UKC

Is it possible to add two down jackets of various FPs and weights, and come up with a measure of what that would be if it was one jacket.

Lets say
One jacket is 600 fill power 300g weight 90/10
another one is 700 fill power 120g weight 90/10

Thanks!

In reply to zimpara:

Yes.

In reply to bouldery bits:

And how does one do this?

In reply to zimpara:

Logarithmic algulus

In reply to Yanis Nayu:
No - Its Logarithmic Anatidae

In reply to zimpara:

Two jackets must be warmer than one of the same combined fill weight because of the layer of air between the two.

In reply to zimpara:

Why would you want to - out of curiosity? Won't "near enough' do?

In reply to Trangia:

What are the possible equations?

In reply to zimpara:

PHD are pitching a sleep system where you drop down to a lighter bag but wear your down jacket to sleep in so as to save pack weight. I guess it's the same idea.

In reply to zimpara:


E=mc2

or am I getting confused.............?

In reply to Trangia: Possibly ME + RA b = PHD

In reply to leon 1:

Have some likes!

In reply to zimpara:
The insulation value will be pretty close to the sum of the insulation values. A trapped air gap between them, should it exist, would add some insulation but it is more likely that any air in the gap will be flushed in and out reducing effective insulation (I would guess). However, you don't know what the insulation value is (expressed in kelvin square meters per watt or equivalent is) and so you can't actually do the maths to get the useful quantity, which is the insulation value (you also need the jacket area to calculate a cooling rate).

I guess the answer to your question is 'no'. If you know the weight of down in each jacket (NOT the same as the weight of the jacket you can probably just do a weighted average of the fill power; it probably won't be quite right but shouldn't be too wrong.

In reply to andrewmcleod:

Thanks for teaching these perstering fools something^^ Leon and Co
Cheers Andrew

In reply to zimpara:


Bet they're all grit cretons as well.

In reply to bouldery bits:
nah, alpinists by and large... total chossers lol
Parents always said never trust a stranger with an axe.

In reply to Dave Perry:

Just wondering if I can do without buying a bigger jacket for 6000ers, by buying a lighter one and pairing it with my ME lightline. , so then Ill be more versatile than having a £400 jacket that I use twice

In reply to zimpara:

You are the Marsh Mallow Man and I claim my £5

In reply to olddirtydoggy:


What, you mean like everyone has been doing for years? Sleep Systems, Hydration Systems..... FFS.

In reply to zimpara:

And you could get a third for the 8000ers.

The benefit must depend on fit as well as on an ideal equation. If one gets a bit squashed, which I would have thought is quite likely in places unless designed to be layered, the the overall insulation value will be reduced, perhaps quite severely. This is easily experienced when cramming thicker layers of socks into shoes that don't have the room.

In reply to zimpara:


Of course you can. Blindingly obvious.....

In reply to Robert Durran:

Except the outer one needs to be big and baggy enough not to compress the inner jacket.

In reply to zimpara:

Just wear 17 fleeces.

In reply to bouldery bits:


Or 43 base layers.

In reply to Billy the fish:


Also blindingly obvious.