# Orcaflex Modal Analysis Common Errors And Fixes

> Sub-skill of orcaflex-modal-analysis: Common Errors and Fixes (+1).

- Skill: `vamseeachanta/orcaflex-modal-analysis-common-errors-and-fixes` (Agent Skill)
- Install (CLI): `npx skillmds@latest add vamseeachanta/orcaflex-modal-analysis-common-errors-and-fixes`
- Raw SKILL.md: https://api.skillmd.com/api/skills/vamseeachanta/orcaflex-modal-analysis-common-errors-and-fixes/raw
- Safety review: PASS (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: vamseeachanta (https://skillmd.com/u/vamseeachanta)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/vamseeachanta/orcaflex-modal-analysis-common-errors-and-fixes

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# Common Errors and Fixes (+1)

## Common Errors and Fixes


| Error | Cause | Fix |
|-------|-------|-----|
| `Statics failed to converge` | Model not in equilibrium before modal | Fix statics first (see orcaflex-static-debug skill) |
| `Singular stiffness matrix` | Zero-tension lines or disconnected components | Check all lines have positive tension; verify all connections |
| `No modes found` | lastMode too low or model too simple | Increase `lastMode`; add more DOFs (finer segmentation) |
| Modal analysis hangs | Very large model with too many modes requested | Reduce `lastMode` or simplify model (coarser segments) |
| Unrealistic frequencies | Wrong units (mass, stiffness) or missing added mass | Verify line type properties; check hydrodynamic coefficients |
| Mode shapes all zero for an object | Object not included in modal analysis scope | Add object to `ObjectName` list in config |
| Duplicate frequencies | Symmetric model produces paired modes | Expected for symmetric configurations; modes are degenerate pairs |

## Debugging Modal Issues


```python
def diagnose_modal_failure(model):
    """Pre-check model before modal analysis."""
    issues = []

    # Check statics first
    try:
        model.CalculateStatics()
    except OrcFxAPI.OrcaFlexError as e:
        issues.append(f"Statics failed: {e} — fix statics before modal analysis")

*See sub-skills for full details.*