Reference Line location is not correct

[Steve Jepson]

In a composite wall I have included a vapor barrier for several reasons. It has the minimum default thickness which is 1/64". The reason it needs to have this minimum thickness is because of the graphics display errors you get if you try to set this thickness to 0".

The problem with the reference line in a wall like this is that the reference line does not show up in the correct place relative the material thicknesses that have been assigned to the wall.

For example, 3/4" + 1/2" + 1/64" = 1 17/64"

I can not get the reference line in that location so it will match graphically with the materials. This causes several kinds of problems, some of which are important.

http://screencast.com/t/JLYrOV5c

The workaround is to set the reference line from the Inside, and make the reference line offset per materials from the inside out so that you do not include minimum thickness skins.

To know this in advance would have been nice. It caused me several kinds of problems that were difficult to fix. Dimensions, precision of the model, cleanups, Intersects, Wall Labels, Schedules, etc...

[Laszlo Nagy]

Why do you type 0.01" if you want it to be 1/64"?
why don't you type 1/64"?
0.01" is 1/100", about 2/3 of 1/64".
Maybe this has nothing to do with it, it just caught my eye.

[Steve Jepson]

The minimum skin thickness is 1/64". Anything you type in less than that will default to 1/64". I would like to use 0" but that causes other problems.

The point is that it is not possible to get the reference line where in should be when you have the reference set from the outside face of the wall and when there is one of these minimum thickness skins included in the offset.

[Steve Jepson]

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[Steve Jepson]

I have about 16 Wall Types in this project.

There are no annotations necessary - all of the text you see here is just a matter of turning the label on. That is the main reason I include the vapor retarder in the complex profile. Also, I can use that skin in scheduling that material.

[Steve Jepson]

as you can see in this close up, the reference line is not on the edge of the material where it should based on the dimension I typed in for the Reference Line offset. The only way it is possible to get that reference line in the correct location is to make the reference line relative to the inside of the wall or the core. Not knowing this can cause many problems.

[Steve Jepson]

What you have to do is change the reference to be from the inside of the all and set the reference line distance to match those material widths.

like this - easy fix, however it can cause a mess if you don't know about this and you are lining things up as you work by the reference lines only do discover later that even though you set the reference line dimension correctly, that does not always mean the reference line is where it should be.

http://screencast.com/t/d17Y71rj

As I pointed out before, it is not possible to include one of these min. thickness skins in the offset distance for the reference line and have the reference line in the correct location. The reference line offset in a wall like this needs to be from the core or from the inside or some place that does not include a minimum thickness skin. It's a bug if you ask me.

[Anonymous]

I think Laszlo is right - I get exactly the same in AC15. Typing 0.01" will display 1/64" in the composite but will actually measure something slightly different. Type in 1/64" and it will work correctly.

The image below is a close up of two otherwise identical composites, one with the skin typed in as 0.01" and one typed in as 1/64". The ref line offset is 1 17/64" on both. The thin skin is clearly a different thickness.

[Steve Jepson]

Yes. Your are both right. Typing in 1/64" does make a difference.

I was typing in .001 because it is faster than tying in 1/64" and because it will generate the minimum thickness of 1/64" - sort of like using a snap to locate something you want the computer to choose rather than manually place. I use this kind of thing to flush out 64/ths in a dimension chain when there is no apparent reason for there to be any fractions in the chain.

Once again, the program has proved not to be idiot proof. I don't suppose anyone could have anticipated that a person might type in .001 as a way to make the computer generate the smallest minimum thickness for a skin.

But I think this should be fixed. If the display in the Composite Structures menu for skin thickness reads 1/64" then the reference line should be displayed accordingly.

[Laszlo Nagy]

Steve wrote:
The minimum skin thickness is 1/64". Anything you type in less than that will default to 1/64".

That is not correct. The minimum skin thickness value is zero (which when used gives other problems, as you said).
Internally, it will store the 0.01" value typed. It will only round it in this Dialog to multiples of the value that you have set as a Working Unit Dialog (1/64" in this case) for display purposes. But internally, it will still be 0.01". (If you typed, for example, 0.001" it would round it to 0" for display in the Dialog.) Try to type the exact 1/64", not 0.01".
It is just like rounding of Dimensions. Just because it is rounded to the nearest 1/64" for display it does not mean the value changes to the nearest 1/64".

If you want to test this, switch your Working Units for Model Units to Millimeters with 1 Decimals. You will see it displays 0.3 (0.1" = 0.254 millimeter rounded up to 0.3). If it rounded up to 1/64" it would display 0.4 (0.396875 mm rounded up to 0.4).
(0.396875 mm = 25.4/64 mm)