Ceiling Cove size calculation

Discussion in 'Lighting and Electrics' started by LPdan, Apr 23, 2018.

  1. LPdan

    LPdan Active Member

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    We have a theatre that currently has no light positions on the ceiling, and is planning to add them as part of an upgrade. Presently the idea is to add two pockets of qty (6) ETC Colorsource Spots. What is the best way to calculate the dimensions of the cove opening the contractor will have to cut open to accommodate this quantity of fixtures?
     
  2. JD

    JD Well-Known Member

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    Depends on the throw in feet, how high the ceiling is, and the position of the pipe. In general, the closer it is, the bigger your opening is going to have to be, unless you intend for the fixtures to be below the cove and visible.
    Needless to say, you have to factor in the concept that you would want each fixture to be able to hit any area on the stage and therefore the size of the fixture. Remember, right now you have a "planned" fixture, but things change over the years and you would not want to have to do additional modifications in the future to accommodate a fixture you didn't plan on. On the bright side, the trend is towards smaller units as technology develops.
     
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  3. RickR

    RickR Well-Known Member

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    Some specifics to add to JD's good advice.

    Horizontal:
    Fixtures are routinely spaced 18" apart. Closer is definitely possible but further apart won't gain you much unless they are aiming far from straight out of the pocket. (If so multiply everything by 1.5 or 2) So that's 9' wide, and someone will grumble and want it to be an even 8', and then you'll lose a few inches to framing and trim and you'll have 7'6". That might be OK but it will be tight. Tell them 10' and don't worry about the details. You will have room for a special once in a while.

    Vertical:
    Figure out how a tech will get their hands on the lights to work on it. Below, behind, above or whatever. That tends to take the most space and cause the most regret later. Since that will likely be you, don't put yourself in too tight a squeeze, and remember the shorter/taller person that will replace you.

    Then look at the light beam. It all depends greatly on the actual angles, depth of the pocket and hanging position. Even ventilation can be a concern, as you don't' want to trap fixture heat but also don't want to vent the room into the attic.

    I always draw it out. A line from the center of the light to as high and low as it will ever reach, edge of beam not center. Be generous and paranoid in determining what MIGHT be needed, someday by that crazy director with a keen eye. Then widen the opening a bit so spill isn't too obvious. Will the the audience see the fixture? Do you care if they do? If so move the hanging point back and start all over, after all it's harder to reach the fixture now.

    Oh yeah, movers require a lot more space!! Not now but someday??
     
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  4. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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    Did I miss this or is access from below only?
     
  5. LPdan

    LPdan Active Member

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    Thanks for all this advice!
    Bill, I did not mention either way, but we can access from above in the ceiling crawl space.
     
  6. JohnD

    JohnD Well-Known Member Fight Leukemia

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    Well, since no one has said so yet, It's not just a matter of "some contractor" cutting a couple of holes in the ceiling. It is much more complex than that. Is the ceiling crawl space a plenum? How is the ceiling constructed and suspended? Is it a fire rated barrier? Is a structural engineer involved in this?
     
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  7. Dionysus

    Dionysus Well-Known Member

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    Have to agree with JohnD, there is a lot involved with this.

    How is the hang position (pipe?) to be installed? is an Engineer involved (there should be)?
    Based off of the position of the hang position in the structure, you can then draw a series of sections to plan where and how lights will be needed to point and how much of the ceiling interferes with the beams.
    How far back and how high is this new position? it is in an appropriate location for proper front lighting angles?
    Once all of that is planned. you talk with the contractors and engineers, about making both that and the ceiling modifications happen.
    Id also suggest involving a theatre/lighting consultant as well.
     
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  8. SteveB

    SteveB Well-Known Member

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    A ton of questions on this, in addition to what’s been asked.

    - Once the position is added, is there a catwalk system that allows access ?
    - If no catwalks, are they going to be added ?, so as to allow technicians safe and useful access ?
    - If you have to install a catwalk, how are you going to do that ?, seems you would have to remove entire ceiling sections, install catwalks, install new ceiling.
    - Would it be cheaper to install winched pipes and moving lights ?

    I had a plan once for a catwalk system at our road house. Wouldn’t do that now, I’d do winched pipes and movers.
     
  9. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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    In my work, I have found winched pipes and movers to always be much more expensive than structural and architectural modifications to achieve the same function.

    I'd also suggest two winched battens - one for a focus track - and don't be forced to rely on movers.

    And inevitably, reliance on winched for foh inevitably takes more time in the end than just someone being able to scurry out there, even if on hands and knees.

    Appearance cannot be overlooked. You often have to convince someone higher up that it's ok to see all that gear or accept an attempt to conceal.
     
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