How would you...

Ed Nelson

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Charlotte, NC
join the ends of 2 pieces of 3/4 ply to minimize the seam? I have started on a built in library unit and the base, counter, and top need to be about 12 ft long. My dad suggested scarfing the pieces together using about a 8:1 scarf. What are your suggestions?
 
Hide it or veneer it. One way to hide it is to make the center section a bit taller, if your client approves.
 
I'd scarf it, too ... The longer the scarf, the better the hide ... 45 degrees is not ideal, but sometimes that's the only option - unless you can run 'em vertically somehow - safely.
 
Heres a few ideas(bad or good), bisquits might work. They have ones for plywood. Or maybe a rabbet?(sp) this good make two lips that would hide the joint good.
 
Hi Ed, :wave:
The joint is gonna show :eek: so show it off.:thumb:
I've done some long runs with plywood due to client preference and the joint can't be hidden, unless covered. I have found it quite handsome to inset a piece of 3/4" by 1/4" deep solid stock over the joint after routing a groove for the inlay ( you can make it wider if you like). Since you are doing a 12' piece you can do an 8' and 4' ply with solid inlay at the 4' and 8' distance for aesthetics. Then band the whole piece, or use 4-3' pieces and add three solid inlays, or divide according to the deck top accessories to be used and do a 3', 6', 3' design. Be creative and have fun!:D Biskits or spline with scab under where possible.
Shaz
 
I remember watching a episode of the router workshop over at thewoodworkingchannel.com where they showed having to join to pieces of paneling together.

They ended up using a straight edge and a flush bit to get perfect edges on both pieces. On camera you could barely see the joint.
 
A countertop in my parents dining room is 12 feet and was joined with biscuits. You can run your hand over it and not feel it, but you can see it. I wasn't sure I liked it. Then I asked a few people that were over what they thought of the wall unit. They said it was great. I asked them about the seam. They all went, huh? Then I showed it. Most shrugged like, "That isn't supposed to be there?"

Woodworkers are picky and pick up on things that the "client," wouldn't care about.

Now, as a funny conclusion to this, I made a built in for my father. The counter is 10 1/2 feet. I joined the seem with dowels and you can't feel it. You can see it. It's the first thing he picked up on. With a "too bad about the seam."

:dunno: :huh: :eek:

It's beyond me, but a thought is, use the suggested design feature, but make it symmetrical at both ends. So a 10 foot counter with a joint 24" from both ends with the inlay idea.

Just a thought.
 
Shaz & Sam, I may go that route! Has anyone tried these router bits from Rockler? I wonder how well they would work for this type of application.

I have not used them, BUT I have seen reports with very mixed results. One problem seems to be that the vaneer on the plywood we get today is too thin and brittle and the Burgess bits tend to chip the edges of the ply vaneer in most cases. I think that if you were even able to make a perfect joint with either a scarf, rabbet, or the Burgess bit that it would still show, because most likely the grain of the two pieces wouldn't match. I'm with Shaz and Sam, go with the inlay methods they suggested.
 
Hi Ed,
When you use the router this way join a staight edge on a board longer than your longest cut, then staple a 1/4" plywood to the underside,letting the 1/4" stick out far enough to cut the excess 1/4" ply with your router, running it against the straight edge. With this jig you can see exactly where the edge of the router is going to cut. If this is common knowledge forgive me for the longwinded dissertation.:rolleyes:
Shaz
P.S. This will work when, if using a rectangular plate on the router, you run the same side of the plate against the straight edge all the time.
If the plate is round check to be assured the bit is in the exact center of the plate.
 
Depending upon the plywood you are using, you might be able to get it in 12' lengths. Some types are available in 5'x12' sheets.

Otherwise, I think you'd do well with a simple scarf. Stack the two pieces face to face with the appropriate offset for the scarf. Clamp them so they can't move and plane the joint edge. Make sure the lines of the plies run parallel to each other.

1:12 would be better but 1:8 will work.

Scarfing is very common in boatbuilding and that's the way boat builders would handle it.
 
Gentlemen...what is this scarfing you fellows have mentioned? :huh: It is a term unfamiliar to me.
Shaz

Sir, scarfing is wrapping the plywood up in a long woolen muffler. :D

No actually, a scarf joint is a long beveled joint which creates a nearly long grain glue surface. The typical scarf joint is cut at somewhere between a 1:8 slope and a 1:12 slope. The longer the slope the better the joint.

A plywood scarf is typically cut with feather edges. The slopes run off to an edge similar to that of a chisel.

There are some other types of scarfs, too. Nibbed scarfs have a sort of shoulder instead of a sharp edge. A stepped scarf is also sometimes used to join plywood together. The stepped scarf consists of a series of mating steps which for long faying surfaces good for gluing.

Here are some images I found.

A Scarf joint cut in plywood.
ScarfJoints.JPG


Plywood scarfed, glued and clamped. this for the sides of a 25' long boat.
scarfed_ply.jpg


After the clamps come off.
epoxied_ply.jpg




There are pegged or keyed scarfs and swallowtail scarfs and... But those are used for solid wood and not plywood.

The common feather edged scarf is the easiest to make especially in plywood because the plies give you guidance. Boat builders will frequently stack up a number of sheets with the edges set back the right distance. Then they'll cut the scarf joints on the pieces at once.

The trickiest part of the scarf joint is clamping it while gluing. The joint will want to slide apart. If the project can tolerate it, a board can be screwed down right through the plywood into the work surface below. Just make sure there's some plastic between the plywood and the clamping board and work surface so you don't glue the plywood down.
Hope that helps explain it.
 
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Sir, scarfing is wrapping the plywood up in a long woolen muffler. :D That response is indicitive of either a twisted mind or a very creative and playful father.

No actually, a scarf joint is a long beveled joint which creates a nearly long grain glue surface. The typical scarf joint is cut at somewhere between a 1:8 slope and a 1:12 slope. The longer the slope the better the joint.

A plywood scarf is typically cut with feather edges. The slopes run off to an edge similar to that of a chisel.

There are some other types of scarfs, too. Nibbed scarfs have a sort of shoulder instead of a sharp edge. A stepped scarf is also sometimes used to join plywood together. The stepped scarf consists of a series of mating steps which for long faying surfaces good for gluing.

Here are some images I found.

A Scarf joint cut in plywood.
ScarfJoints.JPG


Plywood scarfed, glued and clamped. this for the sides of a 25' long boat.
scarfed_ply.jpg


After the clamps come off.
epoxied_ply.jpg




There are pegged or keyed scarfs and swallowtail scarfs and... But those are used for solid wood and not plywood.

The common feather edged scarf is the easiest to make especially in plywood because the plies give you guidance. Boat builders will frequently stack up a number of sheets with the edges set back the right distance. Then they'll cut the scarf joints on the pieces at once.

The trickiest part of the scarf joint is clamping it while gluing. The joint will want to slide apart. If the project can tolerate it, a board can be screwed down right through the plywood into the work surface below. Just make sure there's some plastic between the plywood and the clamping board and work surface so you don't glue the plywood down.
Hope that helps explain it.
Hi Dave, Thanks as always, clear and purposeful. I do understand your explanation and the reasons behind most of them, thanks to you. You say clamp the pieces and then plane the surfaces, this too with your explanation I can understand. A good tip, and when glueing up, flood the joint and wrap with long woolen scarf...:rofl: too much!:rofl: :rofl:
Shaz
 
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