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Thread: Not my day: Math question.....

  1. #1

    Not my day: Math question.....

    It must be the heat !!! Can't figure out to convert cylindrical dimensions to cubic feet! Got a Wood Mug that is 5 3/4 inches high x 3 1/4 inches Wide. If the bottle of resin coating can do between 3 to 4 SQ FT, how many Mugs can I do with that one bottle ?

  2. #2
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    Not exact, but if you "straighten those dimensions you have roughly 10 1/4 inches by 5 3/4 inches which comes to roughly 59 sq inches. Add to that another roughly 8.5 inches for the bottom which comes to roughly 68 sq inches. So I would say 2 cups per square foot.

  3. #3
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    Quote Originally Posted by Sam Force View Post
    Not exact, but if you "straighten those dimensions you have roughly 10 1/4 inches by 5 3/4 inches which comes to roughly 59 sq inches. Add to that another roughly 8.5 inches for the bottom which comes to roughly 68 sq inches. So I would say 2 cups per square foot.
    Not clear if the OP wants to do the inside surfaces of the mug too, but might allow for that as well. So, figure 3 or 3.5 mugs per resin bottle; 6-7 mugs if only coating the outside surface. (Don’t think you need cubic feet.)
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    Cut the circle (mug) lengthways down the side and flatten it out to make a rectangle. That makes one side of a rectangle (the width) of 5.75" wide. The length of the rectangle is the circumference of the circle (going around the rim of the mug). C = Pi x D or 3.14 x 3.25" = 10.21" The area of a rectangle = L x W. 5.75" x 10.21" = 58.71 sq in. Now add in the area of the bottom of the mug. Area of a Circle is Pi x Radius squared (I think) or 3.14 x 2.64 = 8.29 sq in. 58.71 + 8.29 = 67 sq in. Double this to cover the entire mug inside and out = 134 sq in. 1 sq ft = 144 sq in (12" x 12"). Looks like you could do somewhere around three to four mugs with some waste, spillage, screwup, etc per bottle. You would be wise to : A) Check my formulas for Area of a Rectangle, Length of a Circumference and Area of a Circle. B) Check my math. Please check my math.
    Last edited by David Eisenhauer; 05-27-2020 at 8:49 PM.
    David

  5. #5
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    The area of a cylinder is: A
    =
    2

    π


    r


    h

    +
    2

    π


    r
    2








    So Height is 5.75"
    Radius is 1.625"
    Assume we only coat outside and bottom of vessel
    Therefore: 2*3.14*1.625*5.75 + 3.14*1.625^2 = 67.00"

    There are 144 in2 per square ft, so 3 ft2 feet would coat 6.4 vessels, 4 sqft would coat 8.6 vessels.

  6. #6
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    I think I did the same math, I assumed he was only coating the inside of the cups with resin.

  7. #7
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    Google is your friend: LINK

    Annotation 2020-05-28 073607.png
    Sharp solves all manner of problems.

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    Eric beat you to it!
    David

  9. #9
    That formula gives you the area of the inside of the subject mug. If that is what the OP is trying to finish, it is correct. But if he is trying to finish the inside and outside, you have to do it twice, once with the inside radius and once with the outside.

  10. #10
    First step is to identify the right equation. Are you looking for cubic ft or square ft.

  11. #11
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    The OP is wanting to know coating area, so sqft. Cubic ft would be volume. His material provides a coverage in sqft / container, not volume per container. And yes, if he is going to do the inside AND outside of the vessel, he will be using approximately 134 in2 of material per vessel, so about 3-4 vessels per container of coating.

  12. #12
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    Quote Originally Posted by Jim Dwight View Post
    That formula gives you the area of the inside of the subject mug. If that is what the OP is trying to finish, it is correct. But if he is trying to finish the inside and outside, you have to do it twice, once with the inside radius and once with the outside.
    Twice? The horror!
    Sharp solves all manner of problems.

  13. #13
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    Quote Originally Posted by Rob Luter View Post
    Twice? The horror!
    How do I calculate thee? Let me count the pi.
    Molann an obair an saor.

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