Bent lamination is the process where multiple strips of wood 1/8'' thick or less are glued together on a form with a caul and clamps holding it down for 24 hours until the glue dries. This accomplishes 3 main goals
- creating the desired curve for the lumbar support
- creating the strength needed
- allowing the back brace to have flexibility.
In this blog entry we will go over the process of creating our bent lamination custom rocking chair back braces.
As you see below each back brace consists of 4 different laminations about 2.2mm thick, we grain match the laminations so make sure you keep everything it order!
We lay out the laminations and begin adding glue in between the layers, we use Tite bond III waterproof with some crazy figure like 4500 psi holding strength. This is one reason anything made from bent lamination is so strong, modern glues are very strong, easy to use and even food safe!
We glue up the back braces in pairs so you should have 2 stacks once all the glue is applied. We stack the back braces making sure no glue is in between separate back braces.
Back braces in form with caul ready for clamping, we use the caul because using the clamps directly on the laminations damages and cups them, not good.
Get some clamps
Start clamping, you should start to see the glue squeeze out, also you must make sure the laminations are all exactly lined up where they should be. The form has some uprights that help keep the laminations where they should be.
It takes 13 clamps per back brace.
All clamps tightened, a good amount of glue squeeze out everywhere, perfect! You can notice some old wood hockey sticks that we use as uprights, of course the glue like to stick to them so we have coated them in a glue resistant film. Made in Canada eh!
With the magic of the internet we have a pair of back braces all done. These are built using one layer of Ebony and 3 layers of walnut.
You can see the desired curve that the laminations now hold, we still have a lot of work to do before they can be used in a custom rocking chair, but we are well on our way now.
I've notice some websites that say there's more risk to a flexible back brace breaking over a solid piece, I disagree especially with how our chair is designed. The rocking chairs we build are designed to allow the back brace to flex without putting stress on the back braces it self. We accomplish this buy using a oval shaped hole at the seat location allowing the back brace end to move back and fourth freely when flexed. Also the hole in the bottom of the headrest is double drilled with a angle towards the front, again allowing the top of the back brace to move freely without causing stress. I will post detailing the stress free movement of our flexible bent laminated back braces in our custom rocking chairs.
Thanks again for stopping by, hope you learned something and if you have any suggestions please let us know!
Paul - Joel