Scratches on swim platform

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STB said:
I can't argue with your logic. Seems sound to me.

Is suggest hopping on Hull Truth or anywhere else you see a thread about it, even a dead one, and asking about single coat coverage.

The two things I wonder about are...

1) whether, if the gel is heavily diluted, it'll still be able to provide good enough 1-coar coverage, and

2) whether it kicks as quickly as a normal gel mix, allowing multiple coats quickly after each other, or if each coat requires more time.

But, again, I'm just wondering. I've never used it.

I look forward to your full report, whatever you use! Can't wait for the pics!
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I have tried twice to apply gelcoat. It has to be a weekend with warm good weather while I also have time, so the timing is important.

The first time I used the paste form gelcoat in the Evercoat repair kit. I thought the paste could be thinned like kids watercolor paint which I could apply using a brush to have a smooth layer, but as it turned out, the gelcoat paste remained to be a paste even after being thinned a lot. When brushed on, it looked rough. I had to sand it down later. One thing to note was the white tint tube in that kit was less than 1/5 of its capacity. The brushed paste was not runny.

IMG20240921184612.jpg


IMG20240921202307.jpg


The second time, I ordered Totalboat laminate white gelcoat, added some black tint from the Evercoat repair kit, 10% styrene, and applied using a preval sprayer. It sprayed easily, but the tint did not fully mix with the gelcoat even though I mixed a long time. The tint clumps were sprayed out and ruined the efforts. So I wiped it clean with a lot of acetone.

The sprayed gelcoat was runny and flowing. Is this expected?

IMG_20241020_195637.jpg


I will try again next time. Does the Evercoat tint not mix well with Totalboat gelcoat? Or did I miss anything?

IMG20241020194456.jpg
 
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Hi PaulGA,

Can you post links to the kit you got the tints from and the gel coat you used? I'll take a look and see if I can sort why they didn't play well together. But, that probably won't fix them not playing well together!

The sprayed gel cost gets runny like that when it is sprayed to thickly for the viscosity. It might also be spraying from too close.

The dimensions you can optimize across are the viscosity of the gelcoat, the distance from the sprayed to the work, and the speed of the stroke.

I always practice on cardboard first and tune my mix until it goes nicely for me.
 
BTW, you are doing the right thing to try and try again. It may be tuition, but the education will be lasting and empowering.
 
STB said:
Hi PaulGA,

Can you post links to the kit you got the tints from and the gel coat you used? I'll take a look and see if I can sort why they didn't play well together. But, that probably won't fix them not playing well together!

The sprayed gel cost gets runny like that when it is sprayed to thickly for the viscosity. It might also be spraying from too close.

The dimensions you can optimize across are the viscosity of the gelcoat, the distance from the sprayed to the work, and the speed of the stroke.

I always practice on cardboard first and tune my mix until it goes nicely for me.
Click to expand...
evercoat gelcoat repair kit
1729515273689.png

TotalBoat marine gelcoat white quart no wax
1729515385078.png


it liquid tint easier to blend with gelcoat?


It's probably spraying too close. spraying the edge while squatting down on the swim platform is awkward and difficult.
 
You will either have to add wax to the laminating gelcoat or spray PVA over it or it won't cure properly. The Evercoat gelcoat tint should mix in just fine, that's an odd result. Any chance it's gone bad and setup?
 
lwarden said:
You will either have to add wax to the laminating gelcoat or spray PVA over it or it won't cure properly. The Evercoat gelcoat tint should mix in just fine, that's an odd result. Any chance it's gone bad and setup?
Click to expand...
I have PVA. Preval sprayer is able to make a mist of PVA easily.

It was said the min temp to gelcoat is 60F, it may not cure properly if the temp is lower. the temperature over the coming weekend is 60/40F, is temp too low during the night for the gelcoat to cure?
 
