What is Gelcoat?

B

Bobby G

New member
Not being a Marine expert, I had to do some research to answer this question. Here's the answer from wikipedia:



"A gelcoat is a material used to provide a high quality finish on the visible surface of a fibre-reinforced composite material. The most common gelcoats are based on epoxy or unsaturated polyester resin chemistry. Gelcoats are modified resins which are applied to moulds in the liquid state."



So, other than the method of application, a Gelcoat finish is not that much different than automotive paint.



Facts about Gelcoat:



1. It needs to be waxed/protected to prevent oxidation.



2. It is damaged by the sun's UV light.



3. It is easily scratched.



4. You can wet sand, cut and buff Gelcoat in the same manner as automotive paint finishes.



When Gelcoat finished parts are removed from their mold, they are rarely perfect (at best, the part can be 99% as good as the mold itself). Most boat manufacturers finish their boats using a muti-step sand, cut and buff process to achieve the final finish.



The good news for boat owners is that Gelcoat is pretty thick (much thicker than automotive paint), so you have a good amount of material for scratch repair.



db
 
I'll have to dissagree on the easily scratched part. I used to work for a cutstom boat trailer builder and I have been around a lot of boats. Gelcoat is much stronger than most automotive paint from what I have seen and been involved with.
 
Danase said:
I'll have to dissagree on the easily scratched part. I used to work for a cutstom boat trailer builder and I have been around a lot of boats. Gelcoat is much stronger than most automotive paint from what I have seen and been involved with.
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Thank you for your input, Bob. I'm simply going by what I have seen watching gelcoat being sanded and buffed.



db
 
I detail boats during the summer and like Bob, I disagree with the scratch part. This is why you wash boats with brushes. To keep a boat looking tip top, you will need to compound/polish/wax a couple times a year.



Greg
 
GregCavi said:
I detail boats during the summer and like Bob, I disagree with the scratch part. This is why you wash boats with brushes. To keep a boat looking tip top, you will need to compound/polish/wax a couple times a year.



Greg
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Thanks for the great feedback, Greg. Look forward to any tips you might have.
 
The outer skin of a fiberglass boat is called the gelcoat. In most cases it is a relatively thin layer of high quality resin pigment that gives the boat its color. The gelcoat helps to protect the layers of fiberglass beneath the surface. From the standpoint of appearance, it is the most important part of the entire laminate.



If not properly maintained from the beginning, almost all gelcoats will begin to fade and lose color and gloss over time. Discoloration from oxidation of the gelcoat does not structurally harm a boat, however, proper maintenance does help protect the fiberglass and improve overall resale value.



The best method of maintaining the gelcoat is to wash the boat often and apply a good coat of quality wax. This should be done at least three or four times a year. The wax on the surface of the boat provides a protective layer, lubricates the gelcoat and keeps the surface smooth. A top coat of premium marine sealant will provide additional protection from harsh environmental conditions.



For older boats that may already have a white chalky oxidation problem, it is usually necessary to use a marine cleaner polish first. If a cleaner polish does not remove the oxidation, then a slightly more abrasive product, such as a heavy duty compound may be needed. Removing oxidation from the gelcoat of a boat is not a simple job, especially if the oxidation has been allowed to build up over several years.



In summary, the easiest and best method for keeping a gelcoat looking new is to establish a regular maintenance routine from the beginning.
 
I also disagree with the part about gelcoat scratching easy. I will say this, once the gelcoat gets chalky, its ALOT of work to get it in the proper condition to wax. If its not polished enough, the wax will soak into the gelcoat and stain it. thats never fun.



if a boat has severe oxidation, expect to be compounding that hull for 1-3 days depending on the size of the boat. I had to compound a dark blue (the darker the color the more work involved) 32' boat a couple months ago and it took me 2 days just to compound the hull.
 
So, why are gelcoats used on boats and "automotive" paint used on cars?



Why isn't car paint used on boats, or by the same token, gelcoat used on cars?
 
