Seastead 1/6 Scale Model Engineering Report

1. Model Dimensions & Weight

Based on Froude scaling, length scales linearly by the ratio (1/6), while weight (mass) scales by the cube of the ratio (1/6³ = 1/216). Acceleration remains constant (1:1) between model and full scale.

Component	Full Scale Dimensions	Model Dimensions (1/6 Scale)
Living Area Length	40 feet (480 inches)	80 inches (6 ft 8 in)
Living Area Width	16 feet (192 inches)	32 inches (2 ft 8 in)
Column Width	4 feet (48 inches)	8 inches
Column Length	24 feet (288 inches)	48 inches (4 ft)
Total Weight	~36,000 lbs	~166.7 lbs

Note: The model weight of ~167 lbs is significant. Ensure your launch and recovery method in Anguilla can handle this load safely.

2. Tension Measurement: Surgical Tubing vs. Digital Scales

Surgical Tubing Analysis

Using surgical tubing as a tension meter is a clever, low-cost analog solution. However, rubber is non-linear (the more you stretch it, the harder it pulls).

Model Range: Standard 1/4" ID surgical tubing typically handles 5 to 15 lbs of tension before stretching excessively or risking failure.
Full Scale Equivalent: Since Force scales by mass ($\lambda^3 = 216$), a 5 lb tension in the model equals 1,080 lbs in full scale. A 10 lb tension equals 2,160 lbs.
Verdict: This is a very reasonable range for checking mooring loads on a 36,000 lb structure. It will tell you if cables are too slack or dangerously tight.

Digital Rope Tension Loggers (Amazon Search)

Finding a waterproof, logging-specific "rope tension meter" under $100 is difficult. Most industrial tension meters cost $500+. However, here are the best alternatives available on Amazon:

Digital Hanging Scales (e.g., Etekcity or Dr. Meter):
Pros: Cheap ($15-$25), easy to put in series with a rope.
Cons: Not waterproof (need a dry bag), and they do not log data over time (they only show current weight).
Fishing Scales: Similar to hanging scales but often more water-resistant. Still lack data logging.
Load Cell Kits (DIY): Search for "HX711 Load Cell Kit". You would need to build a small waterproof box with an Arduino/ESP32 and an SD card module. This is the only way to get true logging on a budget.

Recommendation: Stick with the surgical tubing for visual estimation during the test, or use a standard hanging scale inside a Ziploc bag for spot-checks. True data logging requires a custom DIY electronics build.

3. Wave Height Scaling

To simulate specific sea states in Anguilla, look for wave heights corresponding to the 1/6 length scale.

Target Full Scale Wave	Model Wave Height (Inches)	Model Wave Height (Feet)
3 Feet (Choppy)	6 Inches	0.5 Feet
5 Feet (Moderate)	10 Inches	0.83 Feet
8 Feet (Rough)	16 Inches	1.33 Feet

4. Android Instrumentation & Apps

Recording Acceleration (IMU)

Recommendation: Phyphox (Free, by RWTH Aachen University).
It is the gold standard for mobile sensor experiments. It records Acceleration (x,y,z), Gyroscope (Pitch/Roll/Yaw), and Magnetometer. It can export data to CSV for Excel analysis.

Video with Data Overlay (FPV)

You asked for an app that records video and overlays acceleration data simultaneously.

Phyphox: Can record sensor data, but does not natively overlay it onto a video file in a way that is easy to view later as a "movie".
Data Overlay Camera Apps: There are apps like "Data Overlay Camera" or "Sensor Video" on the Play Store. These are often paid ($5-$10) and can be buggy depending on the phone model.
The "Sync" Method (Recommended):
1. Start recording video on the phone/GoPro.
2. Start recording sensors on Phyphox.
3. Sync Event: Clap your hands loudly or flash a light in front of the camera. This creates a spike in the audio (video) and acceleration (Phyphox) at the exact same millisecond.
4. In post-production, align the clap spike with the video frame. You can then manually type the max G-force onto the video or graph the CSV data alongside the video.

5. Acceleration Metrics: Sliding & Comfort

In Froude scaling, Acceleration is invariant (1:1). This means if an object slides on the model, it will slide on the full-scale seastead under the same conditions.

Sliding Plates (Friction)

The coefficient of friction ($\mu$) for a ceramic plate on a wooden/table surface is roughly 0.3 to 0.5.

Metric: Objects begin to slide when lateral acceleration exceeds $\mu \times g$.
Threshold: If your model records lateral accelerations greater than 0.3g to 0.5g (approx 3 to 5 m/s²), you should expect dishes to slide on the full-scale version.

Human Comfort (Seasickness)

0.1g - 0.2g: Noticeable motion, generally comfortable for most.
0.2g - 0.4g: Uncomfortable, high risk of seasickness for passengers not used to it.
> 0.5g: Dangerous for walking; objects will fly off tables.

The Water Cup Test: Your idea of a glass with rocks and water is excellent.
If the water splashes out of the cup in the model, it will splash out in full scale.
If the water surface angle exceeds 15 degrees consistently, the full-scale environment will be very uncomfortable.

6. Additional Measurement Recommendations

Beyond video and tension, consider these low-cost additions:

Leak Detection: Place a small amount of water-soluble dye (food coloring) in the bilge (bottom) of the model columns. If you see colored water trailing behind the model, you have a leak.
Structural Strain: If the columns are wood, glue a small strip of printer paper across a joint. If the paper tears, the joint is flexing too much.
Mooring Angle: Use a waterproof protractor or a printed angle guide on the shore tripod to measure the angle of the mooring line. A steep angle indicates high vertical lift forces.
Time Scaling for Video: Remember that time moves faster in the model.
Scale Factor for Time = $\sqrt{1/6} \approx 0.408$.
To make the model video look "real" (full scale speed), you must slow the footage down to roughly 40% speed (or 2.5x slower).

Seastead 1/6 Scale Model Analysis