Top Quilt shell sizing adjustment for loft? (measure twice, cut once)

[JoeBobJr]

Making a two top quilts with vertical torso and horizontal footbox baffles similar to a HG Burrow or UGQ Bandit.

I am bit uncertain when planning accurate shell measurements and baffle spacing for vertical baffles in the torso section in order to come up with 2.5" lofted chambers for 20* quilts. Plan to use 2.25” baffles and space them closer to 4” apart. 5” spacing that seems to be the MYOG standard and i want to go a bit narrower fot improved down control. Intend to overstuff the chambers 20% and am not overly worried about differential cut for a TQ like I would be for a UQ. I have used the CatsplatV2 and DIY Quilt Calcs spreadsheets in attempt to design this. As far as I can tell the DIY Quilt Calcs have multiple baffle design options, but none of them are vertical. My best solution was to insert my numbers into the Test Top Quilt (No Differential) tab in order to get overall fabric dimensions. I found that the overall shell dimensions don’t change regardless of how many chambers you input in the 1st yellow cell. It looks like my best bet is to slightly increase the baffle spacing on my design drawing so that it scales out to match the additional fabric size to adjust for shrinkage due to loft. Obviously, perimeter seam allowances have to be accounted for.

If I am missing something I would really appreciate advice and experience from those who have done this many times.
55-80 TQ layout.JPGTQ test no diff.JPG

[HoosierT]

A couple of things. Achieving a "lofted" width of 55" won't be possible with standard 58" wide fabrics. Based on my calculation, you will lose roughly .3" of width per chamber due to lofting (based on 2" baffle height/ 2.5" loft). I would also recommend a total baffle of height of 2". It's generally recommended to have 1/2" difference between finished baffle height and desired loft height and most 20* quilts have 2" baffles with 2.5" loft. If you're shooting for a sewn width of 55" after all sewing, including edge seams, then you'll be fine. Now, the other issue I see is that your outside baffles are smaller, which is the opposite of what you want. The outside baffles should be baffle width + 1/2 baffle height to compensate for the radius that will be formed then the outsides round to meet each other. Assuming you're comfortable with a 1/2" seam allowance, which adds a total of 1" to each shell, here is what I recommend:

1st option - 12 baffles, outside baffles are 5.4", inside 10 baffles are 4.4". Fabric cut width of 55.8". Total sewn width of 54.8" Estimated lofted width of 49.2".

Option 2 (full fabric width - 58") - 13 baffles, outside baffles are 5.23", inside 11 baffles are 4.23". No cutting, full width. Total sewn width of 57". Estimated lofted width of 51.1".

Let me know if that helps.

[JoeBobJr]

HoosierT - Thanks for the reply, it definitely helps. I modded the numbers on my baffle layout following your option 2 suggestion. My intent with 1st quilt I make is to get max width out of standard 58" fabric. 2nd quilt needs to be closer to 60" for my buddy that bought 2lbs of 850FP down for both from downlinens. My labor, math and materials in exchange for the down. I should be able to seam vertical fabric strips, essentially sewing on the out 5.23" baffles to main quilt fabric of fifteen 4.23" baffles. Adding 2 more 4.23 baffles chambers to the width prior to the outer 5.23" ones should push the width out the about 59" lofted.

In practice I see all of these numbers rounding to 4.25" & 5.25" widths as I don't see .02" as a realistic measurable difference for my cutting / sewing skill level. I am decent, but that is ultra precise and more of a "on paper" calculation than real life practice.

Thanks51 lofted.JPG

[HoosierT]

Very good and yes I agree on theoretical vs practical. For that reason, I starter from both outside edges when marking baffles and meeting in the middle. In your case, round up to the “.25” number and start from both outside edges. What you’ll end up with is a 4” center baffle. No big deal at all and will never be noticed.

[HoosierT]

Also, if you care to know how I sew baffles, I put out a video on YouTube.
https://youtu.be/__y6tw3MwU4

[JoeBobJr]

Thanks for sharing the link. Very helpful

[JoeBobJr]

Finally came back to post pics of the finished quilt. Have slept multiple times down to low 20s and I am confident that with 15oz, which I calc out as 2oz overstuff, it would be comfortable to 15*.IMG_20190125_130647331.jpgIMG_20190127_105231931.jpg

[ylnfrt]

NICE looking TQ JBJr, I don't see the 4" center baffle- you did good Keep us updated on it's performance and how your buddies TQ works out.

[HoosierT]

Nice work!