big bowl - - - failure?

[Raul McCai]

I got a couple huge pieces of green sycamore This one is Chinese I believe.
I turned a rough blank about 18" dia. left it about an inch thick and put it away to dry and the gnomes of warpback mountain got into it. Now I fear the isn't sufficient wood to true it up.

Any one ever have any success at altering a warp? heat steam pressure. I suppose I could build a steam box.

 

[hockenbery]

You have a data point that 1” is not thick enough for an 18” bowl. 2” thick you could likely get a trued bowl with a 1/2” wall.

What you can do is turn a smaller bowl from it. 12” likely - 10” certain - 14” possibly.

I have not tried to reshape dried wood. You have to consider how much time and expense You want to dedicate to the project.
Me. I would just turn more bowls and try for a wall thickness of 10% of diameter if more.

 

[Raul McCai]

I may try steaming it. All I'm missing is a plywood box the right size I got propane and a monster burner and a tank to boil in and silicone tubing. I can't bring myself to just throw it away. It's the biggest hunk of wood I have ever had. And I near killed myself getting it.

I've read about boat builders using steam to dry big cants of wood. I wonder if steaming would be a good and fast way to dry a fresh green turning with the piece clamped in some kind of frame to prevent movement as it dried.

10% of diameter or more. Learn sumpin new ever day.

 

[Joe Greiner]

If you have a pot big enough, you could go a little further and boil it for about 10 minutes. Such wood becomes amazingly elastic, and can be clamped for a few days to dry in the "deformed" shape. After machining, boil it again to re-warp it for a mystifying final shape.

This is the process for the impossible nail-in-wood letter "E." Also for the wood arrow through holes in a bottle.

Here's another trick with boiling wood: http://www.aawforum.org/community/index.php?media/un-golf-ball.10378/

 

[Owen Lowe]

10% of diameter or more. Learn sumpin new ever day.

10% is the generally accepted safe measure. American sycamore shrinks about 8.5% tangential to the rings so 10% is a minimum I’d aim for. However, too much more and you not only slow down drying but you also risk the splitting due to the inflexibility of the bowl to allow the inevitable warping to occur. Some woods only shrink 5-6% tangentially so 8-10% is a safe measure for them and you’d speed drying time.

I get most of this type of info from The Wood Database (http://www.wood-database.com) or the USDA Forest Service publications (Google is your friend here).

 

[Mike Johnson]

Boiling the bowl would be easier to do and achieve the same results.
After boiling place it under a press or stack some weight on the bottom of the bowl
pressing the rim onto a flat surface and let it dry that way. This should get the bowl
back to a round shape so you can turn it true.

 

[olaf Vogel]

Any one ever have any success at altering a warp? heat steam pressure. I suppose I could build a steam box.

Nope. As the wood dries, certain stresses are created by shrinkage of wood cells. Boiling, steeming won’t change that shrinkage. So it should pop right back.

However, it might break down the wood lignins to stress.

 

[hockenbery]

Johannesen Michelson came up with a method of bending the hats he turns from wet wood using clamps and rubber bands. He takes advantage of moving the wood in the direction it wants to go as it dries and he is able to direct the outcome.

I am familiar with wood compression and expansion I have steamed out a lot of dents with a wet cloth and and iron. Michael Hosulak’s pimpled fruit.

I have done a tiny bit of wood bending. This is bending the long grain of the wood.
Bending cross grain breaks the wood. Really thin pieces can be bent like The small bowl shaped inserts Trent Bosch uses in his vessels of illusion.

I would like to be surprised that you will be able to reshape your bowl instead of breaking it.

This is a nice overview on bending including by wood cracks when it fails to bend
http://www.learnsteambending.com/steam-bending

 

[odie]

try for a wall thickness of 10% of diameter if more.

so 10% is a minimum I’d aim for

Well, there you have it, Raul......10% of the diameter is a well established minimum wall thickness for seasoning roughed bowls.

so 10% is a minimum I’d aim for. However, too much more and you not only slow down drying but you also risk the splitting due to the inflexibility of the bowl to allow the inevitable warping to occur.

My minimum is closer to 15%, but I realize and accept that the roughed bowl will take longer to reach stabilization. Owen, are you experiencing splitting in your seasoned bowls, due to warping? I've had a few that did split for other reasons, but I can't recall of any that did due to the warping......and, some have warped quite a bit. Possibly my success rate is due to the very slow rate of releasing moisture.....because of my using around 15% as a standard, instead of the usual 10%.....?

-----odie-----

 

[Jeff Farris]

I've read about boat builders using steam to dry big cants of wood. I wonder if steaming would be a good and fast way to dry a fresh green turning with the piece clamped in some kind of frame to prevent movement as it dried.

