UAS Construction Update for 12/05/2014
Answer to Last Month’s Puzzler
Last month we asked the question on why bubbles formed in the silicone window joint. (See Post on Oct 31) This question turned out to be more of a puzzler than I had expected. We received several good theories and some not so good. Here are some of the answers we received.
- Something left on edges of glass that reacted with the silicone causing gas bubbles.
- Calking gun not uniform and backing off a little and allowing an air bubble to form.
- Edges of glass not cleaned and the silicone lost “grip” of the glass when it cured. Thus creating small suction cup bubbles. (See Oct 17 Entry for suction cup physics)
- Silicone emits gas as it cures. When the Silicone is too thick the gas gets trapped inside the silicone joint causing bubbles.
- Silicone not stored properly causing it to go bad.
- The bubble ferry…… and it gets feathers caught when the silicone dries too fast.
- The glass has a film sandwiched in the center so it will not shatter if it breaks. This film is emitting a gas or is reacting with the Silicone creating gas bubbles.
- There is movement in the joint as it cures causing the bubbles to stretch or tear. Movement can as little as someone leaning up against a pane of glass.
These answers came from Contractors, Architects, Engineers and the Silicone manufacture’s Product Manager. All of these answers have a sense of plausibility. However, none of them address all of the questions in our puzzler, particularly why bubbles only formed on one side of the joint, why some sections had large bubbles and some small bubbles, why some sections had no bubbles.
Feather Bubble Suspended in Silicone
My theory is that it is a combination of answers 4, 7 and 8. It may not be the cut and dry answer you were hoping for, but it’s my answer and I’m sticking to it.
Good Luck on finals next week and lets all hope your exams have easier questions than “Why did bubbles form in the Silicone joint of the UAS Freshman Residential Housing conference room glass wall”.
UAS Construction Update for 11/21/2014
Inspection with a View
The Architectural Team performed an inspection of the exterior metal siding and window flashing. The weather was excellent for an outside inspection, considering it is the third week in November. The inspection team found the Contractors work to be good with just a couple of items that need to address. Providing the weather holds, the Contractor has another couple of weeks completing the siding and window flashing on Hall #2. We greatly appreciate patience our UAS freshmen have had the past couple of months while the finishing touches are being made to the UAS Freshman Hall.
Metal Siding Inspection
Inspection with a View
I have received several Theories’ on the puzzler asked last month on why bubbles appeared in the clear silicone glass joints in the seminar room. All of these Theories start out with a good basis. However, they do not stand up to all of the facts we have in this scenario. The design team has a call into the silicone manufacturer to see if they have a better Theory. Until then, let’s just hold tight.
Puzzler for the Week
Many of life’s great discoveries have been made with someone asked Why? and then spent the time and energy to figure it out. We also learn more and retain that knowledge when we ask Why. I am not going to try and discuss the great questions asked by Mr. Cosby like “Why is there Air”. But, we did run across an interesting puzzler this week at the UAS Freshman Residential Housing project.
The fourth floor seminar room looks out over the UAS campus, Auke Lake and Mendenhall Glacier through several large panes of 1/2-inch thick glass. The contractor filled used a special clear silicone to fill the space in-between adjoining panes of glass. They used the electric calking gun so the placement of the silicone is very continuous and uniform. The first day that the silicone was installed, it looked good. However, over the next couple of days air bubbles formed in the silicone.
View from UAS Freshman Residential Hall seminar room.
The Puzzler for the week is:
- Why did air bubbles form in the Silicone?
- Why there were no air bubbles the first day when it was installed?
- Why did air bubbles form only on one side of the joint in some locations?
- Why did lots of small air bubbles form in some sections while large bubbles form in other sections?
- Why do some air bubbles have what looks like a small feather coming out of them?
e-mail your answers to firstname.lastname@example.org by noon November 6, 2014.
The top 3 answers will be included in next week’s UAS Construction Update.
UAS Construction Update for 10/17/2014
497 lbs of Glass
How do you lift a 497 pound piece of glass 50 feet in the air?
Very Carefully (Banda Bing).
No, with four suction cups and a fork lift.
