Purpose: Estimate the hydrodynamic drag of the three wing‑shaped buoyancy legs, compare it with a round cylinder of equal volume, and relate it to conventional displacement vessels of similar weight and length.
| Parameter | Value | Comment |
|---|---|---|
| Number of legs | 3 | One at each vertex of the triangular frame |
| Leg length (overall) | 19 ft | Vertical span from deck to tip |
| Submerged length (≈50 %) | 9.5 ft | Only the lower half contributes to hydrodynamic drag |
| Chord (horizontal fore‑aft) | 10 ft | Leading edge – trailing edge distance |
| Maximum thickness (height) | 3 ft | ≈30 % thickness‑to‑chord ratio → very blunt NACA‑type profile |
| Planform area per leg (submerged) | 10 ft × 9.5 ft = 95 ft² | Chord × submerged length |
| Total planform area (3 legs) | 3 × 95 ft² = 285 ft² | Reference area used for wing‑drag calculation |
| Water density (seawater) | ρ = 1.940 slug / ft³ | ≈64.3 lb / ft³ |
| Kinematic viscosity | ν = 1.05 × 10⁻⁵ ft² / s | ≈1.0 × 10⁻⁶ m² / s |
For a streamlined shape the drag force is expressed as:
where:
Dynamic pressure (q) is:
| Speed (knots) | V (ft / s) | V² (ft² / s²) | q (lb / ft²) |
|---|---|---|---|
| 4 kn | 6.75 ft / s | 45.6 | 44.2 lb / ft² |
| 6 kn | 10.13 ft / s | 102.6 | 99.5 lb / ft² |
A 30 % thickness‑to‑chord NACA‑type section is much blunter than a typical thin wing. Published data for thick NACA airfoils (e.g., NACA 0030) at Reynolds numbers of 5 × 10⁶–10⁷ give a profile‑drag coefficient (Cd,0) in the range 0.015 – 0.045. For the present estimate we adopt three representative values:
| Speed | Cd | Drag D (lbf) | Power* (hp) |
|---|---|---|---|
| 4 kn | 0.015 | ≈ 190 lb | ≈ 4.6 hp |
| 0.025 | ≈ 315 lb | ≈ 7.6 hp | |
| 0.045 | ≈ 570 lb | ≈ 13.9 hp | |
| 6 kn | 0.015 | ≈ 425 lb | ≈ 15.5 hp |
| 0.025 | ≈ 710 lb | ≈ 25.9 hp | |
| 0.045 | ≈ 1 280 lb | ≈ 46.7 hp |
*Power = D · V / 550 ft·lb / s · hp⁻¹.
A cylindrical float that displaces the same water volume (≈ 285 ft³ per leg) would have a diameter of about 6 ft and a submerged frontal area of 6 ft × 9.5 ft = 57 ft² per leg (171 ft² total). The drag coefficient for a smooth cylinder in cross‑flow in this Reynolds‑number regime is ≈ 1.0.
| Speed | Cylinder Drag (lbf) | Wing‑Leg Drag (mid‑estimate) | Drag‑Reduction Factor |
|---|---|---|---|
| 4 kn | ≈ 7 560 lb | ≈ 315 lb | ≈ 24 × |
| 6 kn | ≈ 17 000 lb | ≈ 710 lb | ≈ 24 × |
The wing‑shaped legs reduce drag by roughly one order of magnitude compared with a blunt cylindrical float of equal volume.
A typical 45‑ft trawler with a displacement of ~55 000 lb has a wetted surface area (WSA) of about 500 ft². Using a skin‑friction coefficient Cf ≈ 0.002 (moderately rough hull):
| Speed | Drag (lbf) |
|---|---|
| 4 kn | ≈ 70 lb |
| 6 kn | ≈ 150 lb |
Thus, the wing‑leg drag (mid‑estimate) is about 2 – 5 times higher than a conventional hull of similar weight.
An 80‑ft catamaran typically has two slender hulls (≈ 70 ft each) with a combined WSA ≈ 1 300 ft². With Cf ≈ 0.002:
| Speed | Drag (lbf) |
|---|---|
| 4 kn | ≈ 110 lb |
| 6 kn | ≈ 250 lb |
The wing‑leg drag is still modestly higher (≈ 3 – 4 ×) but in the same order of magnitude as a catamaran of comparable length.
The combination of a large triangular platform with three vertical wing‑shaped buoyancy legs is novel for seasteading applications. However, analogous ideas appear in related fields:
No commercial vessel or seastead design that the author is aware of combines a wide triangular deck with three vertical NACA‑profile wings intended primarily for low‑drag locomotion and solar‑panel real‑estate. The concept is therefore novel in this specific application.
| Aspect | Estimated Value | Interpretation |
|---|---|---|
| Drag coefficient of wing‑leg | 0.015 – 0.045 (mid ≈ 0.025) | Blunt NACA‑type profile, but still ≈ 25 × lower than a round cylinder |
| Total drag @ 4 kn | ≈ 190 – 570 lb (mid ≈ 315 lb) | Requires ~5–14 hp to overcome |
| Total drag @ 6 kn | ≈ 425 – 1 280 lb (mid ≈ 710 lb) | Requires ~16–47 hp to overcome |
| Drag vs. cylinder | ≈ 24 × lower | Significant advantage over simple pontoons |
| Drag vs. similar‑weight trawler | ≈ 2 – 5 × higher | Higher drag, but the platform offers vastly more deck area & solar exposure |
| Drag vs. similar‑length catamaran | ≈ 3 – 4 × higher | Comparable to a conventional multi‑hull, with added stability from three legs |
The wing‑shaped legs provide a large reduction in drag compared with conventional pontoons (≈ 20‑25 ×) while still delivering the required buoyancy. Their drag is higher than a sleek displacement hull or catamaran, but the trade‑off is acceptable given the massive exposed roof area for solar panels, the open porch design, and the inherent stability of a three‑point support. The concept is not presently in use, making it a potentially valuable innovation for mobile seasteads that need both low‑speed efficiency and large renewable‑energy capture.
All calculations are order‑of‑magnitude estimates based on standard hydrodynamics formulas. Final design should involve CFD modelling and model‑tank testing to refine the drag coefficient and to account for wave‑making, viscous effects, and appendage interactions.