My First Experience With Epoxy… Finger Joints

Posted by Zachary Wiest in Epoxy

When I got home from work today I saw a box sitting in my driveway.  True to CLC’s word, the replacement epoxy was overnighted.  Having only cut gains on the #1 panels, I knew I had more gains to cut, but was excited to start playing with this stuff.  I read over the manual’s words on epoxy a few times and was confident to get started.

Because marine ply comes in lengths of about 8 feet, pieces must obviously be joined together to form the 15′ panels on the boat.  To do this, CLC produces the panels with a finger joint. These joints look like puzzle pieces.  When the bow and stern sections of a panel are placed together, these finger joints lock into place.  A thickened epoxy is used to essentially glue the pieces together.  Epoxy mixed with a silicone powder called Cab-O-Fill is used to thicken the mixture and ultimately strengthen the joint.

Before I go into detail on my first epoxy job I want to commend MAS Epoxies on their excellent pump system.  Epoxy is really two parts: a resin and a hardener.  The epoxy I have must be mixed at a 2:1 ratio (Resin:Hardener).  To make this process easy the resin pump squirts out twice the amount per stroke as the hardener pump.  This way you always get the proper mix.

So anyways, let me tell you how it went.  I started by mixing up about 4 ounces of the stuff.  Next, I slowly added the Cab-o-Fill to reach the desired “mustard” consistency that the manual calls for.  I was pretty timid and did not realize just how much thickener I would need to add.  It was a lot more than expected!  When the mixture was ready I used a brush to “paint” the epoxy onto the edges of the finger joints where they would contact each other.  I started with the port #1 panel.  Now that the two pieces were properly coated (so were my gloves) it was time to join bow to stern.  It wasn’t as easy as I thought it would be.  These pieces, while precision cut, fit together TIGHT!  I probably spent 15 minutes on the first panel, pushing the fingers together with my thumbs.  Boy are my thumbs sore from all that pressure!

After the port #1 panel was assembled I moved onto the starboard panel.  I used the same process but realized that I could more quickly apply the epoxy by just using my gloved fingers.  This proved effective, especially as the epoxy started to get less “mustardy” and more “peanut buttery” as it slowly cured.  When these panels were joined, I placed a sheet of plastic on top of the port side and laid the starboard side on top of that.  This is to make sure the port and starboard panels match.  When I was confident they looked good together, I put some more plastic over top and added some scrap wood and weight to assist with the gluing.  I repeated this same process for the bottom panel.

So here is what I learned.  Epoxy isn’t very scary, but it is messy.  I changed gloves frequently.  Also, if you are working in a warm environment like I was (80 degrees) the epoxy starts to cure fast.  I probably could have placed the mixture in the fridge and allow it too cool while I wasn’t actively using it.  If you haven’t picked up on it by now, epoxy cures much quicker in warmer temperatures.  After 24 hours, the joint should be fully cured.

Time Spent: 1.5 Hour

Total Time In Build: 3.0 Hours

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