What Is Yokohama Type Fender

A Yokohama type fender is a floating pneumatic rubber fender—a cylindrical, air-filled, cord-reinforced marine buffer that absorbs berthing energy between a ship and a dock or between two vessels. The name comes from The Yokohama Rubber Co., which commercialized the design in the 1950s; today “Yokohama type fender,” “Yokohama fender,” and “pneumatic rubber fender” are used interchangeably, with performance governed by ISO 17357-1:2014.

Why Is It Called “Yokohama Type” and Not Just “Pneumatic Fender”

Yokohama Rubber pioneered the compressed-air marine fender using tire-cord and rubber-tank technology. Because the brand became the global benchmark, buyers still say “Yokohama type” even when procuring from any ISO-compliant manufacturer.

Key naming logic:

• Yokohama® fender = original branded product
• Yokohama type fender = generic shape/compliance class (pneumatic, floating)
• Pneumatic rubber fender = technical standard term
• Floating pneumatic fender = emphasizes self-buoyancy at the waterline

 

In a purchase spec, “Yokohama type” alone is not enough—always state ISO 17357-1:2014, P50 or P80, diameter × length, and net/sling type.

How a Yokohama Type Fender Works

It uses an air-spring principle, not solid-rubber compression:

1. Vessel approaches → fender floats at waterline, tethered by sling or chain pendant
2. Hull contact → reinforced rubber body compresses
3. Internal air pressure rises uniformly (no local buckling)
4. Kinetic energy converts to air compression + elastic cord-layer strain (up to ~70% absorbed)
5. Reaction force stays low → protects hull and quay
6. Vessel backs off → air re-expands, fender recovers shape

 

At the ISO test point of 60% deflection, makers publish GEA (Guaranteed Energy Absorption) and R (reaction force). A 2500 × 5500 mm P50 fender gives ~943 kJ GEA at ~2019 kN reaction.

Internal Structure (ISO 17357-1 Four Layers)

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The body is vulcanized seamless; chains or slings attach to flanges, never the rubber skin.

Types of Yokohama Type Fenders

Net Type (ISO Type I – Chain & Tire Net)

Chain/wire net with used tires or rubber sleeves around the body.

• Use: VLCC/LNG STS, permanent berths, rough seas
• Pros: Longest abrasion life, hardest impact tolerance
• Size range: Ø500 mm – Ø4500 mm

 

Sling Type (ISO Type II – No Net)

Thick outer rubber + integral lifting slings.

• Use: Yachts, naval, cruise, calm-water temporary berthing
• Pros: Lightweight, non-marking options, fast deploy
• Size range: Ø500 mm – Ø3300 mm[ccitation:2]

 

Hydro-Pneumatic Fender

Part air, part water ballast, held vertically submerged.

• Use: Submarines, low-freeboard hull contact, naval sub-surface ops
• Always custom-engineered

 

P50 vs P80 (Initial Pressure Class)

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Never inflate a P50-rated body to 80 kPa—cord angle and end-ring safety factor differ.

Yokohama Type vs Foam vs Solid Fender

• Yokohama / pneumatic: air spring, floating, low reaction, deflatable for shipping
• Foam-filled: closed-cell foam, floating, no pressure upkeep, heavier
• Solid rubber (cell/cone): fixed to quay, no tidal tracking, higher hull pressure

 

Pneumatic wins for STS, tidal STD, and sensitive hulls.

Where Yokohama Type Fenders Are Used

• Ship-to-ship (STS) crude/LNG/product transfers
• Ship-to-dock (STD) tidal wharves and marginal berths
• FPSO / FSU offloading
• SPM and CBM buoy mooring
• Naval berthing and submarine tendering
• Offshore wind CTV docking
• Emergency lay-by fenders

 

How to Specify One Correctly

Minimum compliant line item:

Yokohama type pneumatic rubber fender, ISO 17357-1:2014, P50, 3300 × 6500 mm, Type I chain-tire-net, with BV prototype test, safety valve, mill cert.

Verify: GEA/R at 60% deflection, cord specification, relief valve on ≥Ø2500 mm, third-party class report (ABS/BV/DNV/CCS/LR).

Maintenance Basics

• Check pressure monthly (±10% of rated)
• Inspect chain nets/tire wear every 3–6 months
• Wash salt, store shaded, away from ozone/heat
• Keep safety valve functional
• Typical service life: 6–10 years with correct care

FAQ

Is Yokohama type fender the same as pneumatic rubber fender?

Yes. “Yokohama type” is the generic trade-origin name; “pneumatic rubber fender” is the ISO technical name. Both mean a floating, air-filled, cord-reinforced marine fender.

What does P50 mean on a Yokohama fender?

P50 means the initial internal air pressure is 50 kPa at 20 °C per ISO 17357-1:2014. P80 means 80 kPa.

Do all Yokohama fenders float?

Yes—by definition a pneumatic Yokohama type fender is self-floating and tracks tide/swell. Fixed “Air Block” variants exist but are not the floating pneumatic class.

How long does a Yokohama type fender last?

6–10 years typical, depending on pressure discipline, net type, and UV exposure.

To choose between a chain-through, cylindrical, and pick-up offshore mooring support buoy, start from the load path: if the mooring chain must pass axially through the float and share tension, specify a chain-through buoy (CTB); if the chain or hose attaches to end fittings and the buoy only lifts a span, use a cylindrical foam buoy (CUB); if you only need to mark and retrieve a submerged line end, a pick-up buoy (PUB) is enough. Size every option by net buoyancy, not gross diameter, and set SWL from the steelwork, not the foam.

This guide gives offshore engineers and procurement a repeatable way to pick the right type, calculate buoyancy, and avoid the spec mistakes that sink SPM and cable-lay jobs.

Support Buoy Basics Before You Compare Types

A foam-filled offshore support buoy is a closed-cell PE/EVA foam core + central steel strength member + PU/polyurea skin. The foam gives permanent displacement; the steel tube, gussets and flanges take tension; the skin resists abrasion, UV and seawater. Puncture the skin and the closed cells still float—unlike air-chambered or steel hollow buoys.

