From Hull to Hydrostatics: Advanced DELFTship Techniques

Mastering DELFTship: A Beginner’s Guide to Boat Design

Introduction

DELFTship is a user-friendly hull design program used by hobbyists and professionals to model boat hulls, analyze hydrostatics, and prepare plans for construction. This guide walks you through the essentials to get started quickly and build a simple, functional hull from concept to basic analysis.

1. Getting started: installation and workspace

• Download and install the latest DELFTship version for your OS from the official site.
• Open DELFTship and create a new project. Choose between “Surface” (for NURBS-style modeling) and “Lines” (for classic lines plan editing). For beginners, use “Surface” to sketch shapes intuitively.
• Familiarize yourself with panels: Viewports (Top, Side, Front, Perspective), the Geometry tree, Properties, and Object tools.

2. Basic workflow overview

1. Define project units and settings (meters/feet, displacement units).
2. Create a centerline and station planes to control cross-sections.
3. Sketch the baseline hull profile (keel, stem, stern) in side view.
4. Place stations and shape the waterlines in plan/top view.
5. Adjust sections in front view or by manipulating control points.
6. Smooth and fair the hull, then run hydrostatic calculations.
7. Export drawings, offsets, or STL for fabrication.

3. Building your first hull (step-by-step)

1. New file: choose “Surface” mode and set units to meters.
2. Create symmetric hull: enable symmetry about the centerplane.
3. Draw baseline: in the Side view, use the Line tool to draw a keel from stern to stem.
4. Add stations: insert evenly spaced station planes along the baseline (e.g., every 0.5–1.0 m for a small boat).
5. Shape waterlines: in Top view, draw half-beam curves at each station matching desired beam.
6. Edit sections: switch to Front view and adjust control points of each station to create desired section shapes (rounded for displacement hulls; fuller for planing).
7. Fair the hull: use smoothing/fairing tools to remove bumps—inspect in Perspective and curvature plots.
8. Close end caps: ensure bow and stern terminate cleanly; use loft/surface tools to produce a watertight hull.
9. Set waterplane and draft: in the Hydrostatics panel, set an initial draft or target displacement.
10. Run hydrostatics: check displacement, center of buoyancy, metacentric height (GM), and waterplane area.

4. Key settings and design considerations

• Hull type: displacement vs. semi-displacement vs. planing—choose section fullness and deadrise accordingly.
• Beam-to-length ratio: typical small displacement boats 0.3–0.4; racing hulls lower, workboats higher.
• Prismatic coefficient (Cp): lower (~0.45–0.55) for tacking/long-keeled sailboats; higher (~0.55–0.65) for planing/power hulls.
• Stability: check transverse metacentric height (GMt) and righting moment curves for sailboats.
• Trim and center of gravity: position tanks/engine to achieve acceptable trim; DELFTship lets you place weights to simulate CG.

5. Fairing, smoothing, and validation

• Use curvature and slope plots to find and correct hollows or bumps.
• Check continuity between stations (C1 or C2 continuity for smoother flows).
• Validate with tank-test equivalence: compare hydrostatic numbers to reference designs of similar boats.

6. Exporting and documentation

• Export offsets (CSV) for lofting or CNC cutting.
• Generate lines plans and station drawings for construction.
• Export STL/OBJ for 3D printing or CFD preprocessing.
• Save incremental versions and back up your work.

7. Common beginner mistakes and quick fixes

• Overly sharp chine or discontinuous sections — smooth control points, enforce C1 continuity.
• Incorrect symmetry/duplicate vertices — run mesh cleanup and reapply symmetry.
• Unrealistic displacement — verify units, waterplane settings, and closed hull.
• Ignoring appendages—add keel, skeg, or transom features early for realistic hydrostatics.

8. Resources to continue learning