# Thread: Rule of thumb for the differential cut??

1. ## Rule of thumb for the differential cut??

How do you guys calculate the amount of "differential fabric" needed for the outer side of the underquilt? is there a rule of thumb, or do i have to resolve to using math at Grizz's level

And for those of you who use darts - do you dart equally in both sides and respectively ends or let it be asymmetric?

2. You got me thinking about this mathematically...

At first it seemed like it might be complex. I started thinking about the geometry, without using any equations, and I think you can simplify things a bit. I'll try to explain verbally knowing full well that a picture will save me a thousand words

We're discussing two curves. The one against the hammock and one spaced away from that curve the distance of your desired loft or baffle size. They aren't exactly semi-circles, but I think that approximation is close enough.

I assumed we're going through 180 degrees, or a half circle.
WI = Width of your inner piece of fabric
WO = width of the outer piece of fabric
B = the size of your baffles
WO = WI + B*pi

That's what I came up with at least. So if you know the size of the inner fabric and your baffle size, you can calculate the size of the outer fabric. Seems too simple, but I double checked my math. I think I solved it right. :P

I'm sure the math whizzes will find a flaw in my logic. I can't get passed the feeling this is too simple :P

Edit: if the math whizzes give my calculation their blessing, I'll use this when I make my own UQ!

3. Whoa. Time to get my protractor out...

Syb

4. @hikelite
Sounds plausible(though still a bit intimidating)

@Syb
+1 on that Whoa

5. I generally use 7 inches on the outside and 6 on the inside. I flunked calculus though........twice.

6. Originally Posted by Dutch
I generally use 7 inches on the outside and 6 on the inside. I flunked calculus though........twice.
Doesn't the distance between baffles vary dependent on the "thickness" of the baffles(or is it so small a difference that it's just an academic discussion)

7. Originally Posted by Bomber
Doesn't the distance between baffles vary dependent on the "thickness" of the baffles(or is it so small a difference that it's just an academic discussion)
I bet it could be caculated precisely, but it seemed to work for both summer and winter quilts for me.

8. Hey... as long as it works

9. I followed Dutch's advice, but tweaked it.
I used the 6"/7" rule and scaled it down to 4". Worked out at 100mm/117mm in proper units .

10. Originally Posted by turnerminator
I followed Dutch's advice, but tweaked it.
I used the 6"/7" rule and scaled it down to 4". Worked out at 100mm/117mm in proper units .
Do you mean spacing between baffles here

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