Repairing holes and cracks above the waterline

Do you want to repair cracks, scratches or holes in your polyester boat yourself? Then quickly read this article! We are happy to explain to you what you can do to repair cracks, scratches or holes in the hull of your polyester boat, so that you can then re-coat the boat. In this article, we will discuss the repair of the above-water part of the boat's hull step-by-step. We also have a step-by-step guide for repairs below the waterline.

Manual for repairing cracks and holes in your polyester boat

Supplies

The quantities of the supplies listed below depend on the size of your boat's hull and, of course, the damage to your boat. If in doubt, please contact us for tailor-made advice. 

You will need various raw materials and tools for this repair. If you order the items below from us, they will often be shipped the same day. This way you can quickly get started with the repair!

Raw materials:

• Epoxy resin (rapid)
• Glass fabric (200gr/m2)
• Cotton fibre

Tools:

• Vent roller 
• Putty spatula 
• Nitrile gloves  
• Mixing spatulas 
• Mixing cups 
• Disposable round brush  
• Kitchen scale
• Acetone (for cleaning the vent roller)
• Scissors (for cutting the glass fabric)
• Sander, grinder with fibre disc and adapter or flap disc

Step 1. Check

The first step in repairing damage to your boat hull is checking where the damage is. This includes cracks, scratches or holes from removed equipment (such as winches, blocks, etc.).

Step 2. Chamfer holes, cracks and scratches

You can chamfer cracks and scratches with a sander or angle grinder with a 4:1 flap disc. You can chamfer larger holes in a 8:1 ratio. When a hole is several centimeters in size, the hole is often chamfered and sealed on both sides.

After grinding out, check whether cracks are not deeper than expected. Wet the sanding area and wipe it dry again. In a crack water will remain longer and become visible again. If this is the case, you can grind out any cracks even deeper.

For large holes, seal the back with a plate covered with a piece of tape so that the epoxy does not stick to it. If the back of the hole is not accessible, stick the plate through the hole and hold it in place with a piece of wire or a roller bracket.

Step 3. Patch the small holes

Before you can start working with epoxy, you must clean and dust the hull and all the parts to be repaired. Once you have done this, you can start making the epoxy. While working with epoxy, wear disposable nitrile gloves.

Small holes, up to 1 cm in diameter, can be sealed with a mixture of epoxy and cotton fibre. By mixing cotton fibre into the epoxy, you get a paste. You can patch the hole with this paste, using a flexible spatula for this. It is necessary to fill the hole to the surface, there may be a small edge (as long as it is closed). 

Step 4. Patch large holes and cracks with epoxy and glass fabric

In this step, we will laminate the larger holes with glass fabric and epoxy. Start by cutting pieces of glass fabric from large to small, according to the size of the crack or hole. Start by laminating the smallest piece of glass fabric using a brush and prepared epoxy. Laminating with epoxy is done as follows:

• Wet the surface with epoxy resin (use a round brush for this). 
• Press the smallest piece of glass fabric into the epoxy. 
• Then press larger pieces of glass fabric into the epoxy and wet it again with resin. 
• After each layer, you need to vent the glass fabric with a vent roller.

Build up several layers in this way, until the fabric is level with the surrounding surface. Now let the epoxy harden. 

For holes that are completely through the hull, the temporary plug can be removed after curing on the inside and, according to the above method, the area can also be sanded diagonally and laminated from the inside. The strength is now fully back.

After working with the epoxy, clean the vent roller with acetone and an unused brush. This prevents the epoxy from hardening in the roller and rendering the roller unusable.

Step 5. Follow-up

After you have patched all the holes, you can sand the whole thing and fair it with epoxy filler. When the hull is completely smooth, you can paint it with our DD lacquer. Do you have any questions about the products in this article or about the method of repairing damage to your boat hull? Feel free to contact our customer service team via email, phone or live chat!