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NEED HELP - project just cupped...

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Forum topic by Fiddy posted 01-04-2019 12:54 PM 537 views 0 times favorited 7 replies Add to Favorites Watch
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Fiddy

230 posts in 2316 days


01-04-2019 12:54 PM

Building a small table for a couple of chair a family friend had from when her daughters were kids. She now has grand kids and needed a table. The table had a slight cup that was present day after glue up, but nothing serious. The base is attached with d-nuts and over sized holes to allow for some movement. This would’ve allowed a small cup to be addressed. Yesterday I got finish on the table, bottom and top. Only thing to note, I wanted to practice with a shellac finish on the underside to start, but my results weren’t stellar so I went with a wipe on poly on the top. Both bottom and top do have adequate coverage though. This morning I went out to apply last coat of poly and with top just sitting there I could see the cup towards the initial problematic end. My shop is and always has been heated. This wood, maple, I’ve had in the shop for probably 2 years or so.

I’m not sure what happened over night to create such a change. The initial glue up was probably 4-5 days ago as an FYI. I’m really not wanting to scrap this top, and I can’t just take off the board at the end and glue another as I hand planed a wide bevel on the underside. Again with all that work, I really hate to walk away at this point.

Any help/idea?

Last night, not really cupped…

This morning with straight edge, all cupping is down at the one end..


7 replies so far

View mahdee's profile

mahdee

4291 posts in 2773 days


#1 posted 01-04-2019 02:59 PM

All I can think of is to flip the board.

-- earthartandfoods.com

View PPK's profile

PPK

1844 posts in 1815 days


#2 posted 01-04-2019 05:50 PM

Dang! That’s severe. WHich way is the grain running? It looks like parallel to your straight edge, which is an odd way to cup. I’d expect it to cup with the grain, not perpendicular. Did you split the boards, and now that they’re split, the tension is coming out? I’m not really sure how to fix…

-- Pete

View LesB's profile

LesB

2858 posts in 4448 days


#3 posted 01-04-2019 05:57 PM

Obviously there is a moisture change that may have resulted in the two different finishes you used.
My first attempt at correcting it would be to apply the poly finish over the shellacked bottom and let it set for a couple of days to see if that helps.

You could try adding stiffeners across the bottom of the table top (glued and screwed) in an attempt to pull the curve out. One on each end and one in the center. Or, as I look at the table a skirt inset an inch or so around the perimeter of the top would help…..or both of those.

-- Les B, Oregon

View MPython's profile

MPython

336 posts in 818 days


#4 posted 01-04-2019 08:11 PM

Take the top off. Place it, concave side down, on your assembly table (I assume that’s an assembly table in your photo) and leave it alone for a while – a day? maybe two or three. Check it frequently. Moisture should gradually escape from the top – more rapidly from the exposed surface – and it should eventually flatten out. At that point, attach some stiffeners to the bottom to keep it flat as has already been suggested, then reattach the top to the base. The finish may retard to escape of moisture to the extent that the top will not return to flat. In that case, try removing there finish and repeating the process.

View NormG's profile

NormG

6508 posts in 4009 days


#5 posted 01-04-2019 08:41 PM

Wow, that is a large cup on the end. Great suggestions to release some of it also. Hope it works out, may take a combination of tactics to resolve.

-- Norman - I never never make a mistake, I just change the design.

View Fiddy's profile

Fiddy

230 posts in 2316 days


#6 posted 01-05-2019 01:01 AM

Hey guys, thanks for all the input/advice. Definitely a strong cup to contend with, but here’s what I tried so far and we’ll see what this does over night. I had initially 4 points of connection on the table/base. They were close to the outside miters of the base, but I did have some room to add two additional further out, so four on one half and two on the other.

I used threaded inserts in the top initially so I added two more of those and on all six I mixed some epoxy to get them really set since I needed to torque down on them a bit. So far epoxy seemed to have added some strength and the additional two did make a difference on the cupped side.

Here’s a side view of the table as of now, cupped side is the right side of the image. It’s definitely much better now that base is attached and the additional bolts.

Issue i’ll have is there is a glue line right at the point where the base ends and clearly no way to pull the overhung area down which is essentially the entire issue.

I placed a straight edge on the section of top right to that glue line and almost dead flat just until it comes close to the glue line. I think it might be good enough if it relaxes back a bit more, hopefully. It’s a table for children and not a commission, but still I want it to be proper so we’ll see.

View Fiddy's profile

Fiddy

230 posts in 2316 days


#7 posted 01-05-2019 06:03 PM

Well I wrappe things up today and think it’ll work – have it all done and will just let it be for some time to make sure nothing else happens, but should be good. Thanks for the input.

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