updated gas tanks

S

SeaSpray

Active member
I have a question for those more familiar with gelcoat.

Since I could not leave my boat at the factory to get the gas tank upgrade Brett shipped me the tanks and installation materials. While I was at the factory he gave me a can of gray gelcoat to match the cockpit floor.

A friend helped me fiberglass the cleats to the floor and that worked out fine. I then did a test with the gelcoat and put about 3oz in a paper cup and added ten drops of hardener. The next morning it was hard.

I then mixed up a little larger batch of gelcoat and added the hardner and painted it on the cleats. The next day what was left in the cup was hard but the coat on the cleats was still wet/soft. After several more days it was the same. My friend suggested coating it with mold release to block any air. I did this on Dec 23rd and checked it today after returning from the holidays. It is still soft!

I am thinking I need to clean it all off with acetone and start over. The gelcoat is in a can with no label. Any suggestions on how to insure that is get hard this time?

Thanks,
Steve
 
being two component the only thing it needs is air oxygen ... too inclosed ??? if the fiberglass is still releasing gas's that could be it .... may need to set for a few days ..
 
Steve-

You're on the right track!

The gel coat won't harden when exposed to the oxygen in air.

Here's kinda how it works for everyone's understanding:

Polyester resin will set up and cure fine in the absence of oxygen from the air. This means that a layer of resin will cure on its side away from the surface, but remain tacky on the top side exposed to air.

This tacky surface allows boatbuilders to apply subsequent layers of resin and glass to previous layers as the tacky surface will bond completely to the layers that follow.

Therefore, the gel coat and all the layers of resin on a boat are layed up with resin called BONDING RESIN which has no wax in it to block out the oxygen.

Each of these layers stays soft on its top surface, and the subsequent layers can be applied one at a time without worring about the resin's surface hardening and preventing the bonding betweeen layers.

The last layer going onto the inside of a mold imust be laid up with SURFACING RESIN which has wax in it to block out the oxygen and allow it to surface harden.

To use gel coat resin on a surface application, you must block out the oxygen by one of several means:

Some folks use wax paper or saran wrap on the surface just after applying the resin to block out the oxygen. This works on small flat surfaces that can be laid up somewhat rough and then sanded smooth later.

A much easier way is to add a SURFACING AGENT OR WAX to the gel coat before you apply it. You can get such an agent at a marine or plastics supply house. The wax blocks out the oxygen, and the gel coat can be applied by brush, spatula, or by spraying.

I really don't know if applying the mold release (polyvinyl alcohol) will do much good after the gel coat has set exposed to air for awhile.

For the simplest solution, you can simply mix another batch of gel coat up wi the SURFACING AGENT and apply it over the first one. They will bond, providing you can remove the mold release first. Try a small test area after cleaning it with acetone or MEK (methy ethyl ketone) to soak up and wash off the mold release.

Maybe someone else has a deeper understanding of this and can add some more detail to this discussion.

Joe.
 
Yes I too think it was the heat, but it may be easier to wash it off then to try to heat a flammable surface. The heat lamp is a good idea though. Hope it works out for ya.
 
Sea wolf's authoritative answer is the one to follow. Air inhibits the cure. Clean it off and start over. I like mylar film as a barrier for gel coat repairs. Some of the kits for gel coat repairs come with a piece in them. Or, hit the office supply store for some, as drafting vellum, which will be frosted on one side.
 
Any temperature below 70 degrees F will retard the gel time. An under-catalyzed gel coat will also result in a slow cure. High moisture and humidity will lengthen the gel time.

Recommend a heat lamp for about 8 hours.
 
Steve-

The heat idea also has considerable merit. However, your under layers did set up ok, right??? So maybe there is already enough heat where you're working!

You might call the factory and see if they have already added the surfacing agent to the gel coat. This would eliminate one unknown quickly.

I thought about using a heat lamp, but figured if it was a lack of wax, you might just make the heat-thinned out resin run all over the place. If you do it as a trial on one cleat patch, monitor it closely as it heats up and thins out initially.

If the gel coat contains wax, eight or more days of waiting should have produced some hardening at least, I'd think. Your average temperature in Brentwood should be about 55 degrees F. The reaction rate (in general) for chemical reactions doubles (or halves) for each 10 degrees ddidfference Celsius, and the 15 degrees difference between 70 and 55 degrees F is only about 8 degrees C. Even with the humidity and lower temperature, it should come around in eight days, but you never know.

So after you give the facory a call you'll know what to do. If it has surfacing agent in it, you probably only need to carefully heat it up for a cure.

If it doesn't you'll have to remove the mold release and bond another coat on top of the first, or simply remove the first one and mix another batch of gel coat up and apply it. In either later case, you'll have to add the missing surfacing agent to the mix.

Let us know how it turns out! Joe.
 
Thanks for the info guys.

The gelcoat in the can does look like it has the surfacing agent in it. That was also why we did the trial batch first and it did seem to set-up with no sticky top surface.

