Why is the dimensions changed when a Flat Pattern is created?

[Anonymous]

I'm trying to make my own skis but when I've created a 3D modell that's looks good and I create a Flat Pattern the dimensions are changed. For example the tip width shoud be 142mm, tail 130mm, waist 105mm but in Flat Pattern the tip width is 144.213mm, tail 130.858mm, waist 104.709mm. These dimensions should not be affected, it's only the length axis dimensions that should be affected.

Why is the dimensions changed when a Flat Pattern is created and how to evade this problem?

[CCarreiras]

HI!

This is perfectly normal.

When you bend something, must occur a compensation value for the bend zone.

Check it Here

https://en.wikipedia.org/wiki/Bending_(metalworking)#K-factor

[Lewis.Young]

Hello,

I have a feeling that it's something to do with the unfold options in the sheet styles editor (e.g. unfold rule)

The folded part will show the exact sizes, but once you turn it into a flat pattern it will take into account the  stretching, deforming of the sheet around the neutral axis

Lewis Young
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[Anonymous]

The original file was overwritten, attached it.

[Anonymous]

Can I unfold the skis without having problems with the width? 

[Anonymous]

So how to "flat pattern" a surface? That would solve it.

[CCarreiras · Accepted solution]

Can you show me where you have problems width problems.

So far i can't see them...

[Anonymous]

You have not measured it in the right position. The widest width at the tip should be 142mm, the widest width at the tail 130mm and the closest distance at the waist should be 105mm. None of this is true with flat pattern.

[Anonymous]

My bad, have dimensioned the top, tail, and waist in the wrong position. I have no problems any more, please delete this thread.