# DIY Differential Cut UQ Calculator

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• 05-29-2012, 17:00
CatSplat
DIY Differential Cut UQ Calculator
When I started out making my DIY down-filled underquilt, I knew I would need to calculate my overall material size to have a sufficient amount of outer shell material to accommodate the "lumps" inherent in the differential design, as well I would have to calculate the required amount of down to fill the baffle volume. The Red River Gorge Underquilt How-To provides some nice starter calculations for fill volume but lacks the means to calculate the outer shell area. As tends to be habitual for engineers, I fired up Excel and created a spreadsheet for calculating material requirements and down fills for underquilts based on the cross-sectional area of the baffles.

The sheet allows you to specify your finished quilt dimensions and baffle design, and will return material dimensions for construction and the amount of down (for an input fill power) required to fill it. Down fill can be adjusted via the Over/Understuff field or by directly altering the "Total Oz. of Down" field.

Two experimental features are also included:
- An approximation of the quilt's overall weight (minus suspension) based on the material sizes, fabric weights, and down, with 15% allowance for stitching and seams.
- A VERY experimental calculation of the quilt's theoretical temperature rating, based on the published design specs for some Underground and HammockGear quilts.

I've attached the sheet for the community's perusal, please give it a look and feel free to suggest any improvements to be made. If you want to un-protect the sheet to play with the formulas, the password is "hammockforums".

-Trevor
• 05-29-2012, 21:08
Brute1100
You have way too much time on your hands... I like it :)
• 05-29-2012, 23:40
hammockhogs
This is great. Just what I was looking for. Thanks..
• 05-30-2012, 00:26
chickenwing
• 05-31-2012, 00:00
CatSplat
I definitely can't argue with having too much time on my hands, haha!

Good suggestion on Gdocs, I will see what it takes to get the file uploaded properly. I will probably take the opportunity to include some more user-friendly instructions.
• 06-14-2012, 00:06
CatSplat
OK, I've added a couple of clarification images and converted it to a Google Docs file. It is protected, so to use it you need to go to File->Make A Copy, which will create a copy in your Docs or Drive account and allow the file to be edited.

http://www.osphoto.ca/hammocks/UnderquiltCalcv2.xlsx
• 07-20-2012, 11:57
Living the Highlife
i love this!! this solves all my planning woes. does this account for seam allowances? and where did you get the math for the beta temperature?
• 07-22-2012, 18:11
CatSplat
Quote:

Originally Posted by HamptonHanger
i love this!! this solves all my planning woes. does this account for seam allowances? and where did you get the math for the beta temperature?

No, you have to do your own seam/hem/channel allowances as they will differ based on skill and design. Just be careful with your math and you'll be fine!

Temp stuff is a scale based on the published specs and temperature ratings of some "commercial" underquilts.
• 08-31-2012, 10:06
GregB
This is really useful for us Newbies. Can we make this a Sticky Post?
• 09-10-2012, 17:53
jordo_99
Finding this to be extremely helpful for my first attempt at a quilt...anything I should be doing differently since I'm looking to make a 72x72 flat quilt?

I could see some slight differences in the "Outer Shell Fabric Width per Baffle" and "Outer Shell Fabric Width" dimensions since it would be flat instead of arched.

...in other words, is this calculator designed to make a pre-curved UQ or is it just a flat UQ that takes the curved shape after it's attached to the hammock?

...I would imagine the former (flat quilt), but it looks like a fair bit of thought and effort have been put into it so I wanted to verify before I start putting together my order.
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