Parametric CAD, Structural Generation, and Weight Estimation Solutions
Hull / Platform: 80' x 40' triangular truss frame frame (7' high) with 4' railings. Covered roof and floor.
Floats: 3 x SWATH-style vertical wings (19' length/draft, 50% submerged). NACA foil profile (10' chord x 3' width). Built-in leading edge ladders.
Living Space: 14' x 45' enclosed centerline structure positioned near the aft edge. Wrap-around open porch, heavily windowed.
Propulsion & Power: 6 x RIM drive thrusters (2 per leg) mounted 3' from bottom. Full-roof solar array.
Active Stabilization: Trailing edge active airplane-style stabilizers (10' span, 1' chord, 6' body, 2' span elevators) with 25% notch pivot point.
Utility: Stern davit system supporting a 14' outboard RIB, drafted sideways in the wind-shadow of the living block.
To design a highly specific system where changing the float spacing automatically redesigns the 3D truss and outputs the weight in Marine Aluminum (Alloy 5083/6061), you need Parametric CAD software. Here are the best solutions categorized by your needs.
FreeCAD is the most robust open-source 3D mechanical CAD program. It features a built-in spreadsheet logic system. You can define variables like "Float Spacing = 40ft" in a spreadsheet, and the geometry will update automatically.
If you or your team have programming experience, CadQuery is an incredibly powerful open-source tool. You build your 3D models using Python scripts.
OpenSCAD uses a descriptive language to compile 3D models. It's excellent for rapid drafting of geometric concepts.
While not open source, Rhino paired with Grasshopper is the absolute global gold standard for parametric marine architecture and complex truss generation. The plugin Karamba3D is specifically made to look at a truss shape, optimize the beam thickness based on loads, and output exact weights.
To accurately get aluminum weights from the CAD drafts, you should format your process like this within your chosen software:
| Component Category | Modeling Technique for Weight Accuracy | Marine Aluminum Target Density |
|---|---|---|
| Triangle Truss (7' High) | Do not model as a solid block. Set standard beam profiles (e.g., 6" Alum pipe, 1/4" wall). Let the software calculate linear length × profile cross-section area. | 2.66 g/cm³ (Alloy 5083/6061) |
| NACA Floats (3x) | Model as "Shells" rather than solids. For example, a 1/2" aluminum plate skin draped over the 10'x3' airfoil with internal bulkheads. | 2.66 g/cm³ |
| Subsystems (Davits, Stabilizers) | Model as standard bounding boxes and assign assumed weights (e.g. Dinghy = 800 lbs, Thrusters = 100 lbs ea) rather than modeling complex metals geometries. | N/A (Use static masses) |
If you want to stick to Open Source, start by downloading FreeCAD. Look at tutorials for the Spreadsheet Workbench to set up your variables (Triangle Length: 80, Triangle Width: 40) and the Arch/BIM Workbench for drawing structural aluminum lattice frames. There are also specific "Aerospace" add-ons in FreeCAD that generate perfect NACA airfoils for your floats just by typing "NACA xxxx" into a box.