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Lizard Hollow Observatory, March 3, 2000: The first segment of the roofing was installed at the South end of the building today, as well as the siding on the North and South walls. |
Lizard Hollow Observatory
Construction Journal
March, 2000:
March 1, 2000 - Electricity (Part II): In anticipation of rain and wind today, I and my
trusty laptop escaped to my favorite cafe for mocha latte and to work on
software. By noon, the sky was blue and the winds were nearly
calm. By mid-afternoon, there were scattered clouds around,
and the winds had picked up to 15-25 mph, out of the South.
In the early afternoon, Ted continued working on building the L-shaped roof hold-down clamps that will attach to the South roof wall. He's making them from a 1-inch thickness of plywood, glued and screwed together, and sheathed in 1/16th-inch sheet-metal. While he did that, I tried to finish up the electrical work. Hampered by a poorly designed GFCI outlet without physically adequate grounding connections for the incoming cable, only the house end of the electrical system was hooked-up by day's end.
March 2, 2000 - Electricity (Part III): Electric power is now available at two locations in the Observatory, on the North and South walls. Ted continued working on the roof-clamps he designed and also installed some metal trim pieces at the main door while I finished up the electrical wiring and started filling in the trench.
Despite careful measuring of the electrical conduit segments' lengths, plus a little extra "in case", the conduit came up too short - by about 0.5" - to allow the final two segments to join completely. The last segment was thus joined only weakly by standard conduit cement. To ensure the joint is water tight, a thick bead of waterproof caulk was applied around the joint and, when the caulk had set up well, duct tape was placed over the caulk to protect it from physical damage while the trench was being back-filled.
Tomorrow, we should begin installing the roof-wall sheet metal.
March 3, 2000 - "Woof, Woof!": It's a roof! Sort of... It took a while to get started this morning because of the coyotes. Or maybe because of the javalinas. We're not sure exactly which was to blame, but one - or more - of them urinated on the roofing sheet metal the night before. Ted, whose room is at the end of the house nearest the construction site, heard a critter walking around on the metal during the night. Neither of us heard coyotes, so it may have been javalinas that necessitated we hose off of the roofing before we installing it. Perhaps that was the javalinas comment on the new obstacle to their nocturnal wanderings.
Once we had clean roofing, we were able to install the first segment of it at the far South end, before the wind increased around noon to about 20 mph. The roofing sections are nominally 36" wide by 12' in length, making them good sail-sized sheets. Frustrated by the wind again, we closed in the North and South walls of the building with sheet metal, an event demanding a celebration almost as wild as the one which we will hold when the roof is finished.
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Lizard Hollow Observatory, March 3, 2000: The first segment of the roofing was installed at the South end of the building today, as well as the siding on the North and South walls. |
We didn't come across any significant problems in installing either the roof segment or the siding. Ben built the frame accurately and solidly, so working with it has been easy. Learning how to drive the screws through the sheet metal and into the studs was tricky, but we soon devised a "system" which allowed us to work fairly quickly. This evening's weather report calls for rain starting on Sunday and continuing through Tuesday, so we're going to get started very early tomorrow morning.
March 4, 2000 - It's a Roof! And a Building!: At last! By lunch, we had installed all five sections of roofing, and it was almost a piece of cake to do. Getting the sections up on to the roof walls was a bit tricky, but we worked out a method in advance that worked well. The only really difficult operation was holding the sections up away from the already-installed edge gasket while sliding them into place.
After lunch, we finished installing the remaining sheet metal siding as the wind gusted to 25 mph and the approaching storm clouds rapidly darkened. We had budgeted approximately 400 sheet metal screws with neoprene washers to install all the siding and the roofing, based on the manufacturer's recommendation, but we soon realized it was going to take more than that to fasten down the sheet metal adequately. As the wind increased and a few occasional drops of rain were sputtering down, we finished installing the last siding section with three screws left.
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The view to the Southwest, showing the completed roofing and siding. This shot was taken after a storm had left a dusting of snow in the surrounding mountains (the Tucson Mountains are in the background, about two miles away). The Observatory's elevation is about 2550', and the snow level was at around 3500'. |
March 11, 2000 - We Revisit the Roof Design: In the last few days, Ted installed the roof hold-down clamps at the South wall, and we began installing the roof-wall sheathing, a shiny flat, 26-gauge galvanized sheet metal. The purpose of the sheathing is to protect the underlying plywood from the sun, which is more destructive of wood than any other single element of the harsh Sonora Desert climate.
Today, we finished installing the roof-wall sheathing. It was quite a relief to finish this last step in the siding installation. It also allowed us to turn our attention to solving a couple of problems that arose during the siding installation.
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Lizard Hollow Observatory, March 7, 2000: The exterior of the building is complete, except for metal corner trim to cover the exposed wood there. |
The first problem that came up was that the South roof wall has sagged enough to prevent the flap door from closing completely. The weight of the roofing metal seems to be counteracting the wire-and-turnbuckle arrangement we installed earlier on that wall. To solve the problem, we raised the South-wall end of the roof to the correct height with wedges and blocks. We can then install a 2x6 beam that attaches to the East and West walls near their South ends. Once the beam is installed, the blocks can be removed, and the wall will be supported in the right position, the beam supplementing the wire-and-turnbuckle.
