Wednesday, December 17, 2008

Creating the Cap Rail

When we last met, I had finished making and gluing the plinth on to the pulpit. The next step is to cover the upper edges of the pulpit with the cap rail.

The cap rail is made up of 11 boards 3/4" thick by 2 3/4" wide. They get mitered where they meet at the corners. Since the corners in the center rear are cut off, they get mitered at that point as well. It gets even more complicated because the pulpit is made of 3 carcases that are bolted together. And there are handles, to boot!

The pieces that sit on top of the handles need to be wide enough that they cover the corner posts, but they also need to be narrow enough that a person can get their hands into the handles and hold on. This means that:

  • The pieces for the wing carcases need to be 2" wide at the rear, then narrow to the thickness of a 3/4" piece of plywood by the handle holes, then widen back to 2" near the point near the miter point.
  • The pieces for the center carcase need to be 1 3/4" wide at the rear, as that's the width of the rear post, then narrow to the thickness of a 3/4" piece of plywood by the handle holes, then widen back up to 1 3/4" near the miter point.
  • The pieces for the center carcase need to widen to 2 3/4" at the front in order to have the proper over hang that the rest of the parts have.

I had originally designed a complicated shape on the end of the front pieces for the wings where they meet the center pieces. They essentially needed to be mitered in two directions. That is, they needed to be mitered to go around the corner of the wing, and they needed to be mitered to meet the overhang on the center carcase. The picture below is a top view of the pulpit, generated by SketchUp, showing the pulpit as I had originally designed it, and it shows what I'm talking about.

The next picture, also from SketchUp, shows the shapes of the center carcase parts. One side is a mirror image of the other. The top piece in the picture is common to the wings. The pieces for the wings are similarly shaped, but wider because of the wider post. The other part is shorter & almost triangular in shape (see the picture above).

As always, I got started by cutting the stock to rough size, jointing, and planing it to thickness. I cut the pieces for everything except the parts that cover the ply partitions that meet 3" wide; I cut the other parts 4 1/2" wide. It was my intention to get the wing pieces & the center pieces from the wider boards.

I started by making the parts for the wings. I made the parts that go over the ends & the front first & mitered them. I used my Osbourne EB3 to cut the miters. I could have used my miter saw, but this worked just as well, and was more convenient, as my miter saw was in the shed.

At first, I decided to miter the front pieces for the wings in one direction only, instead of in two, and just let them meet the center carcase at a butt joint. The wings are only bolted to the center carcase, after all. So I cut the end of the front square & to length and then cut the miter for the mating part. And I made an error.

It turns out I cut this part 1/4" too short. I didn't have my drawing in front of me & I forgot that there is a 1/4" thick faux rail that overlaps the corner. Now I had to make up that 1/4", and I didn't want to just remake the part. I had extra stock, but I've gone through enough at this point, and I was trying to use parts that were cut consecutively from the same board. This makes the grain nearly continuous as it goes around the top.

So I ended up changing the shape of the part that covers the ply partition. I make it longer & added a tongue 1/4" wide that would make up for the missing 1/4" of length of the front piece. And I decided to go ahead & miter the front piece in both directions. This effectively shortened the length of this tongue.

To make this shape, I first added a tall auxiliary fence to my miter stock miter gauge. I then nibbled away about 3/8" to 1/2" of material near where the base of the tongue would meet the miter I needed to meet the front piece. I could then remove the rest of the material to form the tongue by making a stopped rip cut, and the material would fall away free.

I then set my table saw's blade bevel angle to 45° and made the miter cut. Next I returned the blade to 90° and cut the stock to width. This formed a piece from which I would get one half of the handle and the short piece that meets the front piece.

Next I took out my Osbourne EB3 & determined the miter angle that I needed to use to cut the miter piece from the handle piece. That turned out to be exactly 12°. I set the EB3 to that angle. I now determined where I needed to make the cut and carefully lined that point up with the blade. I cut the mitered piece free, and then I turned the remaining piece over (placing the face that had been toward the blade toward the miter gauge) and made the mating miter cut.

To keep everything balanced, I had to make both wings identically, so I repeated these steps for the other wing.

Next, I had to make the parts for the center section. I used a similar procedure, except that I attached the blanks to each other using double stick tape. I made sure the upper faced of both boards faced each other. This allowed me to make both parts for the center section at the same time, and each would be a perfect mirror of the other.

I had to make these parts twice. The first time through, I had made everything perfectly, but then I went & cut the miter for the front piece backwards. There was no way out of this mistake except to remake the parts, which I did. Also, I separated the two parts from each other before I cut the 12° miters, to make sure that the miters were in the right place!

At this point, I attached all of the parts that needed no further shaping to the wings. That is, the parts that all met at a 45° miter. I used glue & pocket hole screws to attach these parts to the carcases. Putting them on the carcase now would protect them from being dropped accidentally & getting banged up.

The next step was to produce two templates for the handle parts. To do this, I took two pieces of 3/4" ply scrap and cut them a little wider than the parts & a few inches longer. Next, I took some measurements from the pulpit & decided where I wanted the curves to be. I transferred the measurements to the ply & drove brads into the proper points.

Next, I took a piece of oak scrap & cut a strip about 1/16" thick from it. I threaded the strip through the brads and that was my curve. I traced the curve with a pencil onto the ply. Then I removed the brads and went to the band saw. After cutting the waste away, I took them to my drill press & installed my 2" drum (the biggest I have). I then sanded everything smooth & to the line.

After the templates were done, I was able to use them to cut the shape I needed out of the stock & pattern route the parts smooth. I then took out my 3/8" radius round over bit & rounded over the edges that needed it. I then did some sanding to blend everything together & make everything smooth.