But how can a suction cup lift 500 pounds? The physics behind the suction cup is a little counter intuitive, but actually very simple.
Suction Cup Physics (not)
This is how I thought a suction cup worked, before I took engineering classes. You place the suction cup up against the window and then with a small pump suck the air out of the inside of the suction cup. The more air you suck out of the cup, the greater the negative pressure created inside the cup force holding the cup onto the window. I thought that the only limitation on the negative force you could create inside the cup was the power of the pump creating the suction force.
Suction Cup Physics
This is how I understand a suction cup works, after I took engineering classes. You place the suction cup up against the window and then with a small pump suck the air out of the inside of the suction cup. However, once you suck out all of the air, there is nothing left inside the cup, it’s a vacuum. It does not matter how powerful the pump is you can’t suck out something that is not there. Since there is nothing inside the suction cup there is any negative pressure, in fact there is no force at all. So what is holding the suction cup on the window? It is the air outside the suction cup that is pushing the cup onto the window. That force is usually one earth atmosphere.
Calculating how much one suction cup can lift is just the force (one atmosphere) times the surface area (area of the suction cup) which can be expressed in the formula F=PA
L = Load that a suction cup can hold
P = Pressure = Atmospheric pressure in Juneau at 9:00 am today is 995 mb = 0.98 Standard Atmosphere = 29.38 in-Mercury = 14.43 pounds/square inch
A = (Pi)(Radius Squared) = (3.14)(11)(11) = 95 square inches
L = (14.43 pounds/square inch)(95 square inches) = 1,370 pounds!
Suction Cup Window Lifter
The Contractor is using a suction cup window lifter by www.powrgrip.com This window lifter has four suction cups attached to adjustable arms connected to a center pivot bearing. This allows workers to attach the lifter to the window lying on its side and then lift it and rotate it into position.
You may think that with four suction cups we could lift (4)(1370) = 5,480 pounds. However, the safety rating on this window lifter is only 700 pounds. Just like most things in life, there are deductions. Suction Cup Window Lifters are no different. There are deductions for; changes in shape of the suction cup, non-perpendicular lifting forces, strength of suction cup materials, changes in atmospheric pressure and safety of workers and by standards.
Lifting a 497 pound window
Placing 497 pound window
Another Wonderful View from the UAS Freshman Housing
Lighting Outage Tonight
There will be no lights in the parking lot and along Auke Lake way tonight October 15, 2014. The Contractor that has installed the new LED lights on campus has removed the old control cabinet and is installing the new control cabinet. This is a two day job and there is no practical way to make a temporary power connection.
New Lighting Control Panel.
All of the UAS parking lots will be dark tonight in addition to the road and sidewalk coming into campus. The Noyse Pavilion and the parking lot lights in front of the new Freshman Housing and the new pathway lights between the parking lot and the Soboleff building are all fed from this control panel and will be off tonight. The courtyard, corridor and chapel by the lake shared parking lot are not affected by this project and will have lights. Lights will be back on tomorrow night. We apologize for the involving this will cause everyone here at UAS. If we are very lucky the clouds will dissipate and we will be able to see the Aurora display that has been very active the past 36 hours.
The UAS Site lighting project will be constructed under two separate phases as shown on the figure below. Phase II is scheduled for construction during the summer of 2015.
UAS Construction Update for 10/03/2014
Perception is Reality
What we perceive to be real, is frequently not factually correct. The new UAS LED lights are a good example. Most new street lights, including the UAS parking lot lights are considered a full cutoff light which directs the light down to the ground and prevents light from escaping up above the light fixture. Because you cannot see a full cutoff light from the side, your mind perceives that the area is not as light.
Standing in the upper UAS parking lot looking back at the lower parking lot lights you notice that the lights become less visible. This is one benefit of full cutoff lights.
