Boat Sheathing with fibreglass.
Sheathing an existing wooden boat hull with fiberglass offers a range of benefits that can greatly enhance your vessel. When properly applied, fiberglass sheathing creates a protective barrier that seals leaks, improves appearance, and reinforces the hull. It also provides superior resistance to knocks, scrapes, and attacks by worm or rot, significantly extending the boat's lifespan.
By repairing any existing holes prior to sheathing, you can ensure a seamless and durable finish that minimizes the need for annual maintenance. Additionally, the sheathing process allows for incorporating desirable features such as non-slip decks. However, it's important to note that some hulls are more suitable for sheathing than others. While hardwoods are generally not ideal due to their low absorbency, most softwoods can be effectively sheathed with excellent results.
Choosing the right resin is crucial for a successful sheathing project. Epoxy, although more expensive, offers superior longevity compared to polyester. However, if you opt for polyester resin, which is more commonly used, it is essential to distinguish between Isophthalic and Orthophthalic types. Isophthalic polyesters, such as Crystic 491 pa, are highly water-resistant and ideal for boatbuilding and sheathing due to their durability. Orthophthalic resin is more commonly used and suitable for many applications.
To embark on your sheathing project, you can find all the necessary materials and tools conveniently available in our shop. Whether you choose epoxy or polyester, proper execution of the sheathing process can result in a boat that surpasses expectations in terms of longevity. Remember, it's crucial to consider the value of your boat and ensure that the sheathing is done correctly, so you can fully reap the benefits of this transformative technique.
Creating a safe work environment
For optimal safety and work conditions, it is crucial to operate in a well-ventilated area with a temperature range of approximately 18-20 degrees Celsius. Smoking or using naked lights must be strictly prohibited in the work area due to potential hazards. Consider constructing a temporary awning or tent to provide a controlled environment. Ensure that the tent has proper ventilation to avoid fumes from the materials used and prevent condensation buildup.
To facilitate the process, set up a sturdy trestle table or a suitable surface to effectively cut the fiberglass material. This will provide a stable and organized workspace, allowing for precise and efficient workmanship. Prioritizing safety and creating an appropriate work environment will contribute to a successful and smooth sheathing project.
Getting materials and equipments prepared
To ensure a successful sheathing project, you will need a few essential materials. Firstly, you'll require a general-purpose lay-up resin and Flowcoat that is Lloyds approved. These products, along with the appropriate catalyst (hardener), will serve as the foundation for your fiberglass application. Additionally, you'll need a high-quality chopped strand matting for reinforcement.
Styrene is another crucial ingredient, with an approximate ratio of 50cc per kilogram of resin for the prime coat. The exact quantities needed will depend on the size of your boat. As a rough estimate, 1 kilogram of resin will cover around 2 ½ square meters of hull surface for the initial sealing coat. For lay-up purposes, 1 kilogram of resin can impregnate approximately one square meter of 450g/m2 glass matting.
For the recommended glass fiber reinforcement, chopped strand mat is highly advised. It is available in rolls that are 92 cm wide and comes in various weights. A single layer of matting is usually sufficient for small boats up to 3 meters in length. For added strength or for larger boats ranging between 3 and 9 meters, it is recommended to use at least two layers of 450g matting.
While some users prefer glass fiber cloth due to its superior flexural strength and reduced finishing requirements, it is important to ensure proper adhesion to the hull to prevent separation issues.
By following these guidelines and using the appropriate materials, you can ensure a reliable and durable fiberglass sheathing for your boat.
Setup
Before beginning the sheathing process, it is essential to ensure that the hull surface is completely accessible. For smaller boats like dinghies, a simple inversion will suffice. However, for larger boats, you may need to roll the boat from side to side alternatively, dividing the sheathing into two halves. Consider using trestles or scaffolding to gain convenient access to all areas of the hull.
To prepare the hull surface, start by removing all old paint, ensuring that the timber is clean and dry. It is recommended to use mechanical methods such as a belt sander or rotating disc for stripping. Avoid using chemical paint strippers or blow lamps as they can leave undesirable deposits on the wood, compromising the adhesion of the resin.
Fill any cracks with catalyzed resin putty, allowing it to harden before smoothing it down flush with the hull. Ensure that the entire hull is clean and dry, free from any contaminants or moisture. This will create an optimal surface for the sheathing process.
By following these preparation steps meticulously, you can establish a clean, dry, and well-prepared hull surface, setting the stage for a successful and durable fiberglass sheathing application.
Mixing the Resin
Prior to use, it is crucial to catalyze all resins. For lay-up purposes, a minimum of 1% catalyst is recommended, with the specific amount depending on the ambient temperature (approximately 10cc catalyst per kilogram of resin). To ensure accurate measurement of the catalyst, use a purpose-designed dispenser, and thoroughly stir it into the resin.
