Mark (TheCraftsmansPath.com) on February 24th, 2009

I’ve been continuing with my operations to rough out and glue up chair components. With the rear legs already roughed out, I next turned my attention to the headrest.

The headrest (as well as the back braces of the chair) curves substantially to provide a more comfortable position while sitting. To obtain the necessary curve for the headrest you either need a very thick piece of stock (with a lot of resulting waste) or the pieces must be put together using a process known as coopering. For this headrest I am coopering individual pieces of stock with the grain oriented vertically.

rough-headrest-piecesThe coopering process is much like the process that would be used to build a wooden barrel. The individual pieces are beveled on along their edges so that when glued together they form a segmented curve. The bevel angle on each edge can vary depending on how much of an overall angle or curve is desired and also how many pieces are being assembled. In my case, I needed an overall width of about 26″ for the headstock with an overall included angle of 40 degrees. I started with six pieces at 8″ high by about 4 to 5 inches wide.  The six pieces provided 5 interior glue joints (the ends of the headstock are not beveled). Each of these joints has two edges to bevel.  Put that all together and you have 10 bevels to provide a total of 40 degrees which equates to 4 degrees per bevel.

headrest-pieces-after-cooperingTo create the bevels I elected to make multiple passes over my jointer with the fence set at 4 degrees from vertical. With a setup for a very light cut (less than 1/32″ per pass) this operation was much safer than using the table saw with the relatively small size of these pieces. After the beveling was done on the jointer I elected to take a few swipes with a hand plane over each edge to eliminate the mill marks and to assure a pristine glue surface.  In the picture you can see the pieces dry fit after beveling the edges.

gluing-up-pairs-1gluing-up-pairs-2three-pairs-glued-upgluing-pairs-to-each-otherfinal-headrest-glue-upheadrest-glue-up-completed

Because of the bevels on these pieces, the glue up operation was very tricky.  The glue up of the six pieces was initially done in three pairs. Next, two pairs were glued to each another with the use of angled blocks faced with sandpaper adhered to the clamps. Because the headrest now exceeded the depth of the heads on my clamps, the final glue up required the addition of some temporary blocks glued to the headrest to act as clamping points. At a later stage, these glue blocks will be cut off and the curve will cut into the headstock at the band saw.  In the pictures you can see the sequence of this series of gluing operations.

table-saw-thin-strip-ripping-jig-1table-saw-thin-strip-ripping-jig-2Setting the glued up headstock aside, I moved on to cutting the thin strips for the laminated rockers and back slats. This was a repetitive operation that required precision and safety.  So, I created a simple jig to allow me to rip thin strips at the table saw to a very tight dimensional tolerance. The jig also allows the strips to be ripped on the waste side of the blade so that strips can be ripped from a larger piece of stock and avoiding the dangers of trying to do this between the blade and the fence.

thin-rocker-strips-rippedEach rocker requires 9 strips at 1/8″ thickness and each back slat requires four strips at 90 thousandths of an inch thickness. For the rockers, I made additional strips because some will be needed to create stacks under each leg where they join the rockers.  I also made some extra strips to create a curved backer for use when these strips are later laminated with a clamping form. There are seven back slats required but I made an extra for safety as well as some additional strips to create a backer. for their glue up as well.  In the picture you can see the resulting strips for the rockers.

Next up: Bent lamination and creating the leg joints in the seat

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4 Responses to “Sculpted Rocking Chair: Coopered Headrest and Ripping Thin Rocker Strips”

  1. Mark,

    Did you make a full size drawing of the headrest to determine the required angles? You were very creative in the clamping on of the headrest. Good job…enjoy your work and how you go about solving your problems. With the rockers are you going to use a vacuum press or two cauls and clamps?

  2. Chuck,

    Thanks for the kind words.

    I do have a full size template of the curve of the headrest. I used it to gauge whether the angle of the coopering was correct. It just touches all of the facets of the curve. I’ll also use it to draw the curve for band sawing later.

    As far as the rockers go, I’ll be covering that in my next post. I have built forms for laminating both the rockers and the back slats. The laminating will be the old fashioned way, I’m afraid – I don’t have a vacuum press!

    –Mark

  3. Mark,

    I watched a video of Sam M. make the rockers using cuals and I think it would be the better way. There is a lot of glue squeeze out in the process…it could be a real mess in a bag. For the rocker, are you going to use PVA or a more ridge type of glue like epoxy or Unibond 800? I have used PVA on a bent lamination for curved desk once and there never has been a problem with creep. I have decided the next time do any lamination I would use either a more ridge glue, since I have learned over time PVA can have a creep issue.

  4. Chuck,

    You are right about the squeeze-out!

    I am using Titebond III on this chair. It dries a bit more rigid than other PVA’s and the dark glue lines work with the Walnut. The bigger issue with the laminations on this chair is open time. I considered going to something like a Urea Resin glue (like Unibond) but I do not have experience with them so, I’m going to stick with the PVA this time to avoid another variable. Hal Taylor uses Titebond for all of his laminations.

    –Mark

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