573
1 INTRODUCTION
Liferafts are the lifesaving appliances used on all
typesvessels.Theirmainadvantagesarelowweight,
low space demands and availability in cases of
sudden disasters. In these cases the life raft,
automatically launched from 4‐5 m depth, by the
hydrostatic release system, is the only chance to
surviveforpeopleinthewater(GerigkM.,2004).
Forthedozensofyearsoperationalcharact
eristics
of liferafts did not change a lot. The main
improvementswere:introductionoflightermaterials,
insulated floor, insulated canopy for better thermal
protection of survivors and different designs of
boarding platforms for easier entry from the water
(Abramowicz‐Gerigk&Burciu, 2012; Abramowicz‐
Gerigk&Burciu,2014).
Thegeneralobjectivesinliferaftdesignarest
illthe
economic issues‐low cost and wide availability of
service. Not very high operational demands are
related to the rules of the International Life Saving
ApplincesCode(LSA),ConventionforSafetyofLife
at Sea (SOLAS, 2008; IMO Resolut
ion MSC. 48(66),
1996)andEuropeanUnionstandards(EUDirectiveof
MarineEquipment96/98/EC,1996).Theresultsofthe
field tests give satisfying results as they are carried
outingoodweatherconditions.
ThesuccessofSARactionatseaisdependenton
time of search and rescue operations. The ti
me to
search,detectionandrescuethesurvivors shouldbe
shorterthantimetosurvive. Timeofsearchaction–
T
Risthesumofthreecomponents(BurciuZ.,Grabski
Fr.,2011):
T
R
=T1+T2+T3 (1)
where:
T
1‐timetoreachthetheatre,
T
2–time of the search in the determined area to the
momentofthesearchobjectdetection,
T
3‐timetogivetheeffectiveaid.
ThedetectionmethodsusedduringSARactionare
visualobservations,radarandthermalimaging.
The research conducted in real sea conditions,
have shown that the main difficulties in search and
detectionofliferaftsare related to theliferaftshape,
constructionmaterial,colourofthecanopy,colourof
the outside pa
rt of the floor and operational
characteristics.
The most important problems recognised in the
liferaftoperationareasfollows:
difficultentryintotheliferaftfromthewatereven
ifboardingplatformisavailable,
Innovative Liferaft
T.Abramowicz‐Gerigk,Z.Burciu,J.Jachowski,E.Kornacka&W.Stefurak
GdyniaMaritimeUniversity,Poland
ABSTRACT:ThepaperpresentthelatestresultsofresearcgcarriedoutwithinR&Dprojectonnewsolutionsof
liferaftconstuction.CFDsimulationsofliferaftperformancearepresented.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 9
Number 4
December 2015
DOI:10.12716/1001.09.04.15
574
notsufficientprotectionfromhypothermia,dueto
thewaterinsidetheliferaft,
difficult or impossible detection by radar, due to
small radar reflective surface, which reduces the
probabilityofdetection,
insufficientstabilityinheavyweatherconditions.
2 LIFERAFTDETECTION
The improved liferaft detection can significantly
decreasetime
tosearch.TheinstrumentsusedbySAR
services can detect search objects using daylight
cameras, thermal imaging and radiolocation. The
improvement can be achieved by increasing the
liferaftsignaturesinallrangesofdetection:thevisible
(VIS and NIR), LIR (thermal IR) and radar. Use of
modern materials, structural elements
and
technologiesenablestoincreasethethermalsignature
andincreasereflectionoftheliferaftradarsignal.
2.1 Detectionusingthermovision
The temperature relative to the background is an
essential parameter in the search using the thermal
imaging. The improved detection of liferafts in
thermalimagingcanbeobtainedbytheuse
ofworm
materials on the whole surface of the canopy or
applicationofwormelementsonlystrengtheningthe
thermal signature. The example of the thermal
illuminationhistogram ofthematerialsampletested
fortheapplicationontheliferaftcanopyispresented
infigure1.
Points
Points
Figure1 Thermal illumination histogram of a canopy
material‐sampleno10after3minutesfor12V.
2.2 Radar detection
Thetraditionalliferaftsaremadeofrubberorcoated
fabric, which are very good dielectrics. This is the
reasonthey arealmostinvisible onthescreenofthe
navigationalradars.
Thereareseveraltypesofpassiveradarreflectors
used to increase the liferaft reflective characteristics.
