Plywood: scarf,glue,cut or scarf,cut,glue??

[Ron Linton]

Seems that the most common method for preparing plywood side panels or bottom panels for sawn frame or stitch-and-glue construction requires scarfing plywood sheets, gluing the sheets into appropriate lengths, marking patterns for cutting, and then cutting the final panels. Seems like this standard approach would create more waste than another approach: scarf, mark patterns, cut, then glue. At least this way, the unused plywood could be "rearranged" for portions of other panels. Has nybody tried leaving the gluing 'til last?

Ron Linton

[WayGray]

Several times I have done the glueing after drawing patterns and cutting. I did it exactly for the reason you stated; to save plywood waste. I always draw an index line on the adjoining sections to facilitate alignment for glueing BUT, I also cut the patterns slightly oversize, because, if your glue joint is off even a little, over the 15-20 foot length of a full panel, the discrepancy can be significant. I would normally cut the pattern slightly oversize anyway to allow for other possible sources of error, so the difference is minor. It may or may not be the best technique depending on the situation.

[brian.cunningham]

That's how kit boats come.

They cut the pieces out on a CNC router.

Then they cut the scarves.

You put it together after they ship it to you in a box.

[Tomcat]

Just keep two things in mind: Extreme angles at the joint, won't have the same material strength, or flexibility as pieces cut out of prejoined panels, or similar alignments. Of course this can apply in somewhat similar ways to radicaly curved cuts without scarphs, though a ridicaly angled joint would be worse still.

[Ron Linton]

WayGray, glad to see you've already plowed that ground. Will be sure to cut patterns a bit oversized and use index lines too. Thanks for the input.

Brian, of course! I forgot that kits come that way. Hope I can be approximately as accurate as CNC.

Tomcat, I plan to go with 12:1 scarphs either way to maintain material strength.

Thanks guys!

Ron Linton