979
1 INTRODUCTION
Environmental factors and leeway cause the life raft to
drift. Because the raft tent is deformed by wind
pressure, making it challenging to precisely identify
the raft's reference position and search area, the leeway
prediction of the pneumatic life raft represents a
challenging task for search and rescue (SAR) [2].
Available computer programs, such as Sarcass (Search
and Rescue Coordination and Support System), are
used by search and rescue services to specify the search
area. “Unfortunately, these applications do not take
into account shape variation during drift, so they are
not precise for deformable bodies” [10]. Using the
Gdynia Maritime University's prior research, the
authors developed a numerical simulation that
considered the object's shape variability. The results of
the drift simulation, taking into account the variable
windage area of the raft tent, have been described in
previous publications. This article presents an
overview of pneumatic life rafts available on the
market and models their geometric models in the
Rhinoceros program. The article study different shapes
of life rafts and the resulting aerodynamic drag acting
on the above-water part of the raft. The authors believe
that a detailed analysis of the factors determining
leeway may explain this issue and consequently reduce
the search area and increase the effectiveness of rescue
operations.
2 LEEWAY OF PNEUMATIC LIFE RAFT
The leeway of a life raft is the movement of the raft on
the water dependent on the wind pressure acting on
the above-water part of the life raft (Fx) and the
hydrodynamic resistance acting on the underwater
part of the life raft (F0) as shown in Fig.1.
Analysis of the Aerodynamic Drag of Selected
Pneumatic Life Rafts
J. Jachowski & E. Książkiewicz
Gdynia Maritime University, Gdynia, Poland
ABSTRACT: The success of the Search and Rescue (SAR) operation is strongly influenced by the accurate
determination of the search area for the drifting pneumatic life raft, with particular emphasis on leeway. The
article refers to the issue of leeway of life raft. The leeway is directly dependent on the force of wind pressure
acting on the above-water part of the life raft and the hydrodynamic drag acting on the underwater parts of the
life raft. The paper presents a comparison of different types of pneumatic life rafts. The purpose of comparing the
dimensions, shapes and windage areas of different life rafts is to demonstrate the relationship between the shape
and the aerodynamic drag on the above-water part of the life rafts. Research has shown the dependence of
aerodynamic drag on the shape and size of the above-water part of the life raft. The calculations presented in this
study are based on the author’s previous experimental and numerical research and results published in earlier
publications.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 19
Number 3
September 2025
DOI: 10.12716/1001.19.03.32
980
Figure 1. Forces causing leeway (source: current study, print
screen of simulation)[9]
Both forces have a significant effect on the leeway
of the pneumatic life raft and each forces must be taken
into account. Previously performed numerical
calculations allowed to determine: the force of wind
pressure and the force of hydrodynamic drag (taking
into account the variable shape of the flexible structure
of the pneumatic life raft). The authors decided to use
previous results of numerical simulations, the
correctness of which had been verified and published.
Current research and calculations are carried out for
other types of life rafts available on the market.
2.1 Aerodynamic drag of the life raft
The aerodynamic drag of the life raft is a force which is
created by the interaction of air with the surface of the
raft above water. Aerodynamic drag is the result of
friction and pressure changes that occur as a result of
air flowing around the object. Aerodynamic drag is one
of the most important factors affecting the leeway of
the life raft. Factors influencing the aerodynamic drag
of a life raft which is include:
1. The shape of life raft is designed to provide the
highest level of safety in various life- threatening
situations at sea. The shape of the life raft
determines the stability of the raft, capacity,
aerodynamic and hydrodynamic resistance. There
are several typical shapes of life rafts, each of which
has its own characteristics and applications.
− One of the most common shapes are round rafts.
The advantages of this shape are: good stability
on the water even in the event of strong waves,
even distribution of forces from external
conditions and passengers in the raft.
