The First 50 and the X-50

[Antonio Alcalá]

Everybody knows these two designs are made for racing, but for crossing oceans in record time too. The question is if anybody of this forum can calculate the ISO STIX 12217 number of both, motion comfort, capsize ratio, roll acceleration , you know what i mean... in order to compare the sailing performance but the stability criteria between both too. I tried but i didn´t get it.


First 50

Specifications
Rig Dimentions

LOA : 49' 2"
LWL : 43' 6"
Beam : 14' 6"
Mast length (over water) : 72' 1"
Draft (standard) : 7' 11"
Draft (optional) : 9' 2"
Ballast (standard) : 10,516 lbs.
Ballast (optional) : 9,480 lbs.
Displacement : 30,379 lbs. (approx.)
Engine : 75 hp.
Fuel Capacity : 63 gal.
Water Capacity : 143 gal.
Hull / Designer : Briand
Sail Area : 1,493 sq. ft.
Classic Mast
I= 62' 5"
J = 17' 7"
P = 60' 8"
E = 21' 4"

X-50

X-50 DIMENSIONS
Hull length
15.24
m
50.0
ft

LWL
13.14
m
43.1
ft

B. MAX
4.28
m
14.0
ft

BWL 3.63
m 11.9
ft

Standard draft
3.00
m
9.8
ft

Shallow draft 1
2.70
m
8.86
ft

Shallow draft 2
2.40
m 7.87
ft

Ballast
4,690
kg
10,935
lbs

Displ. std. empty approx 12,400
kg
27,338
lbs

Engine diesel
55
kW
75
HP




SAIL AREAS standard
Mainsail 77.0
m2 829.2
ft2
Genoa 1 · 135% 77.9
m2 838.6
ft2
Genoa 3 · 108% 62.3
m2 670.6
ft2
Self-tacking Jib 51.5
m2 554.4
ft2
Spinnaker - All purpuse 194.4
m2 2,092.6
ft2




Best regards

[Guillermo]

Antonio,
I can work out the traditional ratios and paramentes, but not the STIX without the GZ curves. Unluckily X-yachts refuses to release that kind of information. I know because I tried.

Cheers

[Antonio Alcalá]

I understand friend, but what about puma 34 and first 345? Do you have any
information? I´d be interested in knowing stix numbers, motion comfort and capsize ratio of them

Best winds

[Guillermo]

OK Antonio, here something for you:

X-50

Inputs
Lh = 15,24 m
Lwl = 13,14 m
Bmax = 4,28 m
Bwl = 3,85 m
Draught T = 3,00 m
Body draught Tc = 0,60 m
Moulded depth H = 2,03 m
Disp = 12400 kg
Ballast = 4690 kg
Sail area = 128,5 m2
Mast height = 23,5 m
Heeling Arm = 10,60 m
Power = 55,15 KW

Outputs
Length/Beam Ratio (2Lwl + Lh)/3B = 3,23
Lwl/Bwl Ratio Lwl/Bwl = 3,41
WL beam/Body draught Bwl/Tc = 6,42
Ballast/Disp Ratio W/Disp = 0,38
Displacement/Length Ratio D/L = 152,45
Sail Area/Disp. Ratio SA/D = 24,37
Sail Area/Wetted surface SA/WS = 2,87
Power/ Disp. Ratio HP/D = 2,74 HP/ton
Hull speed HSPD = 8,80 Kn
Velocity Ratio VR = 1,21
Capsize Safety Factor CSF = 1,87
Motion Comfort Ratio MCR = 27,50
Righting Moment/Beam RMB = 0,85
Moment of Inertia I = 1542000,08 Lb/ft2
Roll Period T = 3,35 Sec
Roll Acceleration Acc = 0,11 G's
Stability Index SI = 0,78
Angle of Vanishing Stability AVS = 117 º



FIRST 50

Inputs
Lh = 14,99 m
Lwl = 13,26 m
Bmax = 4,45 m
Bwl = 4,00 m
Draught T = 2,41 m
Body draught Tc = 1,05 m
Moulded depth H = 2,10 m
Disp = 13768 kg
Ballast = 4766 kg
Sail area = 111,1 m2
Mast height = 21,97 m
Heeling Arm = 9,75 m
Power = 55,15 KW


Outputs
Length/Beam Ratio (2Lwl + Lh)/3B = 3,11
Lwl/Bwl Ratio Lwl/Bwl = 3,32
WL beam/Body draught Bwl/Tc = 3,81
Ballast/Disp Ratio W/Disp = 0,35
Displacement/Length Ratio D/L = 164,71
Sail Area/Disp. Ratio SA/D = 19,65
Sail Area/Wetted surface SA/WS = 2,36
Power/ Disp. Ratio HP/D = 2,47 HP/ton
Hull speed HSPD = 8,84 Kn
Velocity Ratio VR = 1,13
Capsize Safety Factor CSF = 1,87
Motion Comfort Ratio MCR = 28,97
Righting Moment/Beam RMB = 0,86
Moment of Inertia I = 1850749,97 Lb/ft2
Roll Period T = 3,44 Sec
Roll Acceleration Acc = 0,10 G's
Stability Index SI = 0,77
Angle of Vanishing Stability AVS = 121 º


I have nothing for the Puma and the First.
You can run by yourself their basic ratios at Carl's Calculator:
http://www.image-ination.com/sailcalc.html

Cheers.

