3 ways to repair screw holes with polyester

Many boats have redundant drill holes that are no longer used. A piece of fitting, a holder or something else that used to be there and sometimes it is even uknown what the original purpose of the hole was. In any case, the hole has to go! In this article we give 3 methods to repair screw holes in your boat. Depending on the size of the hole and possibly some other circumstances, you can choose from the following options:

• Fill the hole with topcoat (small hole).
• Fill the hole with fibre filler and finish with topcoat (medium hole).
• Chamfer the hole, laminate and finish with topcoat (large hole).

1. Filling a small hole with topcoat

Follow the steps below to fill a small hole in your boat, such as drill holes up to approximately 5 mm in diameter.

Time needed

Total time: 2 days
Preparation: 10 minutes
Time per hole: 1 minute
Cure time: 1 day (on warm days the waiting time is shorter)

Supplies (tools)

• Countersink drill
• Drilling machine
• Backing pad for polishing discs
• Polishing fleece
• Sanding cork

Supplies (consumables)

• Polyester Topcoat in the desired colour
• MEKP hardener
• Mixing cups
• Mixing spatulas
• Nitrile gloves
• Masking tape
• Sandpaper (grit P320, P400, P600, P800, P1000, P1500 and P2000)
• Coarse polishing compound

How to fill a small hole 

1. Use a drill with a countersink drill to drill out the hole slightly. This will remove any contamination or loose bits.
2. Place a piece of tape under the hole (for a vertical surface) or next to the hole (for a horizontal surface).
3. Mix a small amount of polyester topcoat by adding 2.5-3% MEKP hardener to the resin. Allow for a short processing time. Use the handy scale on the RESION mixing cups to mix small amounts of topcoat. Measure the hardener in drops if necessary.
4. Apply the topcoat to the hole and place the tape over the hole so that the topcoat is still convex. Topcoat shrinks slightly and it is important to have enough material for the sanding process.
5. Now wait for the topcoat to harden. In colder conditions this can take a day, while on warm days it hardens much faster; the topcoat can then be sanded after a few hours.
6. Once the topcoat has hardened, sand the repair. First use grit P320 or P400 and then sand further with P600, P800, P1000, P1500 and P2000.
7. Now sand successively with grit P320 or P400, then P600, P800, P1000, P1500 and P2000. Each sanding should be slightly coarser than the previous one. Start small and tape the surface if necessary. Use waterproof sandpaper on a sanding cork for the best result. Tear a sheet of sandpaper into quarters, soak it in water and fold it around the cork. Sand the repair completely smooth.
8. If additional topcoat is needed, dry the area and reapply topcoat. Sand the repair smooth with the subsequent grits.
9. Use a polishing coat on a drill or polishing machine. Slightly dampen the surface and apply 2-3 drops of polish to the coat. Polish the surface first in vertical strokes, followed by horizontal strokes until the repair has a high gloss appearance.
10. Remove excess polish with a polishing cloth.

2. Filling a medium sized hole with fibre filler

Follow the steps below to fill a medium sized hole in your boat, up to approximately 15 mm in diameter.

Supplies (tools)

• Countersink drill
• Drilling machine
• Backing pad for polishing discs
• Polishing fleece
• Sanding cork

Supplies (consumables)

• Polyester fibre filler
• Polyester topcoat in the desired color
• MEKP hardener
• Mixing cups
• Mixing spatulas
• Nitrile gloves
• Masking tape
• Sandpaper (grit P320, P400, P600, P800, P1000, P1500 and P2000)
• Coarse polishing compound

How to fill a medium sized hole

For holes of approximately 4-15 mm, another method can be used. This is partly the same as the previous method, as finishing with topcoat will always have to be done.

