Greene & Greene Blacker House Office Chair (Splats) - Part VII

This is going to be a pretty long post - so hang on to your britches!  The splat design for this chair is pretty much the same as the Blacker House arm chair:

The dimensions are different as this chair has a larger and bolder back.  In a nutshell, lots of angles!  Here are the splats in their unadulterated state:

Here's the same lumber on their sides:

First thing to note.  We will be hogging off a lot of wood to get our final shapes.  Second, as we see above in the side profile photo, there is very little wiggle room to obtain our side profiles with the 8/4 lumber.

Given all the wood that must be removed one can see why bent lamination and steam bending is popular.  Bent lamination alleviates the need for extra thick wood and allows for very curvy lumbar shapes.   I probably would have tried bent lamination but I wasn't sure how all the inlay and negative space would look.  As for steam bending, well, almost all tropical woods are kiln dried which, according to experts, is not good.  Consequently, I decided to stay with solid 8/4 lumber for the splats.  Nonetheless, as I'm laboring over the effort to remove so much wood I'm thinking that bent lamination may be a valid alternative here.

The mortises for the splats in the rear rail are inline to each other.  Also, the mortises in the crest rail are also inline to each other.  This makes life a bit easier (with the Blacker House arm chair the mortises were not inline but followed an arc).  Consequently, I can determine my tenon angles for all the splats by measuring just one of the crest rail / rear rail mortise pairs.

I install a floating tenon in the crest rail mortise and another one in the rear rail mortise.  Then I glue on a stick of plywood.  This allows me to determine the angle relationship between the two mortises which should be the same for all mortise pairs.  Another thing I do is I glue on a small piece of wood to the back of both floating tenons to locate the shoulder locations.

Next I draw the side profile onto one of the splats.  This tells me where the tenons must go.  I then clamp the tenon template onto the side of the splat making sure that the floating tenons line up properly with the drawing.  I've determined that my reference edge for these splats will be the back - which has been surfaced flat.  I clamp the whole assembly against a true 90 degree surface with the back against the 90 degree surface.

Now I take one of the bevel gauges and determine the bottom tenon angle:

Leaving the tenon template securely clamped to the wood, I unclamp the assembly from the 90 degree surface and carefully rotate the entire assembly and reclamp to the 90 degree surface so I can measure the top tenon angle with my second bevel gauge (the back of the splat is still clamped against the 90 degree surface).   Now we are in business!  Oh yes, remember that small piece of wood glued to the back of the floating tenons?  I use those to mark out my shoulder locations.

My original design called for all the splats to be flush with the front of the crest rail.  Needless to say, flushing the splats requires that the fit be perfect.  Here is an example chair I built a couple years ago where the splat is flush:

Because this chair has 5 splats I decided to make my life easier here and recess the splats a light 1/8" from the crest rail surface which is actually in spirit of the original Greene & Greene style.  Recessing the splats allows me to house the tenons in the crest rail which makes fitting a LOT easier.  No fussing around trying to get the top splat shoulders perfectly flush with the crest rail.  A housed tenon means that the splat shoulders are actually recessed into the bottom of the crest rail a certain amount.  Here is an image of a housed tenon I found on the internet.  This technique is used a lot in the timber frame industry.  The Greene brothers utilized it for furniture as well.

Consequently, for the top shoulders I add a heavy 1/16" to the length of the splat when scribing the shoulders.  Because of the wonders of geometry, I can use the same bevel gauge settings to scribe the shoulders.

Next I use the bandsaw to hog off most of the tenon waste material - necessary to test fit the tenons.

Now its time to cut!  I start with the bottom tenons and use my bevel gauge to set the table saw angle:

My tenon jig here is simply a large block of poplar 4 inches thick.  It has been milled on the jointer and planer and tweaked with a hand plane to get a true 90 degree surface.  Works great.

I cut the front of the tenon for all splats, then I cut the rear face of the tenon. For the rear face I creep to the desired thickness with a couple test cuts.  Since I'll be using the same setting for all the splats, I like to leave the tenon a tad heavy.  I can fine tune the fit with a shoulder plane - as it seems that no matter how hard I try to be consistent there are always small differences in thicknesses at the end.  Now, one can also cut the front shoulders at this time.  But I've decided to trim the shoulders by hand later.

Here are the splats with the tenons cut:

Now its time to start shaping.  I'll use the table saw to hog off some material.   I use my bevel gauges and reset the saw blade to the profile angle - which for the bottom is not the same as the tenon angle!

Here are the splats with the profiles partially defined by the table saw:

Now, its important that the front of the splats be consistent for a comfortable fit.  I will use a template and cut the front profile with the shaper.  I screw the template so the screws go into the waste side of the wood, bandsaw the front profile and take it to the shaper:

I do not let the cutter cut the area that was cut by the table saw.  Now, the shaper works fine for the 4 smaller splats.  What about the wide center splat?  This one is too wide for my shaper tooling.  I clamp the center splat between two of the smaller splats and start hand planing, using the smaller splat surfaces as reference edges:

I'm careful to avoid blowing out the other end since I'm going cross grain.  I had to rotate the assembly a couple times and plane from each direction to avoid blow out..  Here is the result.  Note that I did not cleanup the tops and bottom where the burn marks are (and bubinga definitely burns easy).  I still have my shoulder scribe lines down there and I do not want to lose them

Before shaping any further I need to revisit the tenons and cut them to width - as this will also tell me how to shape the front profiles of the splats:

Now its time to actually fit the tenons.  I have to use a shoulder plane to tweak a few of the tenons.  My goal here is to have a nice tight fit for the center splat.  The outer splats do not need to be so snug.  Also note that my shoulders have yet to be defined.

Now I go back to shaping.  Next I shape the back with the bandsaw.  In the photo below I support the piece with a large block of wood.

The back is still rough.  I'll clean the back up later.  Below I clamp the front profile template to the back and draw out the desired shape.  The top and bottom of the template is centered on my tenons. I then bandsaw the waste away.  I bandsaw the 4 smaller splats first.

As for the center splat I decided to clean the back before cutting the front profile - as I will be doing cross grain work which may result in some blowout at the edges.   Below I am cleaning up a side splat using a rasp, spokeshave and file.  I saved my cut off pieces.  Below the splat is resting on the cut off piece for support.  Shaping is a process that simply requires removing material to the line.  If I go beyond the line then I am either an artist or a frustrated craftsperson.  The spokeshave works pretty well.  However, there are some grain direction changes that can result in tear out with the spokeshave.  The rasp is far less susceptible to grain direction changes.  I always end with a fine file.  The file provides a surface that is easily sanded.  Bubinga, unfortunately, wants to clog up the fine file.

Below I am cleaning up the back of the center splat.  I use a shoulder plane followed with the rasp, spokeshave, and file:

Whew!  A lot of work shaping!  I finally cut the front profile of the center splat and clean the sides.  Below I am using the template to draw the shape:

For some reason I did not take a photo of the center splat shaped.  Oh well.  Now I clean up the shoulders.  Remember, the shoulders for the top will be housed so I am not too concerned about super clean edges up there.  However, the bottom will be visible so I want a good clean fit down there:

The next step is to cut the housed mortises for the splats in the crest rail.  To fit the top I install the splats and the crest rail.  Because the shoulders are about a 1/16" high the crest rail will not sit flush with the rear posts.  I then use a knife to scribe the shoulder locations on the bottom of the crest rail.  Then I use my dremel to cut out the mortise for the housed tenons for all the splats.

Unfortunately, I do not have a shot of the finished result with the splats shaped and fitted.  I'll show that in the next post where I install the 8 small tabs between the splats.