Hexbeam Mast Input Form
Example Data Table
| Scenario | Height | Tube OD | Wind | Hexbeam Area | Guy Levels |
|---|---|---|---|---|---|
| Backyard light mast | 30 ft | 1.75 in | 80 mph | 7 sq ft | 0 |
| Standard guyed mast | 35 ft | 2 in | 90 mph | 8.5 sq ft | 1 |
| Exposed roof edge | 40 ft | 2.5 in | 110 mph | 10 sq ft | 2 |
Formula Used
Wind pressure: q = 0.00256 × V² × G × Kz
Wind force: F = q × Cd × A
Unguyed base moment: M = Fant × Hant + Fmast × Hmast / 2
Guy horizontal capacity: R = (WLL / SFguy − pretension) × cos(θ) × effective guys × levels
Design moment: Md = max(0, M − R × Hguy)
Tube inertia: I = π / 64 × (Do⁴ − Di⁴)
Section modulus: S = I / (Do / 2)
Bending stress: fb = Md × 12 / S
Axial stress: fa = vertical load / tube area
Mast safety factor: SF = yield strength / (fb + fa)
Tip deflection: Δ = P × L³ / (3EI) + w × L⁴ / (8EI)
How to Use This Calculator
- Enter the real mast height, outside diameter, wall thickness, and material properties.
- Add the hexbeam projected area, weight, mount offset, and accessory weight.
- Choose wind speed, gust factor, exposure factor, and drag coefficients.
- Add ice values only when ice load should be included.
- Enter guy line details if the mast uses guys. Use zero guy levels for unguyed checks.
- Enter base moment capacity from a bracket, pier, frame, or engineered support.
- Press the calculate button. Review results above the form.
- Download the CSV or print the result as a PDF for project notes.
Hexbeam Mast Planning Notes
A hexbeam looks gentle on the roof line, but wind still treats it as a broad frame. The mast must resist sideways pressure, antenna weight, ice, coax weight, and twisting from the mount. Good planning starts with realistic numbers. Height is important because moment grows as force acts farther above the base. A small increase in mast height can raise stress sharply.
Wind and Structure Basics
Wind pressure rises with the square of wind speed. That means a high design speed has a large effect. The calculator uses projected area, drag coefficient, gust factor, and exposure factor. These inputs help the estimate match open yards, roof edges, or sheltered sites. The mast tube is checked with its outside diameter, wall thickness, yield strength, and elastic modulus. A larger diameter usually improves stiffness more than a small increase in wall thickness.
Guy Support and Base Demand
Guy wires can lower base moment when they have proper angle, height, and working load. The tool estimates horizontal guy resistance from allowable line tension. It then reduces the base moment within that capacity. This is still a simplified model. Real guy anchors need soil checks, deadman sizing, corrosion protection, and proper turnbuckles. Roof brackets also need framing checks, not only sheathing screws.
Reading the Output
The result compares unguyed moment, guyed moment, bending stress, axial stress, deflection, foundation margin, and guy safety. A low safety factor means the mast is too flexible, too thin, too tall, or too exposed. Try reducing height, increasing diameter, adding guys, or using a stronger tube. Deflection matters because movement can fatigue clamps and loosen fasteners. Compare several scenarios before purchase. Check one calm site case, one exposed case, and one ice case. Save the worst demand for review.
Practical Construction Advice
Use conservative wind speed values. Include future coax, rotator load, brackets, and ice where relevant. Do not rely on nominal pipe size alone. Verify actual outside diameter and wall thickness. Inspect welded seams, holes, and corrosion. Place guys symmetrically when possible. Keep anchors aligned with guy loads. Record every assumption, including terrain, antenna area, and guy spacing. Share the values with a licensed designer when the mast is tall, roof mounted, or near people. Use engineered drawings before buying steel, guys, or anchors.
Frequently Asked Questions
What does this calculator estimate?
It estimates wind pressure, hexbeam force, mast force, base moment, tube stress, deflection, guy line demand, and safety factors for a hexbeam antenna mast.
Can I use it for an unguyed mast?
Yes. Set guy levels to zero. The calculator will use the unguyed base moment and ignore guy reaction in the final mast check.
What wind speed should I enter?
Use a conservative local design wind speed. Roof edges, open terrain, hills, and coastal sites often need higher values than sheltered backyards.
Why is projected area important?
Projected area converts wind pressure into side force. A larger hexbeam area creates higher force, higher base moment, and greater mast bending stress.
Does the tool include mast wind?
Yes. It estimates mast projected area from height and diameter. It then adds mast wind force as a distributed load acting at mid height.
How are guy wires handled?
The calculator estimates allowable horizontal guy reaction from line rating, target safety factor, pretension, angle, effective windward guys, and guy levels.
What is a good mast safety factor?
Higher is better. Many practical checks aim above 1.5 for rough screening. Important or exposed structures should be reviewed by a qualified professional.
Does it design the foundation?
No. It compares design moment against a capacity you enter. Anchor bolts, roof framing, piers, soil, and brackets still need separate design.
Should I include ice load?
Include ice when the site can see freezing rain or heavy icing. Ice adds weight and can increase wind area, stress, and deflection.
Can this replace an engineered design?
No. It is a planning calculator. Use it for early sizing and comparison. Tall, roof mounted, public, or risky installations need professional review.
Why does deflection matter?
Large movement can loosen clamps, fatigue connections, change antenna aim, and damage coax. A stiff mast usually performs better during gusts.