West epoxy vs. varnish finishes

[thepiranhabros]

I thought I'd start a new thread rather than further hijack Mike's step-by-step thread with these questions (and potentially more).

Does anybody have any real-world data they'd be willing to share (based on personal experience) on the UV degradation of West epoxy products versus varnish?

How can you tell when West is breaking down due to UV exposure? I know when varnish is end-of-life when the finish crazes and it flakes off. I assume there are some visual cues for when West is E-O-L, but I wouldn't know what to look for.

Thanks!

[B1PRORACER]

I looked this up on the West System website:

You Are Here: Home » How To Use » Use Guides » Finish Coatings
Finish Coatings
The function of a finish coating like paint or varnish over an epoxy barrier coat, is to decorate the surface and protect the epoxy from sunlight. In doing so, the finish coating extends the life of the epoxy moisture barrier, which, in turn provides a stable base that extends the life of the finish coating. Together the two form a protective system far more durable than either coating by itself.
Protection from sunlight is a primary consideration in the selection of a finish coating. Long term UV (ultraviolet) protection of the barrier coat depends on how well the finish coating itself resists UV and keeps its pigments, or its shield of UV filters on the surface of the epoxy barrier coat. A high gloss finish reflects a higher proportion of the light hitting the surface than a dull surface. All other thing being equal, a white (especially a glossy white) coating will last the longest.

Most types of coatings are compatible with epoxy. Thoroughly cured epoxy is an almost completely inert hard plastic. This means most paint solvents will not soften, swell or react with it. However, it is still a good idea to build a test panel to assure coating compatibility.

Coating types

Latex paints are compatible with epoxy and they do an adequate job of protecting the epoxy barrier from UV radiation. In many architectural applications latex paint may be the most suitable coating to use. Their durability is limited.

Alkyd finishes-enamel, alkyd enamel, marine enamel, acrylic enamel, alkyd modified epoxy, traditional varnish and spar varnish-offer ease of application, low cost, low toxicity, and easy availability. Their disadvantages are low UV resistance and low abrasion resistance.

One-part polyurethanes offer easy application, cleanup and better properties than alkyds. They are also more expensive and some may be incompatible with amine cure epoxy systems such as WEST SYSTEM epoxy, although 207 Hardener may offer better compatibility. Test first.

Epoxy paints are available in one-part and two-part versions. Two-part epoxies offer many characteristics similar to the higher performance polyurethanes. They are durable and chemical resistant, but offer limited UV protection compared to the linear polyurethanes.

Two-part linear polyurethane (LP) paints offer the most durable protection available. LP's are available as pigmented or clear coatings and offer excellent UV protection, gloss retention, abrasion resistance, plus compatibility with epoxy. However, compared to other types of coatings, they are expensive, require more skill to apply and present a greater health hazard, especially when sprayed.

Bottom paints are available in a variety of formulations. Most bottom paint systems are compatible with epoxy and can be applied directly over a prepared epoxy barrier coat. If you are unsure of compatibility or have curing or adhesion problems with a specific bottom paint, use only a primer recommended for that bottom paint over the barrier coat. Follow the recommendations given for preparation of fiberglass surfaces. Other paints, including marine LP's and primers, are not recommended for use below the waterline.

Primers are usually not needed to help a paint film bond to epoxy, although interfacing primers may be required with some specialized bottom paints and high-build primers are useful for hiding scratches or flaws in the substrate. If the instructions on your paint or varnish recommend a specially primed surface, follow the recommendations given for fiberglass preparation. Self-etching primers do not work well on an epoxy coating because of epoxy's chemical resistance.

Polyester gelcoat is a pigmented version of the resin used to build fiberglass boats and other products. Gelcoat is sprayed into a mold before the glass fabric and resin are applied to provide a smooth pre-finished surface when the part is removed from the mold. It is not often used as a post-production finish coating, but it can be applied over epoxy and is useful in some repair situations. Refer to Fiberglass Boat Repair and Maintenance, published by Gougeon Brothers, for detailed information on patching gelcoat over an epoxy repair.