− Rectangular shaped life rafts are often used on
larger vessels because they have more space to
accommodate more persons. The disadvantage
of the shape is weaker stability, especially in
difficult weather conditions.
− Occasionally, there are rafts in the shape of a
trapezium, and rafts with a rigid, inflatable
bottom.
2. The windage area is the surface of the life raft above
the water, which is directly proportional to the
amount of aerodynamic drag. Additionally, the
windage area depends on the dimensions and
shape of the raft, and draft (which results from the
weight of persons in the raft).
3. Wind speed and weather conditions. Wind directly
increases aerodynamic drag, also generating wind
currents and waves. Greater wind pressure means
a greater angle of the raft and deformations of the
tent, which changes the way air flow. Sea waves
influence the wind profile directly at the water
surface.
A detailed analysis of the aerodynamic drag is very
important for further, correct calculations of leeway.
The authors decided to analyse the types of life rafts
available on the market, their dimensions and
parameters.
3 TYPES OF LIFE RAFT WITH DIMENSIONS
One of the basic life-saving equipment to protect
survivors after abandoning a ship is the life raft. The
authors collected information about the types of life
rafts and prepared a short summary in the form of a
Table 1.
Table 1. Types of life rafts (source: current study)
1. Pneumatic life raft ( life raft were carried out in 2000 at the T-3 Low Velocity Tunnel at the Institute of Aviation in Warsaw)
Size of raft
[persons]
L [mm]
H [mm]
Amin [m
2
]
Amax [m
2
]
Amean [m
2
]
Weight of life raft [kg]
6
2290
1190
1.92
2.01
1.96
90
10
2907
1225
2.50
2.62
2.56
110
20
3640
1760
4.50
4.71
4.61
180
981
2. Life raft with square base – manufactured by company Iso raft.
Size of raft
[persons]
L [mm]
H [mm]
Amin [m
2
]
Amax [m
2
]
Amean [m
2
]
Weight of life raft [kg]
4
1634
1170
1.20
1.69
1.47
37,5
6
1956
1200
1.46
2.06
1.79
38,4
10
2458
1300
1.98
2.80
2.44
49
3. Life raft with an oval bottom – manufactured by Boaea.
Size of raft
[persons]
L [mm]
B [mm]
H [mm]
Amin [m
2
]
Amax [m
2
]
Amean [m
2
]
Weight of raft
[kg]
6
2175
2175
1250
1.78
2.23
2.02
90
10
3245
2295
1300
2.45
3.05
2.82
110
15
4110
2700
1350
3.05
3.94
3.60
140
4. Life raft with an oval bottom – manufactured by Boaea.
Size of raft
[persons]
L [mm]
B [mm]
H [mm]
Amin [m
2
]
Amax [m
2
]
Amean [m
2
]
Weight of raft
[kg]
6
2175
2175
1250
1.77
2.29
2.07
90
10
3245
2295
1300
2.50
2.97
2.77
110
15
4110
2700
1350
3.06
3.79
3.49
140
5. Life raft with polygon bottom – manufactured by Viking
Size of raft
[persons]
L [mm]
H [mm]
Amin [m
2
]
Amax [m
2
]
Amean [m
2
]
Weight of life raft [kg]
16
3342
1550
2.85
2.99
2.93
146
25
4076
2030
4.59
4.81
4.72
185
6. Life raft with a hexagonal bottom
Size of raft
[persons]
L [mm]
H [mm]
Amin [m
2
]
Amax [m
2
]
Amean [m2]
Weight of life raft [kg]
10
3070
1540
2.56
2.77
2.62
98
12
3328
1550
2.77
3.00
2.84
109
982
7. Life raft with a stiff inflatable bottom and a stiffened tent- manufactured by Lubawa S.A. The life raft towing performance has been tested
in the towing tank of Ship Design and Research Centre in Gdansk.
