# Keel Fairing



## BarryL (Aug 21, 2003)

Hello,

So, after the soda blaster guy finished removing the old bottom paint, the keel looks like this:










It looks a little better after sanding, but needs a lot of work.

I know that I need to add material to fill the low spots, shape the leading edge, etc. Then I need to fair it smooth, and finally paint it.

What material do I use for filler? This is not structural, just for shaping. Is automotive bondo ok? If not, what sort of inexpensive low density stuff do I use? After the keep is smooth, I will apply a barrier coat.

Should I apply a barrier coat first, then apply filler, then barrier coat it again?

Soon it will be warm enough to start work!

Barry


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## sailingdog (Mar 19, 2006)

You can use thickened epoxy. Don't use the colloidial silica or microballon filler. I'd recommend using the chopped fiberglass filler. Sand through the gelcoat and apply the thickened epoxy to the fiberglass. After it cures, wash it down with water and a scotchbrite pad to remove the amine blush, sand it fair, and then apply the barrier coat.


One question—is the grey and red/brown coloration remaining bottom paint??? If so, then the guy did a really lousy job. If it bottom paint, you'll need to remove it all, down to the gelcoat. BTW, it looks like there is some crazing or alligatoring of the paint or surface. Is that in the gelcoat or just in the remaining paint??


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## ewebster (Oct 7, 2006)

I am just now researching the products and methods for the same project on my boat. It seems that each finish product will have its own recommended steps, products, and procedures to ensure proper adhesion and longevity. I am considering Awlgrip for the topsides and they have a whole set of "directions" available. Haven't researched bottom paints but don't skimp as the labor is the big expense! Bondo absorbs water as does raw fiberglass resin. Find something else! Check online at Anzam Yacht Refurbishing for a great article on how-to Painting Topsides. It has some wisdom that will apply tothe bottm as well. Good luck....


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## sailingfool (Apr 17, 2000)

Absolutely the only way to go for keel fairing is West Systems epoxy products and fillers WEST SYSTEM Epoxy , 410 Microballons in your case. There is a lot of info on their site and you can order a relevant book or video from their Instructional/video page.

Also be sure to get a 3M long board and velcro sanding pads for sanding, see 3M Marine Hookit Fairing Longboards 4-1/2 inches wide x 30 inches long . Very expensive but you want to do this job only once and do it correctly.


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## sailingdog (Mar 19, 2006)

SF-

I'm not a big fan of microballoons for this purpose, as the microballoons are hollow and can absorb water. However, the longboard sanding blocks are a godsend to getting the keel fair.


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## BarryL (Aug 21, 2003)

sailingdog said:


> One question-is the grey and red/brown coloration remaining bottom paint??? If so, then the guy did a really lousy job. If it bottom paint, you'll need to remove it all, down to the gelcoat. BTW, it looks like there is some crazing or alligatoring of the paint or surface. Is that in the gelcoat or just in the remaining paint??


The white is gelcoat. The The light gray is what is left from the previous barrier coat (Interlux 2001). The dark gray is metal keel showing. The red is antifouling paint.

Thank,
Barry


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## sailingdog (Mar 19, 2006)

In that case, he did a pretty crappy job IMHO. Either he should have left the barrier coat alone or he should have cleaned it all off. Is the crazing in the gelcoat??? or just the paint?


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## BarryL (Aug 21, 2003)

sailingdog said:


> In that case, he did a pretty crappy job IMHO. Either he should have left the barrier coat alone or he should have cleaned it all off. Is the crazing in the gelcoat??? or just the paint?


I think the guy did a very good job. There was about 20 years worth of paint on the hull, on top of the original barrier coat. I don't know if the barrier coat was properly applied. The pic at the bottom is the original bottom paint. You can see where large chunks fell off. In other parts the barrier coat adhered very well and the soda blasting didn't touch it. In other places the barrier coat came off.

