The Truth About Gelcoats

[GotemBoat]

Gelcoat – The “Candy Apple” shell of your boat.

Most boats out there today are constructed of either aluminum or FRP (Fiber Reinforced Plastic). This thread is about the latter.

Fiber Reinforced Plastic is a very good form of construction. When done properly the finished material can be stronger and lighter than steel of equivalent size. Conventional techniques dictate that a shiny colorful surface needs to be on the outside of the finished product. Gelcoat becomes the “eye candy” that first gets your attention when you see a boat.

Gelcoat is made primarily of the resin or “plastic” binder used in the FRP construction, and pigment. There is zero reinforcement in gelcoat. It is held together only by the cross-linking of the hardened resin between the pigment particles. Because of this layer of non-reinforced resin, it is prone to local surface damage such as cracking and flaking.

Gelcoat is also very prone to two other types of damage. Oxidation forms when the outer surfaces are exposed to oxygen either from the air or the water the boat is sitting in. It presents as a dull, powdery, rough layer that can easily be seen. Crazing is microscopic cracking of a plastic. It is primarily caused by sunlight interacting with the plastic and furthering the cross-linking process.

Both forms of gelcoat damage are a never-ending nightmare for boat owners. They cannot be stopped, unless of course we all store our boats underground in a sealed plastic bag filled with nitrogen! Not practical! Not going to happen. This damage can be delayed by applying wax and other substances to keep the oxygen from getting into the porous gelcoat layers, but damage from sunlight cannot easily be dismissed.

So what do boat owners do to fight this battle, this WAR? How do we protect vehicles that we use in pursuit of our passions and sometimes our very existence? What do we do to win the “Battle of the Gelcoat” once and forever?

Believe it or not the only way to win, is not to fight. Gelcoat, once damaged cannot be cleaned, renewed or repaired. It can only be removed. It must be sanded off and polished to reveal underlying undamaged material. If there is enough thickness in the original application you may be able to repeat this technique a number of times. However with each successive sanding, the candy shell will be further exposed and damaged until there is none left.

Some will want to rebuild the gelcoat layers by applying new gel coat on top of the old. This will work temporarily, but it is like giving weapons to your enemies. In time the same methods of decay will act on this new application as well.

Most large boat builders are now getting away from gelcoat altogether. Since the battle cannot be won, the new weapon of choice is high quality epoxy paint. Layers of paint are much more resistant to the types of damage that gelcoat suffers. Paint is not as porous and can withstand many years of exposure. Many colors and finishes are available for both above and below the waterline from many different manufactures. Do some research to find out which ones are best for you.

So if you are prepared to keep your boat for the long run, don’t waste your time or your money reapplying gelcoat, it wont last and your will fight it forever. Paint it and be done with it.