Follow all instructions from the coating systems manufacturer. It is a good idea to make a test panel to evaluate the degree of surface preparation required, and the compatibility and handling characteristics of the finish system.

For detailed instruction on the application of these techniques in repair and construction, refer to specific WEST SYSTEM instructional publications and video demos. For complete descriptions of all WEST SYSTEM products, including selection and coverage guides, go to the Product Guide.

To help you identify and prevent potential problems associated with using epoxy, go to the Problem Solver.

For complete information on the hazards associated with epoxy and the precautions you can take to avoid them, go to General Safety Guidelines.

To see how these techniques have been put to use in a wide range of repair and construction applications go to the Projects pages

[Bill Huson]

Yes, I have lots of real world experience - been using WEST since the `80s. Many moons ago 206 hardener was the coating hardener of choice and bare WEST suffered under the sun. My 155ssH boat was bare WEST resin - time to go racing. After one season the WEST was looking shabby. It gets a bit cloudy and dull, then starts to chalk off. I sanded the 15ssH down and recaoted, but alas, time to go racing again! Poor boat never had a decent finish and I think was on it's 3rd WEST recoat when I dropped out of racing. I believe Biily Z has that boat, and another 155ssH I built for my son which had of course a real paint job. Paint it once, done. Even lacquer is more durable than WEST when exposed to UV.

Now I am using 207 hardener which is supposed to be more UV resistant, but WEST still recommends a UV topcoat, such as decent marine spar varnish if you want a bright (wood) finish. My last two builds used 207 kicked resin. And have a few coats of marine spar varnish as well.

I love WEST resin, but it is NOT finish coat varnish.

[BP125V]

bare West?

I thought I'd start a new thread rather than further hijack Mike's step-by-step thread with these questions (and potentially more).

Does anybody have any real-world data they'd be willing to share (based on personal experience) on the UV degradation of West epoxy products versus varnish?

How can you tell when West is breaking down due to UV exposure? I know when varnish is end-of-life when the finish crazes and it flakes off. I assume there are some visual cues for when West is E-O-L, but I wouldn't know what to look for.

Thanks!

simple question for you - what do the insides of my boats look like? one is 7 years old the other 6 both have 207 on the inside. tons of racing and testing time over that time span. Keep the sun off when not in use and the WEST 207 will look like new for MANY years. Skip the tops coats as they will just make more work for you when you need to do repairs.

[Islandmon]

simple question for you - what do the insides of my boats look like? one is 7 years old the other 6 both have 207 on the inside. tons of racing and testing time over that time span. Keep the sun off when not in use and the WEST 207 will look like new for MANY years. Skip the tops coats as they will just make more work for you when you need to do repairs.

Good advise on all counts !

[ZUL8TR]

Epoxy and UV

Here are some test results of 6 epoxies including West with 206 and 207.

http://www.oneoceankayaks.com/Epoxtest.htm

Here is West article on varnish over epoxy

http://www.westsystem.com/ss/assets/Uploads/varnish.pdf

They recommend West 205/207 with varnish top coat.

For race boats that see little sun epoxy 205/207 + varnish, your call?

[johnsonm50]

All good info here. My thoughts are that West because of its strength is best used as a bottom coat. Finish coats are fine & will mostly last longer cosmetically but the saturation of epoxy adds surface strength that finishes dont.

The hydros old & had several finish remnants. I re-did it with West & 2 part 'auto' polyurethane. The poly Im very impressed with, its going into year 3 & has suffered very little deterioration. The runabout is West, the deck- [3rd time] now has 'special clear' 207 & UV-varnish. This seems so far to be the best attempt.
Epoxy can look milky from too thick of a coat, humidity on application & exposure. If its initially clear & gets milky later then exposure to sun is why. Also areas that were from coating thick or humidity are more likely to go bad sooner. Minimizing sun exposure is always a good idea.

[pops67g]

Varnish is fine for furniture.

