need to gelcoat my boat

VE gel coats are good for tooling and chemical resistance, but not much else, they weather so poorly that outdoor use is almost out of the question, as they chalk and yellow rapidly. We stopped making VE gel coats for anything other than tooling, partly because the demand is very low and the weathering issues.



The company I worked for had been making the same products since the late 50's, I started working there in the 70's and worked with, or for them for the next 20 years. I was able to see 30 year old units that had been exposed to very harsh environments the entire time and see how they survived. I was also able to see parts I personally made 20 years earlier, I could see what worked and what didn't. It was amazing that I could see the exact spray pattern I had used on the parts in the fade and discoloration of the gel coat. I knew where I wasn't close enough, where I was too close, where there was overspray on the mold and the thick and thin areas, also the thin areas that were hand painted after the gel coat cured, these were all visible in the finish.

Hand painted areas that are done to cover thin areas on the mold may not bond as well to the gel coat as the laminating resin does, so these areas may peel or blister easier and sooner. This is even more of a problem if putty (resin or gel coat) is used against the gel coat, these areas are much more likely to fail due to a poor bond (for the same reason as stated below). Now I always recommend brushing resin on the gel coat first before applying putty to fill a radius or any contour on the surface (using putty on the back side of gel coat to fill hard to roll areas, or spots that may hold air is common)

Gel coats also don't bond to sanded gel coat as well as a resin will, mostly because of the fillers and pigments. Most of the styrene and resin is being used to wet out the pigments and fillers, so there is less available to stick to the substrate, whatever it might be. That's why I say 80 grit is better.

 

Tynaje

I was typing when you posted.

You are correct that normally when you buff gel coat the shine does not return to what it was when removed from the mold.

There is a very thin layer of resin at the mold surface, resin can hold a gloss, fillers and pigments don't shine as well, so after sanding and removing this layer, the gloss "may" not be as good as it once was. As you thin the gel coat with Duratec clear, you cut the amount of those two products and are adding resin and ?, making the gel coat more translucent, which can make the color look richer and allow it be buffed to a higher gloss. The problem is you are compromising the integrity of the gel coat by adding such large amounts of anything. Softer gel coats tend to be easier to work to get a high gloss, but are less water and UV resistant and in testing Duratec tends to make gel coat softer.

If gel coats were formulated for post coat applications they would work much better for that use, but the market is so small for that type of product, it makes it difficult to justify the R&D costs.

Reworking old gel coat may or may not work, a great deal depends on how well it was applied, the color, type and brand used. I've seen fantastic results and finishes that just never came back.

We do make gel coats that have significantly higher gloss, deeper colors and can be buffed to a much higher gloss. They are fairly new and cost more.

 

alot of great information!!! i have 20 years in collision repair (painter) and play with boats on the side. always loved plastics.

the only gel coat products i have access too locally are from a company called ADVANCED PLASTICS .with their label , so i don't know who's product it really is..
the few sea rays i have done and other boats i would order through mini craft..

i have a catolog from LBI. they make it sound as the ve gel coat is the best for bottoms , etc. so , i guess that is just questionable sales tactitc? if we can sell /market/ it ,good for us? kinda thing?.

so , i guess my next question in gel coat 101 is ....

who or what manufacture makes the best gel coat?

teachers , your up

 

I could see using the Duratec primer on the entire hull, then spray your gelcoat over the Duratec. I never used their product until I built the Cape Fear 38 in '99 and used it to prepair the prototype for tooling. Nothing like turning the production plug into a boat. I had fought using their products because of the high cost. I had always used my own shop putties and then followed by some form of paint. I soon saw the light though. I also prefer automotive Acrylic Urethanes to any marine product,but it is not easy to promote.
As for LBI, be very VERY careful of product shelf life. I had to edit and delete several times to write that short burst.
I really dont expect the application to last the remaing life of the boat, but introducing more moisture would not be a result I want. But if the comparison is paint vs gelcoat, the Duratec/gelcoat method wins in cost, appearance and timely blistering. It is such a pain to deal with those tiny blisters that follow Awlgrip (urethanes)and equally a pain to raise that waterline to help fight those nasty blisters.
One thing I do is to apply the boot top first, just make it as thick as possible and leave it alone. Then tape the topcoat leaving roughy 1/64 of the boot top visible. Pile the topcoat on, color sand and when you are done, there is a smooth molded look and feel.

A good friend is the production manager for a high end production company. He was telling me about a new product that is being introduced to builders by a high end product manufacturer. As you mentioned ondarvr, using high end materials is key, most individuals dont have access to those products. I will have to call and ask him what the stuff is called, they are keeping the "brew" secret so far. But they claim 90 to 94% buff back.
I have always enjoyed talking to Minicraft, they solved so many of my unanswered questions when tooling the 38. Although I have been building boats since the 70's using evey possible resin and material, every boat has been a one off. Those guys were just the best source of info.(Duratec has been their equal for readily available info as well) One of my owners wrote saying Minicraft was no longer selling Duratec and they had formulated their own mix to address this new trend.
I just really like the idea of not having all those thermally unstable primers under paint. Sanding with 80 grit, then gel application, really saves tons of paper costs. Using the gelcoat as a colored primer is handy also, just too many benefits to ignore.
One thing I havent done is to physically weigh all the products, that would be interesting.
So far, a boat I sprayed in 2003 is holding up better than the Urethane on Tynaje, which I srayed in 01, before I accidently came across the gelcoat/Duratec mix (this mixture changed every time I did a boat btw, that IS a pain, keeping the different formulas for these boats ie repairs)
I have to add that I love the paint process, am a car NUTCASE. But if I want to make money and have a happy customer right out of the box, without someone whining about orange peel, dulled areas or the need to redo because conditions changed mid paint, I think you know what the answer is. (yuk long sentence)
The industry really needs to address this..........get ready for waterbased paint out here soon. I know, the "green" paints are amazing in the automotive industry, I watched American Hotrod and saw the killer jobs, but gotta have a killer booth too.
Great GREAT read odarvr.

