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

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 72x20 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!