Steam bending plywood...

[Gene Buckle]

I'm doing some research for a new project and I was wondering if "typical" 1/2" Baltic Birch plywood lends itself to being bent with a steam bender.

My concern is that the glue would fail due to the moisture introduced as part of the bending process.

Thanks.

g.

[Jamie Buxton]

Yeah, generally plywood that's flat isn't bent. Instead, people make bent plywood by laying up multiple layers of thinner stuff. One useful sheet-goods is called bending plywood. It is three-layer plywood whose laminate thicknesses are different from the usual stuff. My local dealers carry something they call 1/8" Italian Bending Poplar. It is actually more like .1" thick, and it is specfically intended for this application.

Search with "bent lamination" on this forum and elsewhere for more info.

[Gene Buckle]

I really don't want to go down the laminate build-up route if I can avoid it.

I wouldn't mind doing it for one or two complex parts, but I am looking at roughly 20+ "ribs" of the same shape. It's a pretty cost sensitive project as well.

Thanks.

g.

[Richard M. Wolfe]

I wouldn't think having the plies in different directions would lend itself to bending very well, although I've never tried it. The only thing I['ve done, and which worked, was to cut a series of kerfs in the back of a piece of plywood used in a curved face cabinet.

[Myk Rian]

What's the project? Sounds like a boat, with 20+ ribs.
Making the laminates could be the best choice, instead of trying to bend ply.

[Jamie Buxton]

I really don't want to go down the laminate build-up route if I can avoid it.

I wouldn't mind doing it for one or two complex parts, but I am looking at roughly 20+ "ribs" of the same shape. It's a pretty cost sensitive project as well.

Thanks.

g.

Actually, bent lamination lends itself nicely to production of multiples. There's an investment in making the bending form. If you use it to make 20+ parts, you distribute that investment over all the parts.

Another nice thing about bent lamination is that most shops find it more repeatable than steam bending. More parts get through the process, and they're more like each other than with steam.

[Peter Quinn]

Plywood was designed to stay flat, not be bent. I doubt you will get any consistent results. Wood bends because all the fibers are going the same direction, and green wood bends better because it's liginum is not hardened. Or air dried bends because it's liginum is not cooked. Plywood has alternating grain orientation, water resistant or exterior rated glue in most BB, and it has been heated to the point of cooked. But if you insist, give it a try and let us know how it works out.


Curved and bent work is expensive for a reason. There is no cheap and simple way out, or it would be widely practiced and publicized to be sure.

[Jay Jolliffe]

I had to make 6 1 1/2" Nosings for some shelves I did. I did bent lamination & they all came out the same. If I steam bent the wood they would not be the same.

[Heath Brandenburg]

Bent Plywood Lamination using 3 ply (1/4"?) baltic birch:
http://www.youtube.com/watch?v=TXAeLwJ8fcw

[Peter Quinn]

Bent Plywood Lamination using 3 ply (1/4"?) baltic birch:
http://www.youtube.com/watch?v=TXAeLwJ8fcw

1/4" BB will not bend that radius with any ease. Too many layers in regular 1/4" BB with alternating orientation. If its strong enough for drawer bottoms its too strong for bending forms. I think its more likely he is using 3 layer 4MM (5/32) birch. He mentioned he had 5 layers, so thats just over 3/4" finished thickness which looks about right.

[Doug Carpenter]

Gene,

maybe we could be more help if we knew what you were doing.

I checked out your link and I am moree confused than ever.:)

I buillt a steam bending rig for a project once and I agree that ply would lend itself to bending. I assume you know about wiggle wood and kerf core plywoods.

Doug

[Joe Jensen]

I can get 1/8" BB ply here locally and I use it for bent laminations. 10" radius is pretty tight for that

[Mike Davis NC]

Gene,

What is the size of the rib and what is the radius of the bend?

I have bent 1/4 inch Birch Plywood about 14 x 18 inch to a 20 inch radius across the width by simply heating it in my kitchen oven at 300° for about an hour. (no steam, no water at all) Then set it in a jig to bend and let it cool overnight. It worked great and had no cracks nor de-lamination.

[Ted Wong]

The glue in Baltic Birch plywood is not water resistant and steam bending will cause the material to delaminate.

[Gene Buckle]

The process would be used for bending ribs for cockpit sides (flight simulators) and canopy bows & frames.

