# Gel-Coat cracking, peeling, flaking. Removal.



## Unclebob (Dec 10, 2008)

Is it legal to buy Dynamite if you sign a waiver saying you're only going to use it to scare away varmints?


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## Brett (Jul 16, 2008)

belt sander, rotary grinder, knife edge, air chisel, C-4... 

Grab a tool, try it, if it works easy use it.
If it makes the job more difficult, grab another tool.
I've used belt and rotary sanders with 40-60 grit to
chew through old gel coat. Taking it off is easy.
Putting it back on afterwards is what takes time.
Don't forget to protect your eyes and lungs,
the dust is nasty.


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## Unclebob (Dec 10, 2008)

I hit the hull once with my 10" Rotary sander and 80 grit, and the gel-coat seemed to clog the paper without making a noticable dent in the moonscape. I am not sure 60 would do much better, IF I can even find 10" discs that are 60 grit. (Bastard size for sure). 

If the 10" Rotary didn't touch it, my belt sander wouldn't have a chance.

I'm considering a large 'flapper' disk for my angle grinder, like this.










Too much?

Can you get C4 from HomeDepot?


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## Brett (Jul 16, 2008)

As Tim the Toolman said "More Power!"
Anything that does the job without damaging the hull.
Never fought with a flapper disk, have used 16 grit when
grinding damaged fiberglass. Try it, find some thing that works.

http://www.tylertool.com/vsm.html


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## Unclebob (Dec 10, 2008)

Argh. If I had known finding 10" Velcro-Backed sanding disks was such a pain in the arse, I wouldn't have bought the thing.

16 grit would surely take it off.

I think I'll give that flapper a shot and see what happens. If nothing else, I can use it for my bunions.


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## Brett (Jul 16, 2008)

Can't you just attach a smaller backing plate to the spindle of the grinder?


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## Unclebob (Dec 10, 2008)

well, yeah, but then I lose several inches worth of sanding prowess.


(a good thought though, that that didn't even cross my mind while driving across town searching for 10" disks. 4 different places)

Thanks Brett. The voice of reason speaks again.


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## Brett (Jul 16, 2008)

The diameter of the tool,
has nothing to do with it's ability to get the job done.
The smaller diameter will allow work in tighter places.
What you lose in size is made up for in effectiveness!


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## Frank_Sebastian (Oct 15, 2007)

Harbor Freight Tools sells a 4" and 4½" grinder. One has a 5/8-11 mandrel and the other a metric? You can buy a backing disk and 16 grit 4" sanding disks at Ace Hardware. The grinders are as low as $19 on sale or maybe $15 everyday. Use the 16 grit disk lightly and see what you run into. I never minded removing old gel-coat, but the long boarding when replacing it is a lot of work.

Frank_S


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## Unclebob (Dec 10, 2008)

I have both of those stores close, will let you know what I try and what works.

LongBoarding? I guess this is something I'm going to learn about soon enough, huh?


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## Brett (Jul 16, 2008)

http://www.jamestowndistributors.com/userportal/siteMap.do?action=map2&catId=3


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## Unclebob (Dec 10, 2008)

> I never minded removing old gel-coat, but the long boarding when replacing it is a lot of work.


If the 'longboarding' is 'A LOT OF WORK' compared to removing gel-coat, I'm starting to get a little nervous.

I spent 6 hours straight yesterday removing gel-coat. I tried a 40 grit 6" sanding pad but it was going to slow. I switched to a 36' Flapper Disk and that took it off faster, but I had to be REAL careful and could only remove about 2" strips at one time. Man, that Gel-Coat is some tough stuff. 

I figure I'm about half way done. Most of the rough-stuff is removed, along with the shoddy repairs to the bow. It seems like the boat was more gel-coat than glass.

In an earlier thread we had talked about a good filler to use, and came up with Quick-Fair.

http://www.jamestowndistributors.com/userportal/show_product.do?pid=757

I am looking at needing probably a gallon, at $150. 

I was wondering if anyone has ever used 'Bondo-Glass' as a filler? I have used it on several fiberglass dune-buggies before with good results. It's hard to sand, but sure is tough.

It would save me some money that I could use for good paint and I could get it local.


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## Bob (Feb 2, 2007)

> Quik Fair - I am looking at needing probably a gallon, at $150.


1.5 gallons - $135 plus tax & S/H

http://boatbuildercentral.com/proddetail.php?prod=S3_QFa_1.5gal

or

1.5 gallons  - $121 plus S/H from Oregon

http://www.fiberglasssupply.com/Product_Catalog/Epoxy/epoxy.html

I've used both of these vendors without issue. You'll get your order the next day (in Florida) with BBC, but pay a little more - or wait a week from FS and pay a little less.


