Keel Fairing

[jimmyb116]

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.

[Maine Sail]

Originally Posted by sailingdog

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..

[BarryL]

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

[sailingdog]

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

[Maine Sail]

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...

[sailingdog]

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.

[BarryL]

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

[US27inKS]

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

[artbyjody]

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!

[Maine Sail]

Originally Posted by US27inKS

On my boat the factory had used bondo.

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