Three facts that decide type selection:

• Foam never carries tensile load. SWL comes from the central tube and end fitting cert.
• Net buoyancy ≠ gross buoyancy. You must subtract the buoy’s own weight in water.
• Type follows geometry of the line. Axial chain-through = CTB. End-to-end pendant = CUB. Messenger/retrieval = PUB.

Chain-Through vs Cylindrical vs Pick-Up: Side-by-Side

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Sources: typical CTB/CUB/PUB spec sheets list 1.5–4.5 t CTB, 1–4 t CUB, 90 kg–1 t PUB classes.

Step 1 — Define What the Buoy Must Lift

List the submerged element:

• Mooring chain diameter & grade (e.g. 76 mm studlink, Grade 3)
• Hose OD + fill (oil-filled hose ≈ 3× empty submerged weight)
• Subsea cable or umbilical wet weight per metre
• Rope/pendant submerged weight

Only the segment the buoy suspends counts, not total scope.

Step 2 — Calculate Net Buoyancy (Not Gross)

B_net = ρ_sw · g · V_displaced − W_buoy Required: B_net ≥ W_submerged_line + F_freeboard_reserve

• ρ_sw ≈ 1025 kg/m³
• W_submerged_line = length × (air weight − buoyancy of that line)
• F_freeboard_reserve = 30–50 % of B_net, to cover tide, current drag, marine growth, bird/rope load

Working rule: load the buoy to 50–60 % of net buoyancy; keep the rest as reserve. A 76 mm chain span of ~20 m submerged weighs ~2.4 t; with hose patch + freeboard reserve, specify a CTB-3500 (3.5 t net), not a 2.5 t class.

Step 3 — Match Type to Load Path

• Chain passes through and must stay centred under tension → CTB with central tube ID cleared for your chain + locking plate/pin.
• Load is end-to-end (hose float, dredge pipe, cable lay float) → CUB with swivel/pad-eye/clevis ends.
• You only need to find and pull up a buried mooring tail → PUB 90 kg–1 t, often with pick-up rope eye.

Do not specify a PUB for SPM midline. Do not specify a CTB when the chain runs alongside a hose—CUB handles it cheaper.

Step 4 — Set SWL from Steelwork

SWL = 1/4–1/5 of steel assembly MBL (tube + flanges + shackle/swivel). Foam diameter does not set SWL. For a 76 mm chain SPM, typical CTB swivel SWL is 10–15 t class with 3.5 t net buoyancy—because the buoy lifts weight but the steel sees dynamic slack-load spikes.

Step 5 — Environment Inputs That Change the Class

• Tidal range > 4 m → bigger freeboard reserve
• Current > 2 kn → treat drag as extra downward static load
• Hs > 2 m → thicker PU (5–10 mm), nylon-reinforced skin option
• Ice / tandem berthing → nylon-filament PU, larger diameter
• Tropical fouling → 10-year PU, plan freshwater rinse

Step 6 — Material Spec Checklist

• Core: cross-linked closed-cell PE or EVA, thermo-laminated on mandrel
• Steel: ST52 central tube, gussets, load flanges, HDG or epoxy
• Skin: 3–10 mm PU elastomer, optional nylon-reinforced
• End fittings: swivel, pad-eye, clevis, crucifix, chain locking plate/pin; WLL cert per item
• Markings: owner tag, net buoyancy, SWL, chain size, year, color per terminal HSE

Decision Shortcut

• SPM terminal, chain is the lifted element → CTB
• Hose/cable/dredge pipe span, end fittings → CUB
• Marking, retrieval, messenger line → PUB
• Mixed hose + chain alongside → CUB for hose, CTB for chain, never one buoy doing both jobs

Common Sizing Mistakes

• Using gross buoyancy in the datasheet instead of net buoyancy
• Loading buoy to 85 % of net lift “because static calc allows it” → zero freeboard in swell
• Matching tube to chain diameter but not to shackle OD through the tube
• Setting SWL from foam diameter
• Forgetting oil-filled hose submerged weight

FAQ

Q: Can a cylindrical buoy replace a chain-through buoy in SPM?

A: Only if the chain does not pass through the buoy and attaches externally to end fittings rated for the load. In most SPM mid-line designs the chain is axial, so CTB is required.

Q: How much net buoyancy for a 76 mm chain SPM mid-line?

A: After catenary calculation, 2.5–4.5 t class CTB per station is typical; never size on chain weight alone—add freeboard reserve.

Q: Is a pick-up buoy a support buoy?

A: Technically yes, but it is a light-duty subtype (90 kg–1 t) for line-end retrieval and marking, not for suspending mooring chain load.

Q: Foam-filled or steel air-can buoy?

A: Foam-filled. Air chambers burst; closed-cell PE/EVA stays unsinkable after skin puncture.

 

Ship Launching Airbags: How to Select the Right Marine Rubber Airbag for Safe Vessel Launching

Marine rubber airbags—also called ship launching airbags, pneumatic rollers, or inflatable marine airbags—have replaced traditional slipways in hundreds of shipyards worldwide. They roll heavy vessels from build site to water with lower cost, faster setup, and no permanent civil works.

But choosing the wrong airbag specification leads to dangerous failures: burst bags, hull damage, or launch abort. This guide gives you the engineering basics, sizing formulas, and procurement checklist to get it right the first time.

What Are Ship Launching Airbags?

A ship launching airbag is a cylindrical, reinforced rubber tube inflated with compressed air to support and move a vessel. The body consists of:

• Inner rubber layer – seals air, resists seawater and abrasion
• Synthetic tire-cord layer(s) – nylon 6 or polyester, 1400dtex/3, providing tensile strength
• Outer rubber layer – protects against abrasion, UV, and impact during rolling

Standard sizes range from 0.8 m to 2.5 m in diameter and 6 m to 26 m in effective length. Working pressure typically sits at 0.08–0.12 MPa, with a safety factor of ≥3:1 per ISO 14409.

Note: “Marine rubber airbag” and “pneumatic roller” are interchangeable terms in most specifications. When sourcing, confirm the supplier uses the exact terminology matching your classification society’s requirements.