I'm trying to come up with an easy to do process that any builder with zero experience can accomplish. Doing laminated lay-ups is the _right_ way to do it, but not necessarily the least expensive. Anyone can throw a few hundred dollars into building this stuff out of laminated Ash, but it takes a truly cheap SOB to do it out of "inappropriate" materials. :D

I've actually given thought to doing building a laminated canopy bow out of 1/8" hardboard from the local BORG. :D

Thanks guys.
g.

[Doug Carpenter]

That's what I shout you were doing. after I looked at your link.

I think wiggle wood or kerf core is the way to go for your canopy sides. Why reinvent the wheel. Although for the most part both of those products bend only one direction. For example I don't think you could do a dome shope with either.

[Doug Carpenter]

After viewing you link that's what I thought you were up to.

I think kerf core or wiggle wood is the way go for the canopy sides. why reinvent the wheel?

If I recall though both of those products only bend on one plane (no pun intended). for example you couldn't do a dome shape.

[Jamie Buxton]

The process would be used for bending ribs for cockpit sides (flight simulators) and canopy bows & frames.

I'm trying to come up with an easy to do process that any builder with zero experience can accomplish. Doing laminated lay-ups is the _right_ way to do it, but not necessarily the least expensive. Anyone can throw a few hundred dollars into building this stuff out of laminated Ash, but it takes a truly cheap SOB to do it out of "inappropriate" materials. :D



You're making flight simulators, and you want to be real cheap about it? Then why the heck are you making curved parts? Curves always cost more than straight stuff. And as far as I know, there's no functional requirement for a flight simulator to have curves. If you want cheap, make it from straight parts.

[Gene Buckle]

Doug: The canopy framing would be something like that found on the P-40 or the Hawker Hurricane. Nothing like the bubble types found on aircraft like the P-51. Also, as far as I know wiggleboard is unobtainium from the BORG. (at least not from the one near me)

Jamie: I did square first - see http://geneb.simpits.org. You're correct that flight simulators don't have to look like airplanes, but what would you rather have in your den or garage? A blocky something or other, or a nice looking fuselage section that suggests a generic WWII fighter look? This project is for people with minimal funds and minimal skills, not goobers like me that can think it up, draw it in AutoCAD, model it in Inventor and then throw it at my ShopBot and let it do all the work.

[Jamie Buxton]

...minimal skills ....

Hmm. Okay, how 'bout making the simulator somewhat like airplanes are built? Cut curved ribs from 3/4" plywood, and straight ribs too if necessary. (Required tools: a saber saw.) Join them together to form a skeleton. (Perhaps screws and glue. So the required tools would be a drill.) Then put a skin on the skeleton with 1/8" plywood. It can bend over the skeleton, and get stapled and glued in place. Or screws if you don't want to require the customer to have a staple gun.

This is pretty much how old planes are built -- a skeleton with a skin. It is lightweight, but can be sturdy.

Your part of the project would be supply templates (probably paper, or even just a PDF file) for the ribs and the skins, and construction instructions.

[Peter Quinn]

Doug: The canopy framing would be something like that found on the P-40 or the Hawker Hurricane. Nothing like the bubble types found on aircraft like the P-51. Also, as far as I know wiggleboard is unobtainium from the BORG. (at least not from the one near me)

Jamie: I did square first - see http://geneb.simpits.org. You're correct that flight simulators don't have to look like airplanes, but what would you rather have in your den or garage? A blocky something or other, or a nice looking fuselage section that suggests a generic WWII fighter look? This project is for people with minimal funds and minimal skills, not goobers like me that can think it up, draw it in AutoCAD, model it in Inventor and then throw it at my ShopBot and let it do all the work.

So you are thinking steam bent curves are somehow going to be an easier solution for the newb builder to handle than a pretty straight forward laminated glue up? Not sure I'm feeling the logic there. It would seem to me you will need most of the same equipment either way (bending form, clamps), with the exception that the steam bending will require a steam generator of some sort, will involve steam and there by much greater risk of getting burnt. Steam burns hurt and steam bending takes some practice and skill by most accounts.

It seems odd to me that you would have to bend plywood at all to make ribs for a simulator cockpit. Just cut the curves out of plywood with a jig saw, spread some glue and screw three pieces of 1/2" together, whamo, very strong ribs that can be skinned with 1/8" masonite (which they definitely sell at the borg near me). Perhaps I am misunderstanding what you are trying to do, but it seems to me absurd to "steam bend) plywood.