PVA and the Preval should be fine to seal it. Can you get a heat lamp on the area? 60F should be ok, but lower than than isn't ideal. Also, you can use a heat gun on a warm setting to help the gelcoat flash off between coats, this works well. If you lay it on when it's cold it will take a long time to flash off between coats. You should let it get to the point where you can just put a fingerprint in it before adding another coat or it will run/sag.
 
lwarden said:
PVA and the Preval should be fine to seal it. Can you get a heat lamp on the area? 60F should be ok, but lower than than isn't ideal. Also, you can use a heat gun on a warm setting to help the gelcoat flash off between coats, this works well. If you lay it on when it's cold it will take a long time to flash off between coats. You should let it get to the point where you can just put a fingerprint in it before adding another coat or it will run/sag.
Click to expand...

below paragraph is from www.fibreglast.com

  1. Ensure that your mold surface is properly prepared and has a Class 'A' finish. For more information on this, please see our Learning Center article- Plug Surface Preparation and Mold Surface Maintenance.
  2. Thin gel coat to your preferred viscosity using #70 Styrene Thinner or #1039/1040 Duratec Clear Hi-Gloss Gel Coat Additive.
  3. You can catalyze gel coat with #69 MEKP at 1.5-2.5%. Due to the lower monomer content for low emissions, we suggest catalyzing the LE gel coat at 2% depending on ambient temperatures. Mix thoroughly to ensure that all gel coat is properly catalyzed.
  4. Apply gel coat to mold surface. Spraying gel coat is recommended for more accurate and consistent coverage. Apply gel coat in 4-5 layers at approximately 5 mils each, allowing 15-20 minutes between layers for a total thickness of 20-25 mils. Use #122-A Gel Coat Thickness Gauge to ensure proper thickness is achieved.
  5. Once gel coat has tacked up, about 20 minutes after final layer has been applied, lay-up of the part can begin.
here are my questions:

Using long sweeping strokes, left to right, right to left, then to right: is this considered one coat?

Is 15-20 minutes wait time between coats a bit too long? I remember the final layer should not wait too long before PVA, otherwise it may not cure

What is the "lay-up of the part" in step 5 above?
 
One coat is just enough material to create a glossy surface, so depending on how far your spray tip is away and how fast you move the gun it might be a couple passes. The instructions above are for making a part off a mold, so you can ignore the lay-up part which would be laying glass and resin over the partially cured gelcoat. You will want to spray the PVA after the last coat has tacked up just like the other layers.

If you are looking for some better guidance, Andy at Boatworks Today on YouTube has some great videos on patching gelcoat.
 
lwarden said:
One coat is just enough material to create a glossy surface, so depending on how far your spray tip is away and how fast you move the gun it might be a couple passes. The instructions above are for making a part off a mold, so you can ignore the lay-up part which would be laying glass and resin over the partially cured gelcoat. You will want to spray the PVA after the last coat has tacked up just like the other layers.

If you are looking for some better guidance, Andy at Boatworks Today on YouTube has some great videos on patching gelcoat.
Click to expand...
Using a heat gun on the low setting (DeWalt DCE530B) to sweep a few times from a distance of about 2 in, is it enough to tack up the coat? So I don't need to wait 15 to 20 minutes before spraying the next coat?

15 minutes is longer than the working time of one batch.
 
paulga said:
Using a heat gun on the low setting (DeWalt DCE530B) to sweep a few times from a distance of about 2 in, is it enough to tack up the coat? So I don't need to wait 15 to 20 minutes before spraying the next coat?

