ENGINEERING TOOL

Bird net support calculator

Net sag and water clearance for bird nets supported by a central cylindrical tower. Adjust cage diameter, tower size, net spec and tension — read sag, lowest-point clearance and net area as you change the inputs.

Cross-section · live

LIVE

Taut profile
Sagged profile
Cage rim

Water clearance1.63mSafe

Lowest point1.63mfrom water surface

Sag0.87m6.7 % of strip length

Net area725m²31.9 kg

Min. tower height0.7mfor ≥ 0.5 m clearance

How the analysis is calculated

The bird net is modeled as a series of radial strips, each running from the tower top edge to the cage rim along a slant of length L = √(((D − d)/2)² + H²).
Each strip carries its own weight under tension T. Sag perpendicular to the slant: s = wL² / (8T), where w = net specific weight (kg/m²) × strip width × g.
Vertical sag component: sagVert = s × cos(α), where α = atan2(H, (D − d)/2). The lowest point is approximately at the strip midpoint.
Net specific weight is taken from the PP master table by twine and mesh, scaled by material density factor (PP base; PE 1.044, UHMWPE 1.066, PA 1.253). Hanging factor accounts for cutting allowance in total weight only, not in sag.
Estimates are indicative. Actual sag depends on installation tension uniformity, wet conditions, dynamic wave or wind loading, and net aging — none of which are modeled here.