Epoxy

So I just used epoxy for the first time ever, not to sure how it went. I cut and epoxyed my chine logs and side rails, but im not sure how they turned out. I followed Raka's manual, but insted of clamping I just put weight on the joints because they warn about over clamping so I thought it would just be easier. When I removed the weight it seems like a strong connection, but there is a slight gap inbetween the pieces. So my question is, did I not have enough weight? Thinking im going to clamp it next time, is it really easy to over clamp?

 

Also the epoxy that got smashed out the sides made the wood darker. Can this be removed by sanding? Im planning on staining and oiling so I would prefer a good looking joint.

 

Any other helpfull tips that you guys have learned in your many years of building that I would be much better off to know before I glue my $$$ plywood?

 

Thanks as always. I was hoping to make it up for the boat show, but everything is taking much longer then I thought, and I would rather not rush through it. Maybe next year!

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Permalink Reply by lhedrick on February 25, 2011 at 5:57pm

You can use weights or clamps.  I use both.  If you use clamp only apply light pressure.  Epoxy is not the same as PVA glue which requires tight clamp pressure.  Epoxy fills gaps very well.  A few epoxy filled gaps are usually not problem.

 

Don't sand epoxy.  Get a carbide edged scraper.  You can get a cheap carbide scraper at Harbor Freight which will work just fine.  The scraper will cut down excess epoxy much faster.  Epoxy which is not fully cured will also load up sandpaper.  After using the scraper then move to the sand paper.  

 

Before going too far, epoxy up a scrap scarf joint.  The next day after the epoxy has cured, smash it or try to brake it by pushing it down on the edge of a work bench.  This will tell you you are doing things right.  Same thing with the plywood.  scarf up some scrap.  Epoxy them and then try to brake them apart.  It will tell you a lot.  You will be amazed how epoxy bonds to stuff.

 

 

Permalink Reply by Scott Hepler on February 25, 2011 at 6:33pm
One thing that saved me a lot of time and sanding was to simply clean up any squeeze out of epoxy with denatured alcohol. If you have any fillets you can wait till the epoxy is just tacky and then take your finger (in a glove) and wet it with alcohol and smooth the epoxy until it is perfectly smooth. No sanding required. Some guy are even using visqueen to put on their panels that are epoxied while it is still wet and then when the epoxy is cured you just peel off the plastic and it is perfectly shiny, again no sanding. If you can heat up the epoxy it will flow better. Lastly, of utmost importance is to make the ratio exact, I used a digital scale to do it by weight but either method, volume or weight make sure it is perfectly ratioed and mixed completely.

Good luck
Permalink Reply by Dave Z on February 25, 2011 at 7:31pm

Did you add a powder (sawdust, microballons, etc) to the wetted epoxy before clamping? 

Permalink Reply by Ben Kittell on February 26, 2011 at 6:33am
Yup, one coat of normal epoxy, then one coat of thickened with silicon.
Permalink Reply by AJ DeRosa on February 25, 2011 at 8:39pm

Epoxy 101 for frames

 

Dry fit frames to proper alignment drill and screw.  Mark mating surfaces.

Coat mating surfaces with epoxy and allow to soak in for 20 minutes.  If it appears to have soaked dry recoat and let set for another 20 min.  Apply thickened epoxy and join pieces.  Insert screws and tighten just enough to get thickened to ooze  abit at the joint.  If you tighten too much you squeeze out the goo and get a glue starved joint. 

if you try to clamp a joint without fasteners the joint will become misaligned.  Don't ask me how I know this.

 

Dave is asking if you did indeed use a thickener in your second coat.  Wood flour, microfibers, sawdust, etc. need to be added to epoxy to create the proper void filling properties for a strong joint.  Add these fillers to epoxy till it gets to the consistency of mayonaise.  A small amount of epoxy goes a long way when adding fillers so start small and get the right consistency.  Trial and error is a good but unforgiving teacher. 

 Larry gives good advice when he suggests practicing on scrap.

 

This advice is for frame joints.  Glueing up scarf joints uses the same glueing technique but the alignment issues are a little different.  There are several threads on this site that discuss these issues. 

 

Enjoy your build.

 

AJ

Permalink Reply by Kevin C. on February 25, 2011 at 9:19pm
once your epoxy has cured on your scarf joint put a little heat from a heat gun to it and scrape off the excess down to the wood then sand.We have made a jig for joining rail scarfs together that consists of a 2' x 4" base with a 2' x 2" perpendicular piece screwed to it creating a 90 deg. "fence" to which you place your two pieces to be scarfed up against and lightly clamp into place.A piece of visquene in between the jig and the pieces being epoxied ensures you don't bond the pieces to the jig.This enables you to correctly and precisely line up your scarf to where you want it and holds it in place until it has cured,then unclamp,remove the visquene and scrape off any excess with a heat gun and scraper.
Permalink Reply by Ben Kittell on February 26, 2011 at 11:08am
So the rail is actualy sidways? Can you do 2 at a time using both sides of the jig? Do you ever have a problem with the epoxy running and leaving the top part less glued?

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