Waterfall Clamping:

[John J Wilson]

Hi all,

I'm in the midst of making a rather large edge-grain black walnut island top with two mitered waterfall sides. The finished dimensions of the top are 122"x 50" x 2" and the waterfall dimensions are 36.5" x 50" x 2"

I don't have clamps long enough to span the 122" run and I have no experience joining massive mitered corners this wide so I'm looking for some advice on how to get the mitered joints tight. I have a load of Jorgenson cabinet master parallel clamps and the Bessey K Body clamps as well, but nothing over 72". Hoping to use what I have here, I came up with this possible setup today:

Waterfall Clamp - Iso.jpgWaterfall Clamp - Side.jpg

I will be using domino tenons in the joints.

The cauls would be made of white oak, the corner squares would be made of 1.5" (2 x 3/4") baltic birch, which would be CNCed square along with parallel knockouts for the clamps. The corner caul would have 1.5" diameter holes bored for visibility of the joint every 10" or so. Since I haven't done this before, I don't know how much clamp pressure I should expect to be exerting for a super tight fit. Will 2 @ 12" bessey k body clamps at either end of a chunk of white oak provide enough strength to pull against?

Any tips you all might have are appreciated, however, I'm not looking to penetrate the surface with any sort of mechanical connection; not even dimple it.

Thanks.

[Matt Day]

You can join two parallel clamps together.
https://youtu.be/_pEpUJc0zBI

[John TenEyck]

Maybe the angled Zipbolt connectors would pull it together. Use Dominos and put a Zipbolt between each of the Dominos to close the joint. If you use epoxy for your glue, it should pull tight w/o needing a lot of force.

http://zipbolt.com.au/portfolio_cate...re-connectors/


John

[Keith Mathewson]

You could use two vacuum pods and any F-clamps you desire.

[johnny means]

Rip some pine or other really soft wood into 90/45/45 degree triangular strips. Glue these cauls onto the adjacent faces running the length of the joint. Be sure the long side of the triangle is glued down. After the glue dries, the cauls will allow you to clamp the joint shut as if it were just square blocks.
After your glue sets, use what ever means handy to remove the bulk of the cauls. This can be accomplished using a router, saw, handplane, or whatever else works. Just be careful not to damage your veneer. Then carefully remove any remaining wood and glue by sanding. I prefer to take my time and use a sanding block.

[John J Wilson]

Thanks for your suggestions, everyone.

Keith, what are the vacuum pods that you speak of? Do you mean the type of suction cups used to carry glass? This suggestion really has me curious and considering flipping my pair of Festool vacuum clamps upside down and putting the board that the 12" K body clamps are holding in my picture behind them.

John, this looks like great hardware. I can't seem to find a way to order a set that doesn't cost more to ship than it does for the hardware itself. I didn't know anything like this existed and I'm going to continue to look for a reasonably priced vendor so I can at least buy a pair to test out. There is about half of this piece that will be exposed on the underside and I would need to see the finished appearance before pulling the trigger. Regardless, I can see many uses for this hardware so it wouldn't hurt to have a few lying around the shop.

Matt, Great low-cost solution in the video you linked to. unfortunately, I only have two pairs that could be joined to give me the length I need, and I'm sure I'll need more than that across 50" to feel comfortable. I will however be using this option in plenty of other situations now that I've seen the video.

Johnny, This piece will be 95% finished by the time it is delivered to the jobsite for installation. All that will be left to do is scribe the floor, cut the sides to match, and glue/clamp before finish sand/monocoat. I would be too nervous to attempt your suggestion in this particular situation.

[Andrew Hughes]

I like Johnnys method since your project will be prefinished you can attach the 45s to a sheet of clean plywood that's clamped back away from the corners.No glue on your nicely finished work.
Good luck

[Jim Morgan]

Or you could glue a sheet of paper between the walnut and the triangular blocks, which would be easy to scrape off. Or you can use hot-melt glue to temporarily secure the blocks to your work (this is one of the few useful applications of hot-melt glue in the workshop). If you do this, I would';t try to use a continuous 50" strip - a bunch of triangles ripped from 2x stock would suffice. Afterwards, use denatured alcohol to weaken the hot-melt glue - the blocks should peel off with minimal residue left behind. The advantage of this method it that it directs clamping force directly perpendicular to the miter and really excels in drawing such joints tightly closed.

[Kevin Jenness]

45 degree clamping ears are the way to go with Dominos. Clamping miters in two directions is an unnecessary pain.

Another way to skin the cat is to fold the miter using packing tape at the outside corner and biscuits oriented across the joint line. At 2" thick you can bury a #20 in the joint. No clamps needed except for a couple of temporary corner blocks to ensure squareness. This requires a well cut joint with no cupping and would not be my choice for such a massive glueup but I have seen it done successfully in solid wood on smaller scale.

Don't forget to eat your Wheaties!

[John J Wilson]

I like Johnnys method since your project will be prefinished you can attach the 45s to a sheet of clean plywood that's clamped back away from the corners.No glue on your nicely finished work.
Good luck

Great solution.

Thanks to everyone for your input.

[Bill Adamsen]

I like Johnny's solution combined with Andrew's comment. It sounds like a great approach. I do a fair amount of panel mitre joining - typically on pre-finished and using the cut/tape/glue/fold method - an approach that is virtually bulletproof. Unfortunately that approach precludes the use of any sort of connector (at least that I've been able to envision). Once you move to a connector - either biscuit or Dominos - it becomes an entirely different ballgame. I find joining long mitered panels with biscuits to be stressful, and I never think hard enough about the problem to "systemize" the approach like you are doing. I would think mounting the 45° block on a sheet of 1/4" plywood or MDF would also work without the risk of marring the surface or finish. Maybe that is what folks were recommending ... I couldn't really tell.

[Matt Day]

Great solution Andrew and Bill!

[Prashun Patel]

I have done exactly as Bill describes. Please use 150 grit sandpaper under the bases of the clamping jigs. Otherwise as you draw the 45 together, the bases will slide. I had to use cabinet clamps to keep them properly positioned.

Check for square.

[Kevin Jenness]

Bill Adamsen,

You actually can fold a miter as thick as the one discussed around biscuits oriented perpendicular to the joint line. We made a number of restaurant tables of 2" pine stave core with this technique at my last job. John's project would be a bit unwieldy to do this way given its size and weight.

Andrew's method is good. I keep a few sizes of these cauls around. For a job this size (50" wide!) the plywood needs to be long enough to get several substantial clamps along each edge of the material, and as Prashun points out should have sandpaper glued to the bottom. You don't want those cauls to start sliding once you commence gluing up.

Even doing one joint the process will take some time. If working alone I would probably use epoxy for the working time, or powdered plastic resin glue.

[John J Wilson]

I've settled on exactly the combination of suggestions that you've listed, Kevin. I've got about 4 weeks until this piece will be installed. During installation, I'll snap a few pictures of the process and then post them here along with any noteworthy comments about this process, for posterity's sake. I really appreciate all of the information from everyone. I feel a lot more prepared for this installation than I did a couple of days ago.