First ever scarf joint question

OK, so I'm 3/4 done scarfing my second piece of 1/2 marine ply in the garage with a power plane, it's only 10:00 at night and my wife decides I'm making too much noise! What gives? Just as well, as I'm probably don't have the courage to epoxy up the joint tonite anyway.

 

 Qusetion: How much west system epoxy with colodial silica should I mix up for a 4 foot 1:12 scarf joint? I finished each scarf with 80 grit on the belt sander. I don't want to waste any more of that stuff than I have too.

 

Thanks

troy

redding, CA

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Permalink Reply by Lawrence E. Long on March 21, 2010 at 4:38am
Get her ear plugs. No, just a SA comment. West is 5/1 if memory serves. Try to set up several "batches" of resin and hardner is separate containers- like yogurt cups or small plastic cups. That way if you don't use it all it can be put back in the jug. Mix the first batch(no thickener) and lay it on- end grain will soak up more- then lay on more unthickend resin so both sides of the scarf are fully saturated with resin. Then the final coat is thickend with cabosil(one side of the scarf) about like maple syrip in cold weather. Not toom much pressure- don't want to starve the joint.
Good Luck My guess is 4- 6oz will do one scarf.
Permalink Reply by Mike Baker on March 21, 2010 at 9:07am
Hey Troy,
It is really hard to mix a batch of west less than 3 oz. because of the 5-1 ratio. Use plastic cups to measure use the pumps to dispense. Get some cheap clear plastic cups at the grocery store, put one inside the other. Pour 1/2 oz water in the inside cup and mark a line with a sharpie on the outside one. Then ad 2-1/2 oz water and mark that line. You now have a measuring cup to meter your batches, put a NEW cup inside the lined cup for each batch don't try to re use a cup. You can make several different size batches with different measuring cups.
Mike
http://bakerwooddriftboats.com
Permalink Reply by peter harris on March 22, 2010 at 7:31am
I did same scarf last night and used 6oz resin/catalyst mixture.
Permalink Reply by Troy Nicolls on March 24, 2010 at 8:00pm
Thanks for all the help. My first scarf joint turned out nearly perfect. However, as I was using slow hardener, I thought I'd have time for dinner after applying the first coat to the scarfed sheets. When I went back in the garage 20 minutes later, a melted plastic cup filled with $10 worth of hardened epoxy lay on the floor. Live and learn.

Troy
Permalink Reply by Randy Dersham on March 25, 2010 at 12:55pm
Yes, the epoxy will dry slower if you spread it out; however, if it is left in a small batch like it was in the cup it will generate enough heat to speed it's cure. Everyone makes that mistake once.
Permalink Reply by Lawrence E. Long on March 25, 2010 at 2:55pm
been there, done that- even to the point it was "smoking" when i got back to the shop
Permalink Reply by Mike Baker on March 25, 2010 at 3:10pm
I was glassing the bottom of my first ever boat and using some old school epoxy (came in metal cans) a friend had given me leftover from a strip built canoe. There was about 1/2 gallon of resin so I threw in the remaining hardener and mixed it all. I am going along laying the glass down, taking my time being all pretty I look over and the can is smoking like crazy. So I pick it up and dump it all on the bottom and try to spread it and it sets almost instantly, what a mess! I think it took me a whole day to belt sand it smooth. The weird thing was I had a few bumble bees that were really attracted to the smell of the epoxy.
Mike

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