This will be fun. Kind of meandering, but hold on, I’ll make a point. Maybe more than one. I promise.
Most of us think of gel coat as the shiny, smooth, color-rich lipstick on the outside of our boats. The fact is, gel coat has a couple of very important functions. Let’s go down this rabbit hole and see where we come out.
Prettification of ugliness
I’m a firm believer in a pretty boat for Mrs. That Guy, and an ugly boat for fish getting. Thing is, there is a difference between “ugly” and “extremely inefficient/potentially dangerous”. We will get into the efficiency and dangerous stuff later.
If you’ve never seen a hull with no gel coat, just the core, glass fibers, hardened resin, and fairing compound (more common on hand-laid hulls), you’ll have to trust me when I tell you they are dang ugly. Dang ugly. Ugly like a toadfish (oyster cracker to those from … norther parts). Sure, it’s technically a boat/fish, but you don’t want your momma to see it let alone anyone that you might want to impress later in the evening if you know what I mean.
So yeah. Gel coat makes for a pretty boat. Keep in mind, gel isn’t the only way to cover up glass. Paint is the other option that folks use. Paint and gel are NOT interchangeable and not all types of resins can be covered with gel and others don’t like paint. That’s a different discussion.
Do you need a pretty boat to catch fish? Nope. Do you need a pretty boat to be safe? No. But you do need to make sure that you know the difference between ugly and damaged. Let’s move on from “gel makes me pretty”.
Water intrusion is water “getting in places it shouldn’t. Basements, roofs, roads, patios, fiberglass hulls. Water has this nasty habit of getting into and destroying things. Gel coat helps protect your hull from water intrusion. Above the waterline, it’s more than salt water. It’s blood, beer, fuel, oils, and other liquids that might be spilled on the deck (or other surfaces). If those things get behind the gel, various chemical and mechanical reactions occur that will eventually weaken the fiberglass. I’m sure you’ve all heard of blisters (more common below the waterline) and delamination (not all delam is water-based).
The reality is that most fiberglass resins are waterproof. The problem is that they are subject to UV degradation and “osmotic intrusion”. Osmotic intrusion is when water gets into the glass as vapor, through the small junctions between the glass and the resin, or any place where the resin is cracked, has been drilled, cut, scratched, etc. A fun thing I did was to take some glass fabric, make a puck of resin and let it cure, weighed it, stuck it in water for a while, then weighed it again. It sucked up water. Quite a bit of water.
Big deal… Throw a layer of gel over that puck and it doesn’t get heavier. Gel protects the glass from water intrusion. This means you are less likely to get water into the glass. That means less probability of blisters, delam and water related weight gain (weight gain in the hull, gel won’t help the waistline).
So if you have chips. cracks, or gouges in your gel above the water line you STILL need to think of them as a water intrusion problem. Sorry. I don’t make the rules here.
Smooth is fast and efficient
Below the waterline, the gel coat provides another essential function, it ensures a smooth surface for the water to flow over. When your boat was designed, the smooth surface was an key factor in your hull’s performance. When cracks, chips, blisters, or other defects disrupt this smooth surface, hull performance drops. This means increased drag, which translates to slower speeds and reduced fuel economy. Sometimes this can even result in dangerous handling issues.
It happens like this. Shane gets on a nice hoo. the team pulls it up to the boat. Jackson gaffs that hoo and something smacks the hull just below the planing waterline. A small chip starts in the gel. End of the day, the team is kicking back running in at 55mph while enjoying a couple brews. Below the water, the gel is fighting the water and losing. The chip slowly gets a bit longer as the water erodes the sharp edges toward the stern. Cavitation sharpens and deepens the chip toward the bow. All goes well at the ramp with just a little bump of the bunk creating a hairline fracture at the edges of the chip. The trailer ride home vibrates the edges of the fracture widening it slightly.
Shane’s little chip/crack may not be noticeable at first. Maybe just a hairline next to a chine. After a few trips and a dozen more dings, Shane’s boat starts to have a hull surface that looks less like a baby’s backside and more like a gravel road. To the water. Water can no flow as smoothly as it used to flow over the bottom of the hull. Shane will see lower top speeds and start spending a more on fuel. Those that keep their boats in the water will recognize this as a “dirty bottom”. Same deal. The bottom isn’t smooth and isn’t efficient. You may not be able to feel this roughness at first. You might see it as lines or spots on the hull.
What gets real fun is when you have asymmetrical issues. If there is significant damage on one side of the hull, you may find the hull “pulls” or needs excessive trim. If you start noticing that you need constant trim or helm to port/starboard, give the hull a thorough inspection (as well as steering and trim systems).
That Guy’s take
Most chicks dig shiny boats. Hell, most guys dig shiny boats. there’s a reason you don’t see them mass-marketing flat finishes on new boats. Boats don’t need to be shiny though. The gel or paint needs to be solid. No chips, cracks, or scratches below the waterline or in high-wetness areas. This includes water, beverage, oil, fuel, or “body fluids” (fish or human). If you see any signs of osmotic blisters or delamination, get it fixed ASAP (but the fixes may not be quick). If you suddenly notice drops in speed and fuel economy, check your bottom, you may need anything from a quick clean/wax to some significant repair.
Gel maintenance is a bitch. I know. That Guy doesn’t offer full gel maintenance for a reason. But when you are doing your normal maintenance (which would be light soap then waxing, only use cutting bompounds if you have significant scratching or heavy oxidation) look for issues. If you see issues you are unwilling or uncomfortable fixing, reach out to That Guy. Chances are he’ll show up and swap stories about smacking docks. He’ll fix the gel too. Mrs. That Guy guarantees it.