I shot my hatch cover yesterday with gel coat and Duratec High Gloss Additive using my Apollo HVLP sprayer. Duratec is an additive much like patch booster that thins gel coat so it can be sprayed. The benefit with Duratec per the manufacturer is an open air cure and gloss finish that does not require sanding. I shot my hatch cover as a test to see if I could use gel coat and Duratec as a solution to spray the gutter area of the new decks I made. I am trying to avoid having to sand the gutters as that would be a major PITA. Here is one deck section showing what the gutters look like so you guys understand why I want to spray and not sand:
The problem I ran into yesterday is that I ended up with several pock mark looking patterns from my gun. The pock marks are deep and are going to require me to sand down almost entirely what was shot. I used a 1.3 mm tip on my gun. I did that because the viscosity with the gel coat/Duratec at the recommended 1:1 mixture is pretty low. Spray distance from the gun to the surface was probably 18-20". Do these pock marks indicate too rich or too lean on the material adjustment? When I went leaner, I was getting a much more sandy looking finish that would indicate too lean to me. Is this an indication the tip size is wrong? I can go down to a 1.0 mm tip or up to a 2.0 mm or even 2.5 mm tip (although I think 2.5 would be too big). Here is what the result was yesterday:
JohnV8R,
John looks like there is some moisture or a contaminate that is trapped in the material or surface that your deck is made of. Used a heat gun or heat lamp to dry out the material sand it all down and re shoot the hatch. Also wipe down with acetone or denatured
Pete Fallon
Thanks for that. I actually used Total Boat Dewaxer & Surface Prep to clean the surface before I shot the gel coat. First time I used that. I don’t know why, but I have not been able to get denatured alcohol at Home Depot here in CA for about 3 months. I clean my gun thoroughly after each use with acetone, BUT the last time I used it was a final coat with Patrick’s Patch Boost trick. I wonder if there might be some residual Patch Boost in my aluminum cup on my gun. Also, I use my MEKP measuring bottle to measure surfacing wax by pouring the wax into the top measuring part of the squeeze bottle. I wonder if there is some contamination in the measuring part of the bottle.
If that pock mark pattern indicates contamination, I at least know where to start.
I guess I’m about to find out if the open air cure from Duratec cures gel coat as hard as wax surfacing agent. I’ll sand it down, thoroughly clean the surface, hit it with a heat gun, and start over.
Thanks!
Last edited by JohnV8r on Aug 30th, '20, 18:37, edited 1 time in total.
JohnV8r,
It really looks like some type of contamination clean your gun pot, measuring bottle and anything else your using to spray gel coat. Water in your air sprayer line could also be a factor. You might even have some contaminated gel coat or gel that got overheated during all the hot weather this summer, we used to keep our gel coat in the refridge or in an air conditioned shipping container especially in hot Florida.
Pete Fallon
My guess is moisture contamination, or maybe oil, in the air. What are you using for a compressor? How are you drying the air? Dryers need to be far down the line from the compressor so the air cools before it hits the dryer. I made a contraption cooler/dryer assembly from copper pipe that works really, really well. The air cools and condenses as it flows through the piping. I stuck a water separator at the outlet just for insurance, but the pipework alone did the job. Exit air was bone dry and cool. Drain valves down low to drain off the condensed water. I saw something like this on the internet, so you know its good! It really works and was 100% easy to make.
I am using an Apollo HVLP turbine, which does not have a tank that could collect moisture. I'm in Northern CA with a current relative humidity of 30%. Moisture isn't the issue here.
I contacted Fiberlay today - the gel coat manufacturer. They referred to this as "fish eye" and gave me some great information:
1. They are 90% certain this is contamination from the way I prepped the surface. The primary thing they think happened here was the way I did the final cleaning with the Total Boat Dewaxer & Surface Prep. I wiped it down several times with a liberal amount of cleaner. However, they told me despite the high flash point if I don't keep the rag moving until there is no wetness left on the surface it will leave contaminants on the surface. It's a small detail, but one that I have never heard mentioned in all the literature I've read about spraying gel coat. They recommended I use acetone to prep the surface.
2. 10% possibility there could have been some contamination in the gun, but the even distribution of the "fish eye" indicates a likely surface contamination.