How Airbag Launching Works

The process follows a predictable sequence:

1. Block removal – wooden or steel support blocks under the hull are removed, leaving the vessel resting on deflated airbags.
2. Inflation – compressors fill airbags to target pressure (monitored by calibrated gauges).
3. Rolling – the vessel moves down the inclined way as airbags deform and rotate beneath the hull.
4. Water entry – the hull floats free; airbags are recovered, deflated, and stored for reuse.

A single set of airbags can launch vessels from tens of tons to over 10,000 tons, depending on specification and quantity.

Key Specifications Buyers Should Verify

Diameter and Effective Length

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Cord Layers (Ply Rating)

Cord layers determine burst pressure. Common configurations:

• 4–5 layers – light duty, small craft
• 6–8 layers – standard commercial launching
• 10–12 layers – heavy vessels, high safety margin

Each synthetic tire-cord layer (nylon 6, 1400dtex/3) provides a minimum breaking strength of ≥310 N per cord. Total burst pressure scales with layer count.

Working Pressure and Safety Factor

Per ISO 14409, minimum safety factor is 3:1 (burst pressure ÷ working pressure). For a 0.10 MPa working pressure, the bag must withstand ≥0.30 MPa in hydrostatic burst test.

How to Calculate Airbag Quantity for Your Vessel

Use this simplified engineering approach:

Step 1 – Determine total hull weight (lightship + outfitting margin + water trapped in hull)

Step 2 – Estimate contact area

Contact width ≈ Diameter × 0.6 (empirical deformation factor) Contact length ≈ sum of effective lengths of all airbags Total contact area = Contact width × Contact length

Step 3 – Calculate required airbag count

Single airbag load capacity = Working pressure × Contact width × Effective length × Safety derating (0.7–0.8) Required count = Total vessel weight ÷ Single airbag load capacity

Example – 500-ton barge, 1.5 m diameter, 12 m effective length, 0.10 MPa working pressure:

• Contact width ≈ 0.9 m
• Single bag capacity ≈ 0.10 MPa × 0.9 m × 12 m × 0.75 ≈ 81 kN ≈ 8.3 tons
• Required count ≈ 500 ÷ 8.3 ≈ 60 airbags (distribute along keel and bilge)

Pro tip: Always add 15–20% buffer above calculated count. Slope irregularities, uneven inflation, and tidal timing all introduce variables you can’t fully control on launch day.

ISO 14409 vs CB/T 3795: What Certificates Importers Should Ask For

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When importing, request:

• Mill test certificate for rubber compound
• Hydrostatic burst test report (video evidence preferred)
• Third-party inspection (CCS, BV, ABS, or DNV) if required by your flag state
• Traceability code on each airbag body

Ship Launching Airbags vs Concrete Slipway: Cost & Site Comparison

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For shipyards launching under 5,000 tons, airbags typically deliver 60–80% cost savings over building a slipway.

Common Failure Modes and How to Avoid Them

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Pre-Launch Inspection Checklist

[ ] Visual inspection – no cuts >50 mm, no cord exposure

[ ] Pressure hold test – inflate to 1.1× WP, hold 30 min, pressure drop <5%

[ ] Relief valve calibrated and installed

[ ] Pressure gauges certified within 12 months

[ ] Slope gradient verified by surveyor

[ ] Tide and wind forecast checked (launch window)

[ ] Recovery boat and crew on standby

[ ] Emergency stop procedure briefed to all personnel

FAQ

How many times can a ship launching airbag be reused?

With proper storage and operation, 80–200 cycles. Inspect after every 10 launches; replace if cord layers show through outer rubber or burst pressure degrades below 2.5× WP.

Can airbags launch a vessel on a sandy or muddy beach?

Yes, but the slope must be graded and compacted. Loose sand increases rolling resistance and can abrade the outer rubber. Lay geotextile or steel plates if ground is soft.

What is the minimum water depth required for airbag launching?

Rule of thumb: water depth at the launch point should be ≥1.5× vessel draft + 0.5 m safety margin. Check local tidal range and launch at high tide if possible.

Do I need classification society approval for airbag launching?

For commercial vessels, most flag states require the launching procedure to be reviewed by a classification society (CCS, BV, ABS, DNV, etc.). The airbags themselves should carry ISO 14409 compliance documentation.

What compressor capacity is needed?

Total air volume = number of airbags × internal volume per airbag. A 1.5 m × 12 m airbag holds ~21 m³. For 60 bags, you need ~1,260 m³. Size compressors to fill all bags within 2–3 hours. Typical setup: 2–3 units at 10–15 m³/min each.

About [Qingdao Ronsen Marine Supplies Co.,Ltd]

[Qingdao Ronsen Marine Supplies Co.,Ltd] has supplied marine rubber airbags to shipyards in [regions/countries] since [year]. Our airbags are manufactured to ISO 14409 standards with nylon 6 cord layers, hydrostatic burst tested, and certified by [CCS/BV/ABS]. We provide technical calculation support and on-site supervision for vessel launching projects.

Need a custom airbag specification for your vessel? Contact our engineering team at [sales@ronsen-marine.com/+86 183 5328 0885] or request a quote through our [Ship Launching Airbags].

[Marine Rubber Airbags] – “View our full range of ISO 14409 marine rubber airbags”

[Rubber Fenders] – “Related: marine fender systems for dock protection”

[Contact/Quote page] – “Get a free airbag quantity calculation for your vessel”

 

ISO 17357 pneumatic fender sizes are the nominal diameter × length combinations (in mm) defined for floating pneumatic rubber fenders under ISO 17357-1:2014 (high-pressure 50 kPa / 80 kPa grades) and ISO 17357-2:2014 (low-pressure ≤7 kPa grade). The most common catalogue range is Ø500 × L1000 mm up to Ø4500 × L12000 mm, with performance rated at 60 ± 5 % deflection.

A size like “3300 × 6500” means a fender 3.3 m in diameter and 6.5 m long—not a cube, not an inner-air volume. Diameter drives hull contact area and reaction force; length drives total energy absorption.

ISO 17357-1:2014 Standard Nominal Sizes (High-Pressure P50 / P80)

All values below are minimum guaranteed energy absorption (GEA) and reaction force (R) at 60 % deflection, taken from the standard supplier performance table. Tolerance on GEA/R is ±10 %.

