Advanced structural mechanics methods in optimization of 49er rig setup

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Advanced structural mechanics methods in
optimization of 49er rig setup

• Piotr Zóltowski MSc
• Gdansk University of Technology
• Department of Structural Mechanics

PYA Sail coach conference Gdansk 9-10.12.2004
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Problem formulation

• Closed class rules
• Manufacturer one-design class
• Sophisticated rig (3 shrouds pairs)
• Nonlinear and complicated interaction of various
  tuneable parameters
• Masts are not repeatable, problems of acquiring
  same setup with different masts

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Working scheme

• Identification of parameters we have influence
  on/ we are allowed to change
• Identification of material and geometrical
  properties
• Production of parametric finite element model of
  rig, which allows for precise evaluation of
  interactions and influences of parameters we may
  change
• Model verification
• Transformation of finite element model results to
  on the water tips and on the water results

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Parameters we may change

• Width and depth of upper spreaders
• Width and depth of lower spreaders
• Low shroud tension (LOOS wire gauge)
• Main shroud tension
• Top shroud tension
• Mast column stiffness (replacement)
• Mast top stiffness (replacement)

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Identification of parametes

• Geometry measurement
• Sections measurement
• Literature data of materials (aluminum, stainless
  steel, CFRP)
• Bending tests of the mast
• Mast natural vibration frequency tests
• Averaged data set for further analysis

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FEM model of the rig

• Uses SOFiSTiK FEM software suite
• Allows determination of deformations and forces
  under arbitrary loading
• Takes into account geometrically nonlinear
  effects like buckling
• Allows for estimation of stress levels in the rig
  components

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Model utilisation

• Estimation of quantitavive and qualitative
  relations between parameters we can tune/change
• Production of easy to use tables which corelate
  mast dedflection with spreader settings and
  shroud tensions

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Definitions
Mast bend deflections Spreaders depth and width
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Top shroud tension influence
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Top shroud tension influence
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Low spreader setup influence
Spreader setup (depth/width)
Forestay tension, Low shroud tension, Main shroud
tension, Top shroud tension,
wide - avg. - narrow
Mast deflections at low shroud attach, lower
spreader, upper spreader
shallow - avg. -
deep
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Model verification

• Comparison of the same tensions applied to the
  model and to the real rig on real boat. (Consider
  the error of the table on backside of LOOS gauge)

Calculations Low shroud attach. 157mm Lower
spreader 243mm Upper spreader
223mm
Measurements 175mm 286mm 241mm
Error -10.3 -14.9 -7.5
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Conclusions

• Apart from discrepances, the model reproduces
  basic mechanics of the rig and makes the rig
  easier to understand
• Having the set of tables it is easier to perform
  tasks like increase top mast deflection by 1.5cm
  not affecting the rest

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Final conclusion

• Scientific support is a good support tool for
  high level sailing athletes and may improve their
  trainig process, however it should not provide
  any more informations than necessary, and also
  should not disturb other elements of the training
  process

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Thank you for your attention