Scarfing Jig

[MICHAEL S]

I am getting ready to start my first boatbuilding project (11'-2" Shellback Dinghy)and need to scarf three plywood joints for the first time. The book I am using to build from (How to Build the Shellback Dinghy by Eric Dow) shows a simple wooden press that I am sure will work fine but I will only need it for one time use. Is there an even simpler way to clamp scarfs. Also I wonder what problems I am likely to encounter as a first time scarfer (Scarfist?, scarf maker?) (My ignorance is obviously profound)

[Ian McColgin]

The easiest thing is to rack up the sheets staggered with the lowest one right on the edge of a bench of some sort. If you want 8:1, stagger 3/8th plywood on 3" increments. Use any kind of hold-down that leaves room at the end for planing and is truely rigid.

Sharpen your plan and go

[MICHAEL S]

Thanx, I feel I understand how to cut the joints (with luck)but a simple way to clamp the glue-up is what I'm looking for. Any ideas?

[JimD]

Originally posted by MICHAEL S:
Thanx, I feel I understand how to cut the joints (with luck)but a simple way to clamp the glue-up is what I'm looking for. Any ideas?Michael, clamping the glue up is the easy part. Any common sense method that keeps the boards from shifting and applies pressure across the joint is will do. If you don't mind a few small holes in the wood you can even nail or screw the boards in place and fill the holes afterwards. And don't worry too much about a lot of pressure anyway because if gluing with thickened epoxy a lot of pressure is a bad thing. It squeezes out the epoxy mix and the joint becomes glue starved and weak.

[jwaldin]

Ian, I think he has already sharpened his "plan' by posting here.

[gary porter]

Michael, the jig as Eric shows you does work quite well and pretty easy to build. I used it for my Shellback and still have it but on bigger boats and such I just use some scrap playwood, visqueen and small sheetrock screws. This works very well and the holes are easy to fill. If your planning on finishing out the inside clear then it would probably be better to clamp it one way or another so as not to have the holes show up later. If your going to paint it then it doesn't really matter. The table part of that jig that Eric shows is usful for cutting the scarf and for other glueing and or sawing operations so I wouldn't discount using it either. Have fun.
Gary

[Stiletto]

As Jim D says , screws or nails can hold things in place. Screwing and nailing while dry and then removing the fasteners and replacing after glueing can make location a bit easier as they find the holes already there and minimise sliding around on a glued joint.

[Steve Lansdowne]

Use waxed paper above and below the glue joint to avoid glueing the scarfed pieces to any adjacent wood with any epoxy that oozes out.

[daddles]

Seeing everyone is dodging the issue as usual.

Get a work bench long enough to support both sheets of ply - you will be screwing into this so make sure you don't mind (not the dining room table). It needs to be more or less flat too. Lay a sheet of plastic down where the joint will be so you don't glue the ply to the bench. Lay your ply down. Smother one scarph with unthickened epoxy (lots, it soaks into the endgrain like blotting paper), the other with thickened epoxy. Place the two glue faces together and slide them back slightly - ie, instead of the feather edge touching the base of the other scarph, move it back about 1/16" - if you don't, you can wind up with a step in the ply. Lay a sheet of plastic over the top, then a strip of scrap ply (1/4" or thicker, it's there to provide pressure) about 6" wide over the joint. Screw it down using screws that pull into the base timber - that's probably not necessary but it does ensure a good, even pressure. Place the screws in two parallel lines, on each side of the scarph but inside it - you are screwing the two sheets together. Put the screws about 6" apart. Pull it down tight enough to squeeze some epoxy out but not all.
If you have trouble lining up your ply because they keep shifting, a couple of screws in each, just back from the joint (into the bench) will hold them in place. When you lift the plastic, you may find an ugly looking glue joint where the glue has squeezed out between the ply and the plastic. Attack it with a long sanding board and it cleans up really quickly.

One man's solution - but it's the way we were taught at TAFE and if that mob of reprobates can get it to work, you should have no problems

Cheers
Richard

[Paul Scheuer]

Bright Idea. From former co-workers. For difficult clamping situations, dab a drop or two of "quick dry" epoxy in the joint along with the regular stuff. You can hold the pieces in your hand until the quick stuff sets and clamps the joint. Quick but not very forgiving.

[Dave Hadfield]

If you don't want screw or nail holes in the joint, a line of old car batteries on a 6in plank of thin plywoood makes a good press.

You definitely need a good table/bench, plus extensions or saw horses at each end.