Monday, October 09, 2006

Cupola Roofs

The next step on the cupolas was to make the octagonal bases for the roofs, indicated by red arrows in the drawing below. Unlike the pressure-treated plywood bottoms in the bases, I wanted these to have some real heft, so I made them from 2 x 8's.

The first step was to once again calculate the octagon dimension I needed. It would be entirely too boring to detail the computations I underwent to determine this fact, but I will say that the online octagon calculator my boss found has indispensable throughout this project. If you're interested, you can see it here. Suffice it to say that I determined the length I needed from each face of the octagon and crosscut my stock to that dimension (with 22 1/2 degree angles at each end so that they'd form the shape I needed when put together).

Once I had a pile of 40 base pieces, I needed to figure out a quick and dirty way to join them together. I decided I'd use biscuits, and I made the marking jig above to save myself from having to make 160 measurements (4 biscuits per piece x 40 pieces = 160 biscuits). The workpiece slid into the jig...

Then the poplar arms were swung until they were parallel to the end of the piece. I marked a line at the end of the swinging chaweeka.

Then I cut the biscuit slots. By the way, when I say biscuits, I mean little ellipses of compressed wood that are inserted in matching slots to join together two pieces of wood. I do not mean the sorts of biscuits one eats. For the best edible biscuits in town, go to Perly's.

After biscuiting the left-hand ends of each piece, I followed the same procedures for the right-hand ends as you can see above.

A coworker helped me glue the biscuits and put them in their slots. One has to work fast when dealing with this many wet biscuits; they swell up fairly quickly, reducing the open glue time one has before everything is set. I included the above picture because it depicts a solution to a problem that has long troubled me. As I've said before, I love band clamps. I particularly love them for clamping large mitered workpieces like these roof bases. One downside to band clamps, though, is that no matter how careful one is, they always seem to get twisted. I've been cussing about this for almost 15 years now, and it finally ocurred to me last week that if I thought about the problem for all of five minutes, I might be able so solve it. It's so obvious, really: Just clamp the ratchet mechanism to a table. Sheesh, I wish I'd started doing this a long time ago!

Here's the assembled roof base.

And here's a simple marking jig I put together to mark where I needed to drill holes.

Finally, a completed roof base. I put the plywood scabs on to add tensile strength as well as to give the lag bolts that will eventually connect the roof to the cupola base something to bite down on.

Tomorrow I'll be posting about gnomes.

Sunday, October 08, 2006

I'm Tired of Cupolas!

I'm tired of thinking in multiples of eight. Enough octagons for a while. Here's a work table I made five or six years ago for the kitchen in my apartment. I wanted a "real" butcher block top, by which I mean one with the grain running top to bottom. All the old butcher blocks I've seen were made that way, I suppose because the harder end grain is more resistant to knife strikes. Apparently, the butcher would use his table all day, then at work's end, he'd pour scalding water on it and scrub it with a stiff wire brush. That's why all the old tables one sees in antique stores are so wallowed out in the center.

I don't know how I could have made this thing without Harrison's Time Saver sander. I started by making a bunch of 1.75" x 1.75" x 40" strips of hard maple, making sure they were dead square by running them through the sander on each face several times. I then glued four of these lengths together at a time resulting in a pile of 3.5" x 3.5" x 40" pieces. I cut these into 3.25" lengths, then glued six of them together to form a single row. Then I started gluing the rows together. Finally, I ran the whole thing through the Time Saver for what seemed like forever to get it nice and flat.

Big lesson learned while making this table: Use MINERAL oil to coat your butcher block if you ever decide to make one, not vegetable oil like I foolishly used. Oh, why didn't I spend half an hour doing research? Why? Why? Why did I spend that half an hour dousing $250 worth of maple endgrain with vegetable oil which quickly went ransid, creating a yucky film on the surface of this top? The poor thing isn't even close to suitable for kitchen use. It's holding my stereo and printer these days. So sad, yet so instructive.