15 minutes is longer than the working time of one batch.
Click to expand...
Yes, a heat gun will make it tack off in a few minutes, just go easy, it doesn't take much heat to flash off the solvents. If the batch is going off too fast for the temperature then back off on the MEKP a few tenths of a %.
 
lwarden said:
Yes, a heat gun will make it tack off in a few minutes, just go easy, it doesn't take much heat to flash off the solvents. If the batch is going off too fast for the temperature then back off on the MEKP a few tenths of a %.
Click to expand...
The guideline on mekp is generally 2% in volume. Totalboat instruction says 14-16 drop per oz resin in 70s degree, and add more in colder temperature. Based on a drop is 0.05ml, 15 drop is already 2.5%. it's a bit generous on the catalyst.
 
lwarden said:
PVA and the Preval should be fine to seal it. Can you get a heat lamp on the area? 60F should be ok, but lower than than isn't ideal. Also, you can use a heat gun on a warm setting to help the gelcoat flash off between coats, this works well. If you lay it on when it's cold it will take a long time to flash off between coats. You should let it get to the point where you can just put a fingerprint in it before adding another coat or it will run/sag.
Click to expand...
Do you need to place a heat lamp near it overnight if the ambient temperature drops to 40, so the gelcoat can cure properly?
 
lwarden said:
A heat lamp is a good idea if temps are that low.
Click to expand...
Are you referring to a heat lamp like this, it's for curing large areas. I didn't find a smaller one.

Is a small 500w Walmart oscillating heater (low setting) and two nights adequate to cure?

1729682879707.png


1729683626098.png
 
That's overkill for such a small area. I have a couple of these I use.

And these for bulbs.
 
lwarden said:
You will either have to add wax to the laminating gelcoat or spray PVA over it or it won't cure properly. The Evercoat gelcoat tint should mix in just fine, that's an odd result. Any chance it's gone bad and setup?
Click to expand...
Does any resin pigment work with gelcoat, like this one ?

 
I don't know about that. If it's for epoxy it probably won't be compatible with polyester. I use these from eplastics.com, but any local fiberglass supply place usually has them. They also have a couple combination yellow/brown mixtures that are good for tinting a bright white to cream used by many boat builders.

2 Oz Bottle Black Pigment at ePlastics

ePlastics stocks and sells pigments for use in a wide variety of epoxy and resins for use in marine, surfboard, and general fiberglass/other palastic projects.
www.eplastics.com www.eplastics.com
 
I did the gelcoat again. Took me about 4 hours to go through the steps -

I drew 1 oz gelcoat into a 2oz container. 1 oz because it's easy to see the 30ml mark on the container and calculate the volume of styrene and mekp. Then I added 3ml styrene then some yellow and brown tint, did color matching. This time I used a liquid tint and Andy's color matching tip, and also an M12 screwdriver with a mixer attachment. This got me a uniform mix of off white color. when the color was close, I added 15 drops of mekp and mix well again, poured the mix to a Preval touchup jar, then started to spray the prepared surface. I did four coats using heat gun in between.

All seemed going well until I started spraying PVA onto this corner. At that time the first sprayer (from west marine) was done, so I switched to the second sprayer (from home depot). both sprayers have exactly the same packaging inside out, but the the HD sprayer was giving some inconsistent spraying. It would make consecutive empty sprays followed by a few splatters, repeating this pattern, making some PVA mess on this corner. PVA was running down into some opaque drops. I don't know why the second sprayer felt different than the first one. This corner may not look good after polishing. If it cures I would mark this project as complete.

IMG20241026203119.jpg

my original plan was to make a new batch using Duratec Clear Hi-Gloss Additive for the 4th (final) coat. this would remove the need of applying PVA. But at that time there was no more natural light for color matching, so I used the PVA method.

One afterthought: just before the final coat, add some duratec additive, mix well then spray. But at that time there were only about 10ml gelcoat left in the jar that contained some styrene. this may work even thought it's difficult to decide how much additive to add.
 
Hey PaulGA,

Sorry I forgot to get back to you about the tints. But, it looks like you sorted it.

I've had bad spray tips on those prevails before. I've always test sprayed onto cardboard first.

But, as long as you let the gelcoat kick before you sprayed the PVA and got good coverage, even if somewhat splattered, you should be fine.

It should polish up nice once cured.

Good work!
 
