Space filler construction for a down vest

[Moondog55]

I'm hoping somebody can assist me with sewing advice on sizing.
I'm not financial at BPL anymore and I can't find the thread when Googling.
I want to make my new vest using an inner and outer shell but with the down constrained inside the shell in sewn though mesh constraint channels.
In general I know I do this by making one side [ the inner layer] the size I need and increasing the outer mesh layer by a dimension based on the loft of the finished vest.
Some guidance is needed on how much extra fabric is needed; which I can guestimate based on the finished loft.
So the question really is how much loft can I expect from 150 grams of down when made into an XXXL vest and what would be the best spacing for the seams?

[Neo]

Hi MD I have some feathers to donate to your collection if you like. A Uniqlo seamless ul puffer that the welded baffles let go and most of the feathers sunk to the lower half! Have replaced it with a synthetic puffy and still use my older patched up Uniqlo feather one too.

[Moondog55]

An ounce of 700FP down probably won't go far in an XXXL vest but thanx.
Poorly welded or is welding weaker than stitching?

[Neo]

Guess welding is weaker than stitches. I don't wear it just walking around town though so no complaints otherwise.

[Moondog55]

Do you want anything for it? PM me and we can sort it out

[Neo]

Nah it's a pif. A couple of short air mats too to go up when I get around to it. They go down in the middle of the night and I'm over looking so sleep okay on foam.

[Warin]

I'm hoping somebody can assist me with sewing advice on sizing.

Some guidance is needed on how much extra fabric is needed; which I can guestimate based on the finished loft.
So the question really is how much loft can I expect from 150 grams of down when made into an XXXL vest and what would be the best spacing for the seams?

Loft from 150 grams of down .. depends on the fill rating??? 700 cubic inches of space, it will be filled by

1 oz of 700 fill power down = 700 cubic inches..

so 28.3495 g of 700 fill = 11.4709 liters( 11470.7 cubic cm)

You can work out 150/28 * 11.47 for liters

Calculate the inner area ... then divide the volume by this area (in square cm) and you have the height of the fill on your inner (in cm).. ~ the same as the spacing for seams .. but most like something a little smaller say -15%?

[Moondog55]

OK So the inner 1400 * 750mm
It's FP is a good bit better than 700 but I'd prefer to be conservative.
It's going to be about 50 to 60mm of loft I think.
If I make the stitch spacing 100mm then the outer layer will need to be 50 to 100mm longer than the inner for every line of stitching.
With eight lines of stitching that means an extra metre of fabric needed, I'll have to go shopping if I don't have enough in my stash.
That sort of loft is about what the Mont Icicle vest has and should be warm enough, maybe even a little too warm

[rider]

There are lots of calculators and assistance on HAMMOCK FORUMS; under quilts need a differential cut to ensure the lofting while one side is pressed against the hanger

You should find some help there