Faded, Chalky and Thin Gelcoat

[Suijin]

Originally Posted by minaret

Ask 'em! Don't have to put the kids on the bus for another 30 min.

I was thinking I'd save them for after your write-up, which I assume would answer a ton of them. They're kinda all over the place but here goes:

My gelcoat is failing at the aft end of the boat, with spider cracks that are proliferating at a good pace, and widening into more than just spider cracks. The boat is 31 years old, and the cracks started after the boat was left uncovered during a winter up north, just before I bought it 5 years ago. There are also areas that are thin, in general, so it's time to take action (next spring/summer).

The deck has molded in nonskid, which I'm not a fan of. The nonskid stands slightly proud of the flat areas. My plan was to sand off the texture, leaving the nonskid areas still proud as a guide for taping off and applying nonskid after regelcoating. Was going to power sand the texture 99% off then long board it that lasts bit to get it as flat and even as possible. How would you do it?

Everything that I can get off will come off and get rebedded. Much of it is bedded with 5200 so should be entertaining. If I have significant repairs after removal, and gel should not go over epoxy, what should I fill and fair with?

What is the minimum size compressor to shoot gelcoat that's not going to burn up or take too long to catch up?

Without previous experience gauging film thickness, I expected to run tests and use a notch gauge. Is that adequate? Does cured gel thickness vary significantly from uncured? How would you advise an amateur to gauge film thickness?

Does it make sense to create sanding blocks for radiused edges that are extensively the same? (i.e. coach side to coach roof) Removing too much material on radiused edges, particularly raised ones, is well getting them even is something I expect is a significant challenge for those without craftsman-level experience.

What would be a good HVLP gun/system choice for DIY applications?

Lots more questions but those are floating around on the top of my head.

[minaret]

Originally Posted by Suijin

I was thinking I'd save them for after your write-up, which I assume would answer a ton of them. They're kinda all over the place but here goes:

My gelcoat is failing at the aft end of the boat, with spider cracks that are proliferating at a good pace, and widening into more than just spider cracks. The boat is 31 years old, and the cracks started after the boat was left uncovered during a winter up north, just before I bought it 5 years ago. There are also areas that are thin, in general, so it's time to take action (next spring/summer).



Spider cracks are often in the glass, not just the gel. Grind a few out and chase those cracks to be sure. If they are in the glass (likely to be some of both), they will need new glass.





The deck has molded in nonskid, which I'm not a fan of. The nonskid stands slightly proud of the flat areas. My plan was to sand off the texture, leaving the nonskid areas still proud as a guide for taping off and applying nonskid after regelcoating. Was going to power sand the texture 99% off then long board it that lasts bit to get it as flat and even as possible. How would you do it?



I usually remove molded skid with a 36 grit 8" soft pad sander, using a DA and a small 3" RO sander for corners. Sometimes I finish with a Mud Hog in 60 depending on the intended finish from there. Pull all hardware first. You should check out my Nauticat 52 refit thread on C&M forum if you haven't yet.






Everything that I can get off will come off and get rebedded. Much of it is bedded with 5200 so should be entertaining. If I have significant repairs after removal, and gel should not go over epoxy, what should I fill and fair with?


Prefer 3M Premium Filler. Vinylester.


DeBond for 5200. Use a sharp stiff scraper and mallet plus this.


Marine Solvents for Removing 5200 | Boating Magazine








What is the minimum size compressor to shoot gelcoat that's not going to burn up or take too long to catch up?


Most cheap cup guns that are good for shooting gel run about 6-9 CFM for HVLP. Done lots of shoots with as little as a 9 CFM 20 gallon rig. You have to take regular breaks to mix more gel anyhow, it's the nature of the beast.





Without previous experience gauging film thickness, I expected to run tests and use a notch gauge. Is that adequate? Does cured gel thickness vary significantly from uncured? How would you advise an amateur to gauge film thickness?



Yes a standard wet film gauge is fine. Practice just a little and you won't need one on your actual work surface. I usually blow on three full wet coats at about an hour apart, depending on temps. Sometimes much less. You wanna shoot a good 10 mils wet per coat, for a final DFT of over 30 mil. Then after you polish you have 25 mil or so left. Manufacturer specs for gel are 16-24 wet mils in the mold for new construction.



Does it make sense to create sanding blocks for radiused edges that are extensively the same? (i.e. coach side to coach roof) Removing too much material on radiused edges, particularly raised ones, is well getting them even is something I expect is a significant challenge for those without craftsman-level experience.