The alligator effect is places where the barrier coat came off in small strips. The gelcoat is fine.

Barry


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## jimmyb116 (Feb 20, 2007)

I am doing just this starting Friday except I will sand the bottom paint off with a large porta cable random orbit sander. And then fair the lead keel and bottom and re-bottom paint. I am going to use west system for the barrier coat and fairing compound, I have used this system before with good results. Best of luck its a messy job but worth it in the end. I second the 3M long board great tool.


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## KeelHaulin (Mar 7, 2006)

Barry-

Go to the MAS website; they have a formula for mixing fairing compound. If you only use glass strand it might be too tough to sand smooth. When you mix the filler you are going to whip in a bunch of air anyway so I don't see a huge issue with the microbaloons or silica. The thoroughly mixed epoxy will prevent water penetration into the filler materials.

Sand the fairing compound within 24-48 hours after it sets. If you don't it might be tough to get it to sand flat to the hull. Don't sand off all the paint that is still on the keel; it is more difficult to get the new paint to stick to the lead than the old paint. Scrub the areas of the lead where it is exposed with scotchbrite and immediately apply some barrier coat paint (or epoxy).

On the rest of the hull; be sure that all of the anti-fouling is removed. If there is some barrier coat paint I don't think it will matter much since you will be applying a new barrier coat anyway. If you are going for a racing bottom finish you will probably want to sand the barrier coat smooth before topcoating with a smooth finish anti-fouling paint.


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## Banshi (Jul 4, 2007)

"Watertight" is a product from Interlux that is designed for exactly this use and it goes on after your first barrier coat. It's a 2 part 1/1 "bondo" type filler that's sands fairly easily. I did find I had to wait overnight for it to fully cure first.


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## sailingfool (Apr 17, 2000)

KeelHaulin said:


> ......... Don't sand off all the paint that is still on the keel; it is more difficult to get the new paint to stick to the lead than the old paint. Scrub the areas of the lead where it is exposed with scotchbrite and immediately apply some barrier coat paint (or epoxy)....


Interlux has a special primer for prepping lead. Grind the entire keel to a bright metal finish, apply Viny-Lux Primewash per instructions at 
yachtpaint.com - the official site of International and Interlux paints then cover with Interprotect 2000E barrier coat.


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## Maine Sail (Jan 6, 2003)

BarryL said:


> Hello,
> What material do I use for filler? This is not structural, just for shaping. Is automotive bondo ok? If not, what sort of inexpensive low density stuff do I use? After the keep is smooth, I will apply a barrier coat.
> 
> Barry


NO Bondo is not OK it will absorb moisture if used bellow the waterline. If your putting a barrier coat over it theres a good possibility it may be fine but I would NOT skimp here if your going to the huge expense of this project.

Use either an epoxy such as West System, System Three or MAS and the appropriate fairing filler (I like the System Three stuff personally) or a Vinylester blister repair filler such as the product that 3M makes called 3M Marine Premium Filler.

I've physically had to remove and repair a number of bad under water patch jobs where Bondo was used and it's NOT fun..

Do it right and use the right products..


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## Freesail99 (Feb 13, 2006)

> I've physically had to remove and repair a number of bad under water patch jobs where Bondo was used!!


Bondo can be very hard stuff and a real pain to remove.


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## Maine Sail (Jan 6, 2003)

Freesail99 said:


> Bondo can be very hard stuff and a real pain to remove.


Hence the *"and it's NOT fun.."* sentiment...!


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## sailingdog (Mar 19, 2006)

BTW, Bondo does make a marine product for this purpose... personally, I wouldn't use it... but that's up to you.


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## artbyjody (Jan 4, 2008)

Keep in mind as well that bondo will usually flake and pop off if you ever have significant strain on the keel, and will seperate...it has drastically different properties than using marine expoxies. In the automotive repair business - bondo as general rule is not used for that purpose and not usually endorsed by an insurance company for any repair....(although some shops will use it as a shortcut but those are shops you would want to stay away from to begin with....for filling a small scratch or something you could get away with it - but I certainly would not trust it at the location your repair is....