Thereflectorsareunfoldedautomaticallyafter
thelife
raftislaunchedortheyshouldbemanuallyinstalled
ontopofthecanopy.Inheavyweatherconditionsthe
process of installation can be very difficult or even
impossible. The chance of the liferaft detection is
therefore dependent mainly on the applied or not
appliedradarreflector,proper
radarinstallationand
itseffectivereflectionarea(Technicalreport,2014).
The effectiveness of radar reflectors used on
liferaftsislimitedduetotheirlowpositionabovethe
water surface about 1.5 m, note less than m (LSA,
2013) The detection also depends on disturbances
causedbywaves.
Theliferaftechoand
disturbancesfromwavescan
make the liferaft invisible in the navigational radar
display(fig.2).
Figure2. Radar echo of a liferaft and disturbances from
waves presented in the navigational radar display
(Technicalreport,2014,SzklarskiA.)
The maximum range of the radar detection very
seldomexceedsthedistanceof0.5‐0.6Nm(Nautical
mile). At the sea state 8 the intensive disturbances
fromthewavesmaketheliferaftinvisible.
Theincreaseofradardetectionprobabilitycanbe
obtainedintwoways:
using the improved radar reflector
mounted
directlyontheliferaftcanopyoronasmallmast,
preferablypneumatic,
addingthereflectiveoutershellonthecanopyor
makingthewholecanopyofthereflectivefabric.
The radar signatures for different reflective
materials in dependence on the distance from the
liferaftarepresentedinfigure
3.
distance [m]
amplitude [V]
Radar signatures
Figure3. Diagram of radar signatures (Technical report,
2014)
The 2D and 3D images of radar reflectivity of a
reflective material sample are presented in figures 4
and5.
575
Figure4.2Dradarreflectivityofareflectivematerialsample
(Technicalreport,2014)
Figure5.3Dradarreflectivityofareflectivematerialsample
(Technicalreport,2014)
3 LIFERAFTSTABILITY
The first model of a liferaft proposed by Gdynia
Maritime University (fig. 6) was designed in
compliancewiththeLSAcode.Accordingtotherules
the total mass of a liferaft, its container and
equipmentshallbenotgreaterthan185kg.
The mass of the proposed
liferaft in full load
condition includes 8 persons 82,5 kg each‐660 kg,
andmassofliferaftwithequipment100kg.Thetotal
weightofthe liferaft with survivors on boardis760
kg. Component weights (m) and areas of related
surfaces of the liferaft model (P) are presented in
figure7.
Figure7. Component weights of the liferaft model
((Technicalreport,2014)
Figure6.Basicparametersoftheproposedliferaft(Technicalreport,2014)
576
The stability calculations were performed
assumingthatthenliferaftisasolidbody.Thecentre
of gravity was determined in coordination system
presentedinfigure8:X
g=0,025m,Yg=0m,Zg=0,32m,
(
Zg‐measuredfromthebottomofliferaft).
Figure8. Model of the 8 persons liferaft (Technical report,
2014)
The range of drafts used for the calculation of
hydrostaticdataispresentedinfigure9.
Figure9. Range of drafts used in calculations (Technical
report,2014)
Thehydrostaticdatacalculatedfortheliferaftare
presented in table 1, where: T [m] – draft, V [m
3
] –
volumeofunderwaterpart,D[t]–buoya ncy, VCB
[mm] – vertical centre of buoyancy Z
g, Aw [m
2
] –
waterlinearea,Mj[tm/m]–momenttotrimper1m,
buoyancyincreaseper1cmdraftincrease.
Thestaticstabilitycurvesofaliferaftarepresented
in figure 10. There were three assumed loading
conditionsanalysed with three different positions of
thecentreofgravity:
2persons
are lyingdownonthe floor,therestis
sittingaroundintheliferaft:zg=0.4m,
all survivors are sitting symmetrically around in
theliferaft:zg=0.5m,
2personsarestanding,therestissittingaroundin
theliferaft:zg=0.8m.
Table1.Hydrostaticdataforliferaft‐draftrangefrom0m
to0.5m.
