Here is a complete, ready-to-use HTML file containing all the scaled calculations, physics notes, app recommendations, and testing guidelines based on Froude scaling principles for your 1:10.5 seastead model. ```html Seastead 1:10.5 Scale Model Testing Guide

🌊 Seastead 1:10.5 Scale Model Testing Guide

All dimensions and physics derived using Froude Scaling Laws (gravity-dominated hydrodynamics). The linear scale factor is λ = 10.5.

📐 Scaled Model Dimensions

Conversion formula: Model (inches) = [Full-Scale Feet × 12] ÷ 10.5

Component / Feature	Full-Scale	Model Target
Left / Right Triangle Sides	70 ft	80.0"
Back Triangle Width	35 ft	40.0"
Truss Height (Floor to Ceiling)	7 ft	8.0"
Leg / Wing Length (Vertical)	19 ft	21.7"
Leg Chord (Fore-Aft)	10 ft	11.4"
Leg Max Thickness (NACA 0030)	3 ft	3.4"
Submerged Depth (50%)	9.5 ft	10.9"
Above-Water Leg Length	9.5 ft	10.9"
RIM Thruster Diameter	1.5 ft	1.7"
Thruster Mount Height (from bottom)	3 ft	3.4"
Dinghy (14' RIB)	14 ft	16.0"
Rear Deck Extension Width	5 ft	5.7"
Stabilizer Main Wingspan	12 ft	13.7"
Stabilizer Main Chord	1.5 ft	1.7"
Stabilizer Fuselage/Body	6 ft	6.9"
Elevator Wingspan	2 ft	2.3"
Elevator Chord	0.5 ft (6")	0.57"

⚖️ Target Model Weight: ~35 lbs
Derived from displacement buoyancy matching. Full-scale submerged foil volume ≈ 635 ft³ × 64 lb/ft³ ≈ 40,600 lbs. Under Froude scaling, mass scales as 1/λ³ → 40,600 ÷ 10.5³ ≈ 35.1 lbs.
Build target: Aim for 33–37 lbs total. Add internal steel/lead ballast if structural materials make it lighter; remove/trim draft if heavier to maintain the 50% waterline.

🌊 Scaled Wave Heights & Test Depths

Wave height scales linearly (1:10.5). To simulate full-scale conditions in Sandy Hill Bay:

Target Full-Scale Waves	Required Model Wave Height
3 ft (Small chop / sheltered)	~3.4 inches
5 ft (Moderate swell)	~5.7 inches
8 ft (Heavy chop / exposed)	~9.1 inches

💡 Water Depth Requirement: To approximate "deep water waves" (where seabottom does not distort wave shape or celerity), depth should exceed half the model wavelength (d > L/2). Without exact wave periods, use this practical rule: Minimum depth ≥ 4 ft, ideally ≥ 8 ft. Shallower than 3 ft will introduce shallow-water celerity changes and bottom drag that invalidate the scaling.

📱 Recommended Android Apps for Motion Data

All smartphones contain 9-axis IMUs (accelerometer, gyroscope, magnetometer). Use these for CSV exportable telemetry:

Phyphox (Free, Academic-grade): Highly recommended. Developed by RWTH Aachen. Offers real-time plotting, exact sampling rate control, and clean CSV export. Has a custom "Roll/Pitch/Yaw & 3-Ax Accel" experiment template.
Physics Toolbox Sensor Suite (Free/Pro): Excellent for simultaneous logging of acceleration, gyroscope, light, and barometer. Very stable for bay deployments.
Sensor Log (Paid, ~$5): Lightweight, logs at configurable Hz, exports to CSV/JSON/GPX. Great for long-duration tests.

GoPro Telemetry Tip: GoPro HERO 9+ embeds raw gyro/acc data in the MP4 metadata. Use free desktop software like Gyroflow or Telemetry Dashboard (Mac) to extract high-frequency (200Hz+) stabilization and acceleration curves after testing.

📊 Acceleration Metrics & Full-Scale Translation

⚠️ Critical Froude Scaling Fact: Under Froude similarity, linear acceleration (a) and gravity (g) are SCALE-INVARIANT (1:1 ratio).

Model: 0.25 g  →  Full Scale: 0.25 g

Sliding Plates/Objects: Start sliding at ~0.20–0.30 g (depends on friction). If your model logger reads >0.25g peak lateral/forward acceleration, expect furniture/items to slide full scale.
Human Comfort / Seasickness Threshold: Sustained low-frequency accel > 0.30 g often induces nausea. Sharp jolts > 0.40 g feel "violent".
Jerk (da/dt): Scales by 1/√λ → Model jerk × 0.308 = Full-scale jerk rate. High jerk indicates slamming/impact loads.
Velocity: Scales by 1/√λ → 0.308. A 2.0 knot model reading ≈ 6.5 knots full scale.
Natural Frequencies: Scales by 1/√λ → 0.308. Measure roll/pitch periods on the model; multiply seconds by √10.5 ≈ 3.24 to get full-scale period.

🧍 Scale Reference Dolls

Standard human height (6 ft = 72 inches) scaled down: 72 ÷ 10.5 = 6.86 inches.

Ideal figure height: 6.9" (roughly 1:9.5 to 1:10 scale).
Commercial 7" action figures (GI Joe, Marvel Legends, Star Wars Black Series) are only 1-2% oversized. They are excellent for video scale reference and are readily available.
Standard 1:12 (6") dolls are acceptable but will appear slightly undersized in video.

🎥 Video Scaling & Frame Rates

Time scales as 1/√λ. Events on the model happen 3.24x faster than reality.

If you shoot at 60 fps, playback at ~18.5 fps (or slow timeline duration by 3.24x) to match full-scale visual perception.
Shore camera: Use optical tracker or fixed reference grid. Apply 3.24x time stretch in post.

🔍 Additional Measurement Recommendations

To extract professional-grade naval architecture data from your bay tests, consider adding:

Method	What it measures	Implementation Tip
AprilTags + Video	6-DOF pose (Heave, Pitch, Roll, Surge, etc.)	Print waterproof AprilTags, stick on deck/wings. Use TagTrack or OpenCV scripts to extract precise motion curves from shore video.
Micro Load Cell / Spring Scale	Mooring/Tether tension	Inline with human-held or mooring line. Calibrate in lbs/kg. Peak tension vs average drag reveals seastead resistance.
Potentiometer / Hall Sensor	Stabilizer elevator deflection & response lag	Mount tiny rotary pot on elevator pivot. Logs actuator effectiveness at model scale (note: angular velocities are ~3.24x faster full-scale equivalent).
Water Level Gauge	Exact local wave height & period	Ultrasonic rangefinder (waterproof) on shore pole or simple graduated staff. Synchronizes wave timing with seastead response.
Dual IMU Setup	Dampens sensor bias / validates structural twist	Place one IMU near front wing, one near back. Compare pitch/heave phase to detect hull flex or truss resonance.

✅ Quick Validation Checklist Before Launch:
1. Model weighs 35 ± 2 lbs & sits at exactly 50% leg draft.
2. RIM thrusters & elevators move freely at scale.
3. Android app logs at ≥50 Hz; phone securely vibration-damped (double-sided foam tape works well).
4. Shore camera includes a fixed reference ruler/known length for pixel-to-inch calibration.
5. Test tether uses elastic/surgical tubing to simulate realistic tension without introducing rigid-body reflection artifacts.

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