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## KeelHaulin (Mar 7, 2006)

You guys crack me up... IIRC "Bondo" is vinylester that has some fillers in it that makes it more workable/shapeable. If you added chopped glass to it it would probably be equivalent to the strand-mat layers of your hull as most hulls are vinylester resin. I still prefer the epoxy with fillers; easy to mix/use and has better adhesion properties.

You can avoid lots of prep work (and lead dust exposure) by not removing the existing paint from the keel; that was why I mentioned not sanding off all the existing paint.


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## Maine Sail (Jan 6, 2003)

KeelHaulin said:


> You guys crack me up... IIRC "Bondo" is vinylester that has some fillers in it that makes it more workable/shapeable.


Bad advice runs rampant on this board. Many people shoot from the hip and make BS claims that can lead to expensive repair bills for others in the future! Be VERY careful what you read on these forums like the statement quoted above!!



KeelHaulin said:


> You guys crack me up... IIRC "Bondo" is vinylester that has some fillers in it that makes it more workable/shapeable.


Keel,

Really? Can you give us a link to a Bondo that is Vinylester then?

Don't bother trying you will wear out your fingers before you find one because Bondo DOES NOT make any vinylester fillers!

The ONLY product made actually falls under the corporate umbrella of the Bondo division of 3M. That product is a new VE product that is sold under the Laminex brand and is part number *#16074 Laminex Marine Premium VE Filler. *Note the VE, or Vinylester, in the NAME!! This product is new and basically a re-branded 3M Marine Premium Filler. The basic rule of thumb in the marine world is this: If it does not specifically say Vinlyester it most likely isn't.

3M owns Bondo, 3M sells Vinylester faring compounds for LOTS of money, because they are EXPENSIVE compared to polyester, do you think they would under cut them selves and sell a pint of VE, under the Bondo brand, for $6.14 when they sell a pint of VE, 3M filler, for over $22.00 per pint?? Vinylester is MUCH more expensive than polyester so I'd love to find a cheaper source!!!

Please research your claims, or be more careful, (maybe you confused polyester and vinylester) before you post so that others may actually benefit in the long run from your advice. It's the polite thing to do..

Jamestown Distributors Bondo Page:

*BRAND:*  Bondo  *Resin Type:*  fillers  *Material:*  Polyester  *Rate Of Cure:*  30 Mins  *Number Of Parts:*  Two Part


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## sailingdog (Mar 19, 2006)

From what a friend, who worked for 3M told me... Regular Bondo consists of polyester resin, with titanium dioxide, glass microballoons, talc and colloidial silica for fillers. Talc and microballoons can absorb water, which makes them less than useful for underwater applications.


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## jimmyb116 (Feb 20, 2007)

Just FYI boats older than mid 80's are made from polyester not vinylester not that I would put bondo on anything west system or mass epoxy would be my first choice and last. Also any filler you put on should be then covered with a barrier coat to stop water.


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## Maine Sail (Jan 6, 2003)

sailingdog said:


> From what a friend, who worked for 3M told me... Regular Bondo consists of polyester resin, with titanium dioxide, glass microballoons, talc and colloidial silica for fillers. Talc and microballoons can absorb water, which makes them less than useful for underwater applications.


Especially in a polyester resin base! In a much more waterproof VE or Epoxy resin it's not as detrimental....

BTW I called Bondo tech support for my answer only because Keel said it with such conviction as in "you guys crack me up". So I second guessed myself and what I already knew.....? The guy at Bondo was quite helpful..


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## BarryL (Aug 21, 2003)

*vinylester vs polyester*

Hello,

Thanks for all the advice so far.

Can someone please tell me why vinylester is better than polyester (or vice versa)?