_______________________________________________
T V D VCB Aw Mj TPC
[m] [m
3
] [t][mm] [m
2
] [tm/m] [t/cm]
_______________________________________________
0.000 0.018 18.400 0.000 5.500 0.900 0.055
0.027 0.170 174.647 0.015 5.567 0.974 0.056
0.054 0.327 335.690 0.024 6.070 1.102 0.061
0.081 0.494 507.025 0.039 6.345 1.167 0.063
0.107 0.667 684.008 0.050 6.490 1.197 0.065
0.134 0.842 863.617 0.069 6.541 1.202 0.065
0.161 1.017 1043.201 0.080 6.488 1.179 0.065
0.188 1.189
1220.125 0.088 6.342 1.131 0.063
0.215 1.356 1391.334 0.093 6.064 1.047 0.061
0.242 1.513 1552.166 0.107 5.555 0.898 0.056
0.268 1.651 1694.216 0.120 5.300 0.811 0.053
0.295 1.804 1850.361 0.133 5.949 0.966 0.059
0.322 1.968 2019.065 0.148 6.276 1.031 0.063
0.349 2.139 2194.669 0.163 6.457 1.056 0.065
0.376 2.314 2373.730
0.178 6.531 1.051 0.065
0.403 2.490 2554.027 0.193 6.540 1.030 0.065
0.429 2.664 2732.734 0.207 6.423 0.971 0.064
0.456 2.833 2906.743 0.222 6.193 0.872 0.062
0.483 2.995 3072.160 0.235 5.778 0.717 0.058
0.510 3.042 3121.208 0.239 5.680 0.698 0.057
_______________________________________________
Figure10. Stability curvesfor different positions of liferaft
centreofgravity(Technicalreport,2014)
4 CONCLUSIONS
Operationalreliabilityofaliferaftisa characteristic
informing whether it fulfils live saving functions in
given hydro‐meteorological conditions. To minimize
thedangerofcapsizinginstrongwindandwaves,in
partially occupied liferafts, the survivors should
always occupy the windward side. In real life the
occupation
is random, therefore in the presented
studytheequaldistributionofsurvivorsandthelevel
static trim were assumed. (Abramowicz‐
Gerigk&Burciu, 2014). The presented preliminary
design should be followed by the numerical
calculations of hydrodynamic and aerodynamic
reaction forces in wind and waves, towing and
recoveryfromthewatercharacteristics
(Burciuetal.,
2001; Marchenko, 1999; Raman‐Nair et al., 2008;
http://data.tc.gc, 2012) to optimize the shapes of
buoyancychambers,ballastpocketsandcanopy.
577
BIBLIGRAPHY
Abramowicz‐Gerigk T., Burciu Z., 2014. Inflatable liferaft
designforoperation–novelsolutions20thInternational
Conference on Hydrodynamics in Ship Design and
Operation. HYDRONAV 2014, Wrocław, Poland, June
2014
Abramowicz‐Gerigk T., Burciu Z., 2012. The influence of
coordinatoronthereliabilityofsearchandrescueaction
at sea.
Scientific Problems of Machines Operation and
MaintenanceNr1/2012p.7‐14
Burciu Z., Grabski Fr., 2011.The experimental and
theoretical study on the reliability of the life rafts.
Reliability Engineering and System Safety 96(2011), p.
1456‐146.
Burciu Z., Rusiński E., Stefurak W., Wach Z., 2001.
Założenia
projektowe urządzenia do podejmowania
ludzi z tratew ratunkowych. V Konferencja Naukowa
Metody doświadczalne w budowie i eksploatacji
maszyn,Wrocław–SzklarskaPoręba,2001,tomI,p.179
–190.
Gerigk M., 2004. On a risk‐based method for safety
assessment of a ship in critical conditions at
the
preliminarydesignstage.PolishMaritimeResearch,No.
1(39),Vol.11,p.8‐13
Marchenko A. V. J., 1999.The floating behaviour of a
smallbodyacteduponbyasurfacewave,J.ApplMaths
Mechs,Vol.63,No.3,p.471478,1999.
Raman‐Nair W., Power J., Simoes
Re A., 2008. Towing
dynamicsofa liferaftand fastrescuecraftin asurface
wave,OceanEngineering35(2008),p.1252–1258.
http://data.tc.gc.ca/archive/eng/innovation/tdc‐summary‐
13000‐13041e‐887.htm. 2012. The development of an
easily recovered liferaft. Transport Canada,
TransportationDevelopmentCentre,(TP13041E).
Technical report. 2014. Innovative means of transport for
search and rescue at sea. Gdynia Maritime University.
Department of Ship Operation. Project No. POiG
01.04.00.00‐272/13
