Builders' Forum Archives
Re: scarf overlap questio
Posted by Dave Houser on Nov 16, 2006
Robert got it right blunt edges will require some scarf surface to show but it should not be more than part of the surface ply.
You should wet both surfaces of the joint with unthickened epoxy and then coat one side with thickened epoxy. The West Systems manual (a good standard no matter what brand epoxy you are using) says the strongest joint filler is chopped fiber so that is what I use. But no matter, the thickened epoxy does add thickness to the joint. So if you pre-fit dry and then glue the joint will be a little thicker than the plywood. If the panels are precut (from a kit) the over all panel length is more important than the joint thickness so measure (also use a string line to maintain the correct alignment). Put tape marks on the floor (or table) to mark the measured distances. If you are gluing panels before lofting (from plans) glue them on a flat supporting surface (covered with polyethylene plastic sheet) and use a steel straight edge, on edge across the top of the wet joint to keep the panels constant thickness. To clamp while the epoxy on a panel sets I secure both panel pieces with weights and then cover the top of the wet aligned join with polyethylene and a 25 pound bag of lead shot.
If you are finishing the sides neat (natural) and want to avoid the uneven color that can occur from the epoxy wetting outside the joint, assemble the joint dry and mask both edges of the joint on both sides as close as you can and then glue the joint. You must remove the tape the day after epoxing or it will be hard to get off. Also use a cabinet scraper to remove any excess epoxy the day after gluing while it is still soft. Scrape just enough to level the epoxy to the wood surface and not remove wood. Do not sand the joint or you will get the dreaded white spot in your finish.
In Response to: scarf overlap question by Antal on Nov 15, 2006