The second problem is that the roof "racks" as it runs down the rails, causing the rails to run into the "pass-throughs" in the roof wall sheathing and the wheels to bind against the rails. This was a problem that we had thought would not occur. Ted's solution involves adding four vertically mounted wheels which run very close to the inside of the rail - i.e., at 90 degrees from the present wheels mounted on the outside of the rails. The inside wheels will prevent the roof from racking as it is moved. We were able to find reasonably priced rubber wheels mounted on ball-bearing axles at Ace Hardware and are building hefty supports for them from 2x6 studs and half-inch bolts.
Additionally, we will install a second 2x6 beam that connects two diagonally opposite roof support "triangles" and runs directly under the roofing metal. The purpose of this beam is to flatten out the roofing metal where it sags from its own weight. (The manufacturer of the roofing metal said that the metal would span ten feet, unsupported except at the ends; it doesn't, quite: recent rains were thankfully light as water accumulated in the "sag" of the roof .)
These projects will take several days to complete. The days are getting hot, and it is only comfortable to work out at the site in the morning and very late afternoon hours. Also, a very welcome house guest arrives next week for a few days, so we will be working somewhat slower on the Observatory for the next two weeks or so.
A conversation with tech support at Celestron has me thinking about a potentially serious problem stemming from our hot summers. Seems that the focusing mechanism grease will run down the Optical Tube Assembly (OTA) and onto the corrector plate at temperatures above 120 F. I installed a maximum-minimum thermometer in the Observatory and will monitor the temperature closely as our summer gallops ever closer...
March 18, 2000 - Getting Closer...: In the last week, we've gotten ever closer to completing the Observatory, but we seem stuck in a frustrating "two steps forward, one step back" kind of process. Of the two major problems we attempted to fix this last week, we succeeded in flattening out the roofing so it will no longer become a small lake when it rains. The potential for further sagging of the South roof wall remains a concern, though, as the new 2x6 beam and gussets failed to maintain the South roof wall height where we wanted it to remain. So, the flap-door still doesn't close completely - it hangs up at its top edge and, depending on how much the roof racks, at one or the other of the East and West edges - and the bottom edge of the roof wall still rides too close to the top plate of the building wall for comfort (about 3/8"). Also, the roof still racks excessively, so the anti-racking wheel assemblies need to be adjusted so that they run in contact with the rail.
To solve the consequences of the sagging roof South end - if not the cause of it - Ted did some re-designs, on the fly: The flap-door latch's female ends were replaced by long tongues of heavy-gauge metal strips, behind which the male end slides; the alternative would have been to move the latches every time the roof sagged, but Ted's re-working of the latch design assures that the flap-door can still be latched if the roof wall sags further. However, the flap-door itself will not fit into the opening in the South roof wall if the wall sags too much further; it was already hanging up on the top side, so we adopted the expedient (i.e., quick and dirty) way of beveling the roof-wall opening's top edge so that the flap door closes freely. Of course, further sagging will mean more chiseling, which ultimately will weaken the 2x6 beam that forms the flap-door's top edge. Meanwhile, the flap-door works while we search for a long-term solution to the problem.
Other tasks completed this week: We installed flat sheet metal over the exterior of the flap-door (a goof-up in ordering the sheet metal), installed sheet-metal trim at the four corners of the building to cover the exposed ends of the corrugated siding (a tale of woe in itself, having to do with not being careful enough in buying the right kind of screws for the job), and figured out how to make the cut-out in the main door for a ventilation louver.
The high and low temperatures inside the building have been averaging 84 F and 55 F respectively this last week. The high temperature on the Northwest side of the house, a mostly shaded area, has been averaging about 80 F.
March 26, 2000 - Rack and Roll: We centered the roof on the rails while it was in the fully-closed position, blocked it in place against accidental movement, and then repositioned the four anti-racking wheels so that the are in good contact with the rail. This completely eliminated any residual racking and, because of the roller bearings on the wheel axes, the roof rolls much easier than without the anti-racking wheels. There are still a couple of warps in the rails, despite our careful efforts to eliminate them at the time they were installed, but they are minor - maximum of about 3/16" deviation - and don't significantly impair the movement of the roof. Repositioning the wheels went very quickly and we had time to install some L-metal rain-kickers and trim pieces at the North and South ends of the building before it got too hot.
Here is a recent picture of the Observatory and some close-ups of structural details. Next month's Journal will have additional structural close-up shots.
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The corner trim metal has been installed in this shot showing the roof in the fully open position. The 8-inch steel-pipe pier can be seen thorugh the open main door of the Observatory. |
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The
Evil Flap-Door Tamed!! |
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This view is of the North roof-wall and shows the two korbels under the eaves and connected with a 2x4 beam to stabilize them and the end of the roof. |
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This interior shot shows the inner side of the flap-door and the two hold-down clamps on either side of it that prevent wind from moving the roof horizontally or vertically. Immediately above the flap door is the trunbuckle-and-wire assembly to counteract the natural tendency of the roof to sag at this end because of the cut-out for the flap-door. |
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