Bending Plywood

[Canuck]

I am working on a small box (for a Grandson) 14" x 25" x 12" high. Wanting to loosely resemble a treasure chest. I was thinking of a curved lid but failed miserably using angle rip cuts on plywood slats (aka coopering) to result in the curve I was looking for!

I prefer to have the lid around 1/2" thick. Are there any tricks to getting the ply to bend to the arch I am looking for using the kerf cutting bending process? (The lid body will sit in a 1/2" rebate in the sides.)

Any input/tricks would be appreciated.

Thanks,

Wayne

 

[pop-pop]

There is such a thing as bending plywood. It will bend across one dimension.

 

[Mike Davis]

Put in the oven at around 250F for 20-30 minutes then press in a mold until cool. I left mine overnight. It kinda hard to tell from this angle but the top of this chest is curved.

BedChest

• Mike Davis
• Jan 7, 2013

 

[cyclopentadiene]

I have constructed numerous skateboard quarter pipes and half pipes. A 7’-9’ radius is easily achievable using 1/2 inch plywood by constructing the frame with 3/4” plywood sides and 2x4s positioned at 6” centers. A positive curve (roll in) or negative curve are relatively easy. I have built 5’-7’ radius transitions but typically use 3-4 layers of 1/4” plywood. Smaller than this radius requires bendable plywood for the layers. Soaking the plywood in water helps a little with a tighter radius. Generally, I do not like a transition <6.5’ radios as it is just not enjoyable to skate and >9’ is too mellow to maintain speed. Elliptical transitions also work fine using the same techniques. The key to any is the support structure. 6” spacing must be used for stability. There must be attachments on the cross members otherwise the structure will warp and pull loose.

 

[mkepke]

Wayne - does this lid need to be made from plywood? 1/2" pine can be bent pretty easily to provide a curved (cupped panel). There are a couple of steps needed to maximize chance of success. Let me know if this of interest and I'll post them.

In fact, I have a design book that lays it all out - and plans for the associated chest too. You are welcome to borrow it if you want to drop by Fuquay.

-Mark
Edit to add a picture of a chest made this way. This is made from construction-grade SYP (albeit dry) ..the metal straps are decorative.

 

[Kelly]

Kerf cuts.

 

[Rwe2156]

Typically this is done as a bent lamination using solid wood sliced to 1/8 (or less depending on the amount of curve). Bit the issue is the wood cracking along the grain. The lamina can be soaked in water or heated to “train” them to the curve prior to bending.

That said, depending on the amount of arc, you can use 2 layers of 1/4” ply or bendable ply.

Personally I think solid wood will look better.

 

[Kelly]

I used kerf cuts on poplar for the top and bottom of this cabinet.
The poplar was 3/4” thick, 22” wide and 32” long.I put cuts about 5/8” deep, about every 3/4”. Then I put it on a form in the vacuum bag and pressed a piece of 1/8” bending ply on both sides. Then mahogany veneer on both sides and edges.

 

[Canuck]

Wayne - does this lid need to be made from plywood? 1/2" pine can be bent pretty easily to provide a curved (cupped panel). There are a couple of steps needed to maximize chance of success. Let me know if this of interest and I'll post them.

In fact, I have a design book that lays it all out - and plans for the associated chest too. You are welcome to borrow it if you want to drop by Fuquay.

-Mark
Edit to add a picture of a chest made this way. This is made from construction-grade SYP (albeit dry)View attachment 221442..the metal straps are decorative.

View attachment 221442

Thanks Mark! This is pretty much what I working on. If you could briefly describe the process to establish the curved lid (in a post here) would be appreciated.

BTW-Do you the title of the book you worked from?)

Thanks again

Wayne

 

[mpholway]

I had a lot of success kerf bending the lid for this treasure chest. The variables are:

• stock thickness,
• cut depth,
• kerf,
• distance between cuts

Play with those variables and test to get the curve you desire. There are myriad Youtube videos that can help you along.