Views: 22 Author: Site Editor Publish Time: 2025-12-29 Origin: Site
In the specification and procurement of SOLAS-compliant marine safety equipment, clarity is critical. When browsing datasheets for lifeboats and rescue boats, you will often see the hull material listed as FRP. However, when speaking with engineers or reading technical comparisons, the term GRP is frequently used.
Are they different? And more importantly, does the material choice matter for your fleet's safety and compliance?
This technical guide clarifies the terminology used in modern shipyard specifications and analyzes why Glass Reinforced Plastic (GRP) remains the superior engineering choice for survival craft across the global maritime industry.
Terminology Check: FRP vs. GRP
Before evaluating the benefits, we must address the most common question from procurement officers: "The spec sheet says FRP, but I am looking for GRP. Is this the same vessel?"
The short answer is: Yes.
FRP (Fiber Reinforced Plastic): This is the broader industry category. It refers to any polymer matrix reinforced with fibers.
GRP (Glass Reinforced Plastic): This is the specific type of FRP used in SOLAS marine equipment. It specifies that the reinforcement fiber is Glass (Fiberglass).
At New Marine, when our technical documents refer to FRP, we are specifically referring to a high-grade GRP composite system. Whether you are deploying a totally enclosed lifeboat or a fast rescue boat, the fundamental material science is the same: a robust composite engineered for the marine environment.
Deconstructing the Material: What Goes Into a Hull?
A "fiberglass" boat is not made of a single material. It is a composite laminate structure. Understanding these layers helps shipowners appreciate why a GRP lifeboat is virtually unsinkable and maintenance-friendly.
1. The Matrix (The Resin)
The "plastic" part of GRP. Manufacturers utilize specific fire-retardant resins (typically polyester or vinylester blends) that cure into a hard, chemically resistant solid.
Corrosion Resistance: This resin acts as the primary barrier against saltwater. Unlike steel which oxidizes, the cured resin is chemically inert and immune to rust.
Fire Safety: The matrix is mixed with specialized fire-retardant additives, ensuring the hull structure maintains its integrity even in high-temperature environments.
2. The Reinforcement (The Glass)
The "muscle" of the boat. If you were to look at the raw materials in a workshop, you would see rolls of woven roving and chopped strand mat.
Woven Roving: A fabric that provides high tensile strength, allowing the boat to withstand the immense G-forces of launching and water entry.
Chopped Strand Mat: A random-fiber mat that provides multi-directional strength and ensures a watertight, seamless bond between the layers.
3. The Buoyancy (The Core)
The "lifeline" of the vessel. The void space between the inner and outer GRP shells is filled with high-density polyurethane foam.
Monocoque Structure: The foam bonds chemically to the GRP skin, creating a solid, single-piece unit that is significantly stronger than a hollow shell.
Unsinkability: The closed-cell foam is hydrophobic (repels water). Even if the outer GRP skin is punctured, the foam prevents water ingress, ensuring the boat remains buoyant.
Engineering Advantages of GRP for Lifeboats and Rescue Boats
Why has the industry largely moved away from steel and aluminum for standard survival craft? The answer lies in the material physics.
1. Elastic vs. Plastic Deformation
Steel/Aluminum: Subject to plastic deformation. If a metal hull hits the ship’s side during a rough recovery, it dents permanently. That dent creates a stress concentration point that compromises structural integrity.
GRP: Exhibits elastic behavior. Upon impact, the composite laminate can flex to absorb the energy and spring back to its original shape. For lifeboats and rescue boats operating in rough seas, this resilience is a critical safety factor.
2. Corrosion and Electrolysis
Steel/Aluminum: Highly reactive to the marine environment. Steel oxidizes (rusts), requiring constant painting, while Aluminum is prone to rapid galvanic corrosion (pitting) if exposed to stray currents or dissimilar metals.
GRP: Chemically inert and non-conductive. It is immune to both rust and electrolysis. This "install and forget" characteristic drastically reduces the maintenance burden and eliminates the risk of hidden hull degradation.
3. Thermal Conductivity
Steel/Aluminum: High thermal conductivity. In a fire scenario, metal hulls transfer external heat rapidly (Aluminum conducts heat 4x faster than steel), quickly turning the interior cabin into an oven.
GRP: Natural thermal insulator. The composite hull acts as a thermal barrier, significantly slowing heat transfer. This buys precious minutes for survivors inside the craft to escape a burning oil slick or endure extreme cold.
Maintenance Reality for GRP: Ensuring Operational Readiness
While GRP is often marketed as "maintenance-free" compared to steel, it is strictly speaking, "low-maintenance." To ensure a service life of 20+ years and compliance with SOLAS regulations, specific care protocols must be followed.
1. Gelcoat Preservation
The outer orange layer (Gelcoat) is the shield that protects the structural laminate.
The Threat: Prolonged UV exposure causes "chalking," where the resin surface degrades into a white powder, making the hull porous.
The Fix: Wash the hull with freshwater monthly to remove salt crystals (which act as magnifying glasses for UV rays). Apply a high-quality marine wax annually to seal the pores and maintain the high-visibility orange color required by LSA codes.
2. Impact Management and Elasticity
Because GRP is rigid, it handles stress differently than metal.
The Threat: Hard impacts with the davit or the boat's side can cause "star cracks" (crazing) in the gelcoat. While often cosmetic, deep cracks can allow water to wick into the glass fibers.
The Fix: Inspect the hull after every drill. Use a SOLAS-approved GRP repair kit (resin and hardener) to seal any deep scratches immediately. Unlike welding steel, this cold-work repair can be safely performed by the crew onboard.
3. Preventing Rust Bleed
A GRP hull doesn't rust, but the fittings attached to it might.
The Threat: Stainless steel fittings (handrails, hatch hinges) can suffer crevice corrosion, causing unsightly rust streaks to bleed onto the GRP.
The Fix: Inspect all hull penetrations and bedding compounds annually. Polish stainless steel fittings to maintain their passive layer. If rust stains appear on the GRP, use an oxalic acid-based cleaner to remove them without damaging the gelcoat.
Conclusion
Whether your datasheet lists it as FRP or GRP, the material science remains the same. You are choosing a vessel engineered for the harsh reality of the ocean: salt, sun, and impact. At New Marine, our manufacturing process is designed to maximize the properties of this material—using hand lay-up techniques to ensure high glass content and structural consistency across our entire product range.
Need a replacement boat that fits your existing davits? Contact our expert team to discuss our full range of SOLAS-compliant GRP lifeboats and rescue boats and find the best fit for your needs.
