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Open-Source Software Options for Seastead Structural Draft Design
Software Options for Draft Structural Design and Weight Estimation
Yes. For what you described, there are several tools that can help, but no single open-source package will fully
take your concept from geometry to a complete marine-aluminum structural design with trustworthy scantlings,
fatigue checks, hydrodynamic loads, and fabrication drawings automatically.
What is realistic is a workflow that combines:
- Parametric 3D geometry
- Structural analysis of trusses, beams, and frames
- Weight and center-of-gravity estimation
- Hydrostatics / buoyancy modeling
- Spreadsheet or script-driven trade studies
Best open-source starting point:
FreeCAD + CalculiX + Python
This is probably the most practical open-source stack for your use case.
Recommended Open-Source Tools
| Software |
Purpose |
Why it may help |
Limits |
| FreeCAD |
3D parametric CAD |
Lets you build the triangular deck frame, living space, float/foil shapes, supports, and solar roof geometry.
Can be scripted with Python, which is very useful for exploring many variants.
|
Marine-specific structural design tools are limited. You will need to create your own modeling conventions.
|
| CalculiX |
Finite element analysis (FEA) |
Can analyze beams, shells, and structural members. Good for checking aluminum trusses, deck framing,
and local stresses if you model them properly.
|
Not marine-specific. Load cases and interpretation are up to you.
|
| Code_Aster |
Advanced FEA |
Very powerful open-source structural solver. Better than many lightweight tools if you need more serious analysis.
|
Steeper learning curve than CalculiX.
|
| OpenFOAM |
Hydrodynamics / CFD |
Could be used later for studying drag, flow around the foil-shaped floats, and thruster interaction.
|
Overkill for early-stage weight estimation. Hard to set up.
|
| GNU Octave / Python (NumPy, SciPy, pandas) |
Trade study calculations |
Excellent for parametric weight estimation, buoyancy calculations, CG calculations, and optimization loops.
|
You must build your own model and assumptions.
|
| Salome-Meca |
Pre/post-processing + Code_Aster |
Useful if you want a GUI-based open-source environment for meshing and structural analysis.
|
More complex workflow than FreeCAD for conceptual design.
|
Best Practical Open-Source Workflow
1. FreeCAD for Parametric Geometry
Use FreeCAD to create a model where the main dimensions are variables:
- Triangle overall dimensions: 80 ft front-to-back, 40 ft beam
- Truss depth: 7 ft
- Living module dimensions
- Float/leg dimensions and vertical immersion
- Locations of thrusters, dinghy supports, stabilizers, solar panels
Then define marine aluminum structural members:
- Pipe or square tube truss members
- Aluminum plate deck and roof panels
- Window frame openings
- Connections to the 3 buoyant legs
FreeCAD can give you:
- Member lengths
- Plate areas
- Volumes
- Mass if density is assigned
- Center of mass
This alone gets you a lot of what you asked for: a draft design and estimated weight of each part.
2. Python Automation
FreeCAD can be controlled with Python scripts. This is important because your problem sounds highly parametric.
For example, you may want to vary:
- Float spacing
- Truss member sizes
- Deck framing spacing
- Living space size
- Roof solar area
- Foil thickness/chord assumptions
A Python script can:
- Build a model variant
- Assign material density for marine aluminum
- Compute total structural mass
- Export a bill of materials
- Estimate CG and compare against buoyancy geometry
3. Structural Checks with CalculiX or Code_Aster
After getting geometry and weights, export or analyze the frame with an FEA solver.
For example:
- Global bending of the triangular platform
- Torsion from uneven wave support on the 3 legs
- Deck deflection
- Stress near leg-to-platform connections
- Local support loads from dinghy mount or stabilizer attachments
For conceptual design, beam elements are often enough at first. Later you could refine critical areas with shell or solid models.
Marine-Specific Tools Worth Knowing About
These are not always open source, but they are relevant:
| Software |
Use |
Comment |
| Rhino + Orca3D |
Marine design / hydrostatics |
Very common in concept-stage marine design, but commercial. |
| GHS |
Hydrostatics / stability |
Professional marine stability software, commercial. |
| Maxsurf |
Hull modeling / hydrostatics / structures |
Commercial and marine-oriented. |
| Delftship |
Hull design / hydrostatics |
Mostly for more conventional hulls; may still help for floats. |
For your unconventional geometry, commercial marine software may not automate much anyway, so a custom parametric workflow may be better.
What You Probably Need the Software to Output
For evaluating design options, I would recommend targeting these outputs:
- Total aluminum weight
- Weight by subsystem
- Main triangular truss
- Deck
- Roof
- Living module walls
- Windows
- Float shells
- Leg attachments
- Dinghy support structure
- Stabilizer structures
- Railings and ladders
- Center of gravity
- Buoyant volume and displaced mass
- Reserve buoyancy
- Estimated draft and trim
- Member list / bill of materials
- Stress and deflection under load cases
Suggested Open-Source Stack for Your Case
Recommended stack:
- FreeCAD for geometry and mass properties
- Python for parametric generation and weight reports
- CalculiX for structural analysis
- Optional: OpenFOAM later for drag and flow
How This Would Work in Practice
A useful conceptual workflow might look like this:
- Define inputs in a JSON, YAML, or Python file:
- overall triangle size
- truss spacing
- member section sizes
- plate thicknesses
- float geometry
- immersion depth
- living area dimensions
- Generate the geometry automatically in FreeCAD
- Assign marine aluminum density
- Export:
- 3D model
- part list
- mass breakdown
- CG estimate
- Send the structural frame to CalculiX
- Run several load cases:
- still water
- one float lifted
- occupancy load
- equipment load
- thruster reaction load
- tow/motion load
- Compare variants automatically
Important Caveat
Conceptual design only:
For something intended to carry people offshore, especially a novel small-waterplane multi-leg platform,
you should expect to need review by a qualified naval architect and structural engineer.
The hard part is not just “can software estimate weight,” but whether the load cases, stability assumptions,
fatigue life, slamming loads, corrosion allowances, and connection design are realistic.
If You Want Something Close to “Automatic Design”
There is no widely used open-source tool that will automatically:
- take your seastead dimensions,
- pick marine aluminum member sizes,
- design a proper truss,
- check marine loads,
- and produce a validated BOM
But you can build a semi-automatic system around FreeCAD and Python that gets surprisingly far for early-stage trade studies.
Bottom-Line Recommendation
If your priority is open source and weight estimation of many variants, I would start with:
- FreeCAD for parametric 3D modeling
- Python for generating variants and reporting weights
- CalculiX for basic structural validation
If your priority becomes marine hydrostatics and stability, you may eventually want to add a commercial marine tool,
or at least a custom hydrostatics model in Python.
Offer
If you want, I can help you with either of these next steps:
- A proposed software workflow diagram for your seastead concept
- A sample FreeCAD/Python parametric model structure
- A JSON schema for storing dimensions and generating weight estimates
- A list of load cases to analyze in CalculiX for this design
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