Our thought was that maybe the surfacing agent was to thin or not enough in the thin layer applied. So I tried the mold release agent. Now I am thinking about getting a heat lamp and trying that for awhile. there is a full cover on the boat that goes over the radar arch so I can stand up and work under the cover. It also should hold some heat in. Being mostly under the splash well should also hold some heat.

It is too bad the tanks did not arrive a week earlier when the weather here was great up to upper 60's. Since starting this it has been mid 50's and rain most days. Oh well!

I hope to get the gelcoat finished so I can get the tanks installed by Monday. After that it is back to work and little time for projects.

Steve
 
With the running around I did today I did not call the factory. I did get a heat lamp and tried it for several hours. It did not seem to do much at all.

I used Acetone to remove the gelcoat from the cleats on one side. It was a much harder job than I thought it would be. Took me about an hour. The gelcoat was thick but soft and the PVA was waxy and together it was a thick sticky mess. But it did come off and did not seem to be cured.

What is interesting is that I had brushed a few stray scratches on the cockpit floor with the gelcoat when I was putting it on. These areas seem to have hardened. I don't understand how a small area could have hardened but the gelcoat on the cleats does not.

Tomorrow I will clean off the other 2 cleats and then mix a small batch of gelcoat. I will paint a small area on one of the cleats and a test patch on a piece of wood that I will leave next to the cleat. Not sure what I will do if the stuff on the wood hardens but the stuff on the cleat does not.

Steve
 
Steve-

This is getting weird!

If the mixture sets up in small amounts elsewhere, but not on the cleats, maybe we'll have too look at them to find the answer.

Perhaps the cleats are carrying away too much of the heat through their metal structure. Do they have metal straps attached to them to help inadvertently carry away heat?

The first fiberglass/resin layers were much thicker, producing and holding the heat longer.

The thin layer of gel coat applied on top of the other layers and the metal may not be able to set up without some help.

The first batch of gel coat might have become unable to be polymerized with moderate heat after laying around exposed to air and having extra PVA applied over the top of it, trapping oxygen and other air gases in the resin and preventing the polymerization bonding.

If all this is true, and not just theoretical B.S., you need to apply a new batch and apply moderate heating from the get-go to drive the setting up process.

Might try it out with a block of wood, a piece of stainless steel, and a couple of screws to simulate the cleats in the boat. Would also give you a test situation to see how much heat you need and can safely apply, etc.

Whatever you do, keep us posted, as this is getting interesting!

Joe.
 
Hi Joe,
I was just getting to this post.

Before applying a new coat of gelcoat I mixed a very carefully measured batch and brushed it on a piece of thin plywood. This time I used significantly more catalyst. I heated it with a heat gun and it hardened in about 15min.

It seemed that I had just not used enough catalyst. So I mixed a new batch and applied it to the cleats. I then heated it for about 30min. It seemed to be getting harder but not like on the plywood. Also, the gelcoat that was beyond where we had used the epoxy and galss was harder that that on the cleat.

At this point I let it sit for an hour or more while I had dinner. When I went back out the gelcoat on the cleats was still very tacky. I spent the next 1 1/5 hrs using the heat gun trying to get it to harden. It was better but still not as hard as the test sample.

The next morning I decided to go ahead and put in the tanks. It was hard enough that there was only some minor scuffing but I was trying to be careful. I don't think it will get fully hard until the temperatures get back above 70 for an extended period.

I don't understand what the difference is. It does seem that the gelcoat has a harder time setting up when it is applied over epoxy and glass versus the vinylester and glass. The gelcoat that is just on the original part of the boat is hard as nails.

I will post some pics in my album.

Steve
 
Steve- Thanks for the info. It will take a person pretty well versed in various types of resin layups to explain this difference in how the gel coat lays up over different surfaces. Hummmmm..... Joe.
 
your first application was the fiberglass ...
your second application was the gel coat ...

would the first application not have to cure for 30 days???
their may be a reaction between the two applications ...
the first is still giving off solvents ...

different systems have spacific recoat times
if nothing else you have everyone guessing .. lol
 
Steve-

I've just done some reading on this topic, and, in general, applying polyester gel coat over epoxy is not recommended.

The polyester gel coat won't set up properly on epoxies especially where unused epoxy catalyist provides amines which interfere with the polyester bonding to the epoxy and the polyester hardening itself.

To properly apply a polyester gel coat to an epoxy resin, the surface must be sanded to remove any wax and amines, washed with solvents, and allowed to breathe in the air. Then a "tying coat" of epoxy paint is recommended, followed by sanding again and then the application of the polyester gel coat.

But some gel coat manufacturers don't recommend it, period.

Here's a couple of links where some of this is discussed:

http://www.epoxyworks.com/22/polyester.html

http://www.systemthree.com/faqs.asp

Enjoy! Joe.
 
Well there you go! My friend that helped me with this has worked with epoxy a far bit but probably not the gelcoat. Wish I had known this before.

Since I want to get the boat back together I will leave it as it is and see if the gelcoat will harden further. Basically it is sound, it's just a matter of if water could eventually penetrate the wood cleats.

Thanks for the research.

Steve
 
Back
Top