Companion forum thread to:

Rab Microlight Jacket Review

I'm curious about the 1.5" spacing of the horizontal quilting/baffles that you see in a lot of these down jackets (Rab, Patagonia, Mtn Hardware, North Face etc).

It seems to me that this is less efficient than using wider baffles (ie. Montbell) because this single layer quilting reduces the loft to zero at every line of stitching. Wouldn't less be better to a certain extent?

Is this done for style reasons? It seems excessive for simply keeping the down in place.

Edited by dandydan on 11/04/2009 01:00:43 MST.

I spent weeks researching insulation jackets. I settled for the Rab Microlight for a handful of reasons. As the article noted, it is very waterproof, tough for its weight, versatile, and certainly best in class.

Unfortunately, my local outdoor shop, Ozark Outdoors, is located in the middle of Too Much Money Street and carries a heavy stock of Patagonia and North Face. Fortunately, they recently started to carry Rab. I was excited to see slightly more technical gear and was thrilled about being able to try Rab gear. The extra large, at 337 grams, layered perfectly with my shells, fit and layered better than the Western Mountaineering jackets I tried, and weighed nearly the same or better as its competitors after storage considerations.

I considered the small baffles as a potential problem for cold spots, but I reckoned the Microlight fabric will go far to help deter that a bit.

Its fair to say, Dan, that a minor consideration for picking up this jacket was how sharp it looked. I can wear it around town without feeling restricted or fat - the many stitches helps that considerably.

Jack

Love the goat(s) pic (and caption)--kudos to Janet!

Great review, as usual, Will. This category is getting crowded with fine contenders.

Cheers,

Rick

Is the neck perhaps a bit loose? If it's going to be loose like this then there isn't much point in having insulation in the neck collar.

I find with quite a few insulated jkts that they don't fit my neck well when zipped up (or really anyones neck besides steroid juicing body builders). It seems like manufacturers in general make the necks too large so they look better when they are unzipped and folded down, and presumably, so they don't risk anyone finding the neck too tight.

This isn't really a knock against the Microlight, but rather something I'd like to see manufacturers in general tighten up. I had a MEC jacket that was way too loose in the neck and as a result I had a lot of heat escaping.

Edited by dandydan on 11/04/2009 14:36:32 MST.

Dan,

Yes, the neck is too loose on Will. Will’s garment reviews are my favorite BPL content. He analyzes garments differently than I do but, I never fail to gain valuable additional insights from his reviews. After his highly recommended review of the WM Hooded Flash, I just had to try one on… I hated it. In a large measure this was because it fit me very differently than it fit Will. The size that maximized my torso warmth (see below), had hood dimensions that were totally ineffective. Compounding that, there were no adjustments to alter any aspect of the fit. It was my most recent reminder that “size matters”.

For any jacket to achieve its maximum insulation potential the neck has to seal, as does the wrists, and waist. Otherwise you have "chimney effect" heat loss when inactive. As your body heats air around your torso, it rises and goes out your neck. This in turn actively draws cold air up from the openings in the waist and wrist area.

You want the body of the jacket to be loose so as to maximize the garment warmth. The air space between the jacket and your next inner layer acts as additional insulation up to a max of about 3/4”. If you are moving, then the “billows effect” will pump both excess moisture and warmth out of your jacket. This is the reason that a down jacket doesn’t loose its insulating value in environments which it would be less than optimal for a down sleeping bag. For UL backpacking you normally only wear your insulation layer when your relatively stationary. Consequently, the warmth doesn’t billow out when you most need it; for example cooking breakfast or dinner. As you become more active, then your MET rate goes up and you want the billows effect to extend your thermal neutral range.

I alter the neck and wrists of many of my jackets to achieve their full warmth potential. All that is required is a needle, some polyester or nylon thread, and about a half hour of time. A neck looks best if it is taken in at both shoulder seams. If you take it in by using a single seam in the back of the neck, you will get a "hump back" material blossoming below the seam. Pin it and then try it on to insure you have the proper size prior to sewing.





The insulation value of an air space falls off rapidly when the air space is any measure thinner than 3/16 inch. The thickness of the insulating air films on each surface is reduced. The R value increases up to about ¾ inch when air convection in this space begins to offset any increase in distance between the surfaces. Although not relevant to jacket fit, the curve remains fairly level in this range with the insulation value near 1 until the curve exceeds 4 inches. Beyond 4 inches, convection currents disturb the air films and cause the R value of the air space to decrease.

Edited by richard295 on 11/04/2009 17:33:12 MST.

Wow that was a great post. Very informative. Thanks.