I'll also have to disagree with Gel Coat being easily scratched...and since when is Wikipedia research? haha All my college courses clearly discredit it as a credible source for any information/papers.
 
paul34 said:
So, why are gelcoats used on boats and "automotive" paint used on cars?



Why isn't car paint used on boats, or by the same token, gelcoat used on cars?
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because gelcoat is alot of durable than paint.



It isnt used on cars because it is alot of work to maintain, and collision repair is difficult to match I would imagine. I'm sure there are other reasons too.



some Gelcoat work ;-)



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I believe some Corvette's (68-82) had gelcoats that where primed and painted over at the factory. I could be wrong though....
 
paul34 said:
So, why are gelcoats used on boats and "automotive" paint used on cars? Why isn't car paint used on boats, or by the same token, gelcoat used on cars?
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Gelcoats are used on boats simply because it is part of the fiberglass molding process. It is my understanding that the gelcoat is sprayed onto the mold after a mold release which allows the combined fiberglass gelcoat to release from the mold. Automotive paints are used on cars as a way to coat the surface material after it has been shaped and formed. Two entirely different processes.
 
My experience with gel coat has also been that it is tough and doesn't scratch easily. I typically use more aggressive products on it then I would ever use on clearcoat including a wool pad on a rotary for oxidized finishes.



When gel coat is oxidized it is extremely difficult to wax. It gets porous and seems to absorb the wax which makes it extremely difficult to remove. They key is using a product with a good UV blocker to avoid the oxidiation.



I just picked up a 23" wellcraft scarab concept late this fall. It's wrapped up now, but I plan to detail the heck out of it in the spring....can't wait!



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My dads 31' convertible has been repainted with AWLGRIP paint and has been holding up great season after season.



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Hope this is not a highjacking......



My dad wants me to do his boat, I've not seen it in a year, but remember it has oxidation. Like a Car do you Clay the gel first then compound, or no Claying needed?
 
Greg Nichols said:
Hope this is not a highjacking......



My dad wants me to do his boat, I've not seen it in a year, but remember it has oxidation. Like a Car do you Clay the gel first then compound, or no Claying needed?
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no need to clay. just wash or pressure wash (pressure washign make things so much easier), then you compound it. I actually left my marine stuff at home and had to do a boat for my dads friend while on vacation so I used my OHC and an orange LC pad and it works great. Foam pads gunk up pretty fast on gelcoat though, I used 3 pads just to do the hull. if its white you wont have to polish or anything after you compound, on a darker color boat you might have to, depends. just make sure you get ALL of the oxidation off, you might have to compound each section 2 or 3 times to get rid of it all. its very time consuming. if you dont get all of it off, the wax will stain where the oxidation is and look like crap.



Have fun....
 
Gelcoat completely blows topcoat paint out of the water in every aspect.



Fact: Gelcoat has less UV protection but if you are not waxing your car or boat every month (yes, every 30 days), then you are WAY outside of your maintenance schedule and you jacked the finish up anyways.



Paint is thin and very pliable. Great for an unstable surface like the thin aluminum on cars but the first time that metal flexes, the Gelcoat will pop off because it is HARD with enough flex for a sold and stable surface. (A finished surface should be mildly more flexible than the surface it is covering to be a solid bond)



Gelcoat is highly manageable and easy to work with if you understand it. (There is a reason many gelcoats from the can do not get completely hard and tack free right out of the can after kicking it off with mekp!)

They have a really good website with tons of great info on gelcoat here Boatcrafts.org • View topic - The gelcoat howto is here.
 
I used to build fiberglass fishing boats and I can tell you Gelcoat is pretty tough stuff once hardened. Gelcoat determines the color of the boat. After the mold has been cleaned, polished, waxed and sprayed with mold release it is sprayed into the mold. Several coats can be applied after which the fiberglass chop is sprayed into the mold on top of the gelcoat and rolled out. Layers of fiberglass mat are then laid in to build thickness and wooden stringers are glassed in to strenghten the hull. It was an itchy job!
 
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