The First 50 and the X-50

Discussion in 'Stability' started by Antonio Alcalá, Jan 3, 2008.

  1. Antonio Alcalá
    Joined: Nov 2006
    Posts: 92
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    Location: Portugal

    Antonio Alcalá Ocean Yachtmaster

    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
     
  2. Guillermo
    Joined: Mar 2005
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    Guillermo Ingeniero Naval

    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
     
    1 person likes this.
  3. Antonio Alcalá
    Joined: Nov 2006
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    Antonio Alcalá Ocean Yachtmaster

    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
     
  4. Guillermo
    Joined: Mar 2005
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    Guillermo Ingeniero Naval

    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.
     
  5. Antonio Alcalá
    Joined: Nov 2006
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    Antonio Alcalá Ocean Yachtmaster

    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
     
  6. Guillermo
    Joined: Mar 2005
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    Guillermo Ingeniero Naval

    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!
     
  7. Antonio Alcalá
    Joined: Nov 2006
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    Antonio Alcalá Ocean Yachtmaster

    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
     
  8. Guillermo
    Joined: Mar 2005
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    Guillermo Ingeniero Naval

    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.
     
  9. Antonio Alcalá
    Joined: Nov 2006
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    Antonio Alcalá Ocean Yachtmaster

    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
     

  10. Guillermo
    Joined: Mar 2005
    Posts: 3,644
    Likes: 185, Points: 63, Legacy Rep: 2247
    Location: Pontevedra, Spain

    Guillermo Ingeniero Naval

    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.
     
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