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## Un-shore (Sep 27, 2007)

unless I'm mistaken, bondo glass is polyester resin, not good for water/boats.

Maybe not an issue if the paint stops the water. 

quick fair would still be your best option for bonding and keeping water out of your glass.


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## Brett (Jul 16, 2008)

Or, make your own bondo out of epoxy and microballons.
Problem is that epoxy is not cheap either.


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## Unclebob (Dec 10, 2008)

> unless I'm mistaken, bondo glass is polyester resin, not good for water/boats.


I dunno, could not find any info about it being polyester resin. It jst says 'waterproof' and 'PERFECT FOR BOATS OR MARINE USE' on the can.

It's 1/3rd the price of Quik-Fair, is very durable, and available local, is the only reason I ask.

I've used it on a few 'glass projects with pretty good success, but not on a boat.


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## Bob (Feb 2, 2007)

> > unless I'm mistaken, bondo glass is polyester resin, not good for water/boats.
> 
> 
> I dunno, could not find any info about it being polyester resin. It jst says 'waterproof' and 'PERFECT FOR BOATS OR MARINE USE' on the can.
> ...


The 1st pictures you posted of the existing gel coat are from a polyester resin based system. 

I think there's a quote that goes something like this - insanity is doing things the same way over & over again, but expecting a different result. 

If it stinks of styrene, it's a polyester based product & I haven't seen a Bondo product that isn't polyester based.  If it was a vinylester based system it would be more expensive than 1/3 of an epoxy product price, but still cheaper than an epoxy based formulation.

Yes, Quik Fair is expensive and a similar, cheaper fairing compound can be made with microballoons, silica, & epoxy, but there's a learning curve.

If you don't want to stick a bunch of money in the hull and don't expect to keep the hull in the water for any extended time, then the Bondo product will probably suffice.  If it's gong to be tied to a dock most of the time, then the polyester system will eventually absorb  water and start the whole process over again.

From 3M's Website...

http://www.3m.com/us/auto_marine_aero/bondo/catalog_item692f.html?itemNbr=211

Section 2 - Hazardous Ingredients
Percent Vapor ACGIH OSHA LD50 LD50 LC50
Hazardous Ingredient weight CAS No. Press. TLV PEL Oral Derm Inhal LEL
*Styrene 15-20%* 100-42-5 4.5 20ppm 100ppm 2650 n. av. 12000 1.1
Fibrous Glass 1-10% 65997-17-3 n. ap. 10mg/m3 15mg/m3 n. av. n. av. n. av. n.ap
LD50 Oral - rat mg/m3, LD50 Dermal - rabbit mg/m3,LC50 Inhalation - rat mg/m3 unless otherwise specified.


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## Unclebob (Dec 10, 2008)

> > > unless I'm mistaken, bondo glass is polyester resin, not good for water/boats.
> >
> >
> > I dunno, could not find any info about it being polyester resin. It jst says 'waterproof' and 'PERFECT FOR BOATS OR MARINE USE' on the can.
> ...


I'm confused. The Gel-Coat that's on my boat now was Polyester based? Why is Polyester based so bad?

The MSDS of BondoGlass says it has Styrene, Glass Fibers, Benzoyl Peroxide, benzoate, and a surfactant in it. 

This is just an old jon-boat I want to repair, repaint, and have look decent, without spending a grip on materials. I plan on using a decent paint on the bottom. I also don't plan on spending months fairing it out to be perfect or anything. I just want to seal the glass, fill some holes and low spots, and throw some paint on it.


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## Gramps (Nov 1, 2007)

Unclebob - yes all gelcoats are polyester based. Polyester based resins are not in themselves evil, epoxy is just far superior. Polyester is not even waterproof!

With that being said, if you just want to use it & make it look decent then the Bondo Glass will work. In the long term any type of epoxy based filling/faring material is much better though.


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## Unclebob (Dec 10, 2008)

I gotcha. Thanks Gramps.


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## paint it black (Nov 3, 2007)

> I gotcha. Thanks Gramps.



You can use Dura-Glass from the company USC. It's much better than Bondo-Glass..........


Stronger, sands easier, less pitting. Runs about 30 a gallon.


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## Brett (Jul 16, 2008)

http://www.merrittsupply.com/USC-Duraglas-Fiberglass-Filled-Filler-Gallon-SKU-24030-P3980.aspx


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## Unclebob (Dec 10, 2008)

> > I gotcha. Thanks Gramps.
> 
> 
> 
> ...


Thanks! I just got some ordered. I had never even heard of the stuff, but it seems to get decent reviews from those that have used it.


