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Thread: Squaring Up Really Long Boards... Tips?

  1. #1
    Join Date
    Jan 2012
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    Squaring Up Really Long Boards... Tips?

    I have a few dozen long boards I need to glue up into large panels. (11' to 16' for each section). They will be about 32" wide.
    I'm gluing up from 1 x 6 S4S stock. (So nominally 3/4" x 5-1/2"). They of course all have some bow, cup, or twist.

    I don't care at all about the look of one flat face (bottom). But obviously need to be able to glue up the edges then clean up the "top" face.

    I started working today and decided that trying to square up each board first was going to kill me, so I proceeded to edge plane them in pairs (so as to limit issues with glue up if my planing wasn't dead 90 degrees). I'm getting shavings the length of the board now with my No. 8 jointer, but when I go to dry fit them there are some small gaps (in the middle) as if the boards edges were bowed.

    My longest good straightedge is an aluminum Veritas one at 4'. Everything seems to look good to it. I can't see any bow by eye sighting down the board. If I just keep planing with the jointer, will it true up? Or for a board this long (11' in this case) is even the 24" long sole of the No. 8 just not long enough?

    I'll be going back at it again tomorrow as I need to get this done and glued up by Tuesday. Any suggestions on how to most efficiently work would be helpful.

    I'm working on an improvised "bench", I make on top of the bar at the job site and some Veritas surface clamps acting in for vices/clamps. (See image). This "bench is about 8' long, I knocked together a bench slave as well for the longer boards. I'm starting on the 11 footers.

    2019-07-03 21.48.42.jpg

    PS. If anyone is wondering, yes this is amatur hour. And I'm both the client and the contractor for this.

  2. #2
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    Hi Erich

    There is a limit to what you can do with match planing. This can - as you have discovered - accentuate anything that is not flat.

    My thought is that you could use coloured chalk on one edge, and rub them together (very small movements) to find the high spots. Then plane these off.

    Regards from Perth

    Derek

  3. #3
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    Lowell, you can call me "My Lord and Master Derek".

    We're all Aussies down here.

    Regards from Perth

    Derek

  4. #4
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    It's just a process of doing some match planing, checking the results, and planing the spots where the boards touch until you get something close enough that you can bring the board edges tight together with only moderate hand pressure. On an 11' board, even a #8 is a short plane.

    The biggest challenge I've found in straightening long boards is finding some way to keep them from flexing under the force of planing. If the board flexes you cannot really get an accurate edge- you try to plane an area you know is a high spot, but under the plane the board flexes out of the way and you can't take a shaving where you need to. So, try to support the underside of the boards as well as you can, so you spend less time chasing your tail.

  5. #5
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    Eric,

    Here is a method that was once described by Stanley Covington:

    It uses a string and three blocks.

    String & Blocks.jpg

    Three blocks are cut to the same size. Next a few fine shavings are taken off the 'test' block. A string line is strung taught over the other two blocks, one at each end of the work to be tested. Then the high and low spots will be easily revealed by sliding the shorter blocks under the string.

    Make sure the string is taught.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  6. #6
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    Erich, the problem with planing in pairs is variations in grain produce variations that are doubled when the edges are brought together. A low spot becomes twice as low. If the edge is a little slanted that will cancel out when you flip them together, keeping the joint straight, this is appealing but commits you to doubling surface errors lengthwise.

    The aim with long boards generally is to have the very slightest concave the length of the board, when the two boards are clamped the faces come together and ensure the end joints are sound. The length of your boards makes this very problematic.

    I would plane all the edges singly then try matching different edges, flip end to end etc and look for the best matches this will minimize the tuning of the edges needed. A bright light behind the edges gives you the low spots, mark the high on the side of one board and tune that until the light goes out. Use lots of clamps!
    ​You can do a lot with very little! You can do a little more with a lot!

