Cherry chest top warping

[Rob Bedle]

I am working on a cherry blanket chest and have glued up a top that is approx. 19" x 40" from three boards that are all about 6" to 7" wide. The top is 3/4" thick. The bottom of the top was finished with three coats of 1# cut of shellac, while the top was finished with Watco Danish Oil yesterday. The cherry was bought about 6 months ago as FAS rough sawn. I planned the top and glued it up before Thanksgiving, but put the Danish oil on yesterday. The cherry color was very light and I am not too happy about that so I set the top in the sun today for about 4 hours to see if it would darken. It is a bright sunny day here - about 75 F, but dry today - say 25% RH. Not hot

I went to bring it in an the boards are all warped and one even developed a small split. The top is unusable.

Any comments on what I did wrong? It is hard for me to believe that 4 hours in the November sun would be enough to cause this. The cherry stock was very light in color and did have sap wood along the edges that I had cut away before the glue up. I am now wondering what the chest box section will do over time. It has dovetail joints at the corners, but wider boards from the same lot of cherry.

Any comments would be appreciated.

Thanks,
Rob

[Robert LaPlaca]

Rob, sorry to hear of your troubles with your project. Assuming the cherry you acquired was kiln dried, this typically yields an moisture content (MC) of about 8%, from your exterior numbers, a piece of wood will be at a equilibrium MC of 5%, so hence the cupping. The top was acclimated to the moisture content in your shop, which presumably was closer to the EMC of the cherry, the finish just slows down the exchange of moisture, it doesn't totally stop it.

For a blanket chest top 19" wide, I would make sure that ends of the new top had breadboard ends, properly executed breadboard ends purpose is to keep cupping under control, and still allow for seasonal movement of the top. Your dovetailed case maybe Ok, as the dovetails should keep the wide boards from cupping..

[Keith Hankins]

Well I saw two things. One you used two diff finishes for the top n bottom. That would be my first statement. The second is putting it in the sun. that will give you some trouble too. You might try putting them back inside weighting them down a bit even ober bending and leave it for a few days and it may recover.

You also did not discuss your milling technique. When going from rough to finish dimensions, did you take even amounts off both sides or take it all from one side? Also, did you take it all down in one pass or did you take some, let it rest and then take some more.

The fact it split in 4hrs troubles me. That almost screams wood that is either not dried properly or, case hardening has occured.

I'd try to recover if its expensive. I had a similar experience once. I made some ling doors out of poplar and thy were strait as could be. Painted them and went in to eat lunch while they dried. The twisted like a son of a gun in an hour. I was going to throw them away, but the wife convinced me to try to save them. I put them on the basement floow with some dumbell weights and tires to hold them down. Left them for a few days and low and behold they straitened out. That was in 1987. That piece and those doors are still in my kitchen.

Good luck man.

[John TenEyck]

I'm with Keith. Different finishes on the to and bottom - not good. Putting it in the sun = really not good, especially if you didn't flip it around to expose both sides equally. That putting cherry in the sun to darken it idea always sounds good but often turns out badly.

I would let it sit in your shop for a few days to see if the cups flatten out again. If they do, I'd rip it where the cracks are, add another piece of stock to make up for what you've lost, and glue it back together. Then sand and finish - equally - on both sides.

John

[Andrew Hughes]

For me it's all about the species I love Working with Cherry but it's hard to find Nice boards with good color.I would not feel comfortable letting them warm up in the sun.Flat sawn Cherry moves alot.
Bread board ends or a Frame and panel top would be better.
You guys on the east coast have the nicest looks Cherry planks.

[Rob Bedle]

I milled both sides in numerous passes from the rough stock, never taking off more than 1/32" or so per pass. The rough wood was 'rough'. The reason for the two finishes was i don't want an oil finish on the inside of the chest as odors might be present over time with the chest closed. Maybe, I should have used shellac on the outside also. The top was glued up for some days before finishing. One of the outer top boards has a nice split about 5" from the edge, not by a glue joint, etc. This makes wonder about the cherry.

What shocked me was that all this occurred in 4 hours or less and not on a 'hot' day. No more sun treatments for me, but I was so concerned about how light colored this batch of cherry was that I wanted to see if it would taken in case I had to use some sort of colored finish on the box body. I did have to cut out a fair amount of sapwood from some of the raw wood before the glue up.

I will look into breadboard ends. I have just enough rough wood left for another top. The warped one in now in my shop and will probably end up in some smaller future project as with the split and warp I am not sure I trust it.

Thanks for the help.
Rob

[Bill McNiel]

Rob,
FWIW-When I put cherry outside to tan in the direct Sunlight I flip it every 15-20 minutes. Never had a warp or twist problem with this approach but that certainly doesn't mean I won't someday. I would try setting the piece out in the Sun again exposing the other side and monitor the progress. What do you have to lose by trying?

Bon chance- Bill

[Cody Armstrong]

The crack in the cherry board may have been there already, just unnoticeable. The sunshine could have been just enough to get it to pop open if there was stress in the board.

[John Lankers]

You have nothing to lose, I would try and weigh it down as Keith is suggesting and depending on the design add cleats to the bottom of the top, just make sure to allow for expansion and contraction.
Another option is to shorten the top and add breadboard ends after the fact, you might even be able to cut the split out completely.