It turns out, though, that I didn't make the dip I needed in these pieces deep enough -- they overhung the handles by about 1/4". So I took out my card scraper & removed the extra material. That was followed by some more sanding.

The last operation before I could attach these parts to the carcases was to cut the parts to length using a plumb cut. I used my bevel gauge to get this angle & transfer it to the miter gauge. And when that was done, I attached them to the carcases.

I put the carcases together & I then did even more sanding & some planing to get the parts smooth & aligned & level. I wanted everything to feel like one handle when the carcases are put together.

The following pictures show the finished cap rails. The first is a 3/4 view from the right front side.

Here's a shot showing the handles.

Looking down on the center section.

And another shot of the handles from the other side.

If you look closely in these pictures, you can see that I also made & installed the lectern support blocks with their shelf pin holes. The lectern will be hinged at the edge closest to the speaker. The shelf pins will then support the lectern & any notes the speaker has at the angle of their choosing. Or they can leave it flat & put a laptop computer on top,

We're getting very close to the end now. Next up, the maple trim goes on.

Monday, December 8, 2008

Here a Plinth, There a Plinth . . .

Time for another update on the pulpit. I'm getting near to the end of it now!

Just to remind you where the pulpit project stands so far: I've got the three carcases put together. I've modified the carcases by cutting off the rear corners on the 4 ply partitions. I've made a design change to add handles at my pastor's request. I've actually made & installed the handles into the ply partitions. The next task to tackle is to make the plinth that goes all the way around the bottom of the pulpit.

For those of you who don't know what a "plinth" is, it's the sub-base that goes all the way around the bottom of the pulpit. It's made of thick boards that are mitered at the outside corners. An ogee trim molding will wrap the bottom, hiding the joints between the plinth & the carcases.

The stock for the plinth I had was 6/4 by 9" x 48". It needed to be thicknessed to 1 5/16" thick. And, of course, I needed to rip the three boards in half before I could joint them. The stock had a few ugly black knots on a couple of the boards, and one board had some perfectly round holes about 1/16" in diameter. These looked like bug holes. The holes weren't growing & there was no dust near the board, so I'm pretty sure the critters were dead. I've never had any wood with such bug tracks in it before, so this was a bit different for me.

After ripping, jointing, and thicknessing, I ripped everything to 4 1/4". The final width needed to be 4", but I wanted to leave some room for adjusting the alignment of the grain, if needed. Next, I cut a 3/4" wide by 3/8" deep rabbet along one edge of each board. The way the pulpit is designed, this rabbet matches up with the 3/8" rabbet I cut on the bottom of the corner posts. The rabbet also give me more gluing surface.

After cutting the rabbet, I had to figure out how to cut up the boards to get the parts I needed. I went back to my SketchUp drawing & took the dimensions from it. Then I imported these into CutList Plus & had it generate the layouts. Then I began to cut the stock.

Because the corners were all mitered, I figured I'd use my 10" chop saw to get good 45° cuts. So I went out & I bought a new 10" thin kerf cross cut blade to use on the chop saw. I mounted the blade & ripped a ply scrap about 36" long to 4 1/2" wide. I intended to use this scrap as an auxiliary fence to back up the cuts on the miter saw & reduce tear out. Then I mounted the auxiliary fence to the saw.

That's when I found that my chop saw doesn't have the capacity to cut through anything that tall. So I tried ripping 1/2" off of the auxiliary fence. The saw cut through the aux fence, so I marked where I wanted to make my first cut on my stock. I put the stock in the saw & lined up my marks. And that's when I found that my saw can't cut all the way through 4 1/4" wide stock, either.

So I removed the new blade from the chop saw, put the chop saw away, and mounted the new blade on my table saw. I then titled the blade to 45°. Some test cuts confirmed the blade was at a true 45°. And I started cutting.

Rather than trust the dimensions on the plan, I tried to determine the length by placing the stock against the place it had to go & marking it. This worked great, yet somehow I managed to screw up one piece in the back of the pulpit. I cut it too short.

The pieces on the back of the wings have one mitered corner & one cut at 90°. The piece in the back on the center section has two 90° corners. When I cut the piece for one of the wings, I measured it. And it came out 5/8" too short.

I didn't discover the problem until after I'd cut the rest of the parts. I just didn't have the stock to remake the part. And given that I am no longer gainfully employed, I didn't have the cash to go out & buy a new piece of stock.

So I tried cutting a miter on the short end & cutting a miter on a piece whose grain matched very closely, in order to make a ship lap joint. I used 5 minute epoxy to glue the two parts together. The end result is a very good match, so the joint should be easy to hide when I get to the finishing steps.

After getting all of the parts to rough length, I then spent about a week or so just trying to get all of the outside mitered corners to meet properly and the parts cut to proper length. It turns out that the corners of some of the posts weren't perfectly square. So even though everything is parallel, I had to carefully remove material, and in some cases add it, in order to get the corners to fit properly.

Once the parts all fit together properly, I had to shape the feet on the plinth. This took a couple of days to complete, given the number of parts. I made a template out of 1/2" MDF and used it to trace the shape on to each board in the proper places, namely, at the mitered corners. Time to cut the shape.

I used a 1" Forstner bit to drill out the arc in the corner where the foot transitions into the bottom, then I used my table saw or band saw to remove the waste material. I used the table saw for those parts that had a foot on one end, and the band saw for those that had feet at both ends. I used a 1" chisel to clean up the transition on those parts that I used the table saw to remove the waste.

After sanding everything, I finally started gluing the parts on to the pulpit. I used glue & clamps only, working with one piece at a time. I'd let it sit for 30 minutes or so before I started on the next piece.

Here are some shots of the pulpit & completed plinth. First, the whole pulpit from the front:

The right wing end:

A close up of the center front:

That's enough for now. Next time, we'll go over the cap rails, which I should finish up today.