Maloof Rocker - Seat Mockup Part 6, Add Legs & a Problem

My original plan was once I had completed the seat mockup I would start construction using the cherry.   However, I changed my mind and decided to put the seat to further use.  I had a section of the 2x6 left so decided to use it to make a set of rear legs to test the fit and procedure of making the leg-to-seat joints.  My thought was that I could also use the mockup as practice for the sculptural part of the construction.  As the 2x6 was not wide enough to make the rear legs according to the pattern I changed the design to make a low back non-rocking chair.   Here are the rough band saw cut modified back legs.

I took one of the rough legs and smoothed out the cut surfaces then double faced taped it to the other leg and used a pattern router bit to make exact duplicates.  After taking all the time to clean up and smooth the cut surfaces I am not sure if it is worth it.  The only exception may be for the reference surfaces, they are probably worth it.

The procedure for cutting and fitting the modified legs is similar to the actual ones.  There are some differences so let’s just say I spent quite a bit of time making angled dados, radiusing corners and talking to myself.  Rather than cover that here on pieces that do not match the final product I will wait until I get there in the real chair.  That said here are a couple of photos of cutting the dados.

The good news was that after all the fussing, double checking the measuring and scratching my head the joints fit just like they were designed.

When I got done with all the work on the rear legs and turning the front legs on the lathe I clamped all the pieces together including a temporary top spacer between the back legs. 

Here is where things went bad.  The front legs are supposed to be straight up and down but mine were slightly splayed out.  The rear legs did open up toward the top but it looked like not enough.  When I got out the measuring tools sure enough things were not lining up the way they were supposed to.  I finally traced the trouble to the outside boards of the seat where I had spent all the time cutting the joints.  The joints were cut right on as shown by how the legs fit into them.  The problem was that each of the outside boards that make up the seat are not level but tilted up causing the legs to rotate by a couple of degrees.  Not a lot, but a couple of degrees over a few feet is enough to mess up the size of the headrest and the form of the chair.

Now I knew what the problem was but had no idea of the why behind it.  I checked the joints between the boards to see if they were tight and that the cuts were all angled correctly, which they were.  I checked the jig I had used for drilling the dowel holes to see if it was off, which it wasn’t.  I even went back though the photos I had taken and they showed everything like it should be.  For the better part of two days I measured and checked every step and cut I had made finding no problem.  I really needed to know why this had happened so I could prevent it on the real chair.

Finally I think I know what happened.  There are a couple of differences between the mock-up and the actual piece.  First is the material, the mock-up is SPF construction lumber, a fairly soft wood while the actual chair will be cherry which is much harder.  Second, the mock-up is made from pieces just under 1 ½” thick while the real seat will be just over 1 ¾” thick.  I think that everything was fine right up to when I glued the seat together.  When I glued up the pieces and clamped them together a combination of the angled joints, softer wood, a thinner material and perhaps uneven clamping pressure caused all the joints to compress and rotate ever so slightly.  With 8 surfaces and the amount of clamping pressure I applied it would not take much to cause a 2 degree rotation.  I usually check for any bowing when I glue up a panel but did not this time.  One thing is for sure I will be checking for this problem when I do the real seat glue-up.

Next Up – The Real Seat: Bevels, Dowels & Leg Joints