Epoxy or Vinylester?

[Ned Ludd]

Hi All,

I have been studying to the point of confusion.

Here's the story, 1976 boat and the trailing edge of the lead keel was factory fared and shaped with foam and the entire keel is glassed with 1 layer of cloth. Due to my own dumb ass I got the bow of the boat too high on the trailer which put too much stress on the trailing edge of the keel and it has cracked the laminate and foam filler off of the trailing edge of the casting. This is not a structural repair.

I know epoxy is better for underwater work since it does not absorb moisture however for bonding and workability purposes I have been reading that I should stick with vinylester resin. The boat was probably built with vinylester and it has a much faster kick time for use outdoors in the spring time.

The overall plan is to: remove loose material, sand and clean lead (Yes I will wear all appropriate PPE), immediately seal lead with 1 coat of resin, add a layer of mat to build up the repair to the surrounding level, then fair with lightweight compound. I am taking a week of PTO for boat work so I can get all of the resin work completed in 1 long day to reduce sanding.

My only real question is what type of resin to use.

 

[dlochner]

Epoxy has better adhesion than polyester and vinyl ester when applied to a cured resin. All resins chemically bond well to themselves (vinyl ester to vinyl ester, etc) before they are fully cured. Once the resins are cured a mechanical bond is necessary and epoxy wins this battle.

Use a fast hardener with the epoxy, it will work better on cold days. As you know, resins will cure faster when warm, get a radiant heater to warm the work area or use plastic sheeting to tent the area and place an electric heater or halogen lamp in the tent to keep things warm.

Some of the dedicated epoxy fairing compounds may have faster cure times than plain thickened epoxy. Check with the manufacturers.

 

[jibes138]

You can get all kinds of epoxy hardeners to either lengthen or shorten your cure time. I have some 5 minute epoxy I use around the house and it actually hardens in 5 minutes. Cure time is also a function of temperature, you can always use a hair drier to speed up the reaction if desired.

 

[kloudie1]

Quick note: Vinylester resin was very rare when the Newport was built.. most likely that polyester resin was used on the faring..

 

[Gunni]

One of my first boat projects as a kid revealed that my foam core material was incompatible with the solvents in my polyester resin. I had to use epoxy.

 

[Ned Ludd]

Thanks for confirming my first thought.

 

[CloudDiver]

Epoxy, for all the reasons @dlochner mentioned above. Epoxy has a much higher secondary bonding strength than polyester or vinylester resins. Epoxy is always better for under waterline repairs because its actually waterproof at a molecular level. Vinylester is way better than polyester resin when it comes to osmosis, but it's still not 100%.
If its cold, like below 60 deg, try building a tarp tent around your work area and use halogen lights to warm things up, also a paint drying gun is handy. Be careful, just warm it, don't cook it. You can easily 'boil' epoxy resin if you go too crazy. If you can get a clear sunny day and the temp is above 60 you can work without the whole tarp tent mess, just use a heat gun for light warming. A gallon of West System epoxy plus hardener and filler plus mini-pumps for measuring will set you back $200, but its a superior product any very easy to use/measure with the mini-pump set.

 

[CloudDiver]

BTW... I use epoxy resin for generally all boat repairs with one exception. Non structural repairs above the waterline which need to be finished with fresh gelcoat, both polyester and vinyl-ester resins will do. Gelcoat is polyester resin based and if applied before what ever glass/resin repairs have fully cured you get a good chemical bond. The old wisdom is that gelcoat does not stick to epoxy, so you can't gelcoat any cured epoxy repair. That actually isn't true and testing has been done (google it, there are videos) that shows gelocat will stick to sanded and prepped (cured) epoxy just fine... I just personally haven't tested it myself.

 

[Charlie Jones s/v Tehani]

Definitely epoxy. There are many brands, all good. I've worked with West, MAAS, Sys 3. and more.
The 2-1 ratio epoxies cure more slowly in cool temps than the WEST 5-1 does.

The only time I use polyester resins anymore is in new layups. Repairs?Always Epoxy

 

[Gene Neill]

BTW... testing has been done (google it, there are videos) that shows gelocat will stick to sanded and prepped (cured) epoxy just fine... I just personally haven't tested it myself.

FWIW, I sprayed gelcoat over the epoxy-based repair on my sliding hatch. No problems after three years.

West Systems also says it will work: http://www.westsystem.com/ss/polyester-over-epoxy/

 

[dlochner]

Boatworks Today did a gelcoat over epoxy test. See it here: https://www.youtube.com/playlist?list=PLV97GZkHhpHOxrZc7r9zdx_w_R-x4fZ9S

West System wrote about it in Epoxyworks. Check their website.

 

[rgranger]

... and one last thing.... epoxy is easier to clean up than poly vinyl. Keep a jug of white vinegar and a roll of paper towels on standby. Epoxy is a poly amide (base) and vinegar is acetic acid. So you can get partially cured epoxy to dissolve in vinegar... so when you get it on your skin, you can clean it off fast. Just clean it up before it fully cures. The ester resins require harsh solvents to clean up and even then, you still have residue.

 

[Ned Ludd]

Thanks for all the tips, off to Englund Marine this weekend for some epoxy.

 

[Charlie Jones s/v Tehani]

Thanks for all the tips, off to Englund Marine this weekend for some epoxy.

Pick up some nitrile gloves too. I NEVER EVER use epoxy ungloved. Been building boats using it since 1976, and do NOT want to become sensitized!!

 

[dlochner]

Pick up some nitrile gloves too. I NEVER EVER use epoxy ungloved. Been building boats using it since 1976, and do NOT want to become sensitized!!

Charlie brings up a good point. Epoxy is not that toxic and is non-toxic when cured. However, excessive skin contact can cause an allergic reaction. Vapors from epoxy curing are not particularly dangerous.

As ranger points out, plain old white vinegar will clean epoxy from skin and other surfaces. Rubbing alcohol and denatured (stove) alcohol also work well.

On the other hand, the solvents used with ester based resins are quite toxic and destructive. Witness the reaction of polyester resin on a styrofoam cup and the vapors should not be inhaled. Styrenes are not good to breathe.

 

[Ned Ludd]

I have a baggie of 500 black night nitrile gloves on hand currently. Chemical safety is a big part of my professional career so proper PPE is a top priority. Thanks for the concern.

 

[rgranger]

Post some pics when you are done....