Thin gelcoat - how thin is too thin?

[laHolland]

We are getting ready to put our new-to-us 36 year old Cal into the water, but we need to make a decision regarding the hull gelcoat. It is chalky, and a guy at the boatyard buffed out a small patch and told me that the gelcoat is pretty thin. I thought the hull was white, but the part he buffed looks slightly blueish.. not sure if the chalk made it look white, or if the blue tint is due to the thinness of the gelcoat. Other than the chalkiness, the gelcoat is sound -- no blisters, scratches, patches, etc.

So, should we use rubbing compound and wax it, or give up on the gelcoat and paint it? I don't want to take any chances re: water intrusion into the fiberglass, especially since the boat has avoided any blisters up to now. But it seems sad to cover up the original, clean, unblemished gelcoat.

[sailingfool]

Sounds like you are talking about your topsides...blisters are a risk in the hull bottom, not the topsides. Polish or compound the topsides...what do you have to lose?

[laHolland]

Topsides never get blisters in the fiberglass, behind the gelcoat?

[TaylorC]

Usually I expect to see green and not blue, but it may be just be thin gelcoat as the yard said - the color comes as you get down to end of the gelcoat and begin to let the plain resin show through.

If you choose to try and go on, pick a compounding agent that is not as coarse, polish it, try not to do it too aggressively, and see what you get. You have nothing to loose but the time it takes to do it.

[dacap06]

Your description is a pretty good match for the above-the-waterline gel coat on the boat I bought last Autumn. Instead of all that rubbing compound and polishing, I tried Polyglow upon the recommendation of a friend. I decided to try it because it involved less removal of gel coat. The cleaning half of the kit gets rid of the loose oxidation without a buffer. Then you then start applying the polish, and it soaks in and binds to the remaining gel coat.

I was skeptical about the results. In fact, I flat-out didn't believe the Poly Glow web site and expected considerably less than it promised, but I became a believer after I saw what 6 coats of the stuff looked like on my hull. The 32oz/32oz kit did my 30' boat with a little left over so that part wasn't an exaggeration either.

I did both parts on the whole hull above the water line in 4 - 5 hours. After coat three or so, it started looking better. With coat six, it looked really good. My hull went from looking like chalk to actually having a reflection. It does not look like new, and it is not permanent -- you'll need to redo it about once a year -- but it is greatly improved.

The stuff is kind of expensive, but in my view it is worth it. I don't remember where I actually ended up buying it, but you can do better than ordering it from the Poly Glow web site. I used Google shopping to find the kit of 32 oz of Poly Prep, 32 oz of Poly Glow, the scrub pad, and the applicator for around $55.

Another fellow in the yard where I was on the hard told me that if you don't keep up with it, it will wear off in patches, and that can look kind of funky. If you decide you don't like it or don't want to keep up with it any more, then strip it off with the Poly Strip.

[camaraderie]

LaHolland...Topsides never get blisters in the fiberglass, behind the gelcoat?

No...sometimes there are voids from a bad layup, but not blisters. Alternatively, if you have a cored hull...there may be delamination. But not osmotic blistering. The voids can be left alone if small or if cracking is taking place they should simply be sanded out, epoxy filled and re-gelcoated or painted (awlgrip2000/imron etc. ) . Actual core delamination is a bigger job and may require professional attention depending on size and core condition. Doesn't sound like any of that is YOUR problem!
If your gelcoat is really worn and can't be brought back by conventional means...I second the use of Poliglow as something that will look good and last for a couple of years. We did a dark blue hull on a 1968 boat with it a couple of years ago and it is still looking better than before we did it!
The only other alternative is a new paint job which is probably $5k for a boat your size these days.

[laHolland]

I'm so glad we don't need to worry about blisters. It sounds like PoliGlow is the the way to go.. Do you put it on by hand? Do you think there would be any issues with painting over it a couple years down the road? PoliGlow also sounds very enticing because we can get the boat in the water faster than it would take to compound/polish..

[Maine Sail]

Unless the boat was wet sanded many times it would be rare and hard to believe the gelcoat is thin unless it was a repair area. Boat yards are in the business of painting boats and make far more money in labor with a new paint job then they do with a buff & puff.

Gelcoat is quite thick when compared to paint and can be buffed lots before wearing it away. Most any gelcoat can be restored and it will cost about 9k less than a paint job.

As was stated Poli-Glow is another option but it is an acrylic coating that does not like fender rash or mooring balls rubbing on it. This is a good option if it is indeed thin. I have a 30 year old boat and even the decks, which get the most UV abuse, are still plenty thick.