1. Use a drill with a countersink to drill out the hole a little. This removes dirt and loose bits. Make sure the hole is clean, beveled and free of loose parts.
2. Apply tape around the hole to protect the surrounding material.
3. Mix the polyester fibre filler and apply it to the hole.
4. Place tape on the fibre filler and press it lightly into the hole. This creates space for the topcoat that will later cover the fibre filler.
5. Allow the fibre filler to harden completely before sanding. Use a flat object to check whether approximately 0.5-1 mm of topcoat can be applied everywhere. If it is too shallow, sand away some material.
6. Mix the polyester topcoat by adding approximately 2% MEKP hardener to the resin. Then apply this to the repair. You can cover this with tape if necessary, but make sure the top coat still bulges.
7. Once the topcoat has hardened, sand the repair. First use grit P320 or P400 and then continue sanding with P600, P800, P1000, P1500 and P2000.
8. Now sand successively with grit P320 or P400, then P600, P800, P1000, P1500 and P2000. Each sanding should be slightly coarser than the previous one. Start small and tape the surface if necessary. Use waterproof sandpaper on a sanding cork for the best result. Tear a sheet of sandpaper into quarters, soak it in water and fold it around the cork. Sand the repair completely smooth.
9. If extra topcoat is needed, dry the area and apply topcoat again. Sand the repair smooth with the subsequent grits.
10. Use a polishing coat on a drill or polishing machine. Slightly dampen the surface and apply 2-3 drops of polish to the coat. Polish the surface first in vertical strokes, followed by horizontal strokes until the repair has a high gloss appearance.

11. Remove excess polishing compound with a polishing cloth.

3. Large hole lamination

For large holes, approximately. 12 mm and larger, or holes in places where watertightness must be guaranteed, it is best to sand out the hole and apply new laminate, after which you apply topcoat.

Supplies (tools)

• Fiber disc with adapter and grinder

Supplies (consumables)

• Polyester laminating resin
• Polyester topcoat in the desired colour
• MEKP hardener
• Glass mat 225 gr/m2
• Mixing cups
• Mixing spatulas
• Nitrile gloves
• Masking tape
• Sandpaper (grit P320, P400, P600, P800, P1000, P1500 and P2000)

Tip: with the polyester repair kit (for minor repairs) and the polyester laminating kit (for major repairs), you will immediately have the right product at home for your laminating job.

How to laminate a large hole 

Follow the steps below to laminate a large hole in your boat.

1. Sand the edges of the area to be repaired at a 1:10 bevel angle. For example, if the hole is 3 mm deep, make the repair 30 mm wide on one side (since you will always be working on both sides, the total width of the repair will be 60 mm plus the size of the hole). If it is possible to reach the back of the hole, you can choose to repair the hole from both sides. Use a grinder with a backing pad and fibre disc for efficient sanding.
2. Cover the area around the hole with tape and plastic.
3. Cut small circles of glass mat, gradually increasing in size, to fill the hole. For small repairs, 225 gr/m2 glass mat is usually used, which gives approximately 0.5 mm thickness per layer.
4. Place a temporary support in the hole, such as tape, cardboard or wood. If the back is accessible, tape it down. If the back is not accessible, use cardboard with a hole and a string that can be pulled through the hole, secured with superglue if necessary.
5. Mix polyester laminating resin with approximately 2% hardener and apply it to the area to be repaired. Now place the largest glass mat and dab it with resin so that it is well soaked. Dab the air bubbles out of the glass mat and then apply the smaller pieces of glass mat, each time well impregnated with polyester. Now let the whole thing harden for 4-6 hours.
6. After hardening, sand the repair. The goal is to sand the repair approximately 0.5-1 mm below the surrounding material so that there is sufficient space for the topcoat. Use a fiber disc or sandpaper with various grits. We recommend sanding the edges with grit P240 or P320 in any case. This allows you to create a nice transition with the topcoat.
7. Mix polyester topcoat with approximately 2% MEKP hardener and apply it to the repair. You can cover this with tape if necessary, but make sure that the topcoat is still slightly convex.
8. After curing, sand the repair with grit P320 or P400 and continue with P600, P800, P1000, P1500, and P2000.
9. Sand successively with grit P320 or P400, then P600, P800, P1000, P1500, and P2000. Start with a slightly coarser grit and use waterproof sandpaper on a sanding cork for an optimal result.
10. If necessary: ​​dry the area and reapply topcoat. Sand the repair smooth with successive grits.

Questions about filling (screw) holes in your boat?

Do you have any questions about filling screw holes with polyester? Please feel free to contact our customer service. We are happy to advise you by email, telephone (+31 (0)85 022 00 90) or WhatsApp. This way we help you make your project a success!