The NEMO concept was discovered by MARIN at the MYS 2015. The concept derives from study on submersible and semi-submersible yachts developed jointly by Edwin van der Mark and Harley O’Neill.

1. SEMI-SUBMERSIBLE YACHT CONCEPT
RETHINKING BEHAVIOUR AT ANCHOR AND
GENESIS OF THE COMFORT DRAFT
24th
International HISWA Symposium on Yacht Design and Yacht Construction
14 and 15 November 2016, Amsterdam, The Netherlands, Amsterdam RAI Convention Centre

2. PRESENTATION OUTLINE
2
• Introduction of the project
• Back to basics
• Stability requirements
• Finding a concept solution (finding Nemo…)
• Seakeeping calculations
• Conclusion & Further work

3. INTRODUCTION OF THE PROJECT
3
The NEMO concept was discovered by MARIN at the
MYS 2015 when meeting Edwin van der Mark. The
concept derives from study on submersible and
semi-submersible yachts developed jointly by Edwin
van der Mark and Harley O’Neill.
This new design allows the Yacht to submerge partially
at anchor and give to the guests splendid views above
and below the water‘s surface.
The main goal was pure aesthetical and design.

4. INTRODUCTION OF THE PROJECT
4
MARIN thought that this feature could bring also hydrodynamic
advantages at zero speed given some adaptation of the design.
If this could be achieved, the name of the submerged draft could
be so-called a comfort draft.
DESIGN + HYDRODYNAMICS
=
INNOVATION
+ ENGINEERING
= PRODUCT

5. INTRODUCTION OF THE PROJECT
5
MARIN thought that this feature could bring also hydrodynamic
advantages at zero speed given some adaptation of the design.
If this could be achieved, the name of the submerged draft could
be so-called a comfort draft.
DESIGN + HYDRODYNAMICS
=
INNOVATION
+ ENGINEERING
= PRODUCT

6. BACK TO BASICS
6

7. BACK TO BASICS
7
Effect of varying the metacentric height on roll response

8. BACK TO BASICS
8
Existing ships of floaters changing drafts in operations

9. BACK TO BASICS
9
Goal is then to change the loading condition
(while changing draft) in order to reduce the
metacentric height and improve the
seakeeping (mainly roll)

10. STABILITY REQUIREMENTS
10
The intact stability requirement according to the IMO code of intact stability applicable
to the monohull Yacht (13-36 passengers)
❖ The area under the righting lever curve (GZ curve) is to be not less than 0.055m.rad up to θ =30 angle of
heel.
❖ The area under the righting lever curve is to be not less than 0.09m.rad up to θ =40° angle of heel or the
angle of down flooding θf if this angle is less than 40°.
❖ The area under the righting lever curve between the angles of heel of 30° and 40° or between 30°and θf,
if this angle is less than 40°, is to be not less than 0.03 m.rad.
❖ The righting lever GZ is to be at least 0.20 m at an angle of heel equal to or greater than 30°.
❖ The maximum righting arm is to occur at an angle of heel preferably exceeding 30° but not less than 25°.
❖ The initial metacentric height GM0 should be not less than 0.15 m.

11. STABILITY REQUIREMENTS
11
The interior spaces that could be used to ballast
the ship and attain the required submerged draft
were used to calculate the new stability.
Symbol Magnitude Unit
Lpp
B
T
V
GMt
KM
KG
LCG
Cb
Cm
Cp
105
17,4
4,2
3526,8
1,4
8,01
6,6
54,7
0,52
0,79
0,66
105
17,4
6,8
7202
0,9
7,795
6,9
52,53
0,71
0,84
0,71
m
m
m
m3
m
m
m
m
m
-
-
-
Figure 2: GZ Curves
By calculating the GZ curves corresponding to the
second loading conditions, we realize that the first
model hull doesn’t respect the intact stability
requirement.