I never put any varnish on the raceboats. I guess I just think a raceboat should be colorful rather than blend in with its surroundings. Bill makes a good point about the repairability problems. Epoxy is easy to refresh when needed in the cockpit and it is fuel proof as well. The bottoms really don't need protection from the sun and they are easier to deal with when it comes time to straighten or repair them. I think a sanded epoxy finish on the bottom is faster than varnish also.

[johnsonm50]

I dont varnish bottoms either, its alot of work you don't need & epoxy is tuff-r.

[Dave M]

Good Question

Great question. Like others have said, I think West needs a protector for lasting the long haul. I wouldn't use varnish unless that is all I had at the time. It works just fine for the application, I just know it is much heavier than the finish I use. I use Automotive Clear Coat sprayed on, one tack layer and one finish layer.

Just my experience, I clear an entire boat with Nasson Clear coat I add close to 2 pounds, maybe slightly over if i am laying it on thick. This is a one time application if done right, spray the tack coat, come back a few minutes later and put the final coat on. Flash Dries in 7 minutes, Dries in 30 minutes, cures in 7 hours. I usually let it sit overnight. To get varnish to have the look I like, it takes several coats and sanding in between coats to get the desired look I like.

I like to keep it simple.

For the bottoms anymore, I simply mix in the West graphite powder and coat the whole bottom. Done, no additional protection needed, and it is supposed to be faster than simply West. I dunno if it is measurable difference.

[johnsonm50]

Great question. Like others have said, I think West needs a protector for lasting the long haul. I wouldn't use varnish unless that is all I had at the time. It works just fine for the application, I just know it is much heavier than the finish I use. I use Automotive Clear Coat sprayed on, one tack layer and one finish layer.

Just my experience, I clear an entire boat with Nasson Clear coat I add close to 2 pounds, maybe slightly over if i am laying it on thick. This is a one time application if done right, spray the tack coat, come back a few minutes later and put the final coat on. Flash Dries in 7 minutes, Dries in 30 minutes, cures in 7 hours. I usually let it sit overnight. To get varnish to have the look I like, it takes several coats and sanding in between coats to get the desired look I like.

I like to keep it simple.

For the bottoms anymore, I simply mix in the West graphite powder and coat the whole bottom. Done, no additional protection needed, and it is supposed to be faster than simply West. I dunno if it is measurable difference.

The graphite might work a little.. In an oval racer there's probably enough acceleration leftover for a boat without to not be disadvantaged much if any. It would be interesting to see kilo testing where any trick could be the trick.

[blueskyracer]

Great question. Like others have said, I think West needs a protector for lasting the long haul. I wouldn't use varnish unless that is all I had at the time. It works just fine for the application, I just know it is much heavier than the finish I use. I use Automotive Clear Coat sprayed on, one tack layer and one finish layer.

Just my experience, I clear an entire boat with Nasson Clear coat I add close to 2 pounds, maybe slightly over if i am laying it on thick. This is a one time application if done right, spray the tack coat, come back a few minutes later and put the final coat on. Flash Dries in 7 minutes, Dries in 30 minutes, cures in 7 hours. I usually let it sit overnight. To get varnish to have the look I like, it takes several coats and sanding in between coats to get the desired look I like.

I like to keep it simple.

For the bottoms anymore, I simply mix in the West graphite powder and coat the whole bottom. Done, no additional protection needed, and it is supposed to be faster than simply West. I dunno if it is measurable difference.

I always loved sprayed on Auto paint back in my younger days but now I hate having to tape everything off and making sure everything is covered for all the over spray. Those that like a tons of extra work go for it. Everyone has their own ideas and they all work for that individual. I do think West system needs protection in some form or another.

[pops67g]

Graphite = overkill

I guess the graphite is OK if it makes you feel better, but when my hydros are running over 90% of the bottom surface is a ways off the water anyway (even in the corners) so I say save the extra for a better propeller or a cold beer.

[Bill Huson]

They recommend West 205/207 with varnish top coat.

For race boats that see little sun epoxy 205/207 + varnish, your call?

I believe it is WEST 105/207 w/varnish topcoats.

[ZUL8TR]

West topcoat

I believe it is WEST 105/207 w/varnish topcoats.

Correct, typo

Thanks