Bowed Table Top - Woodworking Talk - Woodworkers Forum
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post #1 of 15 Old 12-30-2019, 12:18 PM Thread Starter
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Bowed Table Top

hi i have a 18'' x 84'' x 1 3/4'' maple table top it consists of 3 boards laminated together my problem is that it has bowed over the 84'' its approximately 3/8 to 1/2'' theirs going to be no shirt around it so i don't have anything to screw it down to and with just using metal pin legs i'm afraid it will be noticeable and even get worse i was thinking of using two pieces angle iron notched into the underside of the top and then clamp and screw it down hoping to straighten it. I guess my question is i'm i on the right track and is there any advice you can give me when doing this.

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post #2 of 15 Old 12-31-2019, 10:33 AM
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Good morning @gord. Chance you could put a pic of your table? Might help us understand.

I'm going to make some assumptions at your terminology:
"laminated" = your 3 boards are edge glued to make the table 18" wide?
"shirt"/"skirt" = apron, the vertical support beam to structurally strengthen the top?

84" is a long table. It sounds like it certainly needs some support in the middle. Seeing as you don't want to install aprons ... Either adding a center leg, or a stretcher with a center support would probably be prudent.
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post #3 of 15 Old 12-31-2019, 11:35 AM
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Post It's a long top......

Quote:
Originally Posted by gord View Post
hi i have a 18'' x 84'' x 1 3/4'' maple table top it consists of 3 boards laminated together my problem is that it has bowed over the 84'' its approximately 3/8 to 1/2'' theirs going to be no shirt around it so i don't have anything to screw it down to and with just using metal pin legs i'm afraid it will be noticeable and even get worse i was thinking of using two pieces angle iron notched into the underside of the top and then clamp and screw it down hoping to straighten it. I guess my question is i'm i on the right track and is there any advice you can give me when doing this.

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Given an 84" length, where are the support legs in from the ends?
Apparently it's a coffee table?
"Bowed" in this case could mean "sag" downward?
To avoid an apron, run diagonal braces underneath back to the support legs.
Yes, they will be visible, but not many other choices.
A steel angle brace right down the center would be one other choice.
A vertical 2 X 6 or 2 X 4 right down the center would be another barely visible option.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #4 of 15 Old 12-31-2019, 11:41 AM
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Before I go on with some suggestions...............
If I am standing in front of the table, looking at it, I would see a hump in the long direction? Is that correct? Rising from left to right as opposed to front to rear?
Or is it a dip?

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post #5 of 15 Old 01-01-2020, 11:01 AM Thread Starter
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Happy New Year everyone
sorry i don't have a pic at this time, yes 3 boards glued together to make the 18'', i'm thinking we are talking about the same thing skirt/apron standing in front of the table yes its bowed or crowned not a dip left to right this is a table that i'm helping build for my son they have just moved into a small apartment and no room for a full size table so this is backing the couch with stools for eating. Their plan is to use 1/2'' hairpin legs 30'' high so don't think an apron would look good i saw a video with a fellow routering in c channel here is the link
i have talked to a local furniture builder and he uses angle iron to support his table so that was my initial thought i think he runs it front to back to stop the wood from cupping not length wise i'm now thinking about welding angle iron to make a rectangle with cross supports and then router it in to stop any change of cupping as well.

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post #6 of 15 Old 01-01-2020, 11:59 AM
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left to right standing where?

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Happy New Year everyone
sorry i don't have a pic at this time, yes 3 boards glued together to make the 18'', i'm thinking we are talking about the same thing skirt/apron standing in front of the table yes its bowed or crowned not a dip left to right ......this is a table that i'm helping build for my son they have just moved into a small apartment and no room for a full size table so this is backing the couch with stools for eating. Their plan is to use 1/2'' hairpin legs 30'' high so don't think an apron would look good i saw a video with a fellow routering in c channel here is the link How To Install C Channels / Woodworking Tips - YouTube i have talked to a local furniture builder and he uses angle iron to support his table so that was my initial thought i think he runs it front to back ...... to stop the wood from cupping not length wise i'm now thinking about welding angle iron to make a rectangle with cross supports and then router it in to stop any change of cupping as well.

gord & son

It's either bowed along it's length OR cupped across it's width....WHICH?