UAS Parking Lot with Full Cutoff Lights
The International Dark-Sky Association has been working with communities for the past two decades to reduce light pollution. http://www.darksky.org/ They recommend Full Cutoff lights as one is one tool to reduce light pollution. Light pollution is a broad term used to describe multiple lighting problems. I like to think of it as artificial light shining in places you do not want. Light Pollution to Night sky gazers is light that shines up into the sky creating skyglow making it difficult to see the stars. Light Pollution to residents is light that shines into your home or bedroom making it difficult to sleep. Light Pollution to motorists is light from a fellow motorist with xenon headlights or adjacent commercial properties with distracting over bright lighting. Light Pollution to a camper is the other camper wearing a headlamp who blinds you with 120 lumens while telling you stories of past adventures.
While full cutoff lights will help UAS Freshmen to see the northern lights better, they can present problems with pedestrian perception. People walking along a road or pathway at night tend to look up toward the next light they can see, which could be light from a house or a faraway street light. They perceive how dark the pathway they are walking on more by that light in the distance, than the light immediately surrounding them. For an Engineering example: Take two pathways and using full cutoff lights and a light meter, light both paths to 1.0 foot-candles. Then take a bright light and place it at the end of one of the long paths. Because the light at the end of the path is far away and not shining on the path the light meter on the path will still read 1.0 foot-candles. Now take your normal test subject and have them stand on each of the two pathways and have them tell you which one is brighter. They will always say the path with the light at the end is much brighter.
This presents a challenge for using full cutoff lights for pedestrian pathways because even though there may be enough light shining directly on the path to safely walk, (0.5 foot-candle) the person looking down the path cannot see the light coming from a full cutoff lights and will perceive that the pathway is dark and unsafe.
New UAS Pathway Lights to Soboleff
The new pathway lights installed on the pathway down to the Soboleff Building have a mounting bracket below the LED light which deflects enough light that you can see it from the end of the pathway. With this type of light fixture, we will see a trail of lights stretched before us and our minds will perceive that the pathway is lighter, even though my light meter tells me it is the same J
UAS Construction Update for 9/26/2014
Pathway to Soboleff Building: We have been scheduled to pave 3 times now, with no asphalt being placed yet. September in Southeast Alaska does not have the best weather when trying to place Asphalt Pavement. Paving is one of the last items on a construction project and unfortunately this typically happens in August and September, a couple very rainy months for Juneau. The only month that typically has more rain is October. Anytime the weather permits, the paving contractor has been working all over Juneau. UAS is nearing the top of their list and they are planning on paving tomorrow, Saturday, September 27. Let’s all cross or fingers that the weather on Saturday is as good as it is today.
Pathway to Whitehead Building still waiting for Asphalt Pavement.
UAS Site Lighting:
The Contractor installed several of the new pathway LED lights next to the Egan Library walkway. Look for more of these pathway lights to go up on the pathway to the Whitehead Building and along the sidewalk of Auke Lake Way.
UAS Freshman Housing.
The Contractor has been replacing window hinges in the UAS Freshman Residential suites and finishing punch-list items. We appreciate the patience of our UAS Freshmen and apologize for the inconvenience this has caused. Next week we will see a couple of man-lifts working around the outside of the new UAS Freshman Housing while they complete the metal siding around the windows and corners of the building. This work is expected to take several weeks.
UAS Construction Update for 9/19/2014
How many LED’s
How many Light Emitting Diodes (LED’s ) does it take to light the UAS parking lot and access road? I hope that only I have been staying up late at night wondering about this question. Today we get to know the answer. One LED from your headlamp is bright enough to illuminate the trail in front of you. However, it is not bright enough to illuminate a whole street. Therefore, light manufacturers just keep adding LED’s until they have enough light to illuminate a street, parking lot or building. The street lights being used on our project have 4 rows of LED’s with xx in each row. We have 53 street lights on this project. The number of LED’s is calculated as follows:
(4-rows)(10 LED/row)(53-poles) = 2,120 - LED’s
LED Street Light Fixture
The contractor working on our UAS site lighting project has now installed all but a couple of the new street lights. If you come in early or leave late, you have noticed that more and more lights get turned on each day.
New LED Street Light on Auke Lake Way
Keep a watch out next week for the Contractor installing smaller pathway light poles along the Auke Lake Way sidewalk and the pathway down to the roundabout. We will let one of our new UAS freshmen figure out how many LED’s it takes to light the pathway.
