Seastead 1:10.5 Scale Model Testing Protocols

Using Froude scaling laws, we can translate your full-size design into a highly accurate 1:10.5 scaled physical model for testing in Sandy Hill Bay, Anguilla. Below are the precise dimensions, weights, wave heights, and instrumentation guidelines required for your experiment.

1. Froude Scaling Constants

For a scale factor of λ = 10.5, the Froude sealing rules dictate:

Linear Dimension Multiplier: 1 / 10.5 (multiply feet by 1.1428 to get scale inches)
Volume / Weight Multiplier: 1 / 10.5³ = 1 / 1,157.625
Time Multiplier: 1 / √10.5 = 1 / 3.24
Acceleration Multiplier: 1:1 (Model accelerations directly equal full-scale accelerations!)

2. Model Dimensions (in inches)

Component	Full Scale Dimension	1:10.5 Scale Dimension (Inches)
Triangle Sides (Left/Right)	70.0 ft	80.00"
Triangle Back Width	35.0 ft	40.00"
Truss Height (Floor to Ceiling)	7.0 ft	8.00"
Decks (Left/Right of Dinghy)	5.0 ft wide	5.71" wide
Leg Length (Overall)	19.0 ft	21.71"
Leg Draft (Underwater depth)	9.5 ft	10.86"
Leg Chord (NACA 0030)	10.0 ft	11.43"
Leg Thickness	3.0 ft	3.43"
RIM Drives (Diameter)	1.5 ft	1.71"
RIM Drives (Height from bottom)	3.0 ft	3.43"
Dinghy Length	14.0 ft	16.00"
Stabilizer Wingspan	12.0 ft	13.71"
Stabilizer Chord	1.5 ft	1.71"
Stabilizer Body Length	6.0 ft	6.86"
Elevator Wingspan	2.0 ft	2.29"
Elevator Chord	6.0 inches (0.5 ft)	0.57"

3. Target Weight Calculation

Target Model Weight: ~32.4 lbs

How we got this: Since your full-scale weight was not explicitly stated, we derived it from the required Draft (50% of 19ft = 9.5ft).
The cross-sectional area of a NACA 0030 foil (10ft chord, 3ft thick) is approximately 20.55 sq ft. Multiplying by a 9.5ft draft gives 195.2 cubic feet of submerged volume per leg. For 3 legs, the total submerged volume is ~585.6 cubic feet.
At 64 lbs per cubic foot of seawater, the full-scale vessel displaces 37,480 lbs.
Dividing by scaled volume (λ³ = 1157.625), your model must weigh exactly 32.38 lbs (fully loaded with GoPro, phone, and frame) to float perfectly at the 50% waterline mark.

4. Testing Environments: Waves & Angles

Scale Wave Heights

To record appropriate conditions on your marked wooden pole, aim for the following scale wave heights:

3 foot waves: 3.4 inches
5 foot waves: 5.7 inches
8 foot waves: 9.1 inches

Depth for "Deep Water" Waves

In oceanography, a wave is considered a "deep water wave" when depth is greater than half its wavelength. At full scale, 5 to 8-foot waves typically have wavelengths ranging from 150 to 250 feet. At a 1:10.5 scale, those wavelengths become roughly 14 to 24 feet long.

Recommendation: To avoid bottom-shoaling effects and accurately simulate deep water characteristics, conduct your model tests in water that is at least 7 to 12 feet deep in Sandy Hill Bay.

Doll Size for Scale

The average male is 5'9" (69 inches). 69 / 10.5 = 6.57 inches tall.
Standard 1/12th scale action figures (like Marvel Legends or Star Wars Black Series, which are ~6 to 6.5 inches) will be the absolute perfect stand-ins for human passengers on the model decks.

5. Instrumentation: Acceleration, Apps, and Sliding Plates

Translating Accelerations into Real-World Feel

A crucial feature of Froude scaling is that linear acceleration scales at 1:1. This means if your model experiences 0.2g of acceleration on a wave, the full-size seastead would also experience 0.2g!

The static friction coefficient of a ceramic plate on a smooth wooden or plastic table is typically around 0.3. Unsecured objects will begin sliding when lateral acceleration hits roughly 0.3g (2.94 m/s²), which corresponds to a tipping angle of roughly 16.7 degrees.

Quick Guide to Human Comfort Levels (based on ISO 2631):

0.02g - 0.04g: Barely noticeable to most people.
0.05g - 0.10g: Comfort drops. People must widen their stance. Drinks may slosh in cups.
0.15g - 0.20g: Loss of balance. High probability of seasickness over extended periods.
0.30g+: Unsecured items (plates) slide off tables.

Recommended Android Apps

To record IMU (Inertial Measurement Unit) data for velocity, acceleration, pitch, roll, and heave:

Phyphox: Open-source and incredibly powerful. Allows you to record and export accelerometer and gyroscope data directly to CSV. You can even view real-time data from a laptop on the beach if the phone is sharing a hotspot.
Sensor Logger: Clean graphical interface, accurately records 6-DOF (degrees of freedom) data at high sample rates.

        Important Data Note! While Linear Acceleration is 1:1, angular rates are not! Because of the time scale limit (1 / 3.24), the model will snap/roll back and forth 3.24 times faster than the real ship. If your phone gyroscope reads a pitch rate of 10 degrees per second, the full-size ship will pitch at about 3.1 degrees per second.
    

6. Visual Aids & Camera Setup

The Glass of Water

Placing a glass of water on the model is an excellent visual tool. However, internal sloshing (the fluid dynamics inside the cup) does not perfectly scale unless the fluid's viscosity is also adjusted. Adding rocks inside the cup (as you mentioned) acts as a fantastic baffle to break up harmonic sloshing and gives a realistic representation of a spilled drink!

Time Dilated Video (Frame-rate Scaling)

Because time is scaled by √10.5 (3.24), the model will react artificially "fast" to the naked eye. To make it look heavy and simulate reality:

Shoot your shore camera at exactly 100 frames per second (fps).
Conform the playback to roughly 30 frames per second in your editing software.
100 / 30 = 3.33, which is almost exactly matching your required 3.24 time dilation factor! When played back at 30 fps, the water splashing and the heave of the hull will look exactly like a 37,000 lb, 70-foot structure in real life.

GoPro Placement

Place the GoPro at a scaled height of human eye level. Since human eyes are around 5'4" to 5'6" off the floor, mount the GoPro lens about 6 inches off your model's deck. When the footage is slowed down 3.24x, it will give an incredibly immersive, accurate 1st-person visualization of a storm.

7. Other Suggested Measurements

Mooring Line Tension: Put an inline digital spring scale (luggage scale) on the mooring line you use to hold the model. Since force scales by volume (λ³), if the model exerts a peak pull of 4 lbs in a scale 8-foot wave, you can estimate the full-scale mooring hardware must withstand 4 * 1157 = 4,628 lbs of surge force!
High-Contrast Tracking Markers: Put bright neon green or pink sticky dots at exactly the center of gravity (CG), the bow point, and the stern point of the model. Later, you can feed your shore camera video into free kinematic software like Tracker Video Analysis to plot highly precise millimeter-scale heave, pitch, and yaw charts.
Draft Marks: Paint alternating black and white vertical draft markings directly on the leading edge of the NACA foil legs (1-inch intervals). Your GoPro will capture exactly how far the floats are plunging into the wave troughs dynamically.

Prepared for the Seastead Research & Development Team — Good luck in Anguilla!