Fill Density

[DAVE DREHER]

I searched for quit awhile and just could not find an answer. What I'm doing is filling a exped type sleeping pad. And maybe the answer was there but I did not understand. anyway

My question is what is the optimal density or compression for down.

The one I'm using is a 750 fill weight I can calculate the approximate area of my bag,,I just can't find a formula for calculating the best fill percentage,,,I don't mind an overfill of sorts, but dont want to under fill.

Any formulas out there? Or rules of thumb.

Thanks

[>> Bender <<]

Dave,

For garments and sleeping bags the rule of thumb is 10-20% overfill. In a sleeping pad you do not have to rely on the down to loft the shell material. This means you can get away with very little down; it will still fully loft and provide useful insulation value. The amount of down used versus R value is roughly linear until you start getting into extreme over stuffing. For a ballpark figure using a standard 72×20 pad I would give 5oz of down an R value of 5 and so on. I say ballpark because design and many other factors do play a role.

I know it can be a tricky topic to research because most of the available information is related to garments, sleeping bags and quilts. I would love to see lab testing done specifically for down mats.

Good luck on the project Dave. Keep us updated and be sure to post some pictures!

[Author]

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