Size of raft
[persons]
L [mm]
H [mm]
Amin [m
2
]
Amax [m
2
]
Amean [m
2
]
Weight of life raft [kg]
Size of raft
[persons]
6
2650
1600
3.30
3.58
3.44
80
6
8. Life raft with a grid, inflatable bottom and stiffened tent by Lubawa S. A.
Size of raft
[persons]
L [mm]
H [mm]
Amin [m
2
]
Amax [m
2
]
Amean [m
2
]
Weight of life raft [kg]
Size of raft
[persons]
10
2830
1240
2.53
2.62
2.58
100
10
The table contains: the main dimensions of the life rafts and the modeled shapes of these rafts in three views. The parameters of the life rafts
used in the Tab.1: L [mm] – life raft length; H [mm] –life raft height; Amin – minimum cross-sectional area of the raft [m
2
]; Amax – maximum
cross-sectional area of the raft [m
2
]; Amean- mean frontal cross- sectional area of the life raft [m
2
].
The geometric models of the life rafts were
modelled in the 3D Rhinoceros program, which was
then used to determine and calculate the cross-
sectional areas of each life raft as shown in Fig.2 and
Fig.3.
Figure 2. Cross-sectional of life raft (source: current study)
Figure 3. An example of a cross-sectional surface made for an
oval 15 person life raft by Boaea (source: current study)
For the cross-sectional area: A1, A2, A3, the mean
cross-sectional area of the raft Amean was calculated:
2
1 2 3
[]
3
mean
A A A
Am
++
=
]
Geometric models of the life rafts are necessary to
perform numerical calculations of the aerodynamic
drag. Therefore, the authors created geometric models
and their cross- sections for all life rafts listed in the
Tab.1.
4 CALCULATIONS AND RESULTS
The results of the tunnel tests show that the value of
forces is function of the shape and inflow wind [11].
Previous studies have provided information on the
distribution of the wind profile affecting the part of the
life raft above the water as show in Fig.4 [9]. The
obtained wind profile was used for the current
calculations. This knowledge was essential for
modelling environmental conditions during numerical
research.
Figure 4. Aerodynamic wind force causing leeway (source:
current study)
For all presented life raft models the following
analysis was performed: cross- sectional area of the
above- water and underwater surfaces as shown in
Fig. 2.
983
Table 2. Life raft parameters (source: current study)
Life raft
number
from the
TAB.1
Size of
life raft
[persons]
Amean [m
2
]
- cross-
sectional
area
Amean /
number
of
persons
[m
2
/no of
person]
Total
weight
[kg] =
raft + 2
persons
Total
weight
[kg] = raft
+ max
persons
on board
T [m] –
draft of
the life
raft (2
persons
on board)
T [m] -
draft of
the life
raft (max
person
son
board)
Underwater
cross-
sectional area
(2 persons on
board) [m
2
]
Underwater
cross- sectional
area ( max
persons on
board) [m
2
]
Percentage of
underwater to
above-water
area (2 persons
on board)
Percentage of
underwater to
above-water
area (max
persons board)
1
6
1.96
0.33
250
585
0.06
0.14
0.131
0.244
7%
14%
10
2.56
0.26
270
935
0.04
0.14
0.134
0.363
6%
17%
20
4.61
0.23
340
1830
0.03
0.18
0.129
0.556
3%
14%
2
4
1.47
0.37
197.5
367.5
0.07
0.14
0.109
0.220
8%
17%
6
1.79
0.30
198.4
533.4
0.05
0.14
0.101
0.256
6%
16%
10
2.44
0.24
209
874
0.03
0.14
0.072
0.320
3%
15%
3
6
2.02
0.34
250
585
0.05
0.12
0.081
0.179
4%
10%
10
2.82
0.28
270
935
0.04
0.13
0.046
0.210
2%
8%
15
3.60
0.24
300
1377.5
0.03
0.12
0.046
0.256
1%
8%
4
6
2.07
0.35
250
585
0.05
0.12
0.081
0.179
4%
9%
10
2.77
0.28
270
935
0.04
0.13
0.046
0.210
2%
8%
15
3.49
0.23
300
1377.5
0.03
0.12
0.046
0.256
1%
8%
5
16
2.93
0.18
306
1466
0.03
0.17
0.121
0.491
4%
20%
25
4.72
0.19
345
2247.5
0.03
0.17
0.134
0.633
3%
16%
6
10
2.62
0.26
258
923
0.03
0.12
0.119
0.411
5%
19%
12
2.84
0.24
269
1099
0.03
0.13
0.114
0.445
4%
19%
7
6
3.44
0.57
240
575
0.04
0.10
0.084
0.233
3%
7%
8
10
2.58
0.26
260
925
0.04
0.15
0.223
0.483
9%
22%
The analysis examined two loading scenarios, one
with a fully occupied raft and the other with two
