Catamaran Hull Drag Optimization for Science Fair

ISEF Category: Engineering Technology: Statics and Dynamics

Subcategory: Naval Systems  ·  Difficulty: Advanced  ·  Setup: University Lab  ·  Time: Full Year

The Hook

A tiny shape change on a boat can make a big drag change. That means your model catamaran can teach you real naval design, not just hobby tinkering. If your measurements and simulation agree, you get a project that feels like engineering, not guesswork.

What Is It?

This project studies how the shape of a catamaran hull changes drag, which is the force that resists motion through water. Think of drag like the effort needed to pull a hand through a bathtub. A smoother shape, a narrower hull, or a different spacing between the two hulls can make that pull easier or harder.

You will compare real towing data from a printed model with computer fluid simulation in OpenFOAM. CFD, or computational fluid dynamics, means using a computer model to predict how water flows around the boat. The goal is not just to make a boat that goes faster. The goal is to find which shape changes reduce resistance, then test whether the simulation predicts the same trend as the pool measurements.

Why This Is a Good Topic

This is a strong science fair topic because you can change one shape variable at a time and measure a real output, drag force. It connects to ship design, racing, and energy use in transport. You can also learn how to compare experiments with simulations, which is a big step up from a simple build-and-test project.

Research Questions

• How does hull spacing affect total drag on a one meter catamaran?
• What is the effect of hull width on towing force at the same speed?
• Does changing hull cross-section shape reduce measured drag compared with a baseline design?
• To what extent does trim angle change drag for the printed catamaran model?
• Which hull shape gives the best match between tow-test data and OpenFOAM predictions?
• How does surface roughness change the gap between CFD results and measured drag?

Basic Materials

• One meter catamaran model, 3D printer or printed hull parts, waterproof assembly materials, backyard pool or long test tank, fishing line, inline load cell or force sensor, digital scale, tape measure, marked tow path, stopwatch, laptop for data logging, ruler or calipers, waterproof marker, notebook.

Advanced Materials

• One meter modular catamaran model, 3D printer, resin or filament with known material properties, load cell with data acquisition, motion guide or towing carriage, wave-suppression plates, flow visualization dye, submerged reference markers, water temperature sensor, access to a calibrated tank or university towing setup, OpenFOAM-capable computer, post-processing software.

Software & Tools

• OpenFOAM: Simulates water flow around each hull shape so you can compare predicted and measured drag.
• ParaView: Visualizes pressure, velocity, and wake patterns from your CFD runs.
• Python: Cleans tow-test data, fits curves, and compares drag across designs.
• ImageJ: Measures printed hull dimensions and checks whether each prototype matches your intended geometry.
• Google Sheets: Organizes raw force data and helps you build graphs quickly.

Experiment Steps

1. Define one hull variable to change first, such as spacing, width, or bow shape.
2. Build a baseline model and a small set of controlled variants that differ only in that one feature.
3. Plan a tow-test method that keeps speed, alignment, and water conditions as consistent as possible.
4. Set up a calibration plan so the load cell output converts into a real drag force.
5. Build a CFD model that matches the physical geometry and uses the same test conditions.
6. Compare simulation and tow-test trends, then decide which design changes both methods agree are better.

Common Pitfalls

• Letting the tow line angle change, which adds sideways force and inflates the drag reading.
• Using models that differ in more than one shape feature, which makes the results impossible to interpret.
• Skipping load-cell calibration, which turns force data into numbers you cannot trust.
• Comparing CFD output to raw tow force without matching speed, scale, and water conditions.
• Printing hulls with rough or warped surfaces, which changes drag more than the design idea you wanted to test.

What Makes This Competitive

A strong version of this project does more than compare a few boat shapes. You need a clean experimental method, a calibrated force measurement, and a CFD model that predicts the same ranking as the pool tests. Better projects test uncertainty, not just averages, and explain where the simulation fails. If you can identify which geometric change matters most and why, your work starts to look like real design research.

Project Variations

• Compare catamaran hull spacing across three ratios while holding hull shape fixed.
• Test whether a rounded bow or a flatter bow gives lower drag at the same tow speed.
• Add a surface finish comparison, such as smooth versus lightly textured hulls, to study roughness effects.

Learn More

• OpenFOAM User Guide: Search the OpenFOAM documentation for setup, meshing, and multiphase flow basics.
• NOAA National Data Buoy Center: Use it to understand water conditions, wave effects, and measurement context for marine experiments.
• MIT OpenCourseWare Fluid Mechanics: Find lecture notes and problem sets on drag, lift, and boundary layers.
• NASA Glenn Research Center Beginner's Guide to Aerodynamics: Read the sections on drag forces and flow behavior for clear fundamentals.
• Journal of Ship Research: Search the journal for papers on catamaran resistance, hull spacing, and towing tests through your school library or PubMed-style journal access portals if available.