck bottom α against the horizontal increase
WDLx
the wet deck pressure of the wet deck or crossbeams, see item 11 of Table 5 and corresponding figure.
For sailing trimarans, the wet-deck height is measured perpendicular to a sloped plan angled from D ,
WL
cutting it a C and at x = 0,5 L and the float axis at key point 17 of Figure 2 d) to e) at the height Z
L WL WDT
above its bottom; see left part of Figure 2 d). This point 17 needs not be taken higher than the point at
which the float is dipped in the water in sail configuration S of ISO 12215-10 (apparent wind speed
C1
where the full sail area begins to be reduced).
For motor trimarans, the wet-deck height is measured perpendicular to the same sloped plan as for
sailing trimarans but angled so that point 17 is taken at a height 0,5 Z above the float’s bottom.
WDT
NOTE This sloped plan for trimarans considers the "envelope" of the waterline both when the craft heels
when beating upwind and when it is close to upright when running.
6.1.4 Crossbeams
Crossbeams for catamarans and trimarans are defined in Table 4.
For local loads, the front and bottom parts of crossbeams lower than Z are considered as part of the
WDTx
wet deck bottom, and the parts above are considered side or deck whether they are below or above Z
SDTMx
8 © ISO 2020 – All rights reserved

ISO 12215-7:2020(E)
a) Typical sailing catamaran, side view
b) Typical sailing catamaran, view at main section and any section x
---------------------
...