I own a Microlight Vest from Rab and am very happy with it. I experienced the same issue with loosing down, but its not too bad. In the summer I also use it as a pillow at night, and in the winter I layer it with my Klättermusen Loke for some very nice warmth. Great piece of UL gear, for a good price.

Edited by skullmonkey on 11/04/2009 23:51:24 MST.

> For any jacket to achieve its maximum insulation potential the neck has to seal, as does the wrists, and WAIST.

... said Richard

On which subject, what's with the lack of waist drawcords on modern shells? All canvas/ventile etc. mountain anoraks used to have them.

I really miss one on my Patagonia Ascentionist soft shell, which I otherwise love and wear pretty much all the time on the hills from Autumn to Spring. The hem seals ok but the cut on the torso is fairly loose - I bought mine sized to go over plenty of insulation if necessary, although it's usually fine over a baselayer or two when I'm moving. I'm sure being able to snug the waist in would make it a lot more thermally efficient than walking around in a loose bag of convecting air.

Why does almost nobody do this any more? I assume it's purely about looks over function.

(Yes I know I could, in theory, learn to sew well enough to put a waist drawcord in myself. Maybe I even will one day)

Edited by AlanL on 11/05/2009 00:18:08 MST.

Richard, would you be willing to hazard an estimated CLO for this jacket?

Reason I ask is I've always backed away from low loft down things (OK, this one might be considered low-medium loft) because the fabric weight is much more than the insulation weight ... diluting the value for the $$$ paid for good quality down.

The outer shell weighs 1.3oz/yd^2 and the inner (30d) probably 1.1oz/yd^2 (1.2-1.3 if it contains ANY DWR) ... easily more than the weight of the down (which I might guess to be around 1.5oz/yd^2 based on Will's data of 4.4oz of down fill in a size large).

Jim,

Based on my lab testing of many down jackets last year, they are most closely correlated with warmth based on their amount of fill. The Rab Microlight (M) has 4.4 oz of (750+) fill. I previously posted the iclo values for the Montbell product line. The Rab Microlight is closest in insulation value to the MB Alpine Light Down’s 4 oz and 2.51 Iclo. Factoring for the slightly different fill weight, I estimate that the Rab Microlight would test ~ 4.4/4 * 2.51 = 2.761. Assume you wore typical a typical winter weight base layer clothes grouping (1 clo) under the jacket and used it for typical camp activities (1.5 MET). Also assume you are an average male. This would yield a comfort to extreme temp range of ~37F to 19F. Sanity testing the physics calculations versus Will’s real world experience, they jive. He said, “The Microlight Jacket is warm down to about freezing at a low activity level…”

You have a valid point about the relative contribution of the non insulation component of a jacket. Your solution to only use high insulation jackets is one option. Another option is to mitigate the non-insulation weight by selecting very high tenacity / low denier nylon fiber fabrics. Use that in combination with an appropriately sized shell to handle the potential abrasion and water repellency issues. The second approach yields the additional benefit of a significant increase in the insulation efficiency of sewn through down insulation. The seam channels form insulating air gaps between the jacket and the shell (hard or Windshirt). It also eliminates the potential water leakage from down channel seams.

Edited by richard295 on 11/06/2009 09:07:53 MST.

This jacket seems very heavy compared to my Backpacking light cocoon

It is heavier, but it should be quite a bit warmer than the Cocoon, plus you can actually buy one!

My Cocoon is my favorite piece of year. I can't believe the warmth it provides.

Another great review from Will!

AC

Like the Yeti Purity Jacket, there are so many horizontal baffels on the Rab Microlight Jacket, and I wonder why just like Dan said before. It makes no sense - its heavier (more stitches) and colder (more cold spots), and it is not necessary (see PHD Utra Down Vest: http://www.phdesigns.co.uk/product_info.php?cat=111&products_id=202 wich can cope with only 7 horinzontal baffels). Taking the loss and the medium quality of the down into account (PHD uses 900 cuin), this jacket is not the real winner for me. Or am I missing something maybe?

Thanks for the CLO info Richard.

I wasn't actually saying to use high insulation jackets only. What I tried (failed) to convey is that if cost is much of a factor (is for me) then spend $$$ on down for those situations where you need a high CLO value that could only be provided by a lot of bulk and weight if you use synthetics.

Regarding a separate shell. Yes, yes and yes! For me, winter clothing starts with oversized wind pants, shell mittens and hooded shell jacket ... both with good closures on all openings. Then I can insulate underneath those to match the day's conditions.

I'm puzzled why the fill-power wasn't explained better. Rab use European fill-power ratings, so 750 EU is equivelant to 850 US. More details on this Rab page HERE

I've a phd UL on order - 900 EU fill power!

"I've a phd UL on order - 900 EU fill power!"


How many ounces/grams of down? I'll bet you don't know? ;)