DIY Differential Cut UQ Calculator

[GadgetUK437]

My next step is to add my formulas into a copy of the CatSplat calculator.

Here are my workings, so far, if you wish to see what is going on,
https://dl.dropboxusercontent.com/u/...ferential.xlsx

[Wanderlost]

This is the spreadsheet I've been tweaking.

I've made a few adjustments that are mostly cosmetic.

• I added a data tab with fabric weights and the temp calculating stuff onto it. This mainly just cleans up the "front page" for me.
• Now, you can pick the weight of both your inner and outer fabric from a drop down list. This allows for quick fiddling with different fabrics to see how it'll affect final weight.
• In the desktop version, I locked all spaces except the green background spaces. Those are the input spaces.
• I'm working on adapting it for a basic cinching top quilt.

[jellyfish]

This is the spreadsheet I've been tweaking.

I've made a few adjustments that are mostly cosmetic.

• I added a data tab with fabric weights and the temp calculating stuff onto it. This mainly just cleans up the "front page" for me.
• Now, you can pick the weight of both your inner and outer fabric from a drop down list. This allows for quick fiddling with different fabrics to see how it'll affect final weight.
• In the desktop version, I locked all spaces except the green background spaces. Those are the input spaces.
• I'm working on adapting it for a basic cinching top quilt.

Beautiful. Thanks for your hard work.

What are your thoughts on a differential for the length?

[Wanderlost]

Beautiful. Thanks for your hard work.

What are your thoughts on a differential for the length?

I've honestly never really thought about it. At a glance and off the cuff, I don't really consider it as much a necessity...at least on a full length quilt. The area with longitudinal taper is just beyond your head and feet, so it won't affect your insulation much. On a 3/4 length? I could see a bit of differential cut being useful on the leg end of the UQ.

[onesojourner]

I've honestly never really thought about it. At a glance and off the cuff, I don't really consider it as much a necessity...at least on a full length quilt. The area with longitudinal taper is just beyond your head and feet, so it won't affect your insulation much. On a 3/4 length? I could see a bit of differential cut being useful on the leg end of the UQ.

I am still testing but with my quilt the effect is pretty huge. I lost about an inch of loft at my butt. Taking 2 inches out of my inner layer has gotten that back.

[GadgetUK437]

What are your thoughts on a differential for the length?

I posted this in another thread recently -

There are two components to lengthwise skin differential.
Firstly there's the bit you need to add on for the end walls (2 x baffle depth, e.g. for 3" baffles you need to add 6" to the outer skin length). Unless you are a contrarian (like me) and are doing separate panels for your end walls (and sidewalls, in my case).
Secondly there is the differential due to the inner skin curving at a smaller radius than the outer, as it bends around a curved object... your butt!
I have been working on this myself, taking careful measurements of my Phoenix and adding to the head and leg shelf to get something approximating an Incubator,


After drafting it out, I realised that there will be very little difference to the inner and outer skin, less than 2mm.

This is because it is not just a simple curve, it is a S-curve (two in fact, one behind the head, the other behind the butt), so the length differential cancels each other out.
This doesn't mean that it isn't important, just that it isn't simple.

These are some of my shaped baffles (using recycled CDT material, not noseeum) and the templates
(the white one is the finished shape, beige is the template for the darts)


Referring back to post #110, I have incorporated my new formulas into the calculator here,
https://docs.google.com/spreadsheets...it?usp=sharing
(let me know if you can use it, there are separate pages for imperial or metric input)

I am doing a series of 3 UQs using the new formulas, so I will report back.

[jellyfish]

I posted this in another thread recently -

These are some of my shaped baffles (using recycled CDT material, not noseeum) and the templates
(the white one is the finished shape, beige is the template for the darts)


Referring back to post #110, I have incorporated my new formulas into the calculator here,
https://docs.google.com/spreadsheets...it?usp=sharing

I am doing a series of 3 UQs using the new formulas, so I will report back.

Sweet! I am looking forward to your reports. Your baffles remind me of the stripes I sewed on a giant striped bass consume that I made for a parade. Very very cool.

[GadgetUK437]

I am still testing but with my quilt the effect is pretty huge. I lost about an inch of loft at my butt. Taking 2 inches out of my inner layer has gotten that back.

Did you use straight baffles or shaped?

[GadgetUK437]

Sweet! I am looking forward to your reports

I shall post up a build thread... but I like to wait until I have completed it, so I can present it as a fait accompli.
(prolly best, given my championship standard procrastination skills!)

[GadgetUK437]

Using my version of the formula works out with a greater contained volume each time, so more down required.
With thin quilts it's only fractions of an ounce, but with 3" thick quilt it is nearly 1.5 oz.

I dunno how CatSplat's original formula for cross-sectional area works, but this is how I worked it out;

A1 is easy enough, it's just the area of the outer circle minus the inner circle, divided by the number o- so;
A1 = (πR² - πr²) / (number of baffle tubes * 2)

A2 is a bit more fiddly, the puffyness of each chamber is a function of the baffle height (Hb) and the max chamber height (Hc), it's the area of a segment of a circle,
A2 = ((arc radius²) * ACOS((arc radius - arc depth) / arc radius)) - (arc radius - arc depth * (SQRT((2 * arc radius * arc depth) - (arc depth²))))
(where arc depth = Hc - Hb)