RAB Top Bag Questions

Rab makes top-quality stuff. I have their Drillium jacket (eVent) and it is fantastic. Their website with that bag does not list a temp rating. The bag weighs 19.4 ounces and its fill weight is 7.05 ounces.
http://www.rab.uk.com/equipment/sleeping_bags/the_quantum_series—116/

Feathered Friend's 30 degree bag with the least fill is has 11.5 ounces of down. WM's Highlite has 8 oz of fill and is rated to 35 degrees. The Nunatak Arc Edge in medium has 5.5 ounces of fill and is rated to 40; the Arc Specialist and Ghost have 8 ounces down fill and is rated to 32. Finally, the GG SleepLight (by Nunatak) has 7 oz of down fill in regular and is rated to about 32 degrees. The Sleeplight also does not have any down underneath of it.

Looking at these specs and the continuation of the Rab bags, I would venture an unscientific guess that the bag would carry about a 40 degree rating.

Richard Nisley could give you a scientific answer by calculating CLO values – he's your best bet for a dependable answer.

Rab are a well respected brand here in the UK. They make quality kit, and i own / have owned a lot of their gear. Have a look at their website here

I currently use the previous version of the RAB top bag (15 oz) for three season backpacking. The website rated mine as a 32 degree F bag in the past, but I am usually chilly at that temp (I sometimes don't have enough ground insulation when using the GG nightlight torso). This new bag has been reviewed by BPL.

Thank y'all. That is exactly what I wanted to know.

Kyle,
Rab is indeed well respected but isnt necessarily on the SUL side. The Tpobag AR is down with primaloft in the underside of the foot box (ostensibly so that if you use it on short pad or not in full shelter that part can wet a bit and still perform)
I looked seriously into them (for a lightweight summerish bag) and here is some data (excuse my metric):
Rab topbag AR – rated(-1C) Tot weight 564g, fill wt200g 850US down 133g/sqm PL1 foot; price 200$; has hood, no zip
Nunatak Catabatic – rated 0C, totwt 397g, fillwt – 227g 800+US, price 347$, no hood, no zip but you can ask for custom
WM Hilite – rated +2C, totwt 455g, fill 225g 850+US, hood, half zip, 260$
Nunatak sub alpinist – rated +2, 397g, 156g, 340$, center half zip with great hood
PHD – Minimus assuming MX fabric and 900down options – rated 0~+5, 425g, 180g 900EU (!!!!), 280$, no zip but can put one in since custom

so basically the Rab is good gear and pretty cheap but not reallt UL and you pay a price in flexibility when you go for a topbag

also note that on WM you might get lucky and find a used/sale since it is relatively big brand

Mike

Mike,
So which bag did you end up going with. It looks like I was a little to optimistic (and my ignorance is showing) about the RAB Top Bag, because I am looking for a bag that'll be comfortable at about 20 degrees(F).

Kyle,
I already own a WM versalite and a Nunatak custom Alpinist with overfill that Tom thinks he would rate at around 10F. On top of that i have two 45F bags that are OK but not SUL and i have just ordered an MLDXP 2.5oz quilt…..
My plan (and it might not work for others…or for me for that matter) is to buy a SUL summer bag (im closing in on the PHD or Nunatak just cause i love customability) and take my MB down inner/parka +pants or PAta MPpants+ RAB primaloft/montane PL jacket + down booties to sleep down to about 20~25 hopefully.
I will use the MLD quilt when humidity or exposed conditions (like bivi/rain) and can easily layer the MLD quilt on top of th esummer bag (or any other one for taht matter) since it doesnt have a fully closed footbox like the Nunatak ARCs.
So my system is going to be:
Dry/tent=summerbag+clothes down to 20F
Exposed=MLD+clothes down to probabaly 25~30F
20~10=summer+MLD
below 10 or so=Alpinist+MLD

I havent tested this yet, but as stated i am copying a fellow BPL guy (john fredricks) and the concept of the MLD quilt as top bag makes sense cause its synthetic (so dew point will probabaly be in it and not the down which is better) and has a fully openable construction which means can be thrwon over any girth bag w/o loft compression issues

Mike