What's stronger, laminate or solid wood?

[DennisCA]

I'm just thinking what's the strongest way to get a round, bent piece of wood? There are two options as I see it,

1) Sawing it out from a piece of solid wood on the bandsaw
2) Making a bunch of thin slices that you steam bend and glue together

I have a hunch the 2nd option would be stronger as it would be composed of a lot more wood glue and that is stronger than wood and all the wood fibers would run along the length of the piece and not end abruptly along its length.

Another question is, would the laminate piece still be stronger if it was made from softwood, while the solid piece was made from hardwood?

 

[heimlaga]

There are three factors involved:
-The volume coefficient. This is a factor that always appears in strenght calculations. A thick piece of wood is always more likely to have hidden weaknesses inside than a thin piece. A laminated piece evens out the weaknesses along the whole lenght of the timber and is therefore considerably stronger under ideal environmental conditions. The thinner the strips of wood are the stronger the lamination will be so steaming is usually not required.
-Wood fibres not following the bend do not contribute much to the strength. If you take apart the engine bed of an old wooden boat you are very likely to find that the floors (bottom part of the engine bed frames) are made from straight grained wood cut to a curved shape. Over the years the ends have usually split off and the frame is broken and does not serve it's purpose. That is the reason why old wooden boats with inboard motors often leak badly in the area under the engine. A curved piece that is going to be strong must be cut from a curved tree with the grain following the curve as close as possible. A good boatbuilder always looks for grown crooks. I have uprooted a few tree stumps for that very purpose when repairing boats. A lamination always follows the curve perfectly.
-Submerged in bilge water in an open boat even a not very good grown crook is likely to be stronger than a lamination. Especially in Finland where boats are hauled ashore for the winter and dry out every spring while waiting for the ice to melt. There are lots of forces coming to play inside a lamination that schrinks and swells with changing moisture content over and over again and that tends to create inner fractures weakening the lamination over time. Leaked diesel fuel and engine oil in the bilge water also may contribute to the failiour of some glues I suppose. For indoors use a lamination is always stronger than a grown crook or a curved piece made from straight grained timber.

This was just the pieces of knowledge I gained when repairing two old wooden boats......... I am not a boatbuilder.

So....if you are going to use it indoors or at least under a roof laminate it for maximum strenght. If you are repairing a boat you need to find a crooked tree if you want maximum strenght. That is true regardless of the kind of wood you use.

 

[custard]

Making a bunch of thin slices that you steam bend and glue together

Dennis, you don't have to steam to bend them, get them down to about 2 or 3mm thick and they'll bend with F clamps and a male pattern former.

And for all practical furniture purposes the result is way, way stronger than a sawn alternative.

There was a forum post just a few days ago from a guy who did his first lamination, and very neat it was too.

 

[mseries]

My instinct tells me laminating will be stronger but I think it depends on the applicaion, the size of the piece and way in which forces will be applied. For my laminated piece, which custard refers to, I bent five leaves around quarter round form of about 100mm radius. My leaves are 1.2mm thick and didn't need steaming.

 

[woodpig]

If you've got the time, training a tree branch to grow in the shape you need would be pretty strong once harvested. :lol:
The old sailing ships made use of naturally occurring bends in tree branches.

 

[DennisCA]

Thanks for the answers, ripping some thin strips and laminating them sounds like an economic and superior alternative to cutting out and wasting hardwood.