Starting my build

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Re: Starting my build

Postby torkcm » Tue Oct 08, 2019 4:19 pm

Squigie wrote:
torkcm wrote:I'm also in the planning stages of my build and I found a pretty accurate way to estimate weight of materials used. I'm using sketchup to design my teardrop and it can tell you the volume of each piece designed. So say I have .75" x 1.5" x 42" long piece of plywood, the volume comes to 47.25 cu inches. Take that number and multiply it by the density of the material, plywood in this case. 47.25 x 0.02170138889 = 1.02 lbs for that piece. I know its tedious to do but sketchup handles a lot of the hard work and I can get the weight estimate pretty much spot on using a spreadsheet with a list of everything plotted out. I found that once everything was listed I was over my initial goal of 700 lbs by 190 and it's still climbing.

Sample list of densities for different materials
Material lbs per cu in
plywood 0.02170138889
aluminum 0.098
xps foam 0.001157407407

I do the same ... manually.

My old CAD program (long abandoned by AutoDesk) is so incompatible with the latest computer OS updates that it's nearly unusable.
I can't get Fusion 360 to do what I need.
And I went so long without an active license for SolidWorks that I'm hesitant to even jump back into that separate-file-for-every-part pain in the butt. (I do have a free license now. I'm just skeeered.)

So, I'm still using graph paper and a calculator. :NC

If you want numbers as precise as possible, be sure to look up the weight per sheet of the actual thickness of plywood you're using - and from that specific manufacturer, if possible.
Different thicknesses have different densities, due to different ply thicknesses and ratios of glue to wood.
If you take the different thicknesses of a type of ply offered by one manufacturer, for example, and graph them by weight (or density), the result is not linear.

For 'ballpark' numbers, there's no need to be that picky. But if you're really trying to get an accurate estimate, it makes a difference.
The first design that I worked up a weight estimate for (now abandoned for excessive use of heavy plywood) had an 83 lb difference between using a generic plywood density (based on 1/2" I think) and the listed densities of the different thicknesses from the actual manufacturer that I can get here. Represented a different way: The difference between estimates was 8.9%; or 930 lbs (generic) vs 1,013 lbs (specific). On some builds, that's not a big deal. On others, 9% is huge - whether 9% over or 9% under.
I def know what you mean on different types of wood weighing more or less. I had went to the big box stores to sample lumber and there were way heavier types of wood that where the same thickness. I have started to turn my basement into a shop for the build. Had a cnc machine I just opened that sat in the box for 8 years lol. It's almost complete. Gunna be doing a sandwich style tear with cnc cuts on ply.Image

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Re: Starting my build

Postby twisted lines » Tue Oct 08, 2019 5:16 pm

torkcm wrote: Gunna be doing a sandwich style tear with cnc cuts on ply.


You are going to make a mess of that room :lol:
5.5 X 10 Flatback Benroy in a pile,
And it's growing!
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Re: Starting my build

Postby torkcm » Tue Oct 08, 2019 5:43 pm

twisted lines wrote:
torkcm wrote: Gunna be doing a sandwich style tear with cnc cuts on ply.


You are going to make a mess of that room
Lol I know right. Dust collector setup is next.

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Re: Starting my build

Postby retep » Wed Oct 09, 2019 10:47 am

So jealous lol. Think that would be so fun to make all that sawdust.

Nice setup!!!

Peter


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Re: Starting my build

Postby Jimmyg » Thu Oct 10, 2019 7:30 pm

I'm a drafter so I have my own 3d program called Alibre Design so I'm getting pretty good weights. I'm verifying as I get parts and material. My job is in a fabrication shop where we build equipment to mount on trucks, so some stuff I can get for dealer cost. I've got people, :thumbsup: my boss and one of the guys in the shop have built and refurbished trailers. I also have a brother who is a cabinet maker, so i access to suppliers and 10' router . Once I get this final design (I hope) done, I'll post it.
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