Veleros que aguantan el mal tiempo y los que nunca lo haran

[Cedemont]

Lo mas importante de este post, en mi opinion, es que la gente sepa lo que compra.Y lo que compra es un STIX, asi de claro, y atencion hay STIX muy altos a muy bajo precio ( Puma 34) y otros muy bajos a un alto precio ( Hanse 531).

Pongo los numeros de mi barco, para que compareis,calculado por Guillermo Gefaell, amigo mio. Navego en un Beneteau 473 retocado.

Beneteau Oceanis Clipper 473
Some data for this boat, with the 2.10 m keel, 3300 kg ballast version

Overall Hull Length = 14,16 m
Length Waterline = 13,35 m
Flooded Buoyancy (Y/N) = N
Beam Waterline = 3,9 m
Beam = 4,33 m
Displacement MSC = 12000 kg (estimative. Light:11500)
Height of CE above DWL = 6,47 m
Height of CLR below DWL = 0,64 m
Angle of vanishing stability = 126 deg
Downflooding angle = 110 deg (estimative) (COMIENZA A INUNDARSE DE AGUA EN ESA ESCORA)
GZ at downflooding angle = 0,323 m
GZ at 90 degrees = 0,569 m
Sail Area 114,38 = sq.m
Area to flooding (Agz) = 87,77 m.deg
Area to AVS = 91,5 m.deg

With these numbers STIX goes up to almost 60, very far away from the 48 figure provided with the info from the manufacturer. Lowering downflooding angle to 90º (not probable) and correcting GZ lever and area under GZ curve for this value, STIX comes down to around 50 (Another example of the utmost importance of this angle for the STIX calculation). We realize here the difficulty to check these calculations against the boayards' ones, as they don't provide enough data.

'Old' ratios and estimatives for her:

Length/Beam Ratio L/B = 3,14
Ballast/Disp Ratio W/Disp = 0,28
Displacement/Length Ratio D/L = 140,68
Sail Area/Disp. Ratio SA/D = 17,99
Power/ Disp. Ratio HP/D = 3,78 HP/ton (powerful engine)
Hull speed HSPD = 8,87 Kn
Potential Maximum Speed PMS = 9,73 Kn
Velocity Ratio VR = 1,18
Capsize Safety Factor CSF = 1,91
Motion Comfort Ratio MCR = 26,55
Heft Ratio HF = 0,88
Angle of Vanishing Stability AVS = 126º
Roll Period T = 2,76 sec
Roll Acceleration Acc = 0,16 G's
Stability Index SI = 0,64
Dellenbaugh Angle DA = 13,56 º

Initial Metacentric height GMo = 1,40 m
Righting Arm 10º GZ10 = 0,24 m
Righting Arm 20º GZ20 = 0,44 m
Righting Arm 30º GZ30 = 0,60 m (coincides pretty well!)

So, although these last 'old' numbers are not a great deal for a boat intended to be a passagemaker, STIX goes high (relatively much higher than the other Oceanis), because of the low center of gravity (bulbed keel).

As we've seen before, STIX favours big positive areas under the GZ curve (due to low VCG in this case, as in all bulbed keelers), but does not take into account the negative-positive areas ratio (in this case over the maximum of 20% recommended by Andrew Blyth) and also, because of this and because it doesn't take into account inertias, categorises as blue water boats ones with very short rolling periods, as this one, which not only makes for uncomfortable movements, but also calls for dangerous situations when in breaking waves.
Attached Files ALZADO BENETEAU.pdf (8.1 KB, 97 views) GRAFICAS 2.pdf (19.5 KB, 89 views)

Es decir, yo me compre un 473 sabiendo que era el Beneteau con mayor puntuacion de STIX, muy superior a su eslora en pies. Otro excelente barco es el 393, que con solo 39 pies puntua 43 de STIX.