This is the simplest scarfing jig we've come up with so far. A piece of melamine with a slot in it, set on a stack of staggered Meranti plywood. 10 scarf joints in about as many minutes. A little belt sanding cleaned up the rough edges. This pile of wood is for the sides of two more Briggsian dories which are in line after the Euphrates is out the door.

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Comment by Brad Dimock on March 17, 2010 at 10:14pm
Well...ummmm, I... uhhh fired up the duh jig again the other night to scarf the bottom panels and had pretty much catastrophic results. A-diggin and a-gougin' and a-cussin. I'm not sure what went wrong--or what went right last time, but I finally gave up and did it by hand with the power planer and a belt sander.

Comment by Brad Dimock on March 1, 2010 at 7:12pm
Yeah, I am not fan of the sound of the screaming router and enjoy the handwork when I can get away with it. Sometimes productivity makes me go the noisy route though.

When we were building the Holmstrom replica in Roger Fletcher's shop in 2001, I insisted on driving a vast number of the screws with an old Yankee screwdriver, to the annoyance of a few who thought the screw gun made more sense. Until I told them that Rolf Holmstrom had given me the Yankee, saying, "If you're going to build the boat, you should have this. It was Buzz's." Then everyone had to drive few screws the old way.
Comment by lhedrick on March 1, 2010 at 7:01pm
Okay, got it.

Thanks for all the detail.

I actually like hand planing but it takes time. Kind of a slow relaxing thing in a fast paced world.

Old school but, I wouldn't want to do 50 at a time.

Comment by Brad Dimock on February 28, 2010 at 9:38pm
You've got the basic idea. Each sheet of 1/4 plywood is precisely 2 " back from the one beneath it, giving an 8:1 slope. You could do any slope you wanted with this same jig. If you look closely in the top image you can see the strip of 1/4" Meranti tacked to the bottom of the trailing edge of the jig. It rides along on the already-scarfed slope and holds the jig in the proper plane.

I ripped along pretty quickly, taking about 1/8" off with each slide up and down the jig. Once I got a ways into the scarf, I went around and came at it from the other side. When I got close to cutting through to the previous scarf--see lower picture--I laid a second strip of 1/4 Meranti on the far scarf-slope to catch the leading edge of the jig, lest I suddenly plunge into $500 worth of Meranti with a mega-gouge.

I massaged the whole pile afterward with a belt sander to smooth out the cuts and straighten a few errant lines. This whole jig was an outgrowth of my last attempt, which was to stack the wood in a similar fashion and belt-sand the whole pile into submission. Man, did THAT take a while! This jig worked way, way better--make me giggle it was so easy. We named it the the "DUH" jig. Patent pending.

Also note the strangely shaped board clamped to the pile of plywood. That is a 2x4 with an arc cut into it so it is only 3/4" thick at each end. When clamped flat it puts great pressure on the center of the pile, keeping the plywood from bowing upward and screwing up the middle of the scarf. I also use that board to clamp the scarf joint when I am gluing it up.

Two things we learned:

1) The strip(s) that go beneath the jig must be the exact same thickness as the cutting blade of the router that protrudes below the jig. Otherwise the scarf will begin to climb or sink as you progress.

2) Shavings build up beneath the jig very quickly and begin to lift the jig off the slope of plywood. Every inch or so you need to lift the jig quickly and vacuum or blow the shavings away so the jig is sitting cleanly on the target wood.

This jig is great for massive numbers of boards at once--not so great for one or two. But you could build up a little slope of scrap wood to make the jig work right if you were running lesser numbers. I'll be doing two sheets of 3/8 for the floor of one of the boats next week and can let you know how we adapt it.
Comment by lhedrick on February 28, 2010 at 7:39am

I have been looking for a better way cut scarfs for a long time. I like using a plane but it takes a bit too long and I hate doing this type of cut with a circular saw.

I have thought of a router jig for along time. In the image you posted it look like you just stager the plywood, the jig is flat and just sits on top. So you slide it along as one side is cut away and the other side still sits on top of the uncut section. How to do you cut the last section? From the picture it looks like you move the jig to the cut section then put the router on the other side of the fence. Do I have it right?

I seems that as you cut away a section the high spots of each step in the stack would then be gone and the jig would want to tip to the right based on the view of the top photo.

I am missing something.

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