I was browsing the Jamestown site, and came upon these two products that, to my uneducated eye, appear to be used for the same purpose:

3M Marine Premium Filler

Evercoat Formula 27

One is vinylester the other polyester.

I don't care about the price, I don't need that much stuff. All things being equal, I would go with 3M.

Thanks again,
Barry


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## sailingdog (Mar 19, 2006)

Vinylester resin resists osmosis far better than polyester resin. Epoxy resists osmosis better than either PE or VE resins.


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## Maine Sail (Jan 6, 2003)

*
Epoxy:* Epoxy offers incredible toughness and voracious bonding strength. Good quality epoxy resins, West System, MAS or System Three stick to other materials with around 2,000-p.s.i.. In contrast, that adhesion drops to around 500-p.s.i. for vinylester resins  (which is less than 3M 5200 BTW) and believe it or not polyester resins are even less adhesive than VE's.

Epoxy is very resistant to moisture absorption. A hull built with epoxy resin does not require a barrier coat at all. Epoxy has been used for barrier coating for years with great success. While not 100% impervious to moisture it is the best available resin for water protection.

Epoxy will bond dissimilar or already-cured materials which makes repair work easy, predictable and very strong. Epoxy sticks and bonds to most all laminating fibers as well as offering excellent results for future repair-ability success.

Epoxy resins have a much steeper learning curve that requires practice, forethought and planning by the user.

Epoxy resins, in most instances, require over night cure so they can drag out the length of a project such as fairing.

*

Vinylester (VE):* VE is stronger than polyester and cheaper than epoxy resins. VE resins offer excellent resistance to moisture absorption and penetration. VE is far better at resistance to moisture than polyester resin. 

Like PE resins VE is very sensitive to humidity and temperature so working windows are far more limited than with epoxy resisns. On occasion, VE won't fully kick and cure if the temp and humidity don't agree. This means do not apply it to a cold lead keel! VE does not like to stick to cured substrates the way epoxy does but it will stick far better than PE resins and is fine for fairing a keel provided you follow the temp/humidity and instruction carefully.

VE fairing compounds are usually ready for sanding in as little as 30 minutes meaning you can fair a keel in one day!



*Polyester (PE):* PE is far and away the least expensive and most widely used resin in the marine industry, even today. It delivers the weakest adhesion (similar to 3M 4200) and is most likely to absorb moisture! PE should NOT be used bellow the waterline but, if it is, it must be covered with a VE resin or Epoxy based barrier coat to prevent moisture penetration.

PE also likes and tends to shrink when curing. PE is best used with fiberglass cloth and fibers and does not like to bond to exotics Kevlar or Carbon Fiber (why Hinckley builds AND laminates with VE because they use Kevlar and CF to build their hulls) Comparatively speaking PE fractures easier and is far more brittle than either VE or Epoxy. 

Most boat builders today still laminate hulls with PE but the gelcoat sprayed into the mold is made with VE as a moisture/barrier coat. Just because the gelcoat is VE does not mean the hull was laminated using VE. Some builders such as Tartan/C&C are using epoxy resins to laminate but these builders are far and few between due to the added cost!


Hope this helps...


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## sailingdog (Mar 19, 2006)

One other point that Halekai missed. Epoxy resins have the highest tensile strengths of the three resins. 

However, epoxy resins are also the most susceptible to softening and weakening under high temperatures. This is one reason boats made with epoxy resin should not be painted dark colors as a general rule. If you look at the warrantees on many epoxy-composite items, they will have some sort of warning to that effect.


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## BarryL (Aug 21, 2003)

Hi Again,

Thanks to everyone, especially Maine Sail, for the all the advice. I'm going to go with the 3M stuff. This is a simple fairing operation, no need for the strength of epoxy. The keel will be barrier coated before I apply the 3M stuff, then after the bottom paint is applied.

