GRP & Fibreglass Laminating: Hand Lay-Up, Spray Lay-Up & RTM

Quantum provides GRP/fibreglass lamination for bespoke parts, prototypes and repeat production.

Using hand lay, spray lay and RTM Lite, we match the process to the part, finish and volume.

That helps buyers assess suitability early and choose a practical route for production.

GRP & Fibreglass Laminating for Composite Manufacturing GRP laminating is the core process behind many fibreglass components in composite manufacturing. It suits bespoke work, repeat production and a wide range of part sizes and shapes. Features such as inserts, brackets and reinforcements can also be built in during production.
	Laminate Build-Up Affects Strength, Weight And Long-Term Performance. Glass choice, thickness, reinforcement and core materials all make a difference. The aim is to achieve the required stiffness, durability and finish without adding unnecessary weight. That is why fibreglass lay-up decisions are always specific to the application.
Our GRP Laminating Methods These are the different laminating methods we offer: Hand lay Spray lay RTM Lite	Hand lay suits many different parts and also suited to more complex components covering differing volume requirements. Spray lay can be a faster, lower cost option for larger, more open products. RTM Lite is a closed mould process that improves weight and thickness consistency while giving a smoother internal finish.
Starting with Moulds and Composite Gelcoats The quality of the finish is determined by the quality of the mould and the application of the gelcoat. Consequently, the mould construction and finish are a focus and priority at Quantum. The finest gelcoat finishes can match the gloss and visual quality of a painted finish. The first step is applying the gelcoat to the mould. The gelcoat may be applied by hand or by spray, and typically is black or white, but in many cases is also a coloured finish. We select gelcoats from leading suppliers, and give special attention during our lamination training to the quality and application of the gelcoats. This enables us to deliver a high quality finish, every time.
	Our Hand Lay Process This is the most common fibreglass laminating method; typically used for complex parts or where it is cost-effective. Projects which start with small volumes can be hand laid to begin with, and converted to other methods as volumes increase.
Once the gelcoat is sufficiently cured, fibreglass mat is wetted out with resin and laid on the mould and then “rollered” to ensure there are no air bubbles or cavities; this cures into a strong, stiff and lightweight product. The application of a controlled thickness fibreglass mat means that finished part thicknesses can be more tightly controlled than processes such as spray lay. Multiple layers of mat or other core material, such as foam, are applied to build up to the required thickness and strength.
	Spray Lay Lamination This can be a lower cost solution as it allows for a faster layup of parts and is typically suited to larger, more open products. It requires specialist equipment, more operator protection and effective extraction, together with a skilled operator to ensure the correct thickness with minimum build up in corners.
A specifically designed “Choppy gun” is then used to apply the fibreglass, resin and catalyst all at the same time. This is done by a trained operator, following a spraying pattern which deposits an even thickness of the fibreglass onto the mould; depth gauges are used to check the required thickness is achieved.	The glass is fed from continuous reels, which is chopped into short lengths in the gun head itself – hence the name ‘choppy gun’. Like hand lay-up, multiple layers can be built up to provide the required thickness and strength. Again, a topcoat can be added, and the part is left to cure before being extracted from the mould.
	Resin Transfer Moulding - RTM Lite Unlike spray and hand lay parts, RTM Lite is a closed mould process using an upper and lower mould, as opposed to just one mould with the spray/hand lay process. RTM Lite provides a step up in quality, offering better weight and thickness consistency, together with an excellent smooth internal surface finish. Whilst mould costs are higher due to there being two moulds, it is often a preferred choice on lower volume projects due to the advantages in consistency and inner surface finish. For larger volumes, RTM is an even more cost-effective solution.
The gelcoat is applied to one or both of the mould surfaces, with reinforcements and features fitted as needed onto either the upper or lower mould. The two halves are closed, and a vacuum applied to keep the mould sealed. The resin is then introduced into the mould with a specialised injection machine. A separate vacuum draws the resin into all parts of the mould where it is maintained until the part has cured. Once cured, we open the mould and extract the part, ready for trimming and finishing.
	Room for Innovation in Composite Lamination In a similar way with the other processes, we can create a broad range of parts with innovative features. For example, we can add foam insulating panels within the part, or build moulds that can generate multiple parts during one injection cycle. The biggest moulding we currently make is a trailer body shell which is big enough to drive a car into! This is believed to be the biggest single-shot RTM-Lite moulded part in the UK. After investing significant time and resource into challenging the norms of what was believed possible, Quantum were happy to showcase our technical ability in actually being able to consistently make parts of this size. Get a Quote
Additional Features Added During Lamination Features can be added into the part during the production stage such as bosses, threaded inserts, brackets, steel or wood reinforcements. Foam can also be moulded in to maintain stiffness while reducing weight and also as a noise or thermal barrier. An additional coat can be added to the inside of a part for hand or spray lay, known as top coat or flow coat. This is applied at the end of the process to provide a solid colour and smoother finish on the inside of the part.
	Whilst this improves the look, it is not a smooth gloss finish as it conforms to the undulations of the mat and resin. Once laminated, the part is allowed to cure, then removed from the mould for trimming and finishing. Typically, the part is cured sufficiently to remove from the mould after around three hours, but the product continues to cure over the following days. It’s important that the part is supported sympathetically during this curing stage to minimise any distortion. Quantum engineers make dedicated stands, jigs, trollies and stillages in house, all designed to support the parts safely and securely.
Consistency & Repeatability in GRP Laminating Consistency matters as much as part strength. Variation in a composite laminate can affect fit, finish and downstream work, so Quantum’s trained laminators use approved process sheets, regular thickness checks and stable mould support. This helps maintain repeatability across production runs.	Laminating for Bespoke vs Production Components One-off parts and prototypes need a flexible laminating approach, while repeat production needs a process that can hold quality across volume. Planning the composite lamination with future production in mind helps avoid unnecessary change later.
Integration with Tooling, Trimming & Finishing Because the finish quality is impacted by the mould quality and gelcoat application, laminating works best when planned alongside Tooling and Engineering. After cure, the part is removed for trimming and finishing, ready for assembly or bonding where needed.	Partnering with Quantum Quantum combines skilled laminators with in-house moulding support, so laminating decisions are backed by practical manufacturing knowledge. The focus is on consistent build quality, quality finishes and choosing the right process for each part, rather than forcing every job into the same method.
Discuss Your Lamination Requirements Early discussion helps define the laminate, finish level and production method before decisions become harder to change. Whether you are developing a new part or reviewing an existing one, Quantum can help assess the most suitable laminating route.