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12/24/2025Can You Use Salvage Airbags in Shallow Water?
12/26/2025How Are the Inner Rubber Layer and Cord Fabric Layers Built in Ship Launching Airbags?
Ship launching airbags play a critical role in vessel launching, docking, and heavy ship movement. They support massive loads, absorb shock, and allow ships to roll smoothly into the water.
Although they look simple from the outside, ship launching airbags are actually high-performance composite structures. Their reliability depends mainly on two internal elements:
the inner rubber layer (air-tight layer) and the cord fabric reinforcement layers (load-bearing layers).
Let’s take a closer look at how they are built and why they matter.
1. Basic Structure of a Ship Launching Airbag
A typical ship launching airbag consists of three main parts:
- Inner rubber layer – keeps the air inside and maintains pressure.
- Cord fabric reinforcement layers – carry the load and resist internal pressure.
- Outer rubber layer – protects the airbag from abrasion, cuts, and environmental damage.
Each layer has a specific role:
the inner layer seals the air, the cord layers provide strength, and the outer layer protects everything.
In recent years, some manufacturers have upgraded the outer rubber compound, significantly improving abrasion resistance — in some cases by around 100% compared to traditional rubber. This makes a big difference when airbags are used on rough concrete slipways, sandy yards, or steel tracks.
At the same time, the reinforcement structure has also evolved. While standard airbags often use two-strand cord constructions, higher-end designs now use three-strand cords, which provide better fatigue resistance, higher safety margins, and improved load stability.
2. Inner Rubber Layer: What It Does and How It’s Made
Main functions
- Keeps the air inside (airtightness)
- Handles repeated inflation and deflation
- Resists aging, cracking, and fatigue
Material composition
The inner rubber is usually a blend of:
- Natural rubber (NR)
- Synthetic rubbers such as BR, SBR, or IIR
The blend is designed to balance airtightness, elasticity, and durability.
Thickness and process control
The rubber is calendered into sheets with controlled thickness. Too thin means leakage risk; too thick reduces flexibility.
3. Cord Fabric Reinforcement Layers
What they do
The cord layers act as the “skeleton” of the airbag. They:
- Carry the tensile forces from internal air pressure
- Support the ship’s weight
- Prevent bulging and bursting
Cord materials
Common materials include:
- High-tenacity polyester
- Nylon
- Aramid (for special high-performance applications)
Cord structure
Most standard ship launching airbags use two-strand cord structures. More advanced designs use three-strand cords, which offer:
- Higher residual strength if one strand fails
- Better fatigue resistance
- More stable stress distribution
Rubber–cord bonding
Cords are treated with bonding systems (such as RFL) so they adhere strongly to the rubber and don’t delaminate.
4. How the Layers Work Together
A good ship launching airbag is not just about strong materials — it’s about compatibility:
- Matching elasticity between rubber and cords
- Matching elongation behavior under load
- Matching aging and thermal behavior over time
Poor matching leads to internal shear, delamination, and early failure.
5. Structural Differences Between Standard and High-Quality Ship Launching Airbags
| Feature | Standard Airbags | High-Quality Airbags |
|---|---|---|
| Inner rubber | Basic airtight compound | Optimized low-permeation rubber |
| Cord structure | Two-strand cords | Three-strand or high-tenacity cords |
| Outer rubber | Standard abrasion resistance | Enhanced abrasion resistance |
| Manufacturing | Basic molding | Automated, tightly controlled curing |
6. How to Judge Quality from a Structural View
- Check cord material, cord count, and structure
- Ask about abrasion resistance of the outer rubber
- Look for pressure, fatigue, and burst test data
Most suppliers follow ISO 14409 as a reference. Some manufacturers design and test their ship launching airbags well above this standard and treat it as a baseline rather than a limit — which is why their products become benchmarks in the industry.
7. Conclusion
Ship launching airbags are not simple rubber products — they are engineered composite systems.
The inner rubber controls airtightness and lifespan.
The cord layers control strength and safety.
The outer rubber controls durability in real-world working conditions.
Understanding what’s inside the airbag is the key to choosing a safer, longer-lasting, and more cost-effective solution.
FAQ
Q1: What is the inner rubber layer made of?
It’s usually a blend of natural rubber and synthetic rubbers designed for airtightness, elasticity, and aging resistance.
Q2: Why are cord layers so important?
They carry the load, resist internal pressure, and prevent deformation or bursting of the airbag.
Q3: Is a three-strand cord better than a two-strand cord?
Yes. A three-strand structure provides higher safety margins, better fatigue resistance, and more stable load distribution.
Q4: What does ISO 14409 cover?
It specifies performance and testing requirements for ship launching airbags used in vessel launching and handling.
Q5: Does higher abrasion resistance really matter?
Yes. It significantly extends service life, especially on rough or abrasive working surfaces.