[Brian Holcombe]

I've had cherry do strange things even when every step was taken to ensure things would go well. I had one glue up in a set cup after thicknessing even when every other identical glue up thicknesses perfectly, it happened almost immediately after.

[Nelson Howe]

I don't think the two finishes are a problem: it's pretty common to shellac the inside of cases and drawers to avoid the stink of oil based finish. And I'm not a fan of breadboard ends. I would think battens with elongated screw holes to allow for movement would be a good way to control cupping.

Nelson

[Prashun Patel]

Funny, I experience cherry to be stable once dry. When you say, 'sap wood along the edges', if it was along both edges of a particular board, it would imply that board was flat sawn close to the outer edge of the tree, which would mean, it could be prone to cupping or warping.

Can you rip the boards, resurface, and re-glue? You may be able to at least salvage some of the boards. I think battens are a good idea on blanket chest tops.

I would like to see a picture of the top, if you can post it.

[Rob Bedle]

I will attempt to post two photos - never did this before so ....

If i recall there was probably sapwood on both edges on two of the pieces. The third piece on the top had to come from a separate rough sawn board.

My thoughts going forward are to set this top aside and salvage parts of it for another project.

I have one rough sawn board left that has sufficient material for another top. It is almost 8" wide and I think I will skip plane it and rip it into roughly 4" wide planks, let it sit for a few days and then start work on it again. That way I can alternate the grain rings and try to decrease any stresses in the wood. I'll likely go with battens. No more 'sun treatments', but I am glad the failure showed up before i finished the chest and gave it away.

The irony is that I made a walnut chest two years ago in the same dimensions with no issues and it is still fine - but the walnut used was wood that I have had for many years.

The design is loosely based on an article by Christopher Swartz from Woodworking magazine in 2008.

I appreciate all of the comments.

Rob

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[Prashun Patel]

Ok, at the risk of showing my true colors here...

That top looks fine to me. If I scrapped every panel that was < 1/8" out of flat after glue up, I wouldn't complete very many things. I aim for flat, but half the time end up as you have.

I would not worry about the split; just fill it with a tad bit of blackened epoxy. I would think 2 or 3 battens on the underside will draw a little flatter still.

FWIW, if you install rubber bumpers on the corners where the lid meets the case, you will not notice the top being slightly out of flat; it will still sit flat on the corners.

My advice: keep it and complete it. It's looking very good.

[Robin Frierson]

When I build my blanket chest I put three cleats on the inside of the top....attached with oversized screwholes. The top was approx 72 by 30. I was worried it would detract from the top but its closed most of the time and the cleats are nicely shaped and fit well. The top had been flat for 14 years. Breadboard ends are another way to go.

[Rob Bedle]

Thanks for the encouragement, but this is a gift for my future daughter-in-law and being a retired engineer flat is flat. However, I will work on salvaging it with some battens and use it on another project.

I see you are in N.J. - where i was raised. You have the good fortune of being a lot closer to the sources on nice cherry and hardwoods. I worked in NJ and Delaware b4 I retired. It is harder to source nice wood here in TX, but the lower taxes and cost of living let me buy more toys!

[John TenEyck]

Agreed. That's not much cupping and it should flatten out with a little help from cleats on the under side. I'd do just what Prashun said, and keep it.

John

[Rob Bedle]

I now agree - cleats (battens) are the way to go.

[John Lankers]

Looking at the pictures, an unsupported panel like this is not very likely to remain flat for very long. I would do what Prashun is suggesting, cleats under the top and Epoxy in the crack. You invested too much to create this project, don't scrap it.
I always say "If you want perfection buy plastic".

[Al Launier]

Having also an engineering background and striving for perfection in the past, I've come to realize the perfection is not "readily" available, particularly when comparing wood to metal. I've also come to realize that people generally accept what is pleasing to the eye, rather than something was made perfectly. In addition to beauty, value lies in the eyes of the beholder. Less than perfection is sometimes difficult to accept after a career fighting for it, but we survive, and that's what retirement is all about.

Nice work going on there! Keep it & go forward.

[Dan Hulbert]

That's not a flaw, it's a design feature. Intentionally cupped to make a more comfortable bench seat.

+++ on battens.

[Scott Brader]

If I scrapped every panel that was < 1/8" out of flat after glue up, I wouldn't complete very many things. I aim for flat, but half the time end up as you have.

I have to fall into the camp with Prashun, too! I'm an engineer, so "perfection" is the goal; however, I had a boss many years ago who taught me the term "commercially perfect" which was his term for something perfectly acceptable even if it isn't perfect. I have employed that philosophy in my woodworking through the years. I shoot for perfect, but I am not going to lose sleep over tiny imperfections that no one else will probably ever notice. I, too, would never get anything done if I demanded total, true perfection.

Scott

[Rob Bedle]

I was able to salvage the warped top. I ripped the top along the worst crack and re-glued it using many clamps. The smaller crack I filled with colored epoxy and it looks like a large sap stain. The warp is now down to just over 1/32" at the max concave section.

Next I will fabricate some battens - probably 3 - to keep everything relatively flat. I'll have to let the Rockler torque hinges show a little on the back of the lid to make up for the loss of top width, but that is one of the standard ways those hinges are installed.

Left on my own, i would probably have scrapped the top and used my one cherry board held in reserve to try to squeeze out another top.

Thanks again to all of the comments.

Rob