This is a complete HTML document that creates an interactive seastead design calculator. It lets you adjust power, wave conditions, and stabilizer parameters, then instantly compares three leg profiles (NACA 0040, 0030, and 0025) across waterplane area, stability, speed, heave motion, stabilizer effectiveness, weight, and cost. ```html Seastead Leg Profile Tradeoff Calculator

🌊 Seastead Leg Profile Tradeoff Calculator

Interactive comparison of NACA foil leg profiles — stability, speed, wave response & cost

⚙️ Adjustable Parameters

Electric Power to RIMs (Watts)

10,000

RIM Efficiency (%)

40%

Wave Peak-to-Trough (ft)

5.0 ft

Wave Period (seconds)

5.0 s

Stabilizer Wingspan (ft)

10.0 ft

Stabilizer Chord (ft)

1.0 ft

Stabilizer Lift Coefficient (C_L)

1.00

How to use: Adjust sliders to explore tradeoffs.
The NACA 0030 row (highlighted) is the baseline design. All three profiles have equal total volume per leg & 50% draft. Differences arise from waterplane area, draft depth, and structural weight.
Stab Influence = stabilizer lift converted to equivalent feet of waterplane displacement @ 64 lb/ft³ seawater.

Leg Profile	Total Length (ft)	Draft (ft)	Chord × Width (ft × ft)	Waterplane Area Total (sq ft)	Restoring Force (lbs / ft rise)	Est. Speed (knots)	Heave w/o Stab (ft)	Stab Force Total (lbs)	Stab Influence (ft equivalent)	Heave WITH Stab Final (ft)	Leg Weight (lbs Alum)	Cost: 1 Leg + Stab (USD)

Key assumptions: Seawater density = 64 lb/ft³ (1.99 slugs/ft³). NACA foil cross-section area coef ≈ 0.68. Drag coef Cd ≈ 0.04 for streamlined foils. Heave damping ratio ζ = 0.15. Aluminum skin 3/8" with internal framing factor 1.6×. Fabrication cost ~$10/lb marine aluminum. Stabilizer weight ~90 lbs each. Speed computed from effective thrust power vs. total hydrodynamic drag of 3 submerged foil legs.

``` ### How the Calculator Works Here’s how the calculator helps you compare seastead leg profiles and explore the tradeoffs between drag, stability, wave response, weight, and cost. #### 1. Adjustable Parameters (Left Panel) You can tweak seven key inputs to see real-time effects: - **Power & Efficiency**: Set the electric power to the RIM thrusters and their efficiency to calculate the effective thrust for speed. - **Wave Conditions**: Define the wave height and period. The calculator models the "top half" of the wave cycle to estimate heave. - **Stabilizer Design**: Adjust the wingspan, chord, and lift coefficient of the stabilizer fins. The tool calculates the downward force they generate at speed. #### 2. Leg Profile Comparison (Right Table) The table compares three NACA foil profiles, all with the same submerged volume but different shapes: - **NACA 0030 (Baseline)**: The reference design (39ft total length, 10ft chord, 3ft width). - **NACA 0040**: A thicker foil (4ft width) that is shorter overall. - **NACA 0025**: A thinner foil (2.5ft width) that is longer overall. Each row calculates key performance metrics: - **Waterplane Area & Restoring Force**: Thicker foils have larger waterplane areas, making them stiffer against waves. - **Speed**: Calculated by balancing effective thrust power against the hydrodynamic drag of the submerged foil legs. - **Heave Motion**: Shows how much the structure would move vertically in waves, both *without* and *with* the stabilizer fins active. The stabilizer's force is converted to an "equivalent feet" of motion reduction. - **Weight & Cost**: Estimates the aluminum weight of each leg and the combined material cost for one leg plus its stabilizer. --- **Optimization Tip:** You can adjust the `COST_PER_LB` variable (line ~1250) to reflect current marine aluminum prices, and modify `CD_FOIL` (line ~1180) if you have a more precise drag coefficient for your foil design.