[Antonio Alcalá]

Thanks a lot Guillermo. Incredible work! How do you get it? Sources? If i do a first sight to the numbers we´d say the first 50 is better than X-50 according to their construction, ballast, etc. And in that case you probably save a lot of money.

And tell me Guillermo, could you be so kind let me know your estimative numbers of STIX of them?

Best winds

[Guillermo]

Antonio,
Not an incredible work, but just work: taking info from manufacturer's or distributors' pages, measuring on posted drawings or images the missing data, doing some guessing and working out numbers. Just patience and a willing to satisfy my friends....

No way of accurately estimating STIX. I need the proper data and GZ curves for MOC and MLC, as well as downflooding angles. I'm working on an 'STIX estimator', but it's to 'green' yet.

Cheers!

[Antonio Alcalá]

Ok Guillermo. Let´s have a look at these numbers:


First 50


Inputs
Lh = 14,99 m
Lwl = 13,26 m
Bmax = 4,45 m
Bwl = 4,00 m
Draught T = 2,41 m
Body draught Tc = 1,05 m
Moulded depth H = 2,10 m
Disp = 13768 kg
Ballast = 4766 kg
Sail area = 111,1 m2
Mast height = 21,97 m
Heeling Arm = 9,75 m
Power = 55,15 KW


Outputs
Length/Beam Ratio (2Lwl + Lh)/3B = 3,11
Lwl/Bwl Ratio Lwl/Bwl = 3,32
WL beam/Body draught Bwl/Tc = 3,81
Ballast/Disp Ratio W/Disp = 0,35
Displacement/Length Ratio D/L = 164,71
Sail Area/Disp. Ratio SA/D = 19,65
Sail Area/Wetted surface SA/WS = 2,36
Power/ Disp. Ratio HP/D = 2,47 HP/ton
Hull speed HSPD = 8,84 Kn
Velocity Ratio VR = 1,13
Capsize Safety Factor CSF = 1,87
Motion Comfort Ratio MCR = 28,97
Righting Moment/Beam RMB = 0,86
Moment of Inertia I = 1850749,97 Lb/ft2
Roll Period T = 3,44 Sec
Roll Acceleration Acc = 0,10 G's
Stability Index SI = 0,77
Angle of Vanishing Stability AVS = 121 º



BENETEAU OCEANIS CLIPPER 473

Lh = 14.16 m
Lwl = 13.35 m
Bmax = 4.33 m
Bwl = 3.897 m
Draught = 1.7 m
HD = 0.600 m
Disp. Full = 13284 Kg
Disp. Mmsoc = 11851 Kg
Disp. Lightship = 11500 Kg
Ballast = 3700 kg
Sail area = 92.8 m2
Power = 100 HP
Heeling Arm = 7.113 m

Length/Beam Ratio L/B = 3.18 (Bien)
Ballast/Disp Ratio W/Disp = 0.31 (Un poco bajo)
Displacement/Length Ratio D/L = 138.93 (Muy ligero)
Sail Area/Disp. Ratio SA/D = 18.14 (Bien)
Power/ Disp. Ratio HP/D = 3.82 HP/ton (Más que de sobra)
Hull speed HSPD = 8.87 Kn
Potential Maximum Speed PMS = 9.76 Kn
Velocity Ratio VR = 1.10 (Buena potencia vélica)
Capsize Safety Factor CSF = 1.92 (Mejor más bajo)
Motion Comfort Ratio MCR = 26.22 (Bajo)
Heft Ratio HF = 0.87 (Mejor >1)
Downflooding angle: Fd = 90 º (Estimado)
Angle of Vanishing Stability AVS = 115 º (Estimado. Consta 119º)
Roll Period T = 2.73 Sec (Ideal >4.33)
Roll Acceleration Acc = 0.16 G's (Muy alto. Ideal 0.06)
Stability Index SI = 0.63 (Ideal entre 1 y 1.1)



And now, trusting you and your comments, what do you see when we compare both. The First seems to have better sailing performance, but could you explain me the differences between the roll accelleration, and the roll period over them...and what about the AVS? Both are in Category A, but what of these two boats are capable to resist 7 days upwind in a force 7 sea ( tipical conditions coming back of caribean islands to Azores in April)


Best winds

[Guillermo]

From the point of view of those numbers the F 50 seems to be a more adequate oceangoing boat than the O 473.

