Rab Nimbus Jacket Review

1st Jan 2017

Rab Nimbus Jacket

Some time ago I was lucky enough to be involved in some of the testing of Rab's 'synthetic down' garments and I was completely convinced about how useful they would be back then - it is great to see Rab now using this innovative insulation material in some of their jackets.  Synthetic down is a polyester fibre insulation product which mimics down while avoiding its drawbacks.  There are couple of models in the range and I have recently been testing the men's Nimbus......



The Nimbus is a simply featured parka style jacket incorporating a full length YKK Vislon zip, two hard warmer pockets and a zipped internal security pocket.  The hood and cuffs are edged in Lycra and the hood is designed to fit either over or under a helmet.  There is a hem drawcord.

In appearance the Nimbus looks rather similar to Rab's iconic Microlight down jacket but don't be fooled because once you look beyond the appearance this jacket hides its special insulation secret.  This is a essentially a down jacket, but the down is a type of synthetic material called Cirrus and produced by 3M.  Cirrus is designed to mimic the insulating qualities of down while avoiding its drawbacks - largely that down is easily compressed when under another layer and also drastically loses its performance when wet.

The Nimbus has stitched through mini baffles trapping the insulation in place and features Pertex Quantum as the outer shell with a lightweight air permeable nylon lining.  It comes in Rab's regular fit which is designed to fit over other layers and there are a number of colours in the range.


In Use

So is the Nimbus effectively a jacket with the performance of down and yet avoiding its drawbacks?  Sort of.  Firstly, the only thing that will perform as well as down on a weight for weight basis is down (in the higher fill power qualities anyway).  Cirrus insulation is said to be equivalent to 600 fill power down which, while very impressive, still leaves it less insulating when you consider up to 1000 fill power down is now available (although at a significantly higher cost).  It is, however, better insulating than any other type of synthetic insulation currently available.

On the plus side, however, Cirrus is less susceptible to being squashed when worn under other layers and so regains some insulation marks there.  It is also far less affected by moisture and that is where it wins massively and means this jacket is practical for use in a far greater range of conditions.

Rab categorise the Nimbus as a technical all rounder and that is a perfect description.  With down you always need to have in mind how damp the conditions will be but with Cirrus that really isn't an issue at all. Cirrus is said to be twice as insulating as down when wet but also dries quickly and doesn't clump together like wet down is prone to do.  

In use you become almost cavalier about throwing it on in wet weather just because you can!  This has led to some strange looks and comments from friends and clients who think I'm exposing my precious feathers to the rain.....and the devil in me doesn't always explain why I can either!

I tested a Nimbus in size medium and found it roomy enough to wear over a shell and mid layers making it ideal for winter belay duty.  The hood, in my opinion, fits best (and feels cosiest) under a helmet but you could easily pull it over a streamlined helmet without any problem if preferred.  The pockets are placed to be out of the way of a climbing harness if you decide to use it in that way and they work well for warming chilly hands. The internal pocket will easily fit a phone or wallet.  

The other features all work really well too.  The main zip could do with being a 2 way model as sometimes, if I'm using it as a belay jacket, I would like to access the belay plate on my harness by unzipping it, but other than that everything is well thought out and executed with Rab's usual attention to detail. I am really pleased Rab used simple Lycra cuffs (which will stretch over gloves if needed) as they are, in my opinion, far more practical in challenging weather and can't freeze up like Velcro.  

The Nimbus packs neatly into its own pocket and could easily be clipped to a harness for chilly weather climbing or squashes down to a size that, although slightly bulkier than the equivalent down product, is still compact and easily stashable.  Mine has lived pretty much full time in my rucksack over the Autumn months and will be out with me over this winter in all but the most challenging days.

It is a very versatile insulating piece and ideal for the damp UK environment but will perform just as well in any cold conditions.  I also think, at £140 RRP, it is extremely good value.  Full details on the Nimbus are available on the Rab website here and follow the link here to a handy video which explains Cirrus insulation in more detail....

Posted by Paul 

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