http://www.phdesigns.co.uk/product_info ... cts_id=366

Interesting summer/minimal bag option? Been very impressed with the minim ultra and this saves 100g as well as being useful with other bags.

Isn't it the best part of £200? I know ultra-light is the epitome of getting funk all for your money but when I saw the ad for this (or rather the price) it just seemed bonkers.

HYOH mind 8-)

yeah true, but the down they use really is nice ..

Looks chilly, and tbh, would probably give the same insulation as my £20 silk liner which also weighs only 100g

Here's some interesting information about down: Outsideonline.com (US Mag)

For those that can't be bothered clicking, it basically says that down feathers are basically proteins that break down over time...understandable, but it then goes on to say that the higher the loft, the quicker it breaks down. This wasn't something I'd even considered when I bought my sleeping bag (Minim Ultra too)!

For those that can't be bothered clicking, it basically says that down feathers are basically proteins that break down over time...understandable, but it then goes on to say that the higher the loft, the quicker it breaks down. This wasn't something I'd even considered when I bought my sleeping bag (Minim Ultra too)!

Something else to consider too which is sort of related, is the way insulation behaves when it's subjected to wind. High FP down tends to compress more than lower FP, so loses more of its insulation properties in breezy conditions.

So, it's being sold primarily as an addition to an existing bag. If it adds 10 degrees to the rating of a bag, that means that paired with a minim ultra it'll go to -8 degrees. And weigh less than 600g. I reckon that's pretty good, and if you have a light weight bag already, it's cheaper than buying a new single PHD winter bag.

High FP down tends to compress more than lower FP

How Stuart?

Looking at the machine that tests it, fill power is the strength of the down under compression from a load placed upon it, the higher the fill power the less it compresses.

How does it behave differently under load from wind rather than mass?

They've been coming up with some interesting minimalist ideas recently. The Wafer series is next-level lightness, but I actually thought this half-bag looks more interesting:

http://www.phdesigns.co.uk/product_info ... cts_id=365

How Stuart?

Looking at the machine that tests it, fill power is the strength of the down under compression from a load placed upon it, the higher the fill power the less it compresses.

How does it behave differently under load from wind rather than mass?

It was an article on BPL. They tested lots of different types of insulation to see how they dealt with compression due to wind ... I can't recall the exact details but I'll try and find them and post up the general findings.

So, it's being sold primarily as an addition to an existing bag. If it adds 10 degrees to the rating of a bag, that means that paired with a minim ultra it'll go to -8 degrees. And weigh less than 600g. I reckon that's pretty good, and if you have a light weight bag already, it's cheaper than buying a new single PHD winter bag.

I agree ... okay so it's not cheap but if you compare it with something like a Mont-bell Spiral Down Hugger which is designed to do the same job it starts to look more reasonable.

I suppose in the fill power tests, the sides of the vessel the used restricts movement in only allowing down-ward compression (did you see what I did there). In a sleeping bag, the down can move more freely, supposedly if exposed to wind, and lighter/ higher FP down moves more easily than down with a lower FP? Dunno, but it seems like BPL are splitting hairs (or feathers) a bit on this one IYAM. Surely the issue would be overcome by camping in a more sheltered spot?

It was an article on BPL. They tested lots of different types of insulation to see how they dealt with compression due to wind ... I can't recall the exact details but I'll try and find them and post up the general findings.

Sorry ... my BPL membership has expired so I can't access the article but here's a summary of what it was about.


Article Summary:

The wind can rob you of heat in more than one way. We often discuss heat loss as due to several methods, such as conduction, convection, radiation, and transfer of energy by phase change (evaporation). The other less known way that we get cold is because wind compresses our insulation making it less efficient.

Since cooling by conduction, convection, radiation, and evaporation are fairly well known subjects, we will review them only briefly in this study. The main purpose of this report is to discuss the other forms of cooling caused by the compression of insulation during high winds.

ARTICLE OUTLINE

Introduction
Cooling by conduction, convection, radiation, and evaporation
Cooling caused by compression of insulation
Thermal conductivity versus insulation value
Wind pressure
Loft versus density
How much do different insulations compress in the wind
Discussion of percent insulation loss
What does this mean
Warmth for the ounce
Warmth for the buck
Gloves, mittens, and sleeping bag bottoms
What can we do to reduce wind compression?
Extra insulation
Storm shell
Rain shells and wind shells
Fleece or wool
Conclusions
Recommendations