3. There was some existing gel coat that I had sanded down until fair. The last sanding was done with 180 grit paper because I had run out of 120 grit. I had 80 grit and 180 grit. I zigged; should have zagged. They recommended I do a final prep sand with 80 grit, and then lay down a mist coat on the first pass. Wait 60 seconds, and then lay down a wet coat. They stated that would create a better mechanical bond with the surface.
4. They recommended I do an initial pass or two on the areas I don't want to sand/polish with gel coat and 15% MEK (not MEKP) as a thinner. Then come back over it with a 1:1 mixture of gel coat and Duratec High Gloss Additive. I was told I would be happier with the build up that way.
5. I asked if my gel coat got hot if there was a possibility I could damage it so it caused fish eye. I was told gel coat temperature at the time it is sprayed is important due to pot life concerns. However, if you leave your gel coat in the trunk of the car and cook it for a week, it will cause cure problems as the gel coat shelf life will accelerate. That causes cure problems, but not fish eye.
6. The last thing I was told was they think it would be better to use my 2.5mm tip even with the Duratec High Gloss Additive to get the most material out of the spray gun in as little a time. When I told them I used a 1.3 mm tip on this piece, I was told the time required to get gel coat out of the gun cup with a 1.3 mm tip would likely causing different levels of catalyzation that could create problems.
Hope passing that along helps someone down the road.
To get as close to a match on the original Bertram gel coat color used on my Bertram 31, I cut a 3" section of the original sink counter where the gel coat had been covered by the cabinet area on the sink. It never saw the light of day and was, therefore, the most "virgin" color sample I could come up with on Shambala. Fiberlay did the color match and I had them list it as "Bertram 31 Off White." It is available for sale to anyone who asks for it by name.
There could be the possibility the gelcoat is not compatible with the Duaratec ,this does happen and people who sell the stuff typically do not work with it and have no idea. You will always be “the first time they have heard of that “
Try another smaller batch and see if you get the same result
You might also find spraying it 50/50 through a 2.5 it will end up running on you
Let me know if you get a different result, but I have my doubts
Gelcoat and duratec is not sensitive like paint, you can literally put it over a greasy surface and it won’t react like paint when a tiny molecular droplet of contamination causes surface issues
Had to postpone spraying this weekend because of the unusually high 'low' temperatures in the morning and the particulate matter in the air from the CA fires. I will attempt to shoot on Thursday or Friday morning depending on the fires and wind direction.
JohnV8r wrote:Had to postpone spraying this weekend because of the unusually high 'low' temperatures in the morning and the particulate matter in the air from the CA fires. I will attempt to shoot on Thursday or Friday morning depending on the fires and wind direction.
You forgot one thing, as long as you have electricity. Sorry had to say it.
Still waiting due to the fire smoke and particulate matter in the air. Low air temps are problematic (too high) right now until Friday also.
Shambala is on the hard at the Napa Valley Marina. I had to call the marina yesterday to tell them she could go in the water and escape under her own power if necessary.
I just power washed all the ash and debris off from the North Complex fire two weeks ago. Here we go again...
Last edited by JohnV8r on Nov 6th, '20, 20:09, edited 1 time in total.
Re-shot with Duratec after sanding and thoroughly wiping multiple times with acetone. Gun was so well cleaned it looked brand new. No runs with the 2.5mm tip and the HVLP compressor. However, I got fisheye again. At this point I really don't care what the issue is. The Duratec now resides in my trash can waiting for permanent evacuation next week. Duratec is out.
Went back to Capt. Patrick's patch booster method and everything went fine. First two coats were thinned with 10% patch booster. Third coat was thinned at 20% + 10% wax surface seal. I'm through stage three on Capt. Patrick's method. Need to sand and shoot the final coat per Capt. Patrick's method. I'll post pictures once that's done.
i posted it already too- the place that sells it to you will say they dont know why its not working for you, they sell it all the time, etc etc
fact is they dont apply it they just sell it
even some replacement material doesnt make up for the lost time. Always advise a small test batch before committing fully
You definitely called it Rob. I'm never using Duratec again.
Here are a couple of pictures of the hatch once it was shot (but not sanded & polished out) with Capt Patrick's method. The patch booster definitely reduced the orange peel, especially on the horizontal surface:
