Restoring the buoyancy and tightness of the hull is a critical task for every boat owner, whether it is an old wooden boat or a modern one. fiberglassIt is fiberglass for the boat is the versatile material that allows you to create durable, waterproof and durable structures that can withstand the aggressive effects of salt water and ultraviolet light.
The process of creating or repairing the skin is often called “patching”, and the correct selection of components depends not only on the appearance, but also on the safety of the crew.
In this article, we will discuss in detail the physical properties of different types of fabrics, the chemical features of binders and a step-by-step algorithm of actions that will help you perform professional repairs in a home workshop or garage.
Classification and types of glass fabrics for shipbuilding
The basis of any composite material is a reinforcement element, which in our case is fiberglass. The market offers many options for weaving, and the choice of a particular type depends on the geometry of the surface and the required strength. roving-glass (T-11, T-13, T-23), which has a characteristic chess weaving and is characterized by high impregnation with resin.
Smooth or linen weaves are often used to create smooth decorative surfaces or work with complex contours, which are easier to fit into corners without forming folds. Material density is measured in grams per square meter, and for shipbuilding, values from 200 to 600 g / m2 are usually used.
- 🧵 Roving fabrics (T-11, T-13) are ideal for the main thickness of the body due to the high impregnation rate.
- 🎨 Satin fabrics – provide a smooth finishing surface and easily fit complex curved shapes.
- 🛡️ Sickle and glass grids - are used exclusively for local repair of cracks and reinforcement of seams.
⚠️ Warning: Do not use polymer-coated construction glass for the responsible parts of the boat hull. It is designed for wall plastering and has low adhesion to polyester resins, which will result in detachment under load.
When choosing a material, you should also pay attention to the presence of oilers - special compounds that are processed by threads in production. To work with polyester resins, you need fiberglass that has undergone the appropriate treatment, otherwise the binder will simply not be able to properly envelop the threads.
Binder choice: polyester vs epoxy resins
Glass fiber itself does not hold water and does not have strength; these properties are attributed to it by a matrix of polymer resin. polyester and epoxy Resins, each of which has its own unique specifications and application area.
Polyester resins, such as popular NPS-609-21M or IsophtalicThey are low cost, high polymerization rate and easy to use, and are often used in mass-produced boats and for large-scale work, where material cost plays a key role.
Epoxy resins, for example ED-20 When combined with PEPA or TET hardeners, they have superior strength, minimal drying shrinkage and excellent adhesion to various materials, including metal and wood. However, they are much more expensive, sensitive to humidity when applied and require more accurate compliance with mixing proportions.
There is also a compromise option - vinyl ester resins, which combine the ease of working with polyester materials and the chemical resistance of epoxy. The choice of a specific binder should be based on the operating conditions of the boat and compatibility with the existing hull coating.
Required tools and workplace preparation
The quality of the paste depends on the preparation of the surface and the availability of the right tool. Before starting to work, you need to ensure good ventilation of the room, since the pairs of styrene (in polyester resins) and amines (in epoxy) are toxic and flammable.
To apply resin and smooth the fabric, special brush rollers are used that allow you to expel air bubbles from the depths of the layers, which is impossible to achieve with conventional paint rollers, you will also need scales for accurate dosing of components, scissors for cutting fabric and sandpaper.
☑️ Readiness for work
Special attention should be paid to surface preparation. Metal should be cleaned to shine, removing all traces of corrosion, and old fiberglass should be passed to create risks that provide mechanical adhesion. Any oil stains should be removed with a solvent, since fat is the main enemy of adhesion.
If repairs are carried out in the cold, it should be remembered that most resins at temperatures below +15 ° C stop polymerizing or do it extremely slowly, in such cases, you need to heat the room or use special winter hardeners.
Technology of pasting: step-by-step instructions
The process of creating a composite skin requires strict adherence to the sequence of operations, and a violation of the technology at any stage can lead to voids, unsoaked areas or layering of the material in the future.
First, a binder layer (gelcoat or primer) is applied to the prepared surface, after which the first layer of fiberglass is laid, the fabric must be cut with a margin, and its laying is carried out by movements of the roller from the center to the edges to squeeze out air and evenly distribute the resin.