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Non-standard intermediate sizes (600×1000, 700×1500, 1200×2000, 1350×2500, 1700×3000, 3000×5000/6000, 3500×6000/7000, 3600×7200) are also manufactured and certified to the same deflection basis.

ISO 17357-2:2014 Low-Pressure Sizes (≤7 kPa)

Part 2 covers a separate low-pressure product class:

• Clamped-end type: diameter ≤ 2.3 m
• Moulded-end type: diameter ≥ 2.8 m
• Initial pressure 7 kPa unless otherwise agreed
• Same GEA-at-60 %-deflection principle, but different body construction and test regime (leakage, compression recovery >97 %, 3000-cycle durability)

Buyers often confuse “ISO 17357 fender” with “Yokohama fender.” Yokohama is a brand origin; ISO 17357-1 compliance is the spec that matters on a purchase order.

P50 vs P80: Same Size, Different Performance

For the same diameter and length, an 80 kPa fender absorbs ~35–40 % more energy but pushes harder on the hull.

• P50 (50 kPa): lower reaction force, lower hull-surface pressure → LNG, aluminium hulls, yachts, navy, sensitive coatings.
• P80 (80 kPa): higher GEA per fender → large tonnage, high approach velocity, limited fender count.
• Never inflate a P50 body to 80 kPa. Cord-layer safety factor and end-ring design differ between grades.

Example: 3300 × 6500 mm

• P50: 1814 kJ / 3015 kN
• P80: 2532 kJ / 3961 kN

That is why “size alone” never specifies a fender—you must state ISO part + type + initial pressure.

Dimensional Tolerances & Marking (ISO 17357-1)

• Diameter tolerance: +10 % / −5 %
• Length tolerance: +10 % / −5 %
• Measured at rated initial pressure, mid-body average of ≥2 points
• Mandatory marking on body: ISO 17357 part, nominal size, initial pressure (50/80 kPa), serial no., maker, year
• Safety relief valve required at Ø ≥ 2500 mm (optional below if ordered)

Net Type vs Sling Type (Does Not Change Size Table)

ISO 17357-1 defines types by external protection, not by size:

• Type I – Net type: chain-tire net, wire net, or rope net (most common Ø1000 mm+)
• Type I Single: net on one end, metal-free other end
• Type II – Sling type: heavy nylon slings, no hard net, gentler on hull paint (preferred for LNG/yacht)

The GEA/R numbers in the size table apply to the rubber body; net/sling only changes abrasion protection and handling.

How to Choose the Right ISO 17357 Size

1. Calculate design berthing energy (PIANC method: displacement × velocity² × coefficient).
2. Pick a size whose P50 or P80 GEA ≥ design energy × safety margin (usually 1.1–1.25×).
3. Check reaction force R against wharf foundation and hull-panel allowance.
4. Check hull pressure reference value (122–208 kPa in table) against vessel shell limit.
5. Confirm Ø ≥ 2500 mm → safety valve included.
6. Choose net vs sling by hull finish and quay roughness.

Rule of thumb:

• Tug / pilot: 500×1000 to 1000×2000
• Feeder / ro-ro: 1500×3000 to 2000×3500
• Panamax / Aframax: 2500×4000 to 2500×5500
• VLCC / LNG / STS: 3300×6500, 3300×10600, 4500×9000

FAQ (add FAQPage schema for rich snippet)

Q: What is the largest standard ISO 17357 pneumatic fender size?

A: Ø4500 × L12000 mm is the largest commonly catalogued high-pressure size; 4500×9000 is also standard. Larger bespoke units are made but need prototype classification approval.

Q: Are ISO 17357 fender sizes in inches or mm?

A: Always millimetres in the standard (e.g., 3300×6500 mm). Suppliers may quote imperial equivalents but PO must use mm.

Q: Does longer length always mean more energy absorption?

A: For the same diameter, yes—roughly linearly. But reaction force rises with diameter faster than length, so 2500×5500 absorbs more than 2000×3500 despite smaller Ø? No: 2500×5500 (P50 943 kJ) > 2000×3500 (308 kJ). Diameter dominates R; length dominates GEA.

Q: Can I order a non-standard size like 3600×7200?

A: Yes. Custom sizes inside the 500–4500 mm Ø and 1000–12000 mm L envelope are produced, but they require the manufacturer’s certified prototype test, not a straight interpolation of the table.

Q: Is ISO 17357-1:2014 still current?

A: Yes—published 2014, confirmed in 2024. ISO 17357-2:2014 remains the low-pressure companion standard.

 

What Is UHMW-PE Facing Fender Pad?

A UHMW-PE facing fender pad (Ultra-High Molecular Weight Polyethylene facing fender pad) is a thick, machined plastic sheet fixed to the front face of steel fender panels, rubber fenders, lock walls, bridge buttresses, and jetty structures. It acts as the low-friction, wear-resistant contact layer between a vessel hull and the berthing structure.

Unlike timber, rubber, or steel facings, a UHMW-PE fender facing fender pad does not rot, rust, splinter, or stick. Its molecular weight typically ranges from 3 to 9 million g/mol, giving it a unique mix of self-lubrication, impact absorption, and saltwater immunity.

In plain terms: when a ship rubs against a quay, the UHMW-PE pad lets the hull slide instead of scrape—protecting both the boat and the dock.

Why “Facing Fender Pad” and Not Just “Plastic Sheet”?

• Facing = it is the exposed surface that takes the hit.
• Pad = it is a discrete, bolt-on module (not the whole fender).
• UHMW-PE = the polymer grade, not standard HDPE or PP.

Common synonyms Google indexes together:

UHMWPE fender face pad, UHMW PE fender liner, marine fender facing board, UHMW-PE rub strip, dock bumper facing, wharf fender panel pad.

Key Properties of UHMW-PE Facing Fender Pads

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Where Are UHMW-PE Facing Fender Pads Used?

1. Wharf & jetty fender panels – bolted to Super Cell, Cone, V, D, and Arch fenders.
2. Lock gates & canal walls – mitre protection, rub strips, entrance guards.
3. Bridge buttress protection – absorbs tug and barge impact.
4. Offshore platforms & dolphins – survive wave fatigue and UV.
5. Shipyard dry docks – protect hull from steel frames.
6. Workboat beltings & slipways – low-friction launch surfaces.

