Stacked Scarf joints a problem ??

I have all of my ply on my Duck Hybid 12 cut and have the scarf joints for joining ply finished and I made sure that I have both sets for each side beveled the right way. As I completed the last of the bevels and scarfs I noticed that all of the ply scarf joints stack one over the other. As a carpenter whenever we "sheet" a roof or the floor we always stagger our butt joints. Did I mess up? How strong are these joints when glassed and epoxied together? I believe that a fixed form piece is in very close proximity to the scarf joints----Worries or not?? Thanks


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RE: Stacked Scarf joints a problem ??

No, you didn't mess up.  Plenty strong (remember there will be fillets and glass reinforcements).  No worries if your epoxy joints aren't glue starved.  That starvation can result if you use too much pressure when clamping and squeeze out all the epoxy or the end grain sucks all the epoxy away from the joint while curing.  Neatly paint the scarf joints with unthickened epoxy and watch for dry looking spots while you add thickener to part of your mix.  If you are worried about a dry looking area, repaint with unthickened epoxy.  Then add a thin (as in thin) layer of the thickened epoxy and clamp.  There will be squeeze out if you've done it right.  No squeeze-out means not enough epoxy.  Lots of squeeze-out means too much epoxy or too much pressure so you have more to clean up.  If your epoxy-wet scarf surfaces look dry after 10-15 minutes, they need more epoxy.  I usually mix two small pots of epoxy when joining plywwod scarfs;  The first to wet the scarf surfaces and keep them wet, and the second with a runny silica thickener as the final epoxy application as the gap filler (not everyone makes perfect scarfs).  Sorry for the long post.

PS - I've frequently planed across sheer clamp scarf joints and come away with wide, paper-thin shavings with an epoxy joint running all the way across the shaving.  Pulling these apart rips the wood, not the joint.

 Good luck.

RE: Stacked Scarf joints a problem ??

Thanks for the reply--Our internet server modem went out and I just now read your reply. Last night I did resin the scarf joints together and I did as the manual said and added a thickener to get a "mustard consistancy "-it is the new product sent with the MAS kit that replaced the silica. I taped all ajoining sides on both sides and had 1 stack of bottom pieces and 1 of the side pieces with a taped 1x4 board over the joint. For weight I stacked a selection of my larger hand planes from my collection. This morning the resin has not totally cured so removing the tape and shaving the excess resin at the joint seam is much easier..I did the initial shaving of the epoxy and wood  with an extremly sharp chisel and the sharvings of wood and epoxy are as you described. THanks again for your assurances and helpful advice

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