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Flattening wide stock with a bow?

Started by Daren, June 29, 2006, 07:54:00 PM

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Daren

I have some (4/4) 24" wide maple that has been kiln dried for 1 year+ (?) and dead stacked. I was pulling a few slabs today and a couple have a slight bow across. About 1/4" if I lay a straight edge across and measure to the dip in the middle. They have no twist and are straight from end to end. I know I can use them by cutting them narrow and planing them, that is not my question. I could use them whole still and take the bow out with glue/fasteners in a project and make it stay, it is not much. I am thinking about selling some and the bow will turn people off who what the full slab, flat. I guess my question is can they be flattened...And I mean forever, I won't have them bowing again on a customer.
Thanks Daren

Experience is something you don't get until just after you need it.

Tom

What you are describing is "cup".   Cup can't be taken out and have it remain flat.  Most carpenters/furniture makers, etc.  do just what you said you could do.  they cut it narrower, flatten it with a joiner or planer and glue it back.  Optimally, I think they swap ends and/or turn the pieces over before they glue it back so that the grain of one piece will oppose and hold the grain of the other piece from moving.

Den or Don might have some ideas on steaming or rewetting and redrying.

Daren

I feared that... this is stock that is worth MUCH more money wide than ripped and stuck back together.



Like I said, it can be held down/up/whatever easy with proper woodworking... but trying to talk a guy into buying a piece of cupped wood for $8 bft is a little more of a challenge :'(
Experience is something you don't get until just after you need it.

Tom

That's why I cut my wide stock, thick.   I may cut a 24" wide piece 6/4 expecting to eventually get a 4/4 out of it.  If it happens to dry straight, the 6/4 is worth as much or more than the 4/4 anyway.

I'm glad I'm not retailing lumber.  I'd go nutz. :D

Still,  hang onto the phone.  Den or Don haven't spoken yet.  :)

wiam

Could you put a shim under the cup and run it through a planer?  (disclaimer "I have not tried this.") How about a wide jointer?

Will

Tom

wiam,
You can, but, the problem is that you lose too much wood by flattening both sides to end up with a 3/4 inch board.  .....and there's no guarantee that it won't cup again.

The only way to stop cupping, as I understand it, is to dry it green quickly so that it forms a shell.  The shell holds the interior in place while the rest of the water leaves.

Kiln drying wood that has already air dried  some runs the risk of the tensions already being in place.

It takes a good kiln and a good kiln man from the very beginning.

Daren

I sawed this 5/4, I have to have a little OOPS room for tearout, curly can be tricky. It dried to 1 1/8" or so, but the cup throws that all off of course. I ain't in a hurry... I was just digging and found a few that were too pretty to slice up and knew where to come for some input.  I saw mostly wide stuff, the local market is full of 6" stock, I have a thing for the wide ones. So far not much problem. I guess I should add this stuff is heart AND sap, I was trying to get the most from the figured log. I have never had any real problems with 20" plus heart slabs. But this is uniformly curved, not curled on the edges, a full cup across the board.
Experience is something you don't get until just after you need it.

metalspinner

I have a sycamore slab that about 2 1/2" thick that developed quite a cup.  This slab is near 30" wide.  I layed it on my lawn cup side down and covered it with a tarp.  A couple days later it was cupped the other direction!  I flipped it, covered it , and checked it the next morning - then that afternoon and found it near enough to flat to stack it and weigh it down.

This of course was not KD nor a beautiful piece of curly maple.  Maybe you can try it on a less expensive piece and see what happens.  Good luck.
I do what the little voices in my wife's head tell me to do.

Brad_S.

I was going to give the same answer metalspinner gave, only without the tarp part. That method is a closely guarded secrete used by antique restorers to flatten cupped table tops and then charging the customer big bucks for doing so.  :D
"Life is what happens to you while you're busy making other plans." J. Lennon

pigman

The wetting of one side works great for removing cup in wide boards, but when the moisture equilizes again, the cup will return if the board is not held flat  securely.
Bob
Things turn out best for people who make the best of how things turn out.