Lots of stuff on this in my refit thread. Yes I make custom profile sanding blocks, long and short of it. For power tools too. And I often cast radii.




What would be a good HVLP gun/system choice for DIY applications?





https://www.amazon.com/DeVilbiss-802.../dp/B000KSTFJO




Lots more questions but those are floating around on the top of my head.

Ask away, back this evening. Off to do more paint work!

[ramblinrod]

Originally Posted by minaret

I find when I try to spray PVA over gelcoat with wax in the final coat, if a sufficient amount of wax has been used (twice the amount mentioned on the can), the PVA simply beads up on the wax and runs heavily instead of forming a film. One or the other for me, never both.

Yes, it does tend to bead up if a lot of wax is used. I find that 3 or 4 very light coats work OK. One heavy coat beads up awful. I should prolly pick one or the other, but I've had jobs not cure fully with either PVA or wax, but all with both have been fine. (All my work is outdoors, and the curing issues have been when the overnight temps are really low.)

Gel nonskid with cabosil is pretty easy to do, and looks OK, but it's generally way too aggressive for my tastes. A real skin remover.

Au natural, absolutely. I run over it with a random orbital to knock the peaks off.

Molded skid just doesn't add up for me, either. I've done hundreds of repairs on it, got my method down pat. But it just takes so much longer than Griptex skid to do good repairs.

Agreed, I only do this for smaller spot repairs. It is much more labour intensive than Griptex but I prefer not to wreck the original non-skid, when it is just a spot or two that has to be repaired.

Don't even get me started on Kiwigrip. Hard to clean, impossible to make yacht quality repairs that are 100% invisible, and I really don't like the "foot feel".

Agreed! KiwiGrip is fine for the, DIY racer, who wants a no slip surface, cheap, for the least effort, and really doesn't care what it looks like. I try to talk customers out of it. I have applied it, but it's certainly my least favourite solution. I liken it to stone guard for rocker panel repairs on vehicles. Looks like crap, but it's painted.

[SF Bay Dude]

Originally Posted by minaret

Gel is $200 for FIVE gallons. Two part paint is generally actually three part, ie base, converter, and reducer. To do good work you need more than one reducer to match ambient conditions measuring viscosity in the #2 Ford cup.

About to spray my decks and wondering… Awlgrip instructions say to use a Din#4 cup. Is there a reason you use #2?

[alctel]

I was going to use kiwigrip for my nonskid (which is molded gelcoat but COMPLETELY trashed), but I'm not so sure now! Is it really that bad?

[SF Bay Dude]

Originally Posted by alctel

I was going to use kiwigrip for my nonskid (which is molded gelcoat but COMPLETELY trashed), but I'm not so sure now! Is it really that bad?

I did a test patch of it and didn't like it. Seems to grab lots of dirt. Plus, I found it a bit slippery in the colder water where I sail. I am going the griptex route with my decks. Buy a quart and roll some out to see what you think. Best 40 bucks you can spend.

[Celestialsailor]

I have used the aforementioned method of Gelcoat and Cabosil. I make it to a pancake batter consistency and apply with a very short nap roller to achieve tiny stalagmites and dusting the tops off with 100 grit (very lightly).
I have also used LPU and Cabosil with the same methods and success. It cleans easily and IMHO looks way better and cheaper than kiwigrip.

[SF Bay Dude]

Originally Posted by Celestialsailor

I have used the aforementioned method of Gelcoat and Cabosil. I make it to a pancake batter consistency and apply with a very short nap roller to achieve tiny stalagmites and dusting the tops off with 100 grit (very lightly).
I have also used LPU and Cabosil with the same methods and success. It cleans easily and IMHO looks way better and cheaper than kiwigrip.

Wow, read what Francisco did. Yikes. That's why I am grinding myself into the dirt - I just can't trust anybody down there to get the job done properly. Hope you can splash soon!

[Celestialsailor]

Is that your Skookum in the old yard? I'm slashing Friday.

[SF Bay Dude]

That's me! I'm heading south on Friday with many gallons on awlgrip, a compressor, and the stoke to make it right.

[bcc101]

Since the boat is wrapped up for the winter-just cleaned a fresh 8" off the cover this morning- I have a bit of time to research and plan.
Actually I have in the last year been looking into what I can put on the deck once the repairs are complete.
Since I am using epoxy the gel coat is out.