 

don't plan on buying from LBI , just have their catolog ..

so , who are the big players in gel coat? or the best?

i know who the paint players are , but so many different compaines label gel coat as there own when it's really another manufacture...

 

This is what I use, so far.
http://i119.photobucket.com/albums/o145/Tynaje/Bertram%2025/P1010020-1.jpg

I will do my best to contact my friend who runs the Southport Boatworks line and wrangle some names, may have messed up mentioning his companies name though........funny industry really. The tough part is gaining access to these products, even if you are in the business. I have an account with Composites One, they are the most complete source of professional products in one place. HOWEVER, the supplier in NC is far more helpful and pleasant to deal with than the supplier here in RI. I just hate ordering there, just not very friendly and most definately not so familiar with their own stock. Not to mention no real catalog, kind of odd really.

No matter what company you go with, remember shelf life. This stuff goes bad fast.
I sometimes buy "odd Lot" gelcoat drums to make large batches of shop putty to fair hard plugs. The odd lot stuff is beyond shelf life, which just means it will never shine, dont know why. But it is still fine for mixing with micro balloons and silica (aero sil or cabo sil) and provides an ok to sand ultra hard easy to prep for plug surface. Using the odd lot mix, I can wetsand and buff( am not looking for shine, just smooth) and apply the release agents right away and dont need to apply any other hard surface. Well, that is just me trying to save a buck where high dollar products are not needed. Anyone I hired to help fair such stuff did cry all day, but it was always my feeling they were lazy anyway.

 

shelf life AND temperature's, too hot or too cold just once messes with them pretty bad

 

good thread

ok Jack , we spraying the dinghy??

 

what did you use paint or gel

 

i think he's a paint tease heh

 

I have used duratec for many years, I have sprayed many boats with it and never had a complant, the product works great , you can spray gel many ways everyone seems to spray there own way and got there own tricks, fibreglass and gelcoat falls under many unbrellas from autobody, boatwright,aerospace, pipe and duct work, tanks , you name it fibreglass is involed. So as a result many different trades have had a influence on how to work with it, take a painter that has worked all his life painting highend cars and ask him how to spray gel . or take a guy who as been relining holding tanks for the chemical industry you will get two very different answers
Before we had Duratec we had to thin down the gel with styrine or acetone in order to pass it through the gun, the trick was to let the thiners flash off between coats so they didnt get traped, if you know how to do this acetone will do a good job if you dont the job will be a mess, we also use airdry wax added to seal out the air, if the temp is cool the wax can form into little particals and the result will be little pits in the gel after you sand and buffed, if done right the wax will do a good job, another thing guys do is spray a top coat contaning the wax this way the wax is on the top surface and stops the problem with pitting, Pva is also often used once the gel is sprayed a top coat of pva is sprayed over to block the air, this works good but you will have to know the window to spray to soon and you may screw up the job to late and it wont block the air,
to help with the flow and help level the gelcoat guys would often add a little resin in the gel say 10% which i have done myself many times,
gelcoat is not easy to spray i have spent many days sanding and redoing over the years and still have a few of them from time to time,
we have gone from laying up boats in sheds with a chopper gun so resin rich they wiegh a ton to resin inffusion in climate controled shops.
on other thing is the gelcoat containes the UV block not the pigment yes the more pigment the longer the gel will hold up to fading, just tel your sulplier that you want to use durtec and have your pigment ratio incresed to allow you to use duratec,

 

well , i have to say that this thread has got a ton of usefull information!

 

This is the typical type of response when people discuss gel coat, everybody has there own idea of how it's supposed to be used and while there is a grain of truth to many of the opinions, there is also a great deal of misunderstanding.

If you follow the suggestions given by the manufactures the results will be much better and longer lasting, when you wing it as a chemist and start adding things, or using techniques that are not recommended, your chance of having problems increases dramatically.

Resin does work to reduce gel coat and can be better than most other things, thats why resin is an ingredient in most patchaid type products, the resin used in these products is the same high quality resin thats used in the gel coat only unthixed so it will reduce the gel coat with less added. Many laminating resins are of much lower quality than the resin used in gel coat and have terrible weather properties, so they will degrade the product.

Most gel coats have no UV blockers or inhibitors other than the pigment and filler, so adding anything that reduces the % of these allows more UV light to come in contact with the base resin and break it down.

UV inhibitors typically give gel coat a yellow cast, so it will start slighly off color on the yellow side, as the UV inhibitor is used up, the gel coat will sometimes turn whiter before getting yellower on it's own. In the lab we have found little benifit to adding UV products to colored gel coat.

F/G J

You are very correct in people from different trades using gel coat differently, we run into this problem frequently. Gel coat is it's own product and needs to be used and sprayed as gel coat, not like it was an automtive paint or any other paint or coating. Also the same basic rules apply to spraying gel coat no matter what product is being built.

 

now that I am a 3 boat owner I'll provide the test beds for different techniques