How to Fix Cracks in Gelcoat on Boat Surfaces

Man working on the bottom of a boat

Gelcoat cracks (also known as spider cracks) indicate that your boat has suffered from severe structural problems or impact damage. As such, you need to address cracks in gelcoat on boat surfaces immediately to prevent them from spreading. While it is possible to fix these cracks yourself, your best option is to hire a contractor to fix the cracks. A professional seal ensures that the job is performed properly and meets industry standards. 

In addition to fixing the cracks, you may also need to explore the reason for the cracks. If there is damage somewhere else in the boat, you need to fix the damage to prevent further cracks from occurring. If you have any further questions about how to fix cracks in your boat’s gelcoat, contact Pensacola Shipyard today. Our marina has everything you need to repair your vessel. 

What Are Gelcoat Cracks? 

Gelcoat cracks are fine cracks in the gelcoat surface. Other names for gelcoat cracks are spider cracks, stress cracks or hairline cracks. Most stress cracks occur in the gelcoat layer of the fiberglass surface. If caught early, you may be able to seal the cracks yourself. However, once they intensify and spread, you may need to contact a professional to seal the cracks and prevent more from occurring. 

In most cases, gelcoat cracks are a surface or cosmetic issue. You simply need to seal the cracks to prevent them from spreading across the hull surface. However, other cracks may indicate that something is going on behind the surface. In either case, you can always be assured that a tiny crack will expand over time.  

What Causes Gelcoat Cracks? 

Cracks in gelcoat on boat surfaces can appear for various reasons. 

Manufacturing Defect 

Gelcoat cracking may indicate underlying structural problems caused by manufacturing defects. Manufacturers have difficulty striking a balance between high gloss properties and ruggedness. Softer coating materials have a lower gloss, while harder materials have a higher gloss. However, harder coating materials are more likely to crack. 

Environmental Challenges 

Because gelcoat is being made more environmentally friendly, newer products are not always environmentally tolerant. In other words, not all types of gelcoat are designed to withstand the Florida climate. High heat, UV rays, sea spray and other elements can wear down gelcoat in a short period, making it more vulnerable to cracking.

Stress and Movement 

The sea is not easy on your boat. Every time you take the boat out, your vessel works against the waves. Even when it’s docked, the constant flow of water keeps your boat in motion. This constant motion creates a lot of stress on the gelcoat. Eventually, stress cracks form and expand. They need to be sealed and reinforced every time you notice them so that further use doesn’t cause the cracks to expand. 

Older yachts contain thicker gelcoat applications, which are more likely to crack than new gelcoat materials. Water diffusion, waves and rigging stress, thermal shock, impact, or expansion and contraction can lead to gelcoat cracks.  

Different Types of Gelcoat Cracks 

There are three main types of gelcoat cracks. 

1. Radial Crack 

A radial crack is caused by impact or fixtures that are putting a strain on parts of your boat, such as bolted attachments. A crack results from a reverse impact or sharp, localized stress riser. A frontal impact is indicated by a circular pattern, with the diameter of the inner circle related to the size of the impacting object. In other words, the larger the object, the larger the radius of the crack. 

2. Linear Crack 

There are two types of linear cracks: stress field patterns and parallel stress cracks. The primary cause of these cracks is flexed strain on the gelcoat. Parallel stress cracks indicate movement opposite the direction of the cracks. Parallel cracks indicate a distribution of stress over a supported panel surface. The more flexible the panel or surface, the more likely the gelcoat will crack. 

3. Thermal Fatigue Crack 

Thermal fatigue cracks result from constant expansion and contraction of the gelcoat film. Cracks are identified by short discontinuous sections and are usually grouped in sections. Each section is roughly the same size and shape, indicating cracks resulting from the same movement pattern. The contraction and expansion move in the same way across a portion of the surface. 

How to Prevent Gelcoat Cracks 

As a rule, it is almost impossible to prevent gelcoat cracks. Time, use and the elements will eventually have their way with the hull’s surface, leading to radial, linear or thermal cracks. However, there are some things you can do to either prevent early cracking or the expansion of a single crack. 

For instance, you can countersink holes through the gelcoat. This method redistributes the stress onto the structural fiberglass and not the fragile gelcoat. When holes are drilled correctly, you can preserve the gelcoat longer without cracking or chipping.  

How to Repair Gelcoat Cracks 

If you choose to do a DIY gelcoat repair, you can seal hairline cracks using a DIY repair solution kit. The solution applies easily and will seal most cracks. Sealants come in a variety of colors to match your hull. They provide a smooth, streamlined look that restores your boat’s surface. You can complete most repairs in only a few minutes with minimal effort. No special tools or grinding are necessary. 

However, store-bought kits and DIY jobs do not always produce the type of results you are looking for. You may end up unsatisfied with how the surface looks. If so, you may want to hire a professional to grind out the cracks and fill them. If the repair professional does the job right, no one will know the cracks were ever there. The surface will be fully restored with results that will last longer. 

Contact Pensacola Shipyard Today 

Conveniently located on the protected waters of Bayou Chico, we are the Emerald Coast’s premier shipyard. If you need to get your gelcoat repaired, we have the boatyard capabilities and resources to get the job done.

Contact Pensacola Shipyard at 850-780-8441 to schedule service or find out more about our facilities.