I did plan on painting the smooth portions and using Kiwi for the nonskid.
My Paceship has quite a bit of nonskid and I really did not have an issue with the original diamond pattern.
That will all have to be replaced now.

No I am not a racer and would like the boat to look good and be functional.
Also desire to get it into the water before too many years pass.

I am able to do most jobs but am limited as to equipment. Have a generator for power and the boat is outside.
I will follow your discussion with interest.
Bruce

[Hobie_ind]

Originally Posted by Celestialsailor

I have used the aforementioned method of Gelcoat and Cabosil. I make it to a pancake batter consistency and apply with a very short nap roller to achieve tiny stalagmites and dusting the tops off with 100 grit (very lightly).
I have also used LPU and Cabosil with the same methods and success. It cleans easily and IMHO looks way better and cheaper than kiwigrip.

We also replaced the brown faux-teak gelcoat non-skid on our Amel Super Maramu with gelcoat non-skid done this way. Obviously way cooler as we used an off-white colour and I found the grip much improved but not too aggressive. It could get dirty and more difficult to clean than patterned gelcoat but was easily renewed with an acid wash when that occurred. What I really liked was its durability and easy repairability.

Wouldn't hesitate to go with it again, and it ended up being much cheaper than a two pack option. I've never seen a Kiwigrip deck I really liked, but it is cheaper and probably easier to do for the DIY'er.

Good luck.

[Celestialsailor]

When i was in Ca. I had a dock mate show me his Kiwigrip job. I was polite about it and said, "way to go"! But in reality, didn't think much of it.

[Pelagic]

Originally Posted by minaret

Gel is $200 for FIVE gallons. Two part paint is generally actually three part, ie base, converter, and reducer. To do good work you need more than one reducer to match ambient conditions measuring viscosity in the #2 Ford cup. So to do five gallons of mixed paint costs vastly more than five gallons of mixed gel. And will result in much more wastage, due to the nature of paint. Include the cost of the primer, which is also three part. Now add in the cost of a high build primer as well, a third product line which is also three part. Add in the cost of using an epoxy fairing compound for the worst imperfections. Add in the cost of all the sandpaper you will need to sand out those primers, which will generally involve several different grits.

Gel requires no special sprayer, in fact cheap primer guns work best, due to the larger tip sizes. I have also roll applied and polished it, though that makes for more work. A member here did his entire deck in the slip this way. Tint is only required if color matching repairs, if applying new gel to a surface you use it right out of the can just like paint, and then further repairs are also a stock color. Thinners are standard industrial, very cheap and found at any hardware store, unlike the proprietary reducers for LPU, which are quite expensive and absolutely required, even for equipment cleaning. And we haven't even begun to discuss the comparative toxicity and protective equipment required.


This particular excuse for not taking approaches deemed by most in the marine industry as "professional only" is exactly why I frequent CF, to try to convince people that in many cases there is no black magic involved, in fact it's quite simple. I can't tell you how many times I've had to teach very young people who barely had English how to do this stuff in a boatyard, certainly not all of whom were genius' (though some were). Most do pretty good in short order.


I have given a few seminars on exactly this topic now. I remember when I first got into this trade, it was quite common for owners to have their own factory gelcoat aboard and to be versed in it's use at least to some degree. I very rarely see this anymore. It's a shame.

Hi minaret,
This is really intriguing as I am only used to working with Awlgrip and Alexseal on steel boats.

You are absolutely right about the many layers of product and work needed from primer/fairing/high build primer/base coat/ 3 x topcoats with sand in between

So is there any reason why I could not use a gel coat on a previously Awlgrip painted steel hull?

If you say "no".... I'll probably shoot myself later[emoji1]

How does the depth of gloss and gloss retention compare?

[ramblinrod]

Originally Posted by Pelagic

Hi minaret,
This is really intriguing as I am only used to working with Awlgrip and Alexseal on steel boats.

You are absolutely right about the many layers of product and work needed from primer/fairing/high build primer/base coat/ 3 x topcoats with sand in between

So is there any reason why I could not use a gel coat on a previously Awlgrip painted steel hull?

If you say "no".... I'll probably shoot myself later[emoji1]

How does the depth of gloss and gloss retention compare?

Attachment 140119Attachment 140120Attachment 140121

I'm not aware of any way to apply gelcoat over steel. It will adhere to abrade polyester very well, but steel, me thinks not.