UHMW-PE Facing Fender Pad vs Rubber / Steel / Timber

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Source data consolidated from marine fender suppliers.

Installation Basics

• Substrate: clean, flat steel panel (SS316 bolts from rear).
• Hole pattern: countersunk or recessed slots, CNC-drilled to match panel.
• Thermal gap: leave side clearance—UHMW-PE expands ~0.02% per °C.
• Thickness: 20–100 mm typical; 6–150 mm customizable.
• Colors: black standard; blue/yellow/red for visibility.

FAQ (add FAQPage schema for rich results)

Q: What does UHMW-PE stand for?

A: Ultra-High Molecular Weight Polyethylene, a polyethylene with chain weight above 1.5 million g/mol, usually 3–9 million in marine pads.

Q: Is UHMW-PE facing fender pad better than HDPE?

A: Yes for fendering. UHMW-PE has far higher impact strength, abrasion resistance, and low friction than HDPE.

Q: Can UHMW-PE pads be used in cold climates?

A: Yes. They stay tough down to -60 °C to -200 °C depending on grade, with no brittle cracking.

Q: How long does a UHMW-PE fender facing last?

A: Field data shows 15+ years in seawater; rubber fenders alone last 5–8 years, so pads extend system life 2–3×.

Q: Are UHMW-PE facing fender pads recyclable?

A: Yes, 100% recyclable, non-toxic, IMO-compliant, no heavy metal leach.

Buyer’s Mini-Checklist (capture transactional intent)

When sourcing a UHMW-PE facing fender pad, ask for:

• Virgin marine-grade resin (not recycled filler)
• Molecular weight cert (3M+)
• Friction coeff. test (ASTM D1894)
• UV stabiliser confirmation
• CNC hole template drawing
• ISO 9001 / REACH / RoHS or SGS/DNV report

ISO 17357 pneumatic fender sizes are the nominal diameter × length combinations (in mm) defined for floating pneumatic rubber fenders under ISO 17357-1:2014 (high-pressure 50 kPa / 80 kPa grades) and ISO 17357-2:2014 (low-pressure ≤7 kPa grade). The most common catalogue range is Ø500 × L1000 mm up to Ø4500 × L12000 mm, with performance rated at 60 ± 5 % deflection.

A size like “3300 × 6500” means a fender 3.3 m in diameter and 6.5 m long—not a cube, not an inner-air volume. Diameter drives hull contact area and reaction force; length drives total energy absorption.

ISO 17357-1:2014 Standard Nominal Sizes (High-Pressure P50 / P80)

All values below are minimum guaranteed energy absorption (GEA) and reaction force (R) at 60 % deflection, taken from the standard supplier performance table. Tolerance on GEA/R is ±10 %.

[supsystic-tables id=17]

Non-standard intermediate sizes (600×1000, 700×1500, 1200×2000, 1350×2500, 1700×3000, 3000×5000/6000, 3500×6000/7000, 3600×7200) are also manufactured and certified to the same deflection basis.

ISO 17357-2:2014 Low-Pressure Sizes (≤7 kPa)

Part 2 covers a separate low-pressure product class:

• Clamped-end type: diameter ≤ 2.3 m
• Moulded-end type: diameter ≥ 2.8 m
• Initial pressure 7 kPa unless otherwise agreed
• Same GEA-at-60 %-deflection principle, but different body construction and test regime (leakage, compression recovery >97 %, 3000-cycle durability)

 

Buyers often confuse “ISO 17357 fender” with “Yokohama fender.” Yokohama is a brand origin; ISO 17357-1 compliance is the spec that matters on a purchase order.

P50 vs P80: Same Size, Different Performance

For the same diameter and length, an 80 kPa fender absorbs ~35–40 % more energy but pushes harder on the hull.

• P50 (50 kPa): lower reaction force, lower hull-surface pressure → LNG, aluminium hulls, yachts, navy, sensitive coatings.
• P80 (80 kPa): higher GEA per fender → large tonnage, high approach velocity, limited fender count.
• Never inflate a P50 body to 80 kPa. Cord-layer safety factor and end-ring design differ between grades.

Example: 3300 × 6500 mm

• P50: 1814 kJ / 3015 kN
• P80: 2532 kJ / 3961 kN

That is why “size alone” never specifies a fender—you must state ISO part + type + initial pressure.

Dimensional Tolerances & Marking (ISO 17357-1)

• Diameter tolerance: +10 % / −5 %
• Length tolerance: +10 % / −5 %
• Measured at rated initial pressure, mid-body average of ≥2 points
• Mandatory marking on body: ISO 17357 part, nominal size, initial pressure (50/80 kPa), serial no., maker, year
• Safety relief valve required at Ø ≥ 2500 mm (optional below if ordered)

Net Type vs Sling Type (Does Not Change Size Table)

ISO 17357-1 defines types by external protection, not by size:

• Type I – Net type: chain-tire net, wire net, or rope net (most common Ø1000 mm+)
• Type I Single: net on one end, metal-free other end
• Type II – Sling type: heavy nylon slings, no hard net, gentler on hull paint (preferred for LNG/yacht)

The GEA/R numbers in the size table apply to the rubber body; net/sling only changes abrasion protection and handling.

How to Choose the Right ISO 17357 Size

1. Calculate design berthing energy (PIANC method: displacement × velocity² × coefficient).
2. Pick a size whose P50 or P80 GEA ≥ design energy × safety margin (usually 1.1–1.25×).
3. Check reaction force R against wharf foundation and hull-panel allowance.
4. Check hull pressure reference value (122–208 kPa in table) against vessel shell limit.
5. Confirm Ø ≥ 2500 mm → safety valve included.
6. Choose net vs sling by hull finish and quay roughness.

Rule of thumb:

• Tug / pilot: 500×1000 to 1000×2000
• Feeder / ro-ro: 1500×3000 to 2000×3500
• Panamax / Aframax: 2500×4000 to 2500×5500
• VLCC / LNG / STS: 3300×6500, 3300×10600, 4500×9000

FAQ (add FAQPage schema for rich snippet)

Q: What is the largest standard ISO 17357 pneumatic fender size?