12. 12
In order to :
• Satisfy the stability requirement;
• Reduce the ship motions;
• Reduce the capacity of the ballast water necessary to submerge
the Yacht.
We have conceived different hull forms, where, instead of
ballasting to change draft and reduce the GM, we would reduce
the stability also by changing the hull form when sinking.
This is achieved by changing the waterline area while changing
draft.
FINDING A CONCEPT SOLUTION (FINDING NEMO…)

13. 13
Changing the waterline area while changing draft
FINDING A CONCEPT SOLUTION (FINDING NEMO…)
Cross opening full width

14. 14
Changing the waterline area while changing draft
FINDING A CONCEPT SOLUTION (FINDING NEMO…)
Dock

15. 15
Changing the waterline area while changing draft
FINDING A CONCEPT SOLUTION (FINDING NEMO…)
Side gangway over the full length

16. 16
Changing the waterline area while changing draft
FINDING A CONCEPT SOLUTION (FINDING NEMO…)
Mixed solution that could correspond to gangway and side openings.

17. FINDING A CONCEPT SOLUTION (FINDING NEMO…)
17
Symbol Magnitude Unit
Lpp
B
T
V
GMt
KM
KG
LCG
Cb
Cm
Cp
105
17,4
4,2
3526,8
1,4
8,01
6,6
54,7
0,52
0,79
0,66
105
17,4
6,8
6831,6
0,9
6,5
5.6
54,7
0,57
0,77
0,74
m
m
m
m3
m
m
m
m
m
-
-
-
Figure 3: GZ Curves
An expected side effect of the reduced waterline
area was that the vertical plane motions could also
be affected, on top of the roll…
zy

18. T=4.2 m
G
M
GMt=1.4 m
M'
G'
GMt=0.9 m
T=6.8 m
Design draft (departure)
comfort draft (anchor)
• The capacity of the ballast needed to submerge the vessel is around 3387 m3.
• The space dedicated to habitability is 40% less compared to a yacht of the same size.
FINDING A CONCEPT SOLUTION (FINDING NEMO…)

19. 19
• Based on the concept, the designer made a new superstructure and rendering. Such
solution brought by hydrodynamic consideration proved to be even more creative than the
original concept!
FINDING A CONCEPT SOLUTION (FINDING NEMO…)

20. SEAKEEPING CALCULATIONS
20
The calculations are represented in term of RAO, at anchor (zero speed) in beam seas, for 2
loading conditions in order to compare the behaviour of the vessel at the initial draught
(Config_1) and when it submerges (Config_2)
Description Value Unit
Lpp 105 105 [m]
Bwl 15.4 16,7 [m]
Ta 4.2 6,8 [m]
Tf 4.2 6,8 [m]
Displacement 3526.8 7026,3 [m3]
Awp 1238,7 1189,8 [m2]
GMt 1.4 0.9 [m]
LCB 54.8 52,53 [m]
KB 2.5 3,97 [m]
LCG 54.7 52,53 [m]
KG 6.6 5.6 [m]
10.816 15,87 [s]
kxx 6.9 6,9 [m]
kyy 26.25 26.25 [m]
kzz 26.25 26.25 [m]

21. SEAKEEPING CALCULATIONS
21
Figure 5: Roll Excitation Force
Figure 4: Roll RAOs in 1 m amplitude (u=90°)

22. SEAKEEPING CALCULATIONS
22

23. SEAKEEPING CALCULATIONS
23

24. SEAKEEPING CALCULATIONS
24
Figure 6: Heave RAOs in 1 m amplitude (u=90°)

25. SEAKEEPING CALCULATIONS
25

26. SEAKEEPING CALCULATIONS
26

27. SEAKEEPING CALCULATIONS
27
Figure 7: Scatter diagram of the Mediterranean Sea

28. CONCLUSION & FURTHER WORK
28
Creating a comfort draft concept can inherently improve the performance at
anchor of yachts. This is obtained by working on immersion of the hull and
modification of the hull characteristics.
The principle of the comfort draft is:
• Change of waterline area to reduce stability and thus modify excitations;
• New waterline area is achieved in the present concept by the recesses created
in the hull which are immersed when changing draft;
• Such new waterline area could also be achieved by creating side opening (like
with garage doors) and by “flooding” part of the waterline area at intact draft.
Further work should obviously be addressed for the engineering of such solution (interior
arrangements, damaged stability study, noise & vibration ballasting systems and strength
calculation), the possible side effect during ballasting operations (safety, free surface effects), and
the acceptation of such concept for the yards and owners, as well as requirements from
classification societies.

29. THANK YOU !
29
T=4.2 m
G
M
GMt=1.4 m
M'
G'
GMt=0.9 m
T=6.8 m
Design draft (departure)
comfort draft (anchor)