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Laminating bowed boards

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Forum topic by Jonwilliam posted 03-01-2019 08:06 PM 1127 views 0 times favorited 21 replies Add to Favorites Watch
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Jonwilliam

43 posts in 3466 days


03-01-2019 08:06 PM

Topic tags/keywords: oak milling shaping joining roubo bench workbench

Im building a roubo bench and I found a great deal on some 8/4 qsawn oak. I have enough boards for the legs and bottom but not for the top. I didn’t get enough for the top from that sawmill because it looks like he didn’t support the stack of boards very well- only one block on each end.

The remaing boards in the stack have a 1/2” bow in them over 8 feet. So if i try to joint them on my big jointer I’m going to lose a lot of thickness. If they were a uniform thickness I would just force them to comply with clamps and screws. They are not a uniform thickness since they are rough from the bandmill.

Buying the rest of the wood from the big wood suppliers in the area will triple the cost, but it would be straight and almost ready to go. Using the rest of the sawmill wood from the stack would mean by the time I’m done machining it the 8/4 would be reduced to 6/4 or less. Not the end of the world but the fewer boards the better to laminate the top. Oh, and there is a big ol nasty knot at the 6 1/2’ mark on almost each board. Must not have been the cleanest log.

Anybody got any suggestions? I like the idea of ‘encouraging’ the boards to come together but like I said they are not a uniform thickness so the glue mating surface would be quite uneven. But I need a way to flatten the boards without making them straight- make sense?

-- -semper fi


21 replies so far

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therealSteveN

6252 posts in 1424 days


#1 posted 03-01-2019 08:27 PM


I have enough boards for the legs and bottom but not for the top. Oh, and there is a big ol nasty knot at the 6 1/2 mark on almost each board. Must not have been the cleanest log.

Anybody got any suggestions?
- Jonwilliam

You are looking at the entire board as having this cup, curve to it. You mention the knot at 6 1/2’ so they are longer than any bench leg would ever be.

Cut closer to final length will drastically reduce the amount out you are now, and possibly will allow you to finish much closer to your 8/4 size.

Not knowing more, or seeing the wood that’s all I got…..

-- Think safe, be safe

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Jonwilliam

43 posts in 3466 days


#2 posted 03-01-2019 08:39 PM

Final length of the bench will be 8’.

-- -semper fi

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Jonwilliam

43 posts in 3466 days


#3 posted 03-01-2019 08:49 PM

The wood that I can get from the rest of the stack would be for the top. That’s what I need.

-- -semper fi

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SMP

2456 posts in 755 days


#4 posted 03-01-2019 10:07 PM

Well how wide are the boards and how thick is your top going to be? I’m doubting the knots run the whole width unless you got boards just wide enough for the top thickness?

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Jonwilliam

43 posts in 3466 days


#5 posted 03-01-2019 10:49 PM

The width of the boards are anywhere from 4-10”. The top will be 4” thick. The knot at the end of the board is pretty substantial. Its the whole width on the narrower boards. The knot is worse on some boards and not so much on others. Hes got some 40 or so boards left but a quarter of them due to the knot have a foot and a half of unusable material. All of the boards have a bow end to end of about 1/2”. If the wood surface was flat I could just force them together with clamps…but the mill marks and variations in prevent that.

-- -semper fi

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bondogaposis

5840 posts in 3201 days


#6 posted 03-01-2019 11:28 PM

What you have to decide, what is your time is worth. Use cheap wood with a lot more work or buy the good stuff and get it done quickly and less painfully. I know what my decision would be and that is to bypass the junk and use good straight lumber the end product will be better too. My philosophy is this, “money comes and goes, time just goes”.

-- Bondo Gaposis

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Aj2

3335 posts in 2648 days


#7 posted 03-02-2019 02:06 AM

Have you tried facing one flat on the jointer. Maybe you’ll get lucky and the board will relax a bit after you take some of the bow out of the middle.
It would not be a good idea to glue up rough sawn.

