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Discussion Starter · #1 ·
Hello guys and gals,
I have been building a dining room table from pin oak and put the finish on it over the last few days. The top is 10' long, 42 inches wide and about 7/8 thick. The top is made of 7 boards, ranging in width from about 4.5 to 8" wide. They are the full 10' in length. All looked good until I put the last few coats on the top. I sprayed 3 coats on the bottom and then flipped over the top and put 6 coats on the top. When I finished, the top had crowned, making the center of the 42" width about 1/2" higher than the edges. It has been in the house for about 18 hours and now has about a 1/4" gap. Do you think it will lay down as it cures? Should I spray more finish on the bottom to pull it back the other way? I started a fire in the house this morning to help pull some moisture out of the air. Any advice would be appreciated.
 

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Discussion Starter · #3 ·
I have not attached it yet but yes, it will be allowed to move. I wanted to see if it would lay down before I attached.
 

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Well the water in the finish altered the moisture content. I think if you would ignore it for a couple of weeks until the finish cures it might flatten back out on it's own. If not you could screw a couple a boards to the under side and shem them on the ends. That should pull the center down.
 

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As Steve said, you might salvage it. Sticker it on a flat surface with weight on a top, scrap board. Be sure that air can freely circulated to all surfaces. Give it a week or two and see how it looks.

Never lay panel on top of another flat surface. Either stand it on edge away from an outside wall or sticker it Air needs to be able to get to all surfaces until you attach it to its support system above the flat surface by 3/4- 1".
 

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Discussion Starter · #7 ·
Is it crowned across the grain or with the grain? :smile:
The boards are flat with the grain (10 foot dimension) but the top is crowned against the grain, the 42" dimension. I am going to try some pics again. I couldn't get any to post last week.
 

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Discussion Starter · #8 ·
Is it crowned across the grain or with the grain? :smile:
The boards are flat with the grain (10 foot dimension) but the top is crowned against the grain, the 42" dimension. I am going to try some pics again. I couldn't get any to post last week.
 

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Discussion Starter · #9 ·
My hope was that it would flatten in a few weeks. I think it is getting better. I will put a small amount of force on it to help out. I just tried to load pics again with no success, again.
 

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I'm guessing it's likely moisture trapped in the wood more responsible than the moisture in the finish. If the table was acclimated prior to applying the finish, and flat, it's likely it would have cured flat.

I'm thinking just letting it sit may not be enough. You may have to clamp the door beyond flat to have it cure flat, sorta like a spring back. There are other factors that could have affected the top. Made up of a glue up of 7 boards could have produced more clamping pressure on the bottom edges, causing an upward pressure on the centerline...lengthwise.

I would support the two long edges lengthwise, crown up, and use cauls along the center, pulling the centerline down past flat.






.
 

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I would add strongbacks across the bottom of the top as in the photo. Long table needs four or five. These stay permanently to keep the top flat. The center of the strongback is screwed and can be glued for about two inches. The outboard ends of the strongback have elongated screw holes so the width of the table can change with the seasons. I think you can just pull the top flat with the screws and weights. If the top cracks, just saw straight on either side of the crack, joint it and glue up again with strongbacks, adding another piece in if necessary.
 

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Discussion Starter · #12 ·
The top was flat through the whole process up until coat number 4 for the top side. Maybe I didn't give it time to dry between coats. What I did was put #1, wait about an hour for coat #2 then I let it sit for about 8 hours, scuffed with 320, did coat #3, wait 1 hour, coat #4, wait 8 hours, scuffed with 600, coat #5, wait 1 hour, coat #6. I like the idea of the strongbacks. Zircon, Could you show a picture of the slotted hole near the edge?
 

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In the picture you will see that the screws out at the end of the strongbacks have washers around them. The elongated slots are cut in the strongbacks and are under the washers. They are not very long. About 3/8"-just enough to allow for movement of the top. Finish the strongbacks and the underside of the table separately so the parts are not stuck together by the finish.
 

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Discussion Starter · #14 ·
By the way, I checked the moisture tonight (from the bottom) with my Delmhorst pin moisture meter. I got 18 readings with an average of 10.1% and the highest was 10.7...if that matters. I think that is pretty good numbers, aint it?
 

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moisture

I think some of those coats may have been put on to close locking in a lot of moisture if using water base, even after 8 hours those 2 coats are not fully cured , and side with more then four coats that's a lot of water based urethane and moisture on that side ? just my thought n sure tho ??
 

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Discussion Starter · #16 ·
Yes Rico, that's it what I am thinking. I have the wood stove fired up and a 100 lbs. spread across the middle of the table. I think it is getting better. Once it gets flat, I think I will make some strongbacks as mentioned above to help maintain it.
 

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Discussion Starter · #17 ·
Yes Rico, that's it what I am thinking. I have the wood stove fired up and a 100 lbs. spread across the middle of the table. I think it is getting better. Once it gets flat, I think I will make some strongbacks as mentioned above to help maintain it.
 

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While you are drying out the top, you might try brushing some water on the bottom so the bottom can swell and help push it flat.
 

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Discussion Starter · #20 ·
After it had been in the house for 4 days, I removed the weights and attached the Z shaped table top fasteners from Woodcraft on it. I can tell that I forced that last 1/8" out of it but it is flat. I only put the clamps down the middle of the table, leaving the edges to move freely if they need to. I still might do the strongbacks depending on how it does.
 
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