survivors on board. The calculations assumed that each
survivor weighed 82,5 kg on average. In addition, the
calculations should take into account the variable
windage area of the life raft. Then, three cross- sectional
areas of each modelled raft were found. The mean
cross- sectional area was used to make next
calculations. The average ratio of the surface area
above the water to the underwater area for a life raft
with two persons was on average 4% and for maximum
number of persons on board, this ratio increasing to an
average of 14%. This percentage ratio tends to decrease
with increasing raft size and the number of persons on
board.
Based on the developed dataset, the aerodynamic
drag force Fd acting on the life rafts listed in Table 1 was
determined. The calculations were conducted for calm
water conditions, taking into account the wind profile
above sea surface. According to previous experimental
and numerical studies, the aerodynamic drag
coefficient Cd ranges is from 0.5 to 0.7 [9]. For the
purpose of this analysis, a representative value Cd=0,6
was adopted.
The aerodynamic drag force was computed using
the standard drag equation:
2
1
* * * *
2
d d mean
F C A v
=
where:
Fd - the aerodynamic drag force [N],
Cd - the aerodynamic drag coefficient (assumed as
0.6),
- the air density [kg/m
3
],
Amean - the frontal cross- sectional area of the life raft
[m
2
],
v - the wind velocity [m/s].
In this study, the frontal cross- sectional area A was
treated as a variable parameter, dependent on the raft
geometry. Wind speed ranging from 0 to 30 m/s were
considered to evaluate the range of aerodynamic drag
force. To illustrate the influence of raft shape on
aerodynamic performance, the drag force was
calculated as function of wind velocity for all 10-person
raft types with varying geometrical configurations. The
calculation results are presented in the form of a graph
in the Figure 5 and Figure 6.
Figure 5. Aerodynamic drag force for all types of 10-persons
life rafts with 2 persons on board ( source: current study)
Figure 6. Aerodynamic drag force for all types of 10-persons
life rafts with 10 persons on board (source: current study)
The purpose of the presented comparison is to
prove the correctness of the statement that
984
aerodynamic drag depends directly on the windage
area of the above- water part of the life raft. Thus, the
aerodynamic drag force, leeway, and drift of the life
raft are all influenced by its shape. In order to
implement a more precise and contemporary
methodology for the leeway problem, the authors
examine the extent of dependence between these
parameters.
5 CONCLUSIONS
Geometric modeling and parametric analysis of
pneumatic life rafts allow for improved estimation of
leeway, thereby enhancing the accuracy of search area
prediction in maritime Search and Rescue (SAR)
operations. The leeway of a drifting raft is strongly
dependent on aerodynamic drag acting on its above-
water structure. In this study, eight commercially
available life raft models were analyzed in terms of
shape, dimensional parameters, and cross-sectional
areas, which constitute key input variables in
aerodynamic resistance calculations. A comparative
assessment of aerodynamic drag was conducted for 6-
and 10-person life rafts, selected as the most
statistically representative group. The results indicate
a direct correlation between raft occupancy and
immersion depth, which leads to an increased
underwater area and a higher underwater-to-above-
water surface ratio (Aunder water /Aabove water),
increasing from an average of ~4% at minimal
occupancy (2 persons) to ~14% at full occupancy. The
highest drag forces were recorded for rafts no. 3 and 4,
characterized by oval geometries. Smaller rafts showed
a larger wind area per person ratio, which means less
influence of the wind. Conversely, increasing the
number of occupants results in deeper immersion and
greater hydrodynamic resistance.