-- Aj

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BlueRidgeDog

708 posts in 629 days


#8 posted 03-02-2019 02:15 AM

Well….if you have to use it and can’t afford to replace it. Glue two good boards together that have been milled. Run one side of the curved board through the planner…it will smooth it, but not impact the curve. Then glue it up with clamps, the two straight boards will straighten it. When that sets, repeat for the other. No different then putting a curve in some wood with a curved form, just doing the inverse. Do put it in the opposite direction. The amount of curve seems minor to me…assuming you are stacking them side to side vs an edge to edge glue up.

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fuigb

583 posts in 3807 days


#9 posted 03-02-2019 01:35 PM


My philosophy is this, “money comes and goes, time just goes”.
Well said, and I get it. But another quote also applies to some people and pursuits: “because it’s there.” George Mallory & why he wanted to piss around climbing Everest. In the serious part of life -work- most of us probably work against deadlines and to the specifications of a boss. I certainly do, and maybe this is why I elect with my woodworking hobby to piss away time doing things the long and hard way… because in my hobby I can things as they please me.

-- - Crud. Go tell your mother that I need a Band-aid.

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BlueRidgeDog

708 posts in 629 days


#10 posted 03-02-2019 02:23 PM

Odd…If someone wanted to introduce a curve to a board, there would be all sorts of advice on how to do it with laminations and glue, but the inverse seems line the third rail. If you can laminate to curve, you can laminate to straighten. Also…it is a workbench!

View ibewjon's profile

ibewjon

1948 posts in 3643 days


#11 posted 03-02-2019 04:39 PM

Why not cut out the knots, and stagger the joints from end to end? You could buy two higher quality 8’ boards for the two outer faces.

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Jonwilliam

43 posts in 3466 days


#12 posted 03-04-2019 02:30 AM



Odd…If someone wanted to introduce a curve to a board, there would be all sorts of advice on how to do it with laminations and glue, but the inverse seems line the third rail. If you can laminate to curve, you can laminate to straighten. Also…it is a workbench!

- BlueRidgeDog

That’s what I want to do, laminate to straighten. You can do it with 2x stock—but its smooth already and its cross-section is the same everywhere in the board. Key being smooth. My sourced stuff isn’t.


Why not cut out the knots, and stagger the joints from end to end? You could buy two higher quality 8 boards for the two outer faces.

- ibewjon

Staggering, that would be plan ‘C’. Plan ‘B’ is sucking up the cost of stock coming from a bigger supplier. That stuff would work out the gate. I probably will go with B or at worst mill down the bowed stuff and just use a few more pieces.

-- -semper fi

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Steve

2190 posts in 1432 days


#13 posted 03-04-2019 02:40 AM

What happens if you just run the boards through the planer to get the faces smooth, then just glue them up and force out the bow?

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Sylvain

1075 posts in 3349 days


#14 posted 03-04-2019 07:59 AM

I have used some recycled warped boards to do my bench-top.
After laminating the 3 best ones, I cut the next one in two, straightened one face of each half, glued them to the first 3 ones. Then I planed the other edge of the two glued board perpendicular to the obtained top.
Next I took the next warped board and repeated except that I cut it in three parts in such a way that the but joint would not be at the same place along the bench-top.
Rince and repeat.
If you look at an IKEA kitchen counter-top , you will see they made them with multiple boards along the length.
With this method one looses a minimum of wood.
It was an interesting work … and the price of free recycled boards.

-- Sylvain, Brussels, Belgium, Europe - The more I learn, the more there is to learn

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That_Weird_Uncle

57 posts in 568 days


#15 posted 03-04-2019 09:11 AM

If you want an 8 for bench keep in mind it doesn’t need to be made of 8 for boards. I would cut the stock down and remove the low quality sections of material then joint/plane the stick as needed and then as you laminate the material together for your bench top just stagger butt joints of shorter boards so they aren’t lined up. I’ve found that if you can cut a board in the middle of a 1/2” bow you end up with two boards with a significantly smaller bow so you’ll save a lot of material that way. You will need two it three nice 8 footers to place in the outer edge/maybe one in the middle but plan it right and you can use the cheap material while still having an awesome bench. It’s also a good skill building project that will help you master the basics.

-- "The beatings will continue until the morale improves" --Grandpa

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