The PVA doesn't have to be pretty, in fact, you can brush or dab it on. It just needs to be a continuous film over the gelcoat. Go easy on the sanding to remove the orange peal, but it looks pretty good to me.
 
The gelcoat hardened the next day. This is the looks when I removed the tapes today.

Thought to do polishing today, but didn't complete. First, I cleaned the surface using acetone to prepare for sanding. The acetone ate into the new gelcoat and the cloth picked up some. Does this mean the gelcoat has not cured properly?

After the surface air dried, I started sanding using 600grit. The sanding paper gets filled up, but the orange peel did not get smoothed after a long time. Im thinking about getting a P1000 or 800 sanding disc on a polisher to speed up

IMG20241102180524.jpg
 
If the PVA gets sprayed before the gelcoat kicks, it can interfere with the curing at the surface, but as long as PVA coverage was good, it still seals it, and underlying that normally cures fine.

As long as you got good PVA coverage the good depth should be thin.
 
STB said:
If the PVA gets sprayed before the gelcoat kicks, it can interfere with the curing at the surface, but as long as PVA coverage was good, it still seals it, and underlying that normally cures fine.

As long as you got good PVA coverage the good depth should be thin.
Click to expand...
Do you use acetone or just water to prep the surface before doing the polishing the next day?
 
paulga said:
Do you use acetone or just water to prep the surface before doing the polishing the next day?
Click to expand...
I just use water. PVA is super water soluble. Water will clean it as well as the most powerful alternative solvents.

I use acetone to clean gelcoat all the time. Routine exposure for cleaning should be totally safe.

Taken to an extreme, acetone can and will damage gelcoat, causing it to craze, chaulk, goo, etc. But it it takes a lot of exposure for that to happen. Hours? Days? Weeks? Dunno'. Acetone usually evaporates very quickly, making it hard to cause damage, even if you try.

I tried hard (onbscrap material) for an experiment, just to see, by soaking a towel and covering it with a glass dish for days, keeping it wet, and then looking. It got gooey and then as it dried later, failed in a lot of ways. But this was crazy, unrealistic exposure.
 
STB said:
I just use water. PVA is super water soluble. Water will clean it as well as the most powerful alternative solvents.

I use acetone to clean gelcoat all the time. Routine exposure for cleaning should be totally safe.

Taken to an extreme, acetone can and will damage gelcoat, causing it to craze, chaulk, goo, etc. But it it takes a lot of exposure for that to happen. Hours? Days? Weeks? Dunno'. Acetone usually evaporates very quickly, making it hard to cause damage, even if you try.

I tried hard (onbscrap material) for an experiment, just to see, by soaking a towel and covering it with a glass dish for days, keeping it wet, and then looking. It got gooey and then as it dried later, failed in a lot of ways. But this was crazy, unrealistic exposure.
Click to expand...
It has been a week since the gelcoat was applied, and it felt solid to the touch from day 2, so I thought it should be immune to acetone just like seasoned gelcoat. Agreeably it could be PVA destroyed the top layer.

If everything went as supposed and the gelcoat cured properly, will the new gelcoat be acetone-proof from the next day?
 
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Acetone will eat into fresh gelcoat. You only need warm water to remove the pva. If it gummed up the paper after curing for a week it didn’t cure correctly for some reason.
 
lwarden said:
Acetone will eat into fresh gelcoat. You only need warm water to remove the pva. If it gummed up the paper after curing for a week it didn’t cure correctly for some reason.
Click to expand...
Should I sand the new gelcoat completely away, or just light sand using 400 grit, before reapplying gelcoat?
 
I'd sand away anything that could be compromised.

I don't know from experience whether brief exposure to acetone will eat week-old gelcoat or not. But, my intuition is that it shouldn't a week is a long time to cure.
 
It has become too cold during the night for the gelcoat to cure properly
I have to accept what it looks now and potentially redo it next summer
Appreciate your inputs @STB @lwarden
 
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