Algorithm for mixing components:1. Measure the exact amount of resin.
2. Add hardener in a strict proportion (usually 1-2%).
3. Thoroughly stir 2-3 minutes, scraping from the walls.
Apply during the "viability" of the mixture (20-40 minutes).
The subsequent layers are applied either wet (just after the gelling of the previous one) or after grinding the frozen layer, and it is important to avoid water, dust or oil between the layers, as this creates weaknesses in the structure.
When working with epoxy resin in hot weather, add a little less hardener to the mixture than indicated in the instructions to slow the reaction and have time to develop the solution before solidifying.
The thickness is gradually gained: one thick layer is always worse than three thin ones, since an uncontrolled heating (exothermic reaction) can occur in the array of material leading to deformation or even fire.
Comparative table of materials
To simplify the selection of components, the following table compares the main specifications of popular materials used in boat repairs.
| Parameter | T-11 glass fabric (Roving) | Satin glass | Glazed GPU (Serpianka) |
|---|---|---|---|
| Density, g/m2 | ~200-250 | ~160-200 | ~60-100 |
| Impregnability | High. | Medium | Very high. |
| Threatness | High. | Medium | Low. |
| Principal application | Body thickness set | Finish layers, contours | Fissure reinforcement |
Analyzing the data, we can conclude that for the main repair of the bottom, a combination of roving fabrics is best suited, while for the side or complex transitions, it is better to use more plastic materials.
Typical errors and methods of their elimination
Even skilled craftsmen sometimes make mistakes that can cost the boat its life, and one of the most common problems is dry fiberglass, where the resin has not completely soaked the fabric, leaving white unpainted areas inside.
Another common mistake is the temperature or mixing ratios that lead to surface stickiness even after full polymerization time, in which cases the layer often has to be removed mechanically and re-applyed.
⚠️ Warning: Never try to speed up the drying of fiberglass with open fire or powerful heat guns aimed at one point. Local overheating can cause styrene to boil and cavities to form inside the layer.
What to do if the tar is frozen with bubbles?
If the bubbles are few and superficial, you can grind them in and pour them in a thin layer of liquid varnish or resin, and if the bubbles are deep and there are many, the defective layer needs to be sanded to a solid base and remade, because the structural strength is compromised.
To eliminate minor defects and porosity, finishing putty is often used with special car or boat putty with fiberglass, which hide the texture of the fabric and prepare the surface for painting.
Finishing and protection of the coating
Once the required thickness is established and the fiberglass is cured, the surface is usually grinded, starting with the large grain (P60-P80) and gradually moving to the fine grain (P240-P400) to remove the steps between the layers and prepare the base for the paint.
To protect against ultraviolet radiation, which destroys polyester resins (they begin to turn yellow and lose strength), the surface must be painted or covered with gelcoat. Interlux Brightside or Tikkurila Unica.
It is critical to ensure that the fiberglass is completely dry before painting: residual moisture or styrene locked under a layer of paint will cause the coating to swell on the first sunny day.The quality of finishing painting is 90% dependent on the thoroughness of grinding and degreasing the surface of fiberglass before applying enamel.
Regular inspection and timely repair of small chips and scratches will extend the life of your boat for decades, maintaining its driving qualities and appearance.
Questions and Answers (FAQ)
Can I put glass on the wet surface of the boat?
Absolutely not. Moisture is a catalyst for breaking the bond between the resin and the filler, and it also prevents adhesion. The surface must be absolutely dry, clean and fat-free.
How many layers of glass fabric are needed to repair the bottom?
The number of layers depends on the thickness of the original board and the size of the damage. Usually, to restore strength, 3-5 layers of tissue with a density of 200-300 g / m2 are pasted, covering the edges of the damage by 5-10 cm.
How do you better flush the tar off the tools?
The polyester resin is washed off with acetone or styrene while it is liquid, the epoxy resin is washed off with alcohol or special washes, and once it has been solidified, the resin can only be removed mechanically.
Can I use epoxy over polyester?
Yes, epoxy resin has excellent adhesion to polyester. However, on the contrary, you can not do (polyester to epoxy) without special grinding and primer, since the polyester will not stick to a smooth epoxy surface.