10% of diameter or more. Learn sumpin new ever day.

I am reminded of the margarine commercial from the 70s...."You can't fool Mother Nature".

The wood is going to do what the wood is going to do. Yes, you can steam bend it along the grain once it is cut, but stopping a bowl from moving is not very likely...maybe not impossible, but not very likely.

 

[Gary Beasley]

Do you have the walls thinner towards the bottom? As the diameter decreases from the curvature that ten percent translates to a thinner wall and you can get away with that to help the drying time. Glenn Lucas reports that also reduces the incidence of cracking dramatically.

 

[Mark Wollschlager]

You could use this opportunity to be creative with the turned blank.
Sanding, carving, shaping.
The end result may be pleasing to you, and provide useful experience.

 

[Gary Beasley]

I once had a bowl split in three places. I threw it into a container of water and soaked for several days. The bowl mostly returned to its former shape and I rubbed glue into the cracks and put a large hose clamp around the rim and pulled it the rest of the way in and let it sit out to dry. It dried with a nice oval shape and looked good enough to gift to a friend.

 

[robo hippy]

Sycamore is one wood that I have seen that seems to warp as much as Madrone, though the difference is you can tell which way it will warp, and Madrone is pretty unpredictable. It can warp way beyond the 10% rule. You could try soaking it in water for a few days to see what happens. If you try to move it back into shape, use compression like a ring of plywood around the outside. If you try to use expansion, it will crack. Depending on how 'rough' you left it, you may be able to sand it out as is. I prefer the warped bowls...

robo hippy

 

[Raul McCai]

You could use this opportunity to be creative with the turned blank.
Sanding, carving, shaping.

I thought of that. For me the thickness is too great. I want it thin and light. I considered that maybe there might be a way to get a tool to follow the egg shape. Conceivably I could rig my arbortech carver to follow by attaching a "radius planer type base" to it. But That seems too rickety and jerry rigged.

 

[Dennis J Gooding]

I thought of that. For me the thickness is too great. I want it thin and light. I considered that maybe there might be a way to get a tool to follow the egg shape. Conceivably I could rig my arbortech carver to follow by attaching a "radius planer type base" to it. But That seems too rickety and jerry rigged.

If the blank has warped symetrically, I would guess that you could remove a large fraction of the wood by turning the inside and outside before beginning carving and sanding.

 

[john lucas]

After you boil or steam it put a hose clamp around it to bend it back to round, You may have to use clamps on the long side to pull it back to round. then set it down and put weights on it. then cross your fingers and toes and anything else that will cross and hope for the best.

 

[Owen Lowe]

My minimum is closer to 15% <snip> Owen, are you experiencing splitting in your seasoned bowls, due to warping? I've had a few that did split for other reasons, but I can't recall of any that did due to the warping…

Possibly my success rate is due to the very slow rate of releasing moisture.....because of my using around 15% as a standard, instead of the usual 10%.....?

Odie,
If I turn thin from green wood — like 3/8" to 1/2” wall thickness — the bowls warp freely, no matter the regional species I commonly have available. On the few occasions when I've left something on the order of 15% (red oak w/ 8.6% shrinkage) I’ve had 12”-14” rough-outs split across the bottom! To me it makes sense that the drying stresses pulled open the bottom (bark orientation of the tree) just like a split opens up in the side of a log.

Purely my personal experience with an extremely small sample size.

 

[JeffSmith]

Owen - more commonly, in my experience, roughed blanks crack from variations in wall thickness. rim cracks start easily if the edges of the rim aren’t rounded over, bottoms crack when the wall thickness varies too much from the side walls. It’s all about the wood drying evenly throughout the blank. If the outside surface dries before the inside, there can be problems as well. That’s why the variations of bagging, placing in shavings, painting the end grain or the whole blank with end grain sealer, even boiling came about. Each region seems to have a favored method, but its all about leveling the playing field and allowing the wood to dry evenly throughout.

 

[BobCoates]

How about the 60 grit gouge in an angle grinder.

 

[odie]

How about the 60 grit gouge in an angle grinder.

I used the 60 grit gouge on a bowl interior once.....turned out pretty nice, but was really hard on my hands and arms, even though done at a very slow rpm. It was the constant oscillation that got to me. It wasn't done with an angle grinder though, but with my usual Sioux angle drill.

Matter of fact, I think I decided to try this because the seasoned bowl blank warped excessively. If I remember correctly, I was able to bring the bowl to round on the exterior, but was having a difficult time bringing the interior to round.....so, I decided to experiment!

-----odie-----

 

[Gerald Lawrence]

When sanding a ringmaster bowl we start with 60 grit hand held and it works good at getting the rings even.