Geodesic dome help (sketching and measuring in particular)

[NHunsicker]

My appraisal office accepted an assignment of a geodesic dome. Now I've done some reading up on these things, and amazingly enough in the last 180 days we've had another dome sell and a round house sell, so I actually have comps. My biggest issue I'm having is accurately sketching it.

I'm not opposed to going and remeasuring it if I need to, to make sure I have this completed accurately. I've never completed one of these before and assumed (probably wrongly) that I could figure out the angles mathematically and measure the sides :new_newbie:. Of course the more I try and wrap my head around this, the more complicated it seems. It's 10 sided (I don't know if that is typical), where half the sides are 8' even and the rest of the sides are 16'3". They alternate back and forth between side lengths.

I have managed to draw a regular decagon, which I assumed was a good starting point for figuring this out, but now I'm not sure that it was a necessary or even a helpful step.

If anyone is curious I'll be completing the sketch in Apex IV wintotal edition v3.2.something. I've already tried going to my old supervisor with this, but he's never done anything like this before, and I'm better at math and geometry than he is anyway.

Edit:

Thank you mods for correcting my typo.

 

[EDWARD BERRY]

I Had To Call The Area Dealer Last Time I Had One.
Once He Told Me How It Was Laid Out It Was Simple--but I Have Deleted It.

Good Luck,
Ed

 

[Mary Tiernan]

I think it is a requirement to know the width of the house, too.

When I had a geo, I had the width of the house and drew two lines in a criss cross to establish the middle of the house.

Then I drew one side, you say you have alternating sides, 16 and 8 - draw one right triangle of these, then copy it five times. You now have ten sides with alternating lengths - line them up to the width of the house, matching corners using move area, rotate area, etc.

I consider this my template and draw over the lines once the shape/sides are established, then delete the other forms, lines, 5 sides, and I have my house.

It is not perfect, but I also have a disclaimer that dimensions as provided are sufficient for the purpose of the report.

Good luck

 

[Tom Woolford]

I did a round house with 24 straight sides. I just measured the length of the straight section, divided 360 by 24 to determine the angle, then started punching keys: 7r15 enter 24 times. came out perfect.

 

[NHunsicker]

I did a round house with 24 straight sides. I just measured the length of the straight section, divided 360 by 24 to determine the angle, then started punching keys: 7r15 enter 24 times. came out perfect.

Yeah, well that's originally what I was thinking of doing, but then I realized that the different length sides would affect the angles.

 

[Howard Klahr]

Another issue, is that these structures often have more than one interior level. As you go up toward the center of the dome the perimeter increases and then reduces again signifcantly toward the top. Therefore, each level will reflect different floorplate sizes.

A quick shortcut is to see if the building department has a copy of the building plans.

 

[NHunsicker]

Another issue, is that these structures often have more than one interior level. As you go up toward the center of the dome the perimeter increases and then reduces again signifcantly toward the top. Therefore, each level will reflect different floorplate sizes.

A quick shortcut is to see if the building department has a copy of the building plans.

Well the dome I'm appraising at least isn't what you would call a full dome I guess. The bottom floor is a normal vertical wall for the first 4 feet of height, with what appears to be a half dome on top of that. This way, the first floor has ceilings high enough for the entire floor space to be living area. Because of how this is setup, for the first floor I had planned on drawing it as an irregular decagon. I haven't even started to decide how I want to go about tackling the second floor yet, especially since the floor layout of that portion is actually the shape of the dome.

It also doesn't help much that 2 of the 16'3" sides 'pop out' 4'.

Here are a couple of the photos:http://img.photobucket.com/albums/v33/scared0o0rabbit/IMG_1785.jpg
http://img.photobucket.com/albums/v33/scared0o0rabbit/IMG_1784.jpg

 

[wickedness1]

My husband sketched one in Apex a few years ago. I just pulled up his sketch & he had to start with a circle & then go point to point to point.

I remember it took him a while to sketch it's not all that pretty, lol.

 

[NHunsicker]

My husband sketched one in Apex a few years ago. I just pulled up his sketch & he had to start with a circle & then go point to point to point.

I remember it took him a while to sketch it's not all that pretty, lol.

That may just give me an idea.

If I were to take a circle that had a diameter of the width of the dome. Then started at some point on the circle, and made lines that touched the perimeter of the circle on only both ends AND were the right length for the next wall, that should mean I don't need to know the angle, right? Is this an accurate way to sketch this place, or is there something else I'll need too?

 

[Pilgrum]

I have done several of these and have always measured the diameter. Then in apex start with that as a single line and create a 180 degree arc. Left or right. Do the same once more the opposite direction and you have it. I have never been questioned doing it this way and the GLA comes out so close to the Assessor's data it is scary.
Try it. You'll like it.