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bowed cherry tabletop

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Forum topic by CharlesA posted 09-03-2013 09:58 PM 1079 views 0 times favorited 13 replies Add to Favorites Watch
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CharlesA

3019 posts in 1259 days


09-03-2013 09:58 PM

Well, this was stupid.

One of the things I really enjoy doing is edge joining wood. I think it is because it took me some time to get it right. But now I do it without much thought—I’ve been really pleased with my results.

So, I bought 80 bf of cherry from a local sawmill, the first time I’ve purchased from this fellow. He seems top-notch. I cut several strips of 2.5”x50” to glue up for the top of a TV stand. Looks great. I wanted to see what it would look like when it darkened, so I followed the advice from another thread and put it out in the sun for a 4 hours to see how dark it would get. I come home and . . . it is bowed a good half inch on each side! This never occurred to me.

So, is this:
1) what always happened when you put a glued up table top in the son, you idiot;
2) what happens when you aren’t careful how you alternate the grain (I don’t think it is this one since I used parts of three different rough boards and the grain is dramatically different and it curved in a fairly uniform manner0;
3) what happens when the wood, although kiln-dried, isn’t really dry enough (I haven’t ever used a moisture meter)
4) something else?

Charles

-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson


13 replies so far

View madts's profile

madts

1680 posts in 1801 days


#1 posted 09-03-2013 10:01 PM

How thick is the wood?

-- Thor and Odin are still the greatest of Gods.

View CharlesA's profile

CharlesA

3019 posts in 1259 days


#2 posted 09-03-2013 10:07 PM

Hair under 3/4.

-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson

View darinS's profile

darinS

678 posts in 2328 days


#3 posted 09-03-2013 10:11 PM

I am by no means an expert, but it could be that the side facing the sun dried more than the underside causing it to cup.

I do, however, bet a more qualified person will be along shortly to give you a better answer.

-- They say many people die because of alcohol. They never realized how many of them are born because of it.

View pintodeluxe's profile

pintodeluxe

4853 posts in 2274 days


#4 posted 09-03-2013 10:24 PM

If you have a moisture meter you can learn more about the wood. I have had “kiln dried” lumber measure 10%m.c. Needless to say if I bring that wood inside, or in direct sunlight it will dry further. In an air conditioned environment it will dry evenly to 6-8%, so cupping isn’t always an issue. In direct sunlight, it is drying more quickly on one side than the other so it cups or warps.

Cherry is usually flatsawn, which makes the problem worse. Bring the top inside, and let it equalize in your shop for a day or two. With some figure 8 fasteners it will probably flatten out just fine.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View natenaaron's profile

natenaaron

408 posts in 1258 days


#5 posted 09-03-2013 10:27 PM

I use off cuts to check color change. I put a couple pieces of painters tape on the wood. I remove one strip an hour. Really cool progression with cherry.

Sorry to hear about the wood warpage.

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CharlesA

3019 posts in 1259 days


#6 posted 09-03-2013 10:37 PM

I’ve used scrap before as well—I put the top out there because the planed/sanded top had more color variation than I had realized when I glued it up, and I wanted to see if it would even out or remain as it darkened.

-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson

View 404 - Not Found's profile

404 - Not Found

2544 posts in 2430 days


#7 posted 09-03-2013 10:44 PM

Leave the other side out in the sun for a bit and check it regularly, there’s a good chance it will pull back straight. I’ve had panels cup leaving them up against a wall, it’s all to do with uneven moisture loss.

View WDHLT15's profile

WDHLT15

1572 posts in 1937 days


#8 posted 09-04-2013 01:17 AM

Yep, it cupped because it either gained or lost moisture. Could have been dried properly, but gained moisture when put outside if the humidity was high. Or, it could be that the heat from the sun dried the sun side more than the shade side, causing the movement. Drying wood is always a challenge.

-- Danny Located in Perry, GA. Forester. Wood-Mizer LT40HD35 Sawmill. Nyle L53 Dehumidification Kiln. hamsleyhardwood.com

View Nomad62's profile

Nomad62

726 posts in 2419 days


#9 posted 09-04-2013 11:38 PM

My vote would be to put some weight (maybe 20 lbs) on the center to push down while you let it set flat and hopefully straighten itself out. I’ve heard nothing but bad things about putting wood in direct sunlight, but I’d guess there has to be something good about it for something somewhere. Funny how you talk of yourself, great read but don’t be too heavy, we all make errors. Thanx for sharing the bad, it’s what we all learn from.

-- Power tools put us ahead of the monkeys

View mbs's profile

mbs

1606 posts in 2401 days


#10 posted 09-05-2013 03:13 AM

It’s the sun.

-- Sorry the reply is so long. I didn't have time to write a short reply.

View CharlesA's profile

CharlesA

3019 posts in 1259 days


#11 posted 09-05-2013 02:01 PM

Here’s the rest of the story: before I posted on here I flipped the board over for awhile, and that started to reverse the cupping. I did it again for an hour or so yesterday, and it became almost flat on one end with a small cup on the other end. I put it on the workbench with a cinder block on that end, and it is pretty flat now. I am going to leave it sit for another day or two to determine whether or not it is still suitable as a table top (the curve wasn’t uniform)—not sure if it is worth the effort to flatten it with hand planes. If not, then I may use it in smaller pieces and make a new top—not sure.

Thanks to all.

-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson

View Shawn Masterson's profile

Shawn Masterson

1297 posts in 1410 days


#12 posted 09-06-2013 02:20 AM

You know it’s funny wood grows on trees.
there is always more.
look there’s another.

View Rick M's profile

Rick M

7910 posts in 1841 days


#13 posted 09-06-2013 05:14 AM

If you leave it flat on the workbench, it’s likely to cup or bow again.

-- http://thewoodknack.blogspot.com/

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