THis doesn't add up

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THis doesn't add up

Postby Mapacho » Tue May 14, 2019 10:23 am

I'm flattening a dome to produce a fabric cutting plan. I have an eight foot section that I duplicate 16 times to get my total dome. Each section measures eight feet. So 16 x 8 feet = 128 feet. When I measure each section they're 8 feet individually. When I measure the total length it comes out to 127' 11 3/4".

I'm using the unwrap and flatten plugin to get my initial 8 foot section and then I just create copies of that. Anybody have any ideas what's going on? Can I trust that the rest of my dimensions are accurate?? Why would I lose a 1/4"???? I've tried this multiple times and the overall dimension is always incorrect.

Your thoughts would be appreciated! If I'm in the wrong place in the forum let me know - it's my first post.
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Mapacho 
 

Re: THis doesn't add up

Postby Dave R » Tue May 14, 2019 12:30 pm

Increase the precision of your dimensions and check to see that what you are measureing is exactly 8 feet.

How are you creating the sixteen-sided shape with the 8 foot wide sides?

I made a 16-sided polygon with sides at 8 feet, copied one face out and copied it to get a straight run. I get the expected dimension.

I also manually flattened it using Rotate and get the expected result.

I would suspect imprecision in the original model, imprecision in placing copies, or the flatten extension is creating a slightly deformed shape from the original.
Screenshot - 5_14_2019 , 6_13_34 AM.png


It's worth noting that since SketchUp approximates arcs with straight line segments, the sections for the dome portion will be a little short.

It's a good idea when posting with questions like this to include the SketchUp model.
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Re: THis doesn't add up

Postby Mapacho » Tue May 14, 2019 5:15 pm

Thanks for that - never thought to include the original file. I made the dome by using the polygon tool to create the 16-sided circle. Then I used an arc shape and follow me tool to create the roof.

I created one flattened dome piece with unwrap and flatten and then copied it using array - Move/Control x 15 copies.

I'm just curious how you would flatten the sides with rotate? Also, how do you increase the accuracy of the measurements?

As you can tell I'm still learning the program! Much thanks for the reply!
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Mapacho 
 

Re: THis doesn't add up

Postby Mapacho » Tue May 14, 2019 5:17 pm

I just noticed the file I sent is completely messed up with the measurements. I had been practicing something from a tutorial with measurements using the tape measure tool and somehow managed to screw up the original scale of the dome. Sorry about that. I have no idea how to undo it.
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Mapacho 
 

Re: THis doesn't add up

Postby Dave R » Tue May 14, 2019 5:52 pm

I opened the model, measured one of the sides of the domed shape with the Tape Measure tool and set it back to 8 feet long. The overall length of your flattened version then shows the correct dimension.
Screenshot - 5_14_2019 , 11_50_38 AM.png


At this stage it's impossible to identify how you came up short since it's doing what I'd expect.
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Re: THis doesn't add up

Postby Mapacho » Tue May 14, 2019 6:46 pm

Dave - thanks so much for taking the time. Much appreciated!
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