Anyhow, 7 days beating to winward in a force 7 is a not everybody taste's dish. If fetch is 300 km it would build up 5+ m waves (significative), with the ocasional 10 m one. Most probably the weaker link in such conditions is not the boat (asuming it is soundly built and maintained) but the crew. With a MCR just over 26 and SI of 0.63 (case of the O 473), such conditions can impose accelerations able to impair a not well trained crew, when sustained for such a long time.

Cheers.

[Antonio Alcalá]

Let´s see. Here you have e German Frers design for swan, and grand soleil:

Loa = 16,30 m
Lh = 15,78 m
Lwl = 12,89 m
Bmax = 4,75 m
Bwl = 4,28 m
Draught T = 2,40 m
Body draught Tc = 1,00 m (guess)
Disp = 17700 kg (Most probably lightship or MOC)
Ballast = 7300 kg
Sail area = 157,4 m2 (guess: 140 m2 for 100%)
Power = 95 HP


Length/Beam Ratio L/B = 2,9
Lwl/Bwl Ratio Lwl/Bwl = 3,02
Ballast/Disp Ratio W/Disp = 0,41
Displacement/Length Ratio D/L = 230 (around 265 in MLC)
Sail Area/Disp. Ratio SA/D = 20,95
Power/ Disp. Ratio HP/D = 2,44 HP/ton
Hull speed HSPD = 8,71 Kn
Potential Maximum Speed PMS = 9,95 Kn
Velocity Ratio VR = 1,14
Best motoring speed (1.1) CSPD = 7,15 Kn
Capsize Safety Factor CSF = 1,84
Motion Comfort Ratio MCR = 34,20
Heft Ratio HF = 0,97
Roll Period T = 3,94 Sec
Roll Acceleration Acc = 0,09 G's
Stability Index SI = 0,83
Angle of Vanishing Stability AVS = 121 º


And now the First 50, calculated by you


Inputs
Lh = 14,99 m
Lwl = 13,26 m
Bmax = 4,45 m
Bwl = 4,00 m
Draught T = 2,41 m
Body draught Tc = 1,05 m
Moulded depth H = 2,10 m
Disp = 13768 kg
Ballast = 4766 kg
Sail area = 111,1 m2
Mast height = 21,97 m
Heeling Arm = 9,75 m
Power = 55,15 KW


Outputs
Length/Beam Ratio (2Lwl + Lh)/3B = 3,11
Lwl/Bwl Ratio Lwl/Bwl = 3,32
WL beam/Body draught Bwl/Tc = 3,81
Ballast/Disp Ratio W/Disp = 0,35
Displacement/Length Ratio D/L = 164,71
Sail Area/Disp. Ratio SA/D = 19,65
Sail Area/Wetted surface SA/WS = 2,36
Power/ Disp. Ratio HP/D = 2,47 HP/ton
Hull speed HSPD = 8,84 Kn
Velocity Ratio VR = 1,13
Capsize Safety Factor CSF = 1,87
Motion Comfort Ratio MCR = 28,97
Righting Moment/Beam RMB = 0,86
Moment of Inertia I = 1850749,97 Lb/ft2
Roll Period T = 3,44 Sec
Roll Acceleration Acc = 0,10 G's
Stability Index SI = 0,77
Angle of Vanishing Stability AVS = 121 º


Could you tell me in wich of them you´d prefer for suffering a Force 8 gale upwind... now we talk about stability and seaworthiness, anyhow i should be grateful if you tell me something about differences between roll acceleration and roll period in both yatchs, and please consider the crew are prepared for seasickness.

Best winds

[Guillermo]

Antonio,

Relevant parameters for the quality of motion are:

Swan
Motion Comfort Ratio MCR = 34,20
Roll Acceleration Acc = 0,09 G's
Stability Index SI = 0,83

First 50
Motion Comfort Ratio MCR = 28,97
Roll Acceleration Acc = 0,10 G's
Stability Index SI = 0,77

The Swan should show a somewhat better quality of movements.


From the point of view of safety:

Swan
Capsize Safety Factor CSF = 1,84
Angle of Vanishing Stability AVS = 121º

First 50
Capsize Safety Factor CSF = 1,87
Angle of Vanishing Stability AVS = 121 º

From this point of view, they are almost equal.


You have to take all this in its due context. Although based on widely accepted concepts, these numbers are only clues to behaviour, not the real thing. Being the size more or less the same, as differences are not very relevant it's difficult to say which boat will behave better.

Cheers.