Re-conditioned this one last week with a couple of friends...

9:00 am:

9:30 am:

Working down the cove stripe Before/After:

The toughest reflection is always straight on:

The detail in the reflection tells when it's shiny enough to start waxing:

My shoulders still hurt..


She came out amazingly well for a 1987 that was fairly chalky! Actually she looks like she was recently painted..

That's my buddy Tim on the ladder. I am once agian going to make the shamelss plug for Presta Products. I can honestly say that I have no future use for any compounds or polishes other than Presta. My buffing and polishing directions just got a LOT easier.

To say this stuff is amazing at what it does, & does not do for that matter, no "essential oils" or silicones & no swirl marks, would be an understatement.

If a boat is heavily oxidize/chalky the Presta Gel Coat Compound starts at a P800 level & then does amazing things. It finishes with a shine that is not all that far off of Finesse It II and a finish that would not be discernible from Finesse It II to 98% of boaters. These products use a technology called "diminishing grit" which allows the grit to start at a P800 and finish at a level that can be double that or more as it breaks down to smaller particle sizes during use. Based on the shine left with the Gelcoat Compound I'd say that it was finishing at between P1600 & P1800.

Presta Gelcoat Compound (LINK)


ThePresta Ultra Cutting Creme starts a little higher, about P1200 level yet clearly finishes off at a VERY, VERY high level of shine equal or better than that of Finesse It II..

Presta Ultra Cutting Creme (LINK)

I would also like to shamelessly plug the Makita 9227C buffers we used. We had three of them on site that day and not a one of them gave us so much as a hiccup. Mine in particular, and Tim's, have seen some serious use. Our friend Chris made the comment "WOW.... ouch... these things get HOT !!" and this is why you need a machine that can withstand the abuse..

Presta products usually need to be ordered but it is 150% worth every ounce of effort and money you spend.

Actually the prices are better than what you'd pay for lesser quality products at most marine stores.

A 32oz Ultra Cutting Creme is $19.56

A 32oz Gelcoat Compound is $20.92

These are direct from the manufacturer prices so it may cost less if you can find a local Presta distributor.


What we used on this boat:

First Pass = Presta Gelcoat Compound with the Presta 9" black colored wool pad (it is recommended to use the white Presta wool pad with the Gelcoat Compound but we found the black to give higher finish shine. I think Tim was using speeds below the #2 dial setting on the Makita buffer and he was buffing nearly dry but not all the way. One 32oz bottle did the entire Ericson 34.

Second Pass = Presta Ultra Cutting Creme with a 3M Hook It Polishing grade wool pad #05713. This is a neat trick, using a polishing grade pad with a compound. It allows you to have a higher final shine when using a diminishing grit compound than you would using a compound grade pad with the Ultra Cutting Creme diminishing grit product. I was starting at speeds around 2 and finishing off at speeds of about 3.5 - 4 on the Makita buffer. I too was nearly buffing dry but leaving enough wet to not load the pad. (I would not suggest "dry buffing" until you have some experience)

Final Pass = Collinite Fleet Paste Wax #885. Tim's wife applied this with a microfiber foam applicator and a spritz of water from a spray bottle sprayed directly to the hull. It was then wiped and polished up with microfiber rags.

[laHolland]

Wow! Looks gorgeous! Job well done. I would LOVE to get our boat looking that good.

I think I'm going to need to take a closer look at the gel coat to assess its thickness, though I don't doubt the guy who buffed out a little section for us. He knows we are complete do-it-yourselfers (by budgetary necessity). My problem is, I don't know how to judge if the gelcoat is too thin. Obviously, if you start to see the texture of the fiberglass, it's too thin, but is there any indication before that? The part that was buffed does look like a different color.. not bright white, like I expected (the topside gelcoat is white). The buffed part looks like a very translucent blue.

[dacap06]

Originally Posted by laHolland

I'm so glad we don't need to worry about blisters. It sounds like PoliGlow is the the way to go.. Do you put it on by hand? Do you think there would be any issues with painting over it a couple years down the road? PoliGlow also sounds very enticing because we can get the boat in the water faster than it would take to compound/polish..

Yes, you scrub with the Polyprep by hand and you put the Polyglow on by hand. You'll need lots of water for the scrubbing part. I scrubbed for two hours to do my whole boat, and did polishing for 2 - 3, if memory serves.

I would not paint with Polyglow on the gelcoat. Strip it off first.

DaCAP