  7. #7
    Try a spring joint. I would imagine you can find a youtube video on it but is basically a slight "smile" in your edges that cancels out the high spots. Edge Plane your matched boards until you think it is flat. Set your plane to a real light shaving, then plane a single shaving in the middle third only. Then plane one shaving the middle two thirds. Bring the two edges together and you should see a slight gap in the middle tapering to nothing on each end. Using one clamp in the center you should be able to draw it closed easily. If it doesn't close up easily your shavings were too thick. Plane flat and try again. With practice a spring joint is a valuable skill to have. I have glued up a 36" x 72" panel using only one clamp in the middle

    By the way, using a variation of the same technique to edge plane your boards flat when you don't have a long enough straight edge to check. You have to use a #7 or #8 plane for this to work right. Plane the middle quarter, the middle half, the middle 3/4, until hopefully your plane stops taking a shaving thru the middle 3/4 of the board. Then plane the whole length. After one or two passes you should get a continuous shaving, depending on how deep your "smile" in the middle was. When you get that continuous shaving, your board is very likely flat.

  8. #8
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    I've not shot the edges longer than 6 feet - but this was how:

    Snap a line for guidance. (About 1/4" from the edge).
    Don't remove the line.

    Plane a hollow in the center of the first edge to be glued, with the longest plane available, at twice the length of the plane.

    When it will no longer take a shaving, you have established a "hollow". Plane from end to end, until a full width shaving appears, full length of the board.

    Repeat the process with the second board, along the edge that will be offered to the first face.

    When you're close, arrange the boards as shown in your photo - one atop the other and inspect with a light behind the joint.

    The far ends should meet, with a fine gap in the center.

  9. #9
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    How big are these gaps if you cannot detect anything with a 4’ straightedge?

  10. #10
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    You might also want to ensure your face grain is all oriented in the same direction before you glue everything together.

    A spring joint or sprung joint is good for joining a couple of pieces. If a lot of pieces are being used to make a panel, by the time you get out to the edges it could become a lot of internal tension across the central face of your panel. If springing the joint, keep the gap to a minimum at the center.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  11. #11
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    Enough to pass light, but not a sheet of note paper.

  12. #12
    I had to do this exact thing with x 7 x 8ft boards. I had a 26 jointer and a 4 aluminum straight edge. This was my process:

    I laid out the boards and marked the mating edges then I jointed the edge on board #1 perfectly square and as straight as I could sight it with the straight edge. Then I grabbed board #2 and did the mating edge the exact same way. I left board #2 on the bench, grabbed board #1, and set board #1 on top mating edge to mating edge. Id then check two things: First Id check to make sure my edges were truly square by holding a straight edge up to the boards faces and seeing if the result is straight. Assuming its straight, Id then look at the seam and look for gaps. I would mark all the spots where the boards touched and not where there were gaps (gaps were usually at both ends or in the middle). Then Id take board #1 off, grab a smoother or jack, and just hit the spots I marked. Then put board #1 back on and recheck. Rinse and repeat if necessary. Once satisfied, I flipped board #2 and did the other edge and then repeated the process with board #3, etc.. In the end, the board edges will be square and will vary a few thousands in straightness along the length, but its mate will have the opposite waviness so all will be good.

    This sounds like an painful process, but it really doesnt take that much time. The only hard part is getting one board balanced on top of the other to check the seam when they are so long.

  13. #13
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    I am either an Okie or Texan. I live in Texas now, so Texan it is.

  14. #14
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    Today I'm trying to edge joint the boards singly. I'm getting full length shavings with the #8 but when I walk around on the edge with my 4' straight edge I have two-ish high spots (straight edge can be rocked on the "hump" like a tiny see-saw. Simply taking more full length passes doesn't seem to be fixing it. These humps seem to be localized to a small inchish section. I wouldn't expect that would be a big enough "hill" for the #8 to "ride over".

    Thoughts?

  15. #15
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    Quote Originally Posted by Erich Weidner View Post
    Today I'm trying to edge joint the boards singly. I'm getting full length shavings with the #8 but when I walk around on the edge with my 4' straight edge I have two-ish high spots (straight edge can be rocked on the "hump" like a tiny see-saw. Simply taking more full length passes doesn't seem to be fixing it. These humps seem to be localized to a small inchish section. I wouldn't expect that would be a big enough "hill" for the #8 to "ride over".

    Thoughts?
    It is a common result for long planes to produce a convex 'banana' board.

    Sometimes its dimension can be found by relieving pressure on the front of the plane and pressing on the heel once the full length of the plane is on the board. There may be a tendency for the blade to pull the plane into the wood. If this is the case try for a thinner shaving. Then you can work just the middle of the high area.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

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