A: Ø4500 × L12000 mm is the largest commonly catalogued high-pressure size; 4500×9000 is also standard. Larger bespoke units are made but need prototype classification approval.

Q: Are ISO 17357 fender sizes in inches or mm?

A: Always millimetres in the standard (e.g., 3300×6500 mm). Suppliers may quote imperial equivalents but PO must use mm.

Q: Does longer length always mean more energy absorption?

A: For the same diameter, yes—roughly linearly. But reaction force rises with diameter faster than length, so 2500×5500 absorbs more than 2000×3500 despite smaller Ø? No: 2500×5500 (P50 943 kJ) > 2000×3500 (308 kJ). Diameter dominates R; length dominates GEA.

Q: Can I order a non-standard size like 3600×7200?

A: Yes. Custom sizes inside the 500–4500 mm Ø and 1000–12000 mm L envelope are produced, but they require the manufacturer’s certified prototype test, not a straight interpolation of the table.

Q: Is ISO 17357-1:2014 still current?

A: Yes—published 2014, confirmed in 2024. ISO 17357-2:2014 remains the low-pressure companion standard.

If you’ve ever watched a large ship dock, you’ve seen the silent workhorses that make it all possible: rubber fenders. Among the many types available, the D rubber fender (often simply called a “D fender”) is one of the most common and versatile. This guide explains everything you need to know about D-type rubber fenders, from their basic definition to their key benefits and typical uses.

What is a D Rubber Fender?

A D rubber fender is a marine bumper named for its “D”-shaped cross-section. Unlike cylindrical fenders which are round, the D fender features a flat back and a curved, semi-circular front. This shape is not just for aesthetics—it is a functional design that offers unique advantages for berthing and mooring operations.

Typically made from high-quality extruded rubber, D fenders are known for their simplicity, durability, and ease of installation. They are often bolted directly to the side of a dock or vessel, providing a reliable cushioning effect.

How Does a D Rubber Fender Work?

The primary function of any rubber fender is to act as a buffer that absorbs kinetic energy. When a ship makes contact with a dock, it carries significant momentum. Without protection, this impact can damage both the vessel’s hull and the port infrastructure.

Here is how a D rubber fender works:

1. Energy Absorption: When a vessel hits the fender, the curved front of the “D” shape compresses. This compression absorbs the ship’s berthing energy.
2. Force Reduction: By absorbing this energy, the fender reduces the reaction force transferred back to the ship and the dock, minimizing the risk of structural damage.
3. Impact Distribution: The fender helps distribute the impact load over a larger area of the ship’s hull, preventing concentrated stress points that could cause indentation or cracking.

Key Benefits and Characteristics of D Fenders

D fenders are a popular choice in the maritime industry for several reasons:

· Simple and Easy Installation: They can be securely mounted using bolts or flat steel fasteners directly to the structure.
· High Durability: Made from tough rubber compounds like natural rubber, SBR, or EPDM, they resist seawater, sunlight, and ozone, ensuring a long lifespan.
· Wide Range of Applications: They are suitable for various vessels and dock types.
· Customization: D fenders can be extruded in long lengths and cut to size, drilled, or even pre-curved to meet specific project requirements.
· Cost-Effective: Compared to more complex fender systems like cell or cone fenders, D fenders are generally an affordable and effective solution for lower-impact applications.

Common Applications: Where Are They Used?

Because of their versatility, D rubber fenders are used across the maritime industry:

· Tugboats and Workboats: They are frequently installed along the hulls of tugboats, ferries, and patrol boats that make frequent contact with other vessels and docks.
· Small Docks and Harbors: D fenders are an excellent choice for fishing harbors, marinas, and inland waterway docks where smaller vessels are present.
· Jetties and Wharves: They offer reliable protection for small craft jetties and general-purpose wharves.
· As a Protective Band: Small to medium-section D fenders are often used as a continuous protective band along the structures of workboats and barges.

D Fenders vs. Other Types

While D fenders are highly effective, they are best suited for specific scenarios. Here is how they compare to other common rubber fenders:

[supsystic-tables id=14]

How to Choose the Right D Rubber Fender

Selecting the correct fender involves considering several factors:

1. Vessel Size and Weight: Larger, heavier ships generate more berthing energy and may require larger or more D fenders.
2. Docking Speed: The speed at which the vessel approaches the dock directly impacts the energy that needs to be absorbed.
3. Dock Structure: The type of dock or pier and the available mounting space will influence your choice.
4. Environmental Conditions: Consider the weather, water salinity, and UV exposure to select the appropriate rubber compound.

Conclusion

The D rubber fender is a fundamental component of marine protection. Its simple, effective design offers a robust and economical solution for protecting vessels and dock structures in a variety of low-to-medium-impact scenarios. Whether used on a tugboat or a small harbor dock, the D fender remains a trusted choice for maritime professionals worldwide.

Pneumatic vs Foam Fenders: Which Marine Fender Actually Fits Your Berth (2026 Guide)

Choosing between pneumatic and foam-filled fenders is not a spec-sheet footnote—it decides how much downtime, puncture repair, and hull-pressure risk your port, yard, or offshore project absorbs over the next 10 years. Both are “marine fenders,” but they behave nothing alike under cyclic wave load, STS impact, or permanent pile mooring.

This guide breaks down the real-world difference, when each type fails, and how we at Ronsen Marine specify them for clients running ports, OSV fleets, and yacht pontoons.

What Is a Pneumatic Fender?

A pneumatic fender is an inflatable, compressed-air marine fender built from reinforced rubber-nylon plies (Yokohama-type). Impact energy is absorbed by air compression, giving a low reaction force / high energy absorption curve that is friendly to lightweight hulls.

Core traits

• Air-filled, needs inflation pressure checks (typically 50–80 kPa)
• Linear load-deflection, excellent under cyclic (wave) conditions—air doesn’t creep
• Lightweight, easy to relocate, popular for STS (ship-to-ship) and temporary berths
• Puncture = loss of performance; needs spare units and patrol inspection

Ronsen’s pneumatic rubber fender line follows ISO 17357-1S/2S geometry for STS and quay use.

What Is a Foam-Filled Fender?

