Using WEST System epoxy

[Griff in Fairbanks]

WEST System epoxy is a marine epoxy originally developed for wooden boatbuilders.  Although relatively expensive, it is well suited to motorhome building and repair.  It can be used for sealing, bonding, and laminating wood, as well as other materials.  (If I recall correctly, WEST stands for Wood Encapsulation Structural Treatment.)

I use it to seal wood against moisture penetration, bond wood to wood and metal to wood, and create wood/fiberglass laminates.  Pound for pound, wood is four to ten times stronger than the standard fiber reinforced plastic (FRP), commonly called fiberglass.  For the most part, I use fiberglass cloth, bonded to wood substrate with WEST epoxy, to provide abrasion resistance.

Check the WEST System website, as well as their publications, for extensive information on using the epoxy.

The central component, 105 resin, is mixed with various hardeners and fillers, depending upon how you intend to use it.  Unlike the polyester resin used in most FRP, 105 resin is shelf stable until mixed with hardener.

Which of the four hardeners you use depends on your application and working conditions.  The two main hardeners, 205 (fast) and 206 (slow), are the most cost effective and are chosen based on ambient temperature and working time (pot life) needed.  The other two hardeners, 207 (clear) and 209 (extra slow), are more expensive and chosen for special conditions and applications.  (205, 206, and 209 result in an amber-colored plastic that tints the wood, which I prefer.  209 yields a clearer, although still somewhat amber plastic, for a more natural finish on wood.)

The pumps are a must-have, precisely metering the resin and hardener.  The larger pump is for the 105 resin and the two smaller pumps are for 205/206 (5-to-1 by volume) and 297/209 (3-to-1 by volume) hardeners.  Each full stroke of the pumps dispenses the correct amount of resin and hardener.  (You simply pump an equal number of times on the resin and the hardener, depending upon how large a batch of epoxy you need.)  Smooth, even strokes on the pumps help ensure the correct ratio of resin and hardener is achieved.

A final note:  WEST System epoxy doesn't stink anywhere near as much as polyester resin while it's curing.  If you've ever been around FRP while it's curing, you know how it smells and how it stinks up the whole neighborhood.  WEST System epoxy gives off a faint ammonia smell while curing, somewhat like a well-cleaned diaper pail.

[Griff in Fairbanks]

The following is an application chart that gives you some idea how WEST System epoxy can be used.  (It doesn't show the various cloths and mats, such as glass and Kevlar, that can be used with the epoxy.)

[Griff in Fairbanks]

We use 9 ounce Solo brand disposable cups and tongue depressors for mixing the epoxy.  We tried several different kinds of mixing containers and settled on the disposable cups as most effective and convenient.  We prefer the Solo brand because the reinforcing ridge at the bottom is continuous, allowing us to run the mixing stick completely around the inside to ensure the epoxy is well mixed.  (Other brands have small bumps that can hold resin and prevent it from getting mixed throughly.)  We simply throw the cups away after each use, although we may use the same cup several times during a single session.

Tongue depressors have proven to be the best mixing sticks for us.  A few is all we need because we wipe the sticks clean after each use and use them over and over again.  The rounded tips also work nicely for smoothing fillets and we've sharpened a few on a sanding disc for scraping and cleaning squeeze-out from joints.  (See the WEST system website and literature to see how we use them.)

Disposable latex or nitrile gloves are a necessity.  WEST System epoxy can cause a reaction if it gets on the skin of some people, although we've never had a problem.  (I even glued my jeans to my leg one time without any problems other than pulling out a few hairs.)  Even if you're a careful worker, you're bound to get some epoxy on your hands so gloves make clean-up easier.  (For the most part, I wear the gloves to remove the used roller from the roller frame, which tends to be the messiest part of our process.)

If you're allergic to latex, use the more expensive nitrile gloves.  In either case, we wash our hands with soap and water immediately after removing the gloves.  (The only allergic reaction we've ever had was due to the powder on the gloves getting in our eyes ... a common experience for medical personnel.)

[Griff in Fairbanks]

I use short-nap foam paint rollers almost exclusively for applying the resin and rely primarily on my 3" roller frame.  I buy 9" foam rollers from Jamestown Distributors and cut them into 3" sections on my bandsaw.  (A few I cut up into smaller sections to use as applicator brushes -- see the WEST System website and literature for details.)  The only time I use the full 9" rollers is when I'm covering a large area.

The cut-up rollers allow me to throw them away after each use.  I tried foam brushes and inexpensive brushes (sometimes called chip brushes).  The epoxy tends to disintegrate foam brushes and chip brushes tend to leave bristles in the epoxy.  (Epoxy is difficult to completely clean from regular brushes.)

Note:  I strip the roller off the frame and wipe the frame clean with a paper towel immediately after each session ... once the epoxy has set up, it's difficult to remove the roller (and epoxy) from the frame.  (Grabbing the roller to strip it off the frame is the main reason I wear latex gloves.)

I use disposable tray liners to make clean-up easier and I reuse a liner several times, until the leftover set-up epoxy gets thick enough to make the liner unusable.

[Griff in Fairbanks]

The amount of resin we mix with each batch depends on how much we need to cover.  (Experience has taught how to estimate how much to mix ... which we refer to as 'one-shot', 'two-shot', 'three-shot', etc., batches.)

We pump however much resin we plan to use into the mixing cup, using one, two, three, or more full smooth strokes on the resin pump.  We then add an appropriate amount of hardener, using the same number of full smooth strokes on the hardener pump as we used on the resin pump.

We then start mixing the two components using a tongue depressor, scraping the sides of the mixing cup and making sure we get into the 'corner' at the bottom of the cup using the tip of the tongue depressor.  (We use a smooth mixing motion to try to avoid introducing too many air bubbles.)  As we start mixing, the resin/hardener turns cloudy.  Then, as we continue mixing, it clears up.  Once it's completely clear and we start to feel heat from the batch, we pour it into the lined roller pan and begin to roll it out.

Note:  WEST Epoxy generates heat as it 'kicks off' and starts reacting.  Very large, concentrated batches can generate enough heat to melt the mixing cup.  (And, if the epoxy is mixed with wood 'flour' filler, it can start smoking as it 'cooks' the wood flour.)  Spreading out the mixed epoxy, as in a roller pan, slows the reaction, allowing more working time.  Large volumes of epoxy in compact containers (such as the mixing cup) concentrates the heat, causing faster reaction and cure.