Sea-Line Polyester Spray Filler – 1kg / 10kg Kit

Sea-Line Polyester Spray Filler is a two-component polyester putty with a liquid consistency, designed to simplify the final surfacing of large areas on boats and yachts. Traditional fillers are applied by hand with a spatula, which can leave unevenness or lines; in contrast, this spray filler is applied with a spray gun, allowing you to cover expansive surfaces quickly and smoothly, eliminating any seams or transitions between application passes.

When preparing the mixture, the polyester filler base is combined with a specified amount of a paste hardener (typically 2-3% by weight), initiating the curing process. The mixed filler has a relatively short working time (approximately 15-20 minutes at 20°C), so it’s crucial to begin spraying immediately after mixing. You can also add a small amount of Sea-Line Thinner for Polyester Spray Filler (up to 10%) to the mixture to fine-tune the viscosity for perfect spraying – this will ensure a fine atomization and an even coat.

The Sea-Line spray filler is applied in one or two coats, depending on the thickness required (each coat can fill about 100-200 µm of dry film). Thanks to its fluidity, it automatically fills minor sanding scratches and pores in fiberglass or old filler, creating a smooth “poured” layer over the entire surface. In essence, it acts like a heavy-bodied spray primer-surfacer that levels and isolates the underlying substrate and previous repair layers.

After application, the material gels and hardens quickly – in about 3 hours at 20°C (warmer conditions accelerate, colder slow it down). Once fully cured, the spray filler’s surface is uniform and quite smooth to the touch, which makes sanding easier. It sands well, either dry or wet; you can achieve an ideal smooth surface with relatively little effort, because the material is homogeneous and not overly hard. Start with a coarser grit (e.g., P180) to knock down any excess, then finish with P240-P320 for a fine finish.

The leveled surface you get serves as an excellent foundation for priming. The spray filler effectively isolates the layers beneath – this prevents any shrink-back or print-through of old fillers or seams into the new primer and paint. The result is a more uniform and higher-quality final paint job.

Applications and recommendations:

• Major Repairs & Hull Fairing: Ideal whenever you have large areas to fair or smooth out – for example, after substantial hull repairs or after applying multiple layers of filler by hand. With one spray process, you can cover the entire area instead of repeatedly building up and sanding down hand-applied filler. It’s a huge time saver for professional fairing of hulls.
• Surface Types: Sea-Line Polyester Spray Filler is used above the waterline on composites (fiberglass), over existing polyester filler layers, or on metals (steel, aluminum) provided an appropriate epoxy primer is applied first. Do not use it on flexible plastics or directly over old one-component paints without a primer – incompatibility could cause delamination. Always ensure previous coatings are well-adhered and surfaces are sanded and clean.
• Before Painting: After sanding the filler smooth and removing dust, it’s critical to apply a primer (epoxy primer or 1K yacht primer) before topcoat paint. The spray filler itself doesn’t contain anticorrosive pigments, so metal substrates should be primed prior to application and again primed or sealed afterward for full protection. It’s essentially a sanding surfacer, not a final sealer.
• Safety: Spraying polyester filler releases styrene fumes – always work with proper protective equipment (respirator, gloves) in a well-ventilated area or outdoors. Clean your spray gun thoroughly with the appropriate solvent immediately after use, before the mixture can cure inside, to prevent clogs and damage to your equipment.