I'll take pics as I complete the work and update everyone before the boat gets splashed, and then again in the fall after the boat gets hauled.

Barry


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## US27inKS (Feb 6, 2005)

On my boat the factory had used bondo. Bondo is easily removed from the keel with a propane torch. A little heat and scrape it off. Not recommended for fiberglass surfaces of course.

I used epoxy resin with micoballon filler. As mentioned before, epoxy resins adhere better than PE or VE resins, and this is why I used it. After fairing the keel with a longboard (don't even try to do it without one) I coated the keel with resin to seal it, then coated the bottom with 2000E. I havn't had it back out of the water yet, but it has to be better than the factory bondo job. Photo here: Bayliner Buccaneer Sloops


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## artbyjody (Jan 4, 2008)

Good luck Barry - and yes - you'll be glad that you invoked the wisdom here....and even prouder of the work once you are done!


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## Maine Sail (Jan 6, 2003)

US27inKS said:


> On my boat the factory had used bondo.


Yep that sure looks like Bondo! Especially with the moisture intrusion discoloration...


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## Maine Sail (Jan 6, 2003)

US27inKS said:


> On my boat the factory had used bondo. http://groups.msn.com/baylinerbuccaneersloops/us27inkansas.msnw?action=ShowPhoto&PhotoID=3798


Yep that sure looks like Bondo! Especially with the moisture intrusion discoloration...


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## sailingdog (Mar 19, 2006)

halekai36 said:


> Yep that sure looks like Bondo! Especially with the moisture intrusion discoloration...


Which is why you're not supposed to use BONDO on a boat, especially below the waterline.


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## US27inKS (Feb 6, 2005)

halekai36 said:


> Yep that sure looks like Bondo! Especially with the moisture intrusion discoloration...


Actually the picture is after fairing with epoxy and phonelic microballoons. Phonelic is a reddish brown plastic of some sort. they used to make distributor caps out of it. The varied coloration is due to the multiple layers that had to be applied because I'm not good enough to do it in one shot.

The reason for me to have a look at the keel joint in the first place was that the bondo was cracking and falling off. There would have been no reason to sand the original bondo so smooth, or at all. I just heated it with a torch and scraped it of. Besides, bondo is pink.


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## Maine Sail (Jan 6, 2003)

US27inKS said:


> Actually the picture is after fairing with epoxy and phonelic microballoons. Phonelic is a reddish brown plastic of some sort. they used to make distributor caps out of it. The varied coloration is due to the multiple layers that had to be applied because I'm not good enough to do it in one shot.
> 
> The reason for me to have a look at the keel joint in the first place was that the bondo was cracking and falling off. There would have been no reason to sand the original bondo so smooth, or at all. I just heated it with a torch and scraped it of. Besides, bondo is pink.


So what's with all the "crazing", "cracking" and "fissuring" looking areas in that photo?? It looks ratehr delineated to be feathering marks but the pic quality is very low.

That's quite odd & I've never experienced that with epoxy? Polyester, yes, due to shrinkage, but epoxy no....

Also when I mix with epoxy the filler layers, color wise, are not anywhere near that visible or discernible, like they are with a colored creme hardener product such as Bondo..

Which Epoxy and what hardener did you use??

This is how I'm used to seeing multiple fairing layers look.

Photo Linked From Triton381


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## US27inKS (Feb 6, 2005)

Yes the pic quality is low. Size limitations and all. There is always a visible line between layers of filler materials no matter what the material. The reason it is so easily seen is that the pic was taken after coating it with a layer of epoxy resin to help seal it. This made the color differences stand out. You can see that there is a reflection on part of the keel toward the rear. Add a camera flash, and they really stand out. Some of the straighter lines were due to using an old spreader that left lines in the filler, and were filled with the next layer.

I never was very good at spreading filler so that it gets done in 1 or 2 shots. My keel has about 1/4 inch difference between the stub and the lead. It only took me about 5 tries to get it right.


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