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## Unclebob (Dec 10, 2008)

Welp, I mixed up a test batch of DuraGlas last night and gave it a whirl. It seems just like Bondo-Glass to me?

It's too thick to get in the tiny pinholes of the bare glass, and boy is it rough to sand. It fills pretty good when the coat is 1/4", but isn't fine enough to get in the small spots when trying to skim coat.

It will work on a few spots of the hull that I need good strong filler, but I can't imagine applying this to the whole hull and fairing it down. Since the working time is 15 minutes and it needs to go on thick, I imagine I'd end up with a Stucco-looking hull. And hand-sanding would bring me into 2012 with tendonitis.

I guess I'll need some glazing putty, or just start laying on several coats of primer to level out the sanding marks?


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## Brett (Jul 16, 2008)

Never tried Dura-glas, but Marine-tex white goes on thin
and sands well. Thin coat wouldn't need much to apply to
level out the scratches left by sanding.


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## Unclebob (Dec 10, 2008)

Thanks Brett, I have a small Marine-Tex kit I use for minor gel-coat knicks, I'll give that a shot.

I've a feeling I'm gonna have to use a hand-sandable glazing putty, though. It's not just scratches I'm trying to overcome, but small divots and valleys created by my orbital sander. Man, I didn't even notice them when sanding, it was only until I was done and washed the hull down. Nothing real deep, mind you, but a LOT to build up with primer.

I don't think I'll use the orbital again on the curved hull. The pad has 1/2" foam backing, but still was too firm and created 'lines'.


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## Unclebob (Dec 10, 2008)

Anyone ever use Polyester Glazing Putty (Like Evercoat?).


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## Unclebob (Dec 10, 2008)

> Welp, I mixed up a test batch of DuraGlas last night and gave it a whirl. It seems just like Bondo-Glass to me?
> 
> It's too thick to get in the tiny pinholes of the bare glass, and boy is it rough to sand.


I would like to formally retract this statement. I gave it another shot yesterday with much more success. Dura-Glas fills fine if you lay on 1/8" of the stuff and machine sand down. It works better than Bondo-Glass, no pinholes to fill when you're done sanding.

So, I'm nearly at a point to start laying on some high-build primer to fill sanding marks and seal the glass.

Any suggestions? I want something very high-build that's hand sandable. Do I need anything special?


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## Gramps (Nov 1, 2007)

Glad to hear it is working! That type of work would drive me nuts.

I would just suggest a epoxy primer. Guys on Bateau mainly use Silvertip Yacht Primer which is expensive ~$85/gallon. But anything along those lines will work.


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## Unclebob (Dec 10, 2008)

I had no idea it would be this much work, honestly. I've got probably 25 hours in sanding/filling alone, and I'm still a LONG way from being able to paint. Not to mention the mess I'm making!

Does the primer need to be Epoxy if I plan on using Interlux topcoat? Whatever I use, it needs to be very high build and easy to sand by hand. I think 5 coats of primer, sanded between coats, may be needed. If I get something higher build, I may not have to lay on so many coats.


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## Brett (Jul 16, 2008)

I've never used a high build epoxy primer,
Glen-L has a whole page on the subject as does West Systems

I read this just to see what you were asking about:

http://www.maddyhome.com/canardpages/pages/waynehicks/chapter_25_priming.htm

He's building an aircraft and really details the process.


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## Unclebob (Dec 10, 2008)

Great link!

But why, oh why, does everything boat related have to be so complicated? I just want to go fishing..


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## Brett (Jul 16, 2008)

> But why, oh why, does everything boat related have to be so complicated? I just want to go fishing..


Obvious untruth, if you just wanted to go fishing, you would be
sitting in a chair at a nearby pond doing just that. As to boats
being complicated, they're only as complicated as you make them.
Keep 'em simple and rugged and don't worry about a few chips or dings.
Those are called evidence of a good time.


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## Unclebob (Dec 10, 2008)

Good Point. I should be in a chair sitting by a pond right now. It's 80 degrees and beautiful outside. But alas, here I sit, looking out the window, behind six 19" monitors. ( I work at home).


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## noeettica (Sep 23, 2007)

Write the Check 'N Go fishing 

Dave


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## Unclebob (Dec 10, 2008)

Wish I could.

Bump for any ideas on inexpenive filling primer that I can use under Interlux Brightsides.

Remember, probably 75% of the primer is coming back off after sanding. It's just filling scratches and gouges..


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## Unclebob (Dec 10, 2008)

Picked up a quart of Interlux Pre-Koat and a big tube of 3M Marine Putty this morning, and will be giving this stuff a shot today.

I plan on priming the boat first, to see where the putty is needed.


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