Pathway Light Pole Foundation
Pathway to Soboleff Building: The Contractor got notice this morning that the asphalt paving crew will be here today! The Contractor will need to do some additional work after the paving, but hopefully we will have this pathway back open soon.
UAS Freshman Housing.
Next week we will see a couple of man-lifts working around the outside of the new UAS Freshman Housing while they complete the metal siding around the windows and corners of the building. This work is expected to take several weeks.
UAS Construction Update for 9/12/2014
My grandmother told me stories that her mother would heat up a large rock on the wood stove at night. When the rock was nice and warm, she would wrap it up in a towel and put in the bottom of her bed to keep her warm during a cold winter night.
When I moved to Alaska 20+ years ago and had to pay my own heating bills, I turned down the thermostat to the cool to cold side and bought a couple more blankets. Then one year a friend gave us some modern hot rocks. These hot rocks are a cloth bag filled with some type of grain like wheat corn or rice. Now we just pop a hot rock bag into the microwave, heat them up and put them in the bottom of our bed to keep warm at night. Some hot rocks purchased at the store have included spices and fragrances and are intended as a heat or cold pack. The one down side of these hot rocks is that they get cold in the middle of the night and you kick them out onto the floor. That may be why grandmother never got more than 6 hours of sleep at night.
Grandmas Hot Rock
Grandmas Hot Rock2
My Hot Rocks
Each UAS Freshman Housing suite has what you could consider a mega-hot rock. Heating is provided by hydronic heating in the floor. (See Update on November 1, 2013) This system runs hot water through tubes the 4 inch thick concrete floor resulting in a mega-hot rock that weights
(4-inches)(250 Square Feet)(1-foot/12-inches)(150lb/cubic feet) = 12,500 pounds.
This “mega-hot rock” weights 6 tons and will not get cold at night, even if you turn the thermostat all the way down and stop the hot water from flowing through the tubes in the concrete. This mega-hot rock holds so much heat that it takes many, many hours for it to cool down or heat up. Therefore, instead of living in a house that jumped between 56 – 70 everyday like I did, Residents with hydronic floor heating are encouraged to pick a temperature they like and stay at that temperature all the time.
Concrete Pour Last November to Create one Mega Hot Rock
Pathway to Soboleff Building: The Contractor is almost complete with their earth work, set foundations for the handrail and will be installing handrail posts in the next day or so. They will be ready for asphalt pavement sometime next week, and then we just need to have a non-rainy day to get the paving done.
Posts Lined up for New Handrail
Campus Exterior Parking Lot Lighting.
Did you notice that we will lost 35 minutes of daylight last week? Also did you notice that the Contractor got up two rows of LED parking lot lights? The plan for next week is much the same, lose 36 minutes of daylight and install the remaining two rows of parking lot lights. Keep a watch out for new pathway lights showing up on Auke Lake Way.
Light Pole Foundation Proudly Supporting a New LED Light Pole
Pathway to Soboleff Building: The Contractor has removed the existing pavement and has started placing new subgrade along this pathway. This walkway will be closed for about 2-weeks while the contractor is working in this area. When the project is completed it will include a wider asphalt path with a handrail on the right hand side. Once the groundwork is prepared for this walkway, we will need to wait for a non-rainy day to pave this pathway. We all hope there are a few of these days left before snow flies.
Pathway Under Construction
Campus Exterior Parking Lot Lighting.
By the same time next week, we will have lost 35 minutes of daylight! Besides being simply amazing to us Engineers and Astronomers that daylight can change so fast, it makes it difficult for Faculty, Staff and Students who arrive before 6 AM or leave after 7:30 PM with the parking lot lights out. Therefore, we are having the Contractor install some temporary lighting by Monday. This will help tide UAS over until the new LED lighting is installed and turned on. These lights will be installed and turned on in sections, starting with the ones closest to the Egan entrance. The Contractor will have all the LED lights turned on in 3-4 weeks. By that time we will have lost 2 hours and 20 minutes. How does that happen?
Light Pole Foundation Waiting for LED Light Pole