A foam fender has a closed-cell EVA/PE foam core wrapped in polyurea/PU skin with nylon reinforcement—no air, no inflation. Energy is absorbed by foam compression.

Core traits

• Unsinkable, zero puncture risk, zero pressure maintenance
• Higher abrasion/UV/oil resistance via polyurea skin—good for high-traffic docks
• Heavier, higher upfront cost, but near-zero lifecycle service
• Foam slowly recovers after compression; under permanent cyclic load it can creep, so it’s better as floating/offshore than fixed permanent pile fender

Ronsen builds netless sling type, cushion netted (chain+tire), donut pile fenders, and suitcase pendant foam buoys for offshore mooring.

Pneumatic vs Foam Fenders: Side-by-Side

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When to Pick Pneumatic

• Ship-to-ship transfer where fenders move between vessels daily
• Large tankers/bulk carriers needing low hull pressure at high energy
• Temporary project berths (dam construction, salvage) where you deflate and redeploy
• Budget-sensitive first buy with crew available for weekly pressure checks

When to Pick Foam-Filled

• Offshore platforms, windfarm SOVs, OSV side fendering—no one wants a midnight puncture
• Pile/donut applications with tidal rise-fall and turning dolphins
• Yacht marinas and barge fleets where “maintenance-free” beats “cheap”
• High-abrasion environments (tire nets, construction barges, rock dumping)

Rule of thumb: pneumatic wins on cyclic permanence + portability; foam wins on abuse tolerance + zero maintenance.

Common Spec Mistakes Buyers Make

1. Sizing by diameter only—ignore energy/reaction curve vs hull panel strength.
2. Using foam fenders as fixed permanent fenders under constant swell (creep risk).
3. Running pneumatic fenders with no spare—one puncture halts berthing.
4. Ignoring skin chemistry: polyurea > old PU for oil + UV zones.

FAQ

Are foam fenders better than pneumatic?

Not universally. Foam is better for maintenance-free offshore/pile use; pneumatic is better for cyclic STS and portable deployment.

Do foam fenders sink if damaged?

No. Closed-cell EVA/PE core stays buoyant even if skin is cut—unlike pneumatic, which deflates.

Can pneumatic fenders be used permanently?

Yes, but only with scheduled pressure checks and spare inventory; air fatigue is not the issue—rubber-nylon body wear and punctures are.

Which is cheaper long term?

Foam usually wins TCO over 8–10 yrs because no puncture repair, no spares rotation, no labor patrol.

Does Ronsen make both types?

Yes—pneumatic rubber fenders (ISO Yokohama type) and foam-filled fenders (netless, netted, donut, shipboard portable). See Ronsen foam fenders and pneumatic range.

How Shipyards Choose the Right Marine Airbags: Step-by-Step Selection Guide

Choosing the right marine airbags is the difference between a safe 2-hour vessel launch and a hull-damaging, insurance-triggering failure. Modern shipyards no longer treat ship launching airbags as commodity rubber tubes—they specify them like structural components.

This guide breaks down how shipyards choose the right marine airbags using vessel parameters, ISO 14409 compliance, diameter/ply math, layout logic, and supplier vetting.

Why Airbag Selection Is an Engineering Decision

Marine rubber airbags bear the full displacement weight of a vessel across a deformed contact patch. Undersize them and you get:

• Excessive compression (>30%) → cord-layer fatigue
• Pressure spike beyond working pressure → burst risk
• Uneven hull support → keel bending stress

A correct selection balances rated working pressure (WP), bearing capacity per meter (kN/m), diameter vs block height, and number of bags × spacing.

Step 1: Define the Vessel Parameters First

Never size an airbag before locking these:

[supsystic-tables id=12]

Example: a 440-ton Ro-Ro ferry (Lpp 42.5 m, B 12.5 m, Cb 0.55) needs a different matrix than a 8,000 DWT barge.

Step 2: Use the Standard Sizing Logic (Diameter → Length → Ply)

Diameter (D)

Rule of thumb from yard practice:

Airbag diameter should be at least 0.3–0.5 m larger than keel block height so the hull clears blocks before rolling.

Common diameters: 0.8 m, 1.0 m, 1.2 m, 1.5 m, 1.8 m, 2.0 m, up to 2.5 m.

Effective Length (EL)

EL must be ≥ vessel beam for single-row layout; if EL < beam, use staggered or double-row.

Standard EL: 6–18 m (custom to 24 m+).

Cord Layers / Ply Rating

Ply count sets working pressure and bearing capacity:

[supsystic-tables id=13]

A 1.5 m × 15 m 6-layer bag runs ~0.13–0.18 MPa WP and ~110–140 kN/m bearing at safe compression.

Step 3: Run the Bearing-Capacity Check

Simplified selection formula used in yard engineering:

N = K1 × Q × g / (Cb × R × Ld) + N_backup

• N = number of airbags
• K1 = safety factor ≥ 1.2
• Q = vessel weight (ton)
• R = allowable unit bearing capacity (kN/m)
• Ld = effective contact length per bag (m)
• N_backup = 2–4 spare bags

If calculated compression at WP exceeds ~25–30% of D, go up one diameter or add one ply layer.

Step 4: Verify ISO 14409 and Class Certifications

Shipyards procuring for classed projects must reject non-certified bags. Minimum checks:

• ISO 14409:2011 – international standard for ship launching air bags (materials, burst test, compression-recovery, marking)
• Class society approval – CCS, BV, DNV, ABS, LR depending on flag
• Mill test reports – rubber tensile ≥18 MPa, elongation ≥400%, cord strength traceability
• Burst pressure ≥ 2× WP, reputable makers run 3× test

Qingdao-based ISO 14409 factories dominate export supply, but audit before bulk order.

Step 5: Match Airbag Layout to Hull Geometry

Selection is not just per-bag—it is system layout:

• Single row – EL ≥ beam
• Staggered – 0.5×beam ≤ EL < beam
• Double row – beam > 2×EL, or catamaran/barge
• Center spacing ≤ 6 m for steel hulls, min spacing ≥ πD/2 + 0.3 m
• Pre-inflation leak test: <5% pressure loss in 1 h

Step 6: Vet the Supplier Like a Class Surveyor

A shipyard’s purchasing checklist:

1. 10+ years dedicated airbag production (not general rubber)
2. Provides calculation sheet for your vessel, not just a quote
3. OEM options: valve type, end ring, 1260D/1670D cord, color marking
4. Warranty 12 months + on-site launch support availability
5. Reference project list with DWT and launch method (side/end/haul-out)

Low price per bag is irrelevant if WP is overstated by 0.02 MPa.