Thursday, October 05, 2006

Cupola Base Framing Complete

I finished framing the cupola bases today. I had thought this task would be pretty easy, but it turned out to be a tad trickier than I'd anticipated. The first photo below shows one of the completed frames. You'll see that I'm building these things on pallets at this point as they're only going to get heavier over the next week or so until I'm finished. I imagine we'll have to move them out of the shop with forklifts once all is said and done.

My hope had been that by putting the correct length of spacer between each post and drawing the whole assembly together with a band clamp, everything would come out perfectly dimensioned. I still don't know exactly why it didn't work the way I'd planned, although I suspect there were minute (but additive) irregularities in the posts I had made. As you can see in the photo above, I did use the band-clamp strategy, and it did work--just not as smoothly as I'd hoped. Framing the first cupola base took four hours. The subsequent five only took an hour and a half apiece.

Once I'd gotten everyhing in its place, I attached the spacers to the posts with pocket hole screws. The spacers at the bottom were temporary, just placed there to assist in locating the posts. They did, however, serve another function; more on that later.

Screwing the spacers to the posts gave me a way to clamp the posts securely in place, as you can see above.

At the beginning of the week I had pre-drilled holes through the bottom of the bases. I made a simple jig on the drill press table to locate the holes. First I used a 1 1/2" forstener bit to make a hole deep enough to accomodate a lag bolt's head. Then I drilled a 1/2" hole through the center of the first hole. My jig kept the workpiece properly positioned so that all the holes were just where I wanted them.

Once I was positive that I had the post perfectly positioned, I located my drill by using the holes I had pre-drilled earlier in the week into the bottoms of the bases. I bored a deep 13/32" hole up through the base and into each post.

Then I drove long lag bolts through the bottom. I can't stress enough how much I very, very much want these things to stay in one piece when they're being lifted 30 or 40 feet in the air by a crane. That's why I'm incorporating just about every over-building idea I can think of!

Here are the first few base frames sitting in the shop. At this point, I'm moving them around with a pallet jack.

Oh, one last thing: Remember the spacers I'd used to locate the posts? I used those same pieces as the headers between the tops of the posts. That way I could be certain that the interior widths of the frames between each post would share the same dimension top and bottom.

Monday, October 02, 2006

Woodworking Wisdom from Cormac McCarthy

Have you ever noticed how bull-headed so many woodworkers are? Why is that? Why is it that once we've done something the same way once or twice we usually stop looking for ways to improve our technique? Maybe it's what psychologists call "functional fixedness." I don't know. A related thing I've noticed is that many of us are loath to let it show when we're seeing somebody else doing something we didn't know about.

To that end, check out the following quote from Cormac McCarthy's All the Pretty Horses. My wife is reading it right now, and she emailed this to me today.

"They listened with great attention as John Grady answered their questions and they nodded solemnly and they were careful of their demeanor that they not be thought to have opinions on what they heard for like most men skilled at their work they were scornful of any least suggestion of knowing anything not learned at first hand."

Tiny Cupola Roofs

I started the day a tad perplexed about how to proceed with the construction of the cupolas' roofs, so I spent some time making quarter-scale models. I think I pretty much figured out how I want to do it.

The framing structure will basically consist of 8 pressure-treated 2 x 4s which will all meet a central octagonal shaft. There will be all manner of bracing, as well, but the photo above shows just the bare-bones of my plan. I rarely take the time to make models, but they help me when I'm really confused. I saved myself a lot of grief by making this one. If I hadn't, I'd have forgotten that the thickness of the PVC sheathing is greater than 3/4" when on a bias. That would have been a BIG BUMMER as it would have resulted in the roofs overhanging more than they're supposed to.

Here's the model for the roofs' sheathing. You can see where I made notes all over it to correct problems. One major benefit of making this model was that it helped me to figure out the jigs I'll need to get the correct bevels in the right places. I haven't done a cone-shaped thing in a quite a while, so this was a helpful exercise.