How Fibreglass Pools Are Made
How is a Fibreglass Swimming Pool shell made?
The fibreglass pool shell is effectively a one-piece structure made of various layers of fibreglass materials, all melded together. The swimming pool shell typically ends up about 5+mm thick.
The Mould of Swimming Pools
Fibreglass pools are constructed from a mould in our factory. At Pools for Africa, our moulds are made of fibreglass and reinforced on the inside. We start with an orange mould underneath and layer the pool shell on top of it in reverse order, rather than constructing the shell on the inside of a mould. The process is referred to as open mould manufacturing. Before manufacturing of a pool can begin, the mould is thoroughly cleaned and polished to give the pool its smooth shiny finish.
The first layer to be applied to the mould is the mosaic. The chosen mosaic is attached to the mould and then saturated with a clear gel coat (see below) containing UV stabilisers to protect the mosaic in the harsh African summers.
The Gelcoat of Fibreglass Pools
The finish on the inside of the pool is what you see when the pool is in the ground for you to swim in. It’s the second chemical solution to be applied to the mould and is applied as a gel (hence the name: gelcoat). The gelcoat then hardens through a chemical bonding process that strengthens it. The gelcoat used by Pools for Africa is High Performance Iso/ NPG Gelcoat. It is manufactured using purified isophthalic acid, which imparts to the gelcoat excellent scratch, stain and UV resistance, as well as good mechanical properties. The gelcoat that has high durability, including long-term resistance to weathering and chemical attack. As it is applied to a smooth mould it will be smooth and durable when released from the mould and it’s algae-resistant, which is great from a maintenance perspective.
The resin and fibreglass of pools
Once the gelcoat layer has “gelled” it is time to add the fibreglass and resin layer. At Pools for Africa, we use one of two methods to add the fibreglass and resin. The method depends on the customer’s preference between “The Choppergun Method” or the “Hand Lamination Method”. See our post Hand Lamination vs Chopper Gun that discusses the differences between the two methods.
The Choppergun Method for Swimming Pools
Chopper gun manufacturing application is the process whereby the fibres and resin are sprayed onto the mould surface at high pressure, eliminating the chances of dry spots. Mixtures of resin and catalyst are preset and controlled, ensuring an accurate and constant ratio throughout. The Chopper gun chops continuous fibreglass strands into pre-set lengths before spraying it with the resin onto the mould. The resin works as an adhesive so that the fibreglass sticks to itself and to the surrounding layers of the pool shell.
The following analogy that we found on the internet explains the process well: say I blow up a balloon to paper-mâché it and shred newspaper and mix it with glue before applying it, once dried I could pop the balloon and the paper- mâché will hold its shape. I could have painted the balloon with glue alone, but when it dried and I popped the balloon, the glue wouldn’t keep its shape very well because it wouldn’t have much support. On the other hand, I could stick newspaper alone to the balloon, but it wouldn’t stay there without something holding it to the mould (in this case, the balloon).
The resin is the glue to the fibreglass’s paper. When mixed and applied together, they keep the correct shape with proper support. At Pools for Africa, once the mould is covered with the fibreglass: resin mix, we further reinforce areas that need further support such as the corners and steps through hand laminating fibreglass mats to those areas. The Chopper Gun method requires an experienced operator to ensure an even distribution of the fibreglass: resin mix. At Pools for Africa, we are continuously training our staff and as a result, have the necessary experienced people to operate the Chopper Gun.
Hand Laminated Pools are built using fibreglass mats/sheets that are laminated onto the mould with a resin-filled roller, saturating the fibreglass mats with resin. The fibreglass sheets overlap each other ensuring an even minimum coverage throughout the pool.
The next layer is a layer of reinforcing ribs that is applied to the sides of the pool. The reinforcing adds further rigidity to the Pool.
Once cured, the swimming pool is released from the mould and given a finishing cosmetic layer on the outside.
The Pool is then inspected for any defects. Once cleared, the weir, airflow/jets and lights are fitted and the pool is loaded on our trailer for delivery to your home.