Working With Epoxy - Part 3 of 3 Author: Morten Olesen Website: http://www.boatplans.dk Added: Thu, Oct 11, 2007 17:37:19 Category: Hobbies

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In the first two parts of this series on working with epoxy, we covered cautions and the three stages of epoxy, as well as preparation and two-step bonding.  These articles have assumed that everything is going according to plan when building your boat.  This article, however, will take a look at what happens when things go astray.

Even pros will tell you they sometimes make mistakes when using epoxy.  And, because it is a rather unforgiving product, a misstep can lead to serious problems with bringing your boat plans to life.  Let's look at several common problems that might occur when working with epoxy and the recommended course of action to resolve those problems.

Epoxy Doesn't Harden

There are four possible causes of epoxy that fails to harden.  The ratio of hardener to resin might be off, the temperature in your boat-building area might be low, the resin/hardener mixture might not have been mixed properly, or you may have used incompatible products.  (Some epoxy products are only compatible with others of the same brand.  Many won't cure if products contain polyester catalysts.)

If the temperature in the area where you're building your boat is below 41 degrees Fahrenheit (5 degrees Celsius), the epoxy will not cure.  The lower the temperature, the slower the epoxy will set.  You might apply heat to encourage a faster cure, but never add additional hardener. 

If you believe the ratio of hardener to resin is off, the mixture was not combined properly or that incompatible products may have been used, your only course of action is to remove the epoxy and begin again. 

Bonding Does Not Occur

If you're sure the epoxy mixture has been allowed sufficient time to cure thoroughly and a bond has still not occurred, it is likely one of four things has happened.  There is a void at the joint, the surface was not prepped adequately, the bonding area is too small or there was too much pressure from the clamp used.

If the resin has wicked into the surfaces leaving a void at the joint, you can wet out the surfaces before applying thickened epoxy, then continue with the two-step process described in Part 2 of this series.

When the problem lies with the surfaces not being adequately prepped before the epoxy was applied, you'll need to remove the epoxy and begin again.  Be sure you follow the preparation instructions in Part 2 of this series so that your bond will adhere.

Sometimes the stress on the joint is simply too much for the bonding area to bear.  If this is the case, simply add fillets or bonded fasteners and increase the bonding area so that it is adequate for the load on the joint.

Frequently, the pressure from the clamp used simply squeezes out too much epoxy.  When what's left of the epoxy cures, there simply isn't enough to do the job.  Remove the epoxy from the surface and begin again.  When applying the clamp this time, watch to be sure you aren't pressing too much of the epoxy out of the joint.

Paint or Varnish Will Not Cure Over Epoxy

When you finish your project and lay your boat plans to the side, you see a fabulous boat that's ready to take on a new personality with a couple of coats of paint (or varnish).  However, as you apply the paint, you notice it doesn't cure.  Usually there are 3 simple reasons and solutions for this problem.

The epoxy may not have cured fully.  Depending on the temperature and other factors, it may take several days for epoxy to cure.  You might consider applying a little heat to speed the process.  The problem could also lie in the fact that the paint chosen is incompatible with the epoxy products you used.  Check the label of the hardener and resin used, then buy a paint or varnish that meets those criteria.

The last reason is that you neglected to prepare the surface before painting.  The amine blush (cloudy residue) must be removed and the epoxy surface sanded before paints or varnishes will adhere.

Now that you understand more about the challenges epoxy can pose and how to overcome those challenges, you'll be better prepared to get it right the first time.  You can look forward to turning your boat plans into a reality that will take you off into the sunset for years of enjoyment.

About the Author:
Morten Olesen is a master boat builder and Naval Architect. Visit Morten's site http://www.boatplans.dk to get his exclusive line of boat plans which includes 3-D computer models. You'll also get his free Boat Builder Master Course with your order. © 2007, All Rights Reserved