In the event of accidental skin contact with the catalyst, immediately wash it off under running water. If the catalyst splashes into the eyes, flush them under running water for a minimum of fifteen minutes and seek medical attention promptly.
If desired, up to 10% pigment can be added to the resin. It is important to thoroughly stir the pigment into the resin. To ensure sufficient coverage, it is advisable to pigment enough resin to cover the entire hull. From there, working quantities can be decanted and catalyzed as needed. Normally, only the surface coat requires pigmentation. However, for certain colors such as reds, yellows, and dark blues, it is advisable to pigment the lay-up resin as well. If pigmented resin is left unused for more than 12 hours, it should be thoroughly stirred before use.
By following these guidelines, including proper catalyzation and pigment mixing, you can ensure the effective and reliable application of the resin for your sheathing project.
Applying the mixture
Ensure that the surface is thoroughly dry, then begin by priming it with Resin. Thin the Resin with styrene monomer at a ratio of 1 part styrene to 20 parts resin, and catalyze it with 2% catalyst. This will allow the wood to be fully impregnated. Allow the primer coat to cure until it reaches a tacky condition, and then apply a coat of un-thinned catalyzed Resin.
Immediately after applying the Resin coat, place reinforcing glass tape or strips of chopped strand matting in areas that require additional strength, such as the keel, bows, or transom. Use a brush to stipple the Resin into the reinforcing strips, ensuring that the Resin and glass are well worked into angles and corners. To release any trapped air bubbles, employ a metal roller. Next, cover the hull with pre-cut pieces of matting. Overlap each piece by a minimum of 50mm and work and roll the matting, feathering the joint to create an inconspicuous finish. Whenever possible, it is advisable to lay pieces that span the entire length of the hull, as this reduces the number of joints and improves the overall appearance. Use a 'stippling' action with the brush to press the matting into the Resin, avoiding back-and-forth brushing that could separate the fibers. If preferred, a polyester roller can also be used to apply the Resin. Ensure that the matting is thoroughly saturated with Resin, adding more if necessary, while being careful not to over-saturate. Maintain a maximum Resin-to-glass ratio of 2.5:1. Smooth out any wrinkles or air bubbles, paying particular attention to the corners of chines, keel, bows, and transom. In some cases, stapling the matting in position can facilitate the process.
Repeat the same method to add additional layers of matting as required. Avoid leaving more than 24 hours between laminations, as this can greatly reduce adhesion. If more than 24 hours have passed, lightly rub the surface with coarse glass paper and wipe it with Acetone to sensitize the surface. Ensure that the joins in each layer are overlapped by the succeeding layer, with a minimum overlap of 50mm.
Before the final layer sets, cover it with surface tissue, completing the sheathing process with a protective and visually appealing finish.
The surface coat
For the surface coat you will need Flowcoat, this is best conditioned at room temperature before use to achieve correct viscosity, catalyse with 20cc of hardener per kilo of mix and brush the mix carefully over the hull, allow to harden. If you are working outside make sure the weather is correct,i.e warm and dry with little or no wind. Do not Flowcoat late in the day as the temperature drops, thus allowing the curing cycle to be extended, you are far better applying midday when the conditions are just right. It is particularly important to apply the final coats in warm, dry and well ventilated environment.
Polishing the surface
The Flowcoat should provide a smooth surface finish, but you can significantly enhance it by using a special polishing compound with an electrically powered compounding head. If necessary, start by cutting back the surface with 240-grade wet and dry paper, gradually progressing to 800 grit, and if needed, 1200 grit. Once this is done, you can proceed with polishing.
After the resin has fully cured, which typically takes around 10-14 days at 20 degrees Celsius, the hull is ready to be launched. It's important to note that curing may take longer at lower temperatures, but it is not recommended to let it cure below 15 degrees Celsius. If a white bloom appears on the surface, it indicates that the resin was not fully cured. While this won't harm the sheath, it's advisable to dry out the boat, lightly wipe it with acetone, and apply a wax polish. If the bloom persists, you may need to cut back the surface and re-polish for optimal results.
Maintaining your Sheathed Hull
Once in service, the sheath requires minimal maintenance. If any damage occurs, it should be repaired promptly by overlapping the damaged area with mat and resin, ensuring a minimum overlap of 20cm. While the sheath is resistant to rot and worm attack, it may still experience fungal and weed growth on the surface. To mitigate this, it is advisable to apply a coat of anti-fouling.
Please note that for any significant repair work, it is recommended to consult a professional advisor. The advice and information provided here are given in good faith for guidance purposes only and without warranty. Users should carefully assess the information provided and make their own judgment to determine suitability for their specific circumstances.
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