Quick Selection Cheat Sheet

• Fishing boat 30–80 ton → D1.0×L10m, 4-layer, 5–6 pcs
• 300 ton workboat → D1.2×L12m, 6-layer, 6–8 pcs
• 2,000 ton landing craft → D1.5×L15m, 6-layer, 10–12 pcs
• 10,000 DWT barge → D1.8–2.0m, 7–8 layer, 14–18 pcs staggered
• 50,000+ DWT → engineered matrix, 2.0–2.5 m, QS grade, class-witnessed

Always add 2–4 backup airbags per launch.

FAQ (Snippet Targets)

How do shipyards calculate marine airbag quantity?

Using vessel weight, block coefficient, contact length, and allowable kN/m bearing, with a safety factor ≥1.2 and 2–4 spare bags.

What ply rating is best for ship launching?

4–5 ply for small boats, 6–8 ply for mid-size vessels, 9–10+ for heavy barges and large ships. Ply count tracks working pressure.

Is ISO 14409 mandatory?

Not by law everywhere, but required by most classed shipyards and international buyers. It governs materials, burst test, and marking.

Can one airbag size fit all launches?

No. Diameter depends on block height, length on beam, ply on weight. Reusing wrong-size bags is a top cause of launch incidents.

What Is an Arch Rubber Fender? The Practical Engineer Guide (2026)

An arch rubber fender is a solid, arched-cross-section marine fender mounted on quays, pile dolphins, lock walls, or vessel hulls to absorb berthing energy and lower reaction force during docking. Its curved profile spreads impact across a wider face than a flat D-fender, yet stays simpler and cheaper than a cone or cell unit—making it the default choice for fishing harbors, ferry terminals, workboat jetties, and retrofit projects under roughly 10,000–50,000 DWT.

This guide explains what it is, how it absorbs energy, where it beats (or loses to) cone and cell fenders, and how to size one using PIANC / ISO 17357 logic.

What Is an Arch Rubber Fender (Definition)

An arch rubber fender is a single-piece molded solid rubber element with an inverted-U or arch cross-section. It is bolted to a steel mounting plate, often with a UHMW-PE front face panel to cut hull friction.

Core parts:

• Rubber body – natural rubber (NR) / SBR blend, 60%+ NR content for 15–20 yr life
• Steel base plate – anchors to concrete or steel quay
• Optional UHMW-PE pad – low-friction contact face
• Bolts / shear chains – resist pull-out and lateral shear

Unlike pneumatic or foam fenders, it has no air, no bladder, no moving parts—just elastic deformation.

How an Arch Rubber Fender Works

When a vessel touches the berth:

1. The arch cross-section compresses vertically, converting kinetic energy into heat inside the rubber.
2. The curved legs spread reaction force sideways, avoiding stress concentration on the quay face.
3. At rated deflection (usually 50–60% of free height), it returns most of its shape—no permanent set if within design load.
4. UHMW-PE face lets the hull slide instead of gripping, reducing berthing shear.

Typical solid-rubber arch performance band:

• Energy absorption: 15–80 kJ per unit (small–medium berths)
• Reaction force: moderate, higher than cone, lower than cylindrical
• Hull pressure: low–moderate
• Service life: 10–20 years with 6-month visual checks

Arch Fender vs Cone vs Cell (Quick Table)

[supsystic-tables id=10]

Arch wins on price + simplicity; loses on energy density per kg.

Where Arch Rubber Fenders Are Used

• Fishing ports and small craft harbors
• Ferry terminals and Ro-Ro side berths
• Workboat / pilot boat jetties
• Lock chamber walls and corner dolphins
• Retrofit of old quay walls with low allowable reaction
• Inland barge terminals

They are not for 100k+ DWT tankers or high-velocity VLCC berths—use cone or cell there.

How to Size an Arch Fender (PIANC Logic, Simplified)

You do not guess size from a photo. Use the standard berthing energy formula:

E = 0.5 × Cm × M × Vb² × Ce × Cc × Cs

Where:

• Cm = added mass factor (1.3–2.0)
• M = vessel displacement (tonnes)
• Vb = normal berthing velocity (m/s)
• Ce / Cc / Cs = eccentricity, configuration, softness factors

Then:

1. Calculate design energy E (kN·m)
2. Pick arch unit whose catalog energy at 50% deflection ≥ E
3. Check reaction force R ≤ quay allowable
4. Check hull pressure ≤ class approval (usually < 200 kPa for small craft)
5. Space units at ≤ 12–15 m or 0.15 × vessel length

💡 Most specifiers oversize by 20–30% for tidal skew and operator error.

Installation & Maintenance Basics

Install:

• Mount above low-tide line for inspection
• Torque bolts 100–200 Nm, re-check after 3 months
• Horizontal on straight walls, vertical on piles, angled at corners
• Add shear chain if tidal range > 3 m

Maintain:

• Visual check every 6 months (cracks, abrasion, bolt rust)
• Clean salt/debris quarterly
• Re-coat steel parts per ISO 12944 every 2–5 yrs
• Replace if deflection recovery drops below 50% of rating

Arch Rubber Fender FAQ

Is an arch fender the same as a D-fender?

No. Arch has a taller curved leg profile and better energy-per-kilo; D-fender is a flattened D-shape for light craft and narrow edges.

What rubber quality should I specify?

Minimum PIANC G3-type compound: tensile ≥15 MPa, elongation ≥350%, hardness 60±5 Shore A, compression set ≤25% after 70°C×22h.

Can arch fenders handle angled berthing?

They tolerate small skew (≤5°) acceptably. For 10°+ angular hits, cone fenders are better.

How long do they last?

10–15 yrs in high-traffic fishing ports, 15–20 yrs in moderate ferry use, if virgin NR blend and not overloaded.