Ironwood

Daren,

I also cut my boards excessively thick. I understand it is tempting to maxiumize the cool wood but you can't win. :( I would be interested in the dimensions of what you have and if the "live" or flitch edges are still intact, if they are I may be interested in a few slabs de[ending on the cost. Thanks Reid
There is no scarcity of opportunity to make a living at what you love to do, there is only scarcity of resolve to make it happen.- Wayne Dyer

Daren

Reid, I don't have any for sale with a live edge. It was a biggish log I had to 1/4 to get on the mill. I sawed down to a cant in real thin stock for my own use. All I have is stuff like this, some 48" wide books 6'+ long.



Experience is something you don't get until just after you need it.

Den Socling

I don't think there is any permanent fix for cup. Flat sawn with the rings centered is the worse case simply because wood shrinks at different rates in different directions. Drying one side will shrink it flat but it isn't going to stay flat. Cup gets worse as MC goes down so, if the wood is drier than the EMC of where ever its going, you might wait until it has equalized before planing.

jimF

I have "uncupped" boards before.  As said already, after putting it on the lawn to gain moisture, it will again loss moisture and return to the original shape or worse.
The way to fix it is to put wet rags,very wet, on the convex side.  The board will initially get worse.  Take the rags off and let it dry.  When it has dried out, the board will be flat or nearly flat.

Daren

Thanks for all the responces...Once again I jumped the gun with a question, I was just bummed when I saw it cupped. Well the good news is, it's flat again  :D. Just like I dried it. I had 2 boards on sawhorse that were the book in the picture. The cupped one was on top. I went out there after lunch and they are laying there like I never sawed them apart. It is hot and humid here today, that tells me nothing, except from what I am reading can I assume when the air dries it will recup? No biggy, you have to expect wide lumber to move (any lumber I guess). It wasn't much, but it wasn't flat either.
Experience is something you don't get until just after you need it.

Tom

Yep, the humidity is swelling the wood and the lack of it dries it.   The movement causes the cup because the wood moves in different directions according to grain orientation.   One rule of thumb is that it will bend toward the bark.   Flat sawed will tend to bow and cup, while quarter sawed will tend to crook but lay flat.

The centered rings will raise the edges carrying the more vertical grain edges with it, causing cup. While centered rings may make cupping "the worse case", as den says, it also provides equal and opposing pressures from the sides that will minimize crook and twist.  It's just the nature of the beast and something with which wood workers of all ilk must deal.  It's a living thing.  That is what makes you an Artist rather than a scientist.  :)



Daren

Tom I like your picture, I changed it a little to show the types of lumber I have for sale. I will hang it in the shop above the pricelist, that oughta help business with the illustration and all. And we don't have to dig through the stacks, they can just look at the picture and know what they need.


Experience is something you don't get until just after you need it.

Tom

That should tend to belay customer expectations.  :D :D

UNCLEBUCK

I am going to attempt to saw 100,000 bd/ft of oak and ash this year , been practicing stacking green boards into nice stickered stacks but always when I am done I lack anything but cement blocks or something worse so,

I am going to make basically bacon presses for lumber stacks out of lightweight concrete , 2 inch thick ,rebar where needed , 5' X 9' , about 1000 # pounds so can easily be lifted and set on top of stacked and stickered pile , even pressure and a nice roof to boot , a lifetime of use and hopefully it will stop crazy boards from going really crazy .   
UNCLEBUCK    bridge burner/bridge mender

Dan_Shade

that's a good idea, UB

i use 24" planters filled with concrete, I don't have a tractor or anything.  a big concrete plate to put up there would be awesome!
Woodmizer LT40HDG25 / Stihl 066 alaskan
lots of dull bands and chains

There's a fine line between turning firewood into beautiful things and beautiful things into firewood.

joelmar10

Quote from: Daren on June 30, 2006, 04:06:12 PM
Tom I like your picture, I changed it a little to show the types of lumber I have for sale. I will hang it in the shop above the pricelist, that oughta help business with the illustration and all. And we don't have to dig through the stacks, they can just look at the picture and know what they need.




:D :D :D :D :D  Can we assume the cherry is quartersawn?
I used to think I could fix DanG near anything...now I know I can...or I think I can...or maybe I can?

Daren

Quote

:D :D :D :D :D Can we assume the cherry is quartersawn?
Quote

Yea, not that it moves too much. My flat sawn cherry can  :D. The 1/4 sawn oak doesn't move so I was stuck which to put where. I for sure got the maple and DanG sure got the sweet gum right though. :)
Experience is something you don't get until just after you need it.

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