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #7 of 15 Old 01-01-2020, 02:34 PM
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Bowed Table Top

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Originally Posted by gord View Post
Happy New Year everyone

sorry i don't have a pic at this time, yes 3 boards glued together to make the 18'', i'm thinking we are talking about the same thing skirt/apron standing in front of the table yes its bowed or crowned not a dip left to right this is a table that i'm helping build for my son they have just moved into a small apartment and no room for a full size table so this is backing the couch with stools for eating. Their plan is to use 1/2'' hairpin legs 30'' high so don't think an apron would look good i saw a video with a fellow routering in c channel here is the link How To Install C Channels / Woodworking Tips - YouTube i have talked to a local furniture builder and he uses angle iron to support his table so that was my initial thought i think he runs it front to back to stop the wood from cupping not length wise i'm now thinking about welding angle iron to make a rectangle with cross supports and then router it in to stop any change of cupping as well.



gord & son


If you attempt to run angle iron across the grain, you need to take wood movement into consideration. Welding a frame will complicate the issue because EVERY bolt hole will need slotting to allow for movement.

If you route a channel into the bottom of the table for the angle iron, that will have to allow for wood movement as well. If you are going to make a frame, why not just make an apron out of wood.
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post #8 of 15 Old 01-01-2020, 04:47 PM Thread Starter
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its bowed across its length just thought i would kill two birds at once with going cross grain as well will have to rethink that i guess, wood apron might not look that good with hairpin legs maybe if i just used angle iron as a apron and not router it in and paint to match the legs i might be on to something here.
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post #9 of 15 Old 01-01-2020, 07:33 PM
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Dude, periods are a thing. Proper punctuation makes things massively easier to read and understand, which will lead to better recommendations for how to fix your problems. The information you get out of a forum is only as good as what you put into it.

Now, getting to the warp, thats a pretty fair amount for a thick top, which would point to problems you want to solve before you try forcing it back into shape. Was this piece not properly dried when you got it, or not properly acclimated to your shop when you started milling it? Was it flat when you finished the glue up? How long did it stay flat? If its warping now, itll warp later unless you figure out why, and nearly 2" of maple isnt going to be the easiest thing to force flat.

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post #10 of 15 Old 01-01-2020, 08:45 PM
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Periods are free.....

Quote:
Originally Posted by gord View Post
its bowed across its length.
(I) just thought i would kill two birds at once with going cross grain as well.
(I) will have to rethink that i guess.
(A) wood apron might not look that good with hairpin legs.
Maybe if i just used angle iron as a apron and not router it in?
and paint to match the legs.
(I) i might be on to something here.

Now this is much easier to read and comprehend.... doncha think?
Wood warping terminology:
Bowed ... think of a long bow and arrow, it's about length.
Cupped ... think of a cup and saucer, dished out in the center.
Typically wood cups across the width and bows down the length.


https://en.wikipedia.org/wiki/Wood_warping







Woodworkers interpret certain words in very specific ways, so we try to answer the question you ask based on the words you use..
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The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #11 of 15 Old 01-02-2020, 10:05 AM
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Professor @woodnthings forgot to add the apostrophe to the first "its" in the first sentence: "It's bowed across its length." :-p

I like the definitions he posted; they are helpful.
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post #12 of 15 Old 01-02-2020, 11:00 AM
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Yes that will work. The top is thick enough to allow for a deep enough groove and rabbet to bury 1x1 angle (I wouldn't go any less than 1x1).


I've also seen this tackled by routing grooves perpendicular to bow (cross grain in your example) on the underside of the board to release some stress, bend back flat and glue splines in the grooves.

Robert
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post #13 of 15 Old 01-02-2020, 01:20 PM Thread Starter
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Thank you for all your suggestions.
I guess i will have to work on my grammar skills.
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post #14 of 15 Old 01-02-2020, 02:21 PM
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Quote:
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Thank you for all your suggestions.
I guess i will have to work on my grammar skills.
One of life's greatest mysteries is if you can read a post and understand it well enough to offer correct grammar why bother.

Work on your woodworking skills, some of the most talented people I have worked with were basically illiterate and yet they managed to succeed at their trade.

Wise men speak because they have something to say; fools because they have to say something -Plato

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post #15 of 15 Old 01-04-2020, 08:00 PM
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Putting metal can help or become a part of the problem.I assume that all boards where not turn up and down with smiling faces with smiles and next a sad face. Alternating can eliminate this problem. You can try the reliefs but for me on 84" I would recut and reassemble and alternate if possible.... good luck on whatever you decide...Bob
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