Backyard Observatory.

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Backyard Observatory.

RobVG — 10/23/2006 4:02:47 PM (archived)

Just a small one- 8'X8'. I poured the pier base last weekend and today I'm pouring the concrete pier itself. I needed to space the three j-bolts that ancor the metal pier in an equilateral triangle within a circle. I'm making a plywood jig to hold the bolts in position when they're plunged into the concrete.

Thanks to all for the ideas.

The whole thread (37 posts)

Question: how do you find 3 points on a plywood circle 120 degrees apart, without a protractor? (n/t) - RobVg - 10/23/2006 3:22:08 AM
- Without a template, you put your anchor bolts in. Drill out the plate. - Bowser - 10/24/2006 6:34:51 AM
  - Slight addendum. - Bowser - 10/24/2006 3:41:35 PM
    - You are correct. - RobVG - 10/24/2006 4:26:51 PM
- Yet another method - Fox - 10/24/2006 2:50:16 AM
  - Oops... Laurie beat me to it. - Fox - 10/24/2006 2:51:19 AM
    - Laurie beat me to it, too. - podrock - 10/24/2006 4:04:21 AM
- Here you go, have a protractor: - podrock - 10/23/2006 4:35:57 PM
  - Or... - podrock - 10/23/2006 5:53:39 PM
  - Sorry, that's a compass. ;) (n/t) - RobVG - 10/23/2006 4:41:01 PM
    - Without the needle, it's a protractor. :) - podrock - 10/23/2006 5:01:16 PM
- If I remember enough geometry... - alcaray - 10/23/2006 3:33:38 PM
  - Close. It's 2R sin (60 degrees). (n/t) - ER - 10/23/2006 5:16:08 PM
    - I used geometry, not trig... - alcaray - 10/23/2006 8:36:56 PM
      - What is "rad-5"? - ER - 10/23/2006 10:51:36 PM
        
        final answer! - alcaray - 10/24/2006 5:09:43 PM
        
        Correct! - ER - 10/24/2006 6:28:41 PM
- Cut a circle out of paper, exactly the same size as your plywood circle - SDF - 10/23/2006 1:19:47 PM
  - Rule of thumb method. This is probably close enough for home carpentry. - ER - 10/23/2006 5:24:00 PM
    - Geometrically precise. Error comes from application - nick hoffman - 10/25/2006 12:36:46 PM
      - belay my last - it was just a senior moment - ER - 10/25/2006 2:56:07 PM
      - Another job for the CRC. - ER - 10/25/2006 1:33:16 PM
- Yes, there is a way! - ER - 10/23/2006 11:04:03 AM
- So... tell us what you're building! (n/t) - Laurie Street - 10/23/2006 5:18:08 AM
  - Backyard Observatory. - RobVG - 10/23/2006 4:02:47 PM
    - re: Backyard Observatory. - Laurie Street - 10/23/2006 4:10:28 PM
      - Sure. - RobVG - 10/23/2006 4:32:49 PM
- Why can't you use a protractor? - ER - 10/23/2006 4:22:17 AM
  - Yes, there is a way! - ER - 10/23/2006 11:00:51 AM
  - re: Why can't you use a protractor? - Laurie Street - 10/23/2006 5:19:24 AM
    - Trisecting the angle--attention Mary Anne - ER - 10/23/2006 1:16:37 PM
      - While we're at it: Cameron's Hydraulic Tables? - Fox - 10/24/2006 2:35:29 AM
      - CRC Handbooks - Laurie Street - 10/23/2006 4:02:00 PM
      - Pocket Ref - SDG - 10/23/2006 3:34:20 PM
  - Because I don't have one smarty pants. - RobVG - 10/23/2006 4:40:17 AM
- It's impossible - Laurie Street - 10/23/2006 3:35:48 AM
  - Thanks Laurie, your method is close enough. (now where did I put that string?) (n/t) - RobVG - 10/23/2006 3:44:38 AM

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