Triangular Seastead Scale Model Analysis

Wave Height Analysis

Based on the video footage and relative proportions (comparing wave crests to the 8-inch diameter floats):

        Estimated Model Wave Heights: 2 to 4 inches (0.05 - 0.10 m)

        Equivalent Full-Scale Wave Heights: 12 to 24 inches (0.3 - 0.6 m)

        Note: These represent moderate sea states (Sea State 2-3) at full scale.

The waves in the test represent 1-2 foot seas at full scale—conditions where a 60-foot vessel would normally cruise comfortably but where smaller craft might experience noticeable motion.

Dynamic Characteristics Analysis

Current Configuration (1/3 Submergence)

With the legs only 33% submerged, your model has approximately:

Displacement: ~50-60 kg (110-130 lbs) total
Waterplane Area: 0.10 m² (150 in²)
Heave Natural Period (Model): ~1.4 seconds
Heave Natural Period (Full Scale): ~3.4-3.6 seconds

Critical Finding: A 3.5-second heave period is quite short for a 60-foot vessel. This places the natural period near the peak energy of typical coastal wave spectra (4-6 second waves), potentially causing resonance and "hobby-horsing" behavior.

Target Configuration (2/3 Submergence)

With twice the ballast (double displacement, same waterplane):

Mass increases by: 2×
Heave Period increases by: √2 ≈ 1.41×
New Heave Period (Full Scale): ~4.9-5.1 seconds

T_heave = 2π√(m / ρgA)
If m → 2m, then T → T×√2

Comparative Seakeeping Analysis

Parameter	Your Seastead (Light)	Your Seastead (Ballasted)	50 ft Catamaran	60 ft Monohull
Beam (Width)	60 ft (triangle)	60 ft (triangle)	25-28 ft	16-18 ft
Heave Period	3.5 s	5.0 s	4.5-6.0 s	5.5-7.0 s
Roll Period	6-8 s	8-11 s	8-12 s	10-14 s
Pitch Stiffness	Very High (widely spaced columns)		Moderate	Moderate
Motion Type	Heave-dominant, low pitch/roll		Heave + Pitch	Roll + Pitch

Key Differences:

Stability: Your 60-foot triangular platform has roughly 3-4× the beam of a monohull and 2× a catamaran. This creates exceptional roll stability and very long roll periods (comfortable, slow rolling).
Heave Response: Unlike boats that plane or have shaped hulls, your cylindrical legs act like "spar buoys"—stiff in heave with high vertical accelerations if the period is wrong.
Pitch/Yaw: The tripod arrangement creates high pitch stiffness. The platform will resist tipping (low pitch amplitude) but may experience higher vertical accelerations at the corners compared to the center.

Acceleration Analysis

Under Froude scaling, accelerations are identical in model and full scale. The video shows the time-scaled motion, so the "feel" of the accelerations you see is representative of full scale.

Current Light Condition Estimates:

a_max ≈ (2π/T)² × z_max
Where T = 3.5s, z_max ≈ 0.3m (1 ft heave in 2 ft waves)
a ≈ 0.97 m/s² ≈ 0.10g average, 0.15-0.20g peaks

Compared to conventional vessels in 2-foot seas:

60 ft Monohull: 0.05-0.08g (smoother, longer period)
50 ft Catamaran: 0.08-0.15g (can be "snappy" due to light displacement)
Your Seastead (Light): 0.10-0.20g (quick heave response)

Sensation: The light configuration likely feels "busier" or more "jiggly" than a heavy boat. The short 3.5-second period means the platform tracks the wave surface closely, creating frequent, short-duration vertical impulses.

Predicted Ballasted Condition:

With 2× Ballast (2/3 submergence):

Heave period increases to ~5.0 seconds
Peak accelerations drop by 30-40% (to ~0.06-0.12g)
Motion becomes "heavier" and more muted
The platform will "filter out" shorter waves better, riding over them rather than following every ripple

Physics Explanation: Doubling the mass increases the inertia while keeping the buoyancy spring rate constant. The system becomes more "sluggish"—it takes longer to oscillate, and for the same wave height, the amplitude of motion decreases (inertial filtering), reducing peak accelerations.

Predictions for Your Next Test

When you add ballast to achieve 2/3 submergence, you should observe:

Slower Oscillations: The model will bob up and down roughly 30% slower (period increasing from ~1.4s to ~2.0s in model time).
Reduced "Chatter": High-frequency motion should disappear. The legs will pierce the water surface more deliberately rather than skimming/bouncing.
Deeper Draft Effect: With 32" draft instead of 16", the center of gravity lowers and the waterplane inertia increases, improving stability.
Wave Transparency: In the same wave field, the ballasted model should show smaller heave amplitude relative to wave height—appearing more "planted" in the water.

        Success Metric: If your target is ocean livability, the ballasted version should feel similar to a heavy 60-foot trawler yacht—slow, predictable motions with low angular accelerations in roll/pitch, and moderate vertical accelerations in heave.
    

Recommendations

Add the Ballast: The math strongly favors the heavier configuration. The 5-second heave period places you in the "sweet spot" between typical wave periods (avoiding resonance) and acceptable responsiveness.
Wave Period Avoidance: At full scale, avoid operating in areas with dominant wave periods of 4-5 seconds (short, steep chop) as this matches your ballasted heave period. Open ocean swell (8-12s) will be much more comfortable.
Comparison Advantage: Unlike the catamaran (which can slam bridging decks) or the monohull (which rolls), your design offers unique "platform stability"—excellent for stationary living, though potentially stiffer in heave than conventional hulls.