Wind pressure depends on the size of the life raft
and the number of occupants on board. Calculations
showed a decrease in wind pressure as follows:
− For a 10-person life raft: a 10% reduction in wind
pressure when comparing full occupancy to only 2
persons on board;
− For a 6-person life raft: a 6% reduction in wind
pressure under the same conditions.
This corresponds to an approximate drag decrease
of 1.3% per additional person on board.
The presented study aims to further improve
algorithms for predicting wind drift and determining
search areas used in SAR (Search and Rescue) planning
tools.
ACKNOWLEDGEMENTS
This research was financed by Gdynia Maritime University
Grant No. WN/2025/PZ/03.
REFERENCES
[1] Abramowicz-Gerigk T., Burciu Z., Jachowski J., Kornacka
E., Wawrzusiszyn M., „Experimental and numerical
investigation of towing resistance of the innovative
pneumatic life raft”, Polish Maritime Research, (94) 2017
Vol. 24, p. 40-47, doi: 10.1515/pomr-2017-0048
[2] Burciu Z., „Method of determining search areas in a
rescue operation at sea” (in Polish), doctoral dissertation,
Naval Academy, Gdynia 1997.
[3] Burciu Z., „Modeling of search areas in terms of the safety
of human transport at sea” (in Polish), Printing House of
Warsaw University of Technology, Warsaw, 2003.
[4] Burciu Z., „Reliability of SAR action in maritime
transport”(in Polish), Printing House of Warsaw
University of Technology, Warsaw 2012.
[5] Burciu Z. & Grabski Fr., “The experimental and
theoretical study on the reliability of the life rafts”,
Reliability Engineering and System Safety, vol. 96, no. 11,
2011, doi: 10.1016/j.ress.2011.06.001.
[6] Breivik Ø., Allen A., Maisondieu Ch., Olagnon M.,
“Advances in search and rescue at sea”, Ocean Dynamics,
vol. 63, no. 1, 2013, p.83-88, doi: 10.1007/s10236-012-0581-
1.
[7] Breivik Ø., Allen A. A., Maisondieu Ch., Roth J. Ch.,
“Wind-induced drift of objects at sea: the leeway field
method”, Appl Ocean Res 2011, p. 100-109, doi:
10.1016/j.apor.2011.01.005.
[8] IAMSAR, Manual, International Aeronautical and
Maritime search and rescue manual, Volume III, Mobile
Facilities, 2005 Edition.
[9] Jachowski J., Książkiewicz E., Szwoch I. „Determination
of the aerodynamic drag of pneumatic life rafts as a factor
for increasing the reliability of rescue operations”, Polish
Maritime Research 3, (111) 2021 Vol. 28, p. 128-136, doi:
10.2478/pomr-2021-0040
[10] Jachowski J., Książkiewicz E. „Numerical Prediction of
Pneumatic Life Raft Performance”, The International
Journal on Marine Navigation and Safety of Sea
Transportation, Volume 18, Number 1, March 2024, p.
229-232, doi: 10.12716/1001.18.01.24
[11] Research report, “Aerodynamic testing of pneumatic
liferafts in the wind tunnel Ø 5m” (in Polish), Report nr
168/BA/2000/D Institute of Aviation, Warsaw 2000.
[12] Xinping Ch., Xiaodi W., Lin M., Kai X., Haiwen T.,
”Predicting drift characteristics of life rafts: Case study of
filed experiments in South China Sea”, Ocean
Engineering, Volume 262, October 2022.
