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Reviews > Sleep Gear > Summer Bags and Liners > Montbell ULAP Thermal Sheet > Test Report by Carol Crooker

December 04, 2007



NAME: Carol Crooker
EMAIL: cmcrooker AT gmail DOT com
AGE: 48
HEIGHT: 5' 10" (1.78 m)
WEIGHT: 165 lb (74.80 kg)
TORSO LENGTH: 19 in (48 cm)
SHOULDER GIRTH: 44 in (112 cm)

For the past 8 years, I've backpacked about 30 days each year. My trips were from 2 to 28 days, with my usual trip being 3 to 6 days long. Most of my trips have been in Arizona with the High Sierras, Oregon, Colorado, Utah, Idaho, Montana, North Carolina, Pennsylvania, and New York thrown in for variety. Weather has varied from 107 F to a low of 0 F (42 to -18 C). Most of my backpacking trips are solo. My three-season base pack weight varies from 13 to 5 pounds (6 - 2 kg), depending on the weather and trip length. My winter base pack weight is about 18 pounds (8 kg). I use a tarp for shelter all year round.



Manufacturer photo

Manufacturer: MontBell
Year of Manufacture: 2007
Manufacturer's Website:
MSRP: US$180
Listed Weight: 14.5 oz (411 g)
Fill Weight: 4.5 oz (128 g)
Temperature Rating: 50 F (10 C)
Fill: 800 fill power down
Shell: Ballistic Airlight (TM) nylon, 15 denier
DWR treatment: POLKATEX (TM)
Maximum User Height: 5 ft 10 in (1.78 m)
Maximum Dimension: 71 - 31.5 in (180 - 80 cm)
Stuffed Size: 4.4 x 8.7 in (11.2 - 22.1 cm)
Color: Muscat

Weight Sleeping Bag: 14.8 oz (420 g)
Weight Stuff Sack: 0.8 oz (23 g)
Loft: 3.0 in (7.6 cm) measured in three places across three chambers, all measurements averaged. Bag was allowed to loft for three days and then "fluffed."
Circumference: Neck 36 in (91 cm), Shoulder 56 in (142 cm), Hip 48 in (122 cm), Foot 34 in (86 cm)


The sleeping bag arrived on July 18, 2007 along with a cotton storage sack and a double drawstring stuff sack. The imprinted label on the sleeping bag and stuff sack as well as the hang tags refer to the "Ultra Light Alpine Down Hugger Thermal Sheet" although the website names this bag the U.L.A.P. Thermal Sheet.

My first thoughts as I pulled the bag out of the box were that is was an "interesting" color, very light weight, narrow and didn't look warm enough for the temperature rating. I could see through the panels in spots where the down was clumped and had settled elsewhere. A zipper runs along one side and the bottom so that the bag can be fully opened. The top of the zipper curves inward above the shoulder to form a neck opening. There is a hook and loop tab at the top of the zipper. The zipper is two-way so the foot can be unzipped for ventilation, or possibly to move around camp. That is something I'll try out during Field Testing. It's nice to be able to wear a sleeping bag when getting up at night.

By "interesting" color, I mean one I don't particularly care for. MontBell calls the color "muskat" which I believe is after the muskat type of white grape used for wine production. The color is what I'd call chartreuse or apple green. However, after a friend pointed out that it is a color found in nature, it is starting to grow on me.

Both sides of the zipper have substantial stiffening tape - stiffer than what I've seen on other lightweight sleeping bags. The neck opening has a drawstring with cordlock. Both the foot end and head end have two loops. The bottom ones could be used to hang the bag for drying and the top two might fit the toggles from the MontBell pillow. The bag is hoodless.

The fabric is very lightweight; I'll be watching for durability during testing. Quality of stitching is excellent. Amazingly for such a light weight bag, it has box baffles rather than being sewn through.

The hang tag is inaccurate. It says the bag has a foot adjustor to shorten the bag - this is not the case on my test bag. It also lists the "Gathered Quilt System" as a feature. The MontBell website defines this as elastic baffles which my test bag does not have as far as I can tell.


The tag attached to the stuff sack gives laundry and storage instructions that are typical of what I've seen on other down gear.


The Thermal Sheet looked much more fluffy after lofting for a couple of days. The down was unclumped and spread more evenly than immediately after shipping. The measured loft of 3 in (7.6 cm), is about the maximum possible. I let the bag loft for several days and fluffed it before making nine measurements and averaging them. I felt more assured that this bag will live up to its temperature rating of 50 F (10 C).

I tried on the bag for size. I was pleased to note that it is plenty long even though I am the maximum recommended height (5 ft 10 in, 1.78 m). The bag is very close fitting - I will see during the Field Test phase what clothing I can wear inside the Thermal Sheet.

The zipper ran easily although I found it awkward to zip around the curve at the shoulder, mainly because there is little room inside the bag to maneuver.

The stuffed size is indeed as listed above. However, it was very difficult to get the sleeping bag into the stuff sack, and I will not do that again unless absolutely needed.


I will use the Thermal Sheet on all my backpacking trips over the next four months. I plan to use it wearing my hiking clothing which is my normal sleep mode, and also see what insulating clothing, if any, will fit in the bag. As the weather on my trips gets cooler I'll see how the Thermal Sheet works as a liner bag inside another bag or under a quilt. I'll use it for ground sleeping and at least once in a hammock. I will sleep in the Thermal Sheet with it zipped up and also spread over me as a quilt.


The Thermal Sheet is well made and the zipper functions smoothly. Out of the box, the down was clumpy leaving large uninsulated spots. After the bag was allowed to loft completely, it started looking like something that would keep me warm at 50 F (10 C). Testing will tell how it performs in the field.

Please check back in two months for my Field Report.



August 25 - 30, Idaho Panhandle along the St Joe River
This six-day packraft trip turned into a two-parter due to very low water levels. It began with three days of backpacking near the upper St Joe River on rocky and forested trails with numerous creek crossings. Elevations ranged from about 4000 ft (1200 m) along the river to 6360 ft (1940 m) along a loop trail.
Starting pack weight was 20 lb (9 kg) with six days of food and without packraft gear.
The next three days consisted of scouting the Skookum Canyon rapids by walking along the asphalt road that parallels the river, running the rapids, driving to a point down river, leaving my car, walking/hitch hiking up the river, then spending two days floating back to my car.
Starting pack weight with the packraft, PFD, paddle and three days of food was about 26 lb (12 kg).
The weather was clear the whole trip with an overnight low of 37 F (3 C) and highs into the 80s F (29 C).

September 27 and 28, Blue Ridge Reservoir in north-central Arizona
This trip introduced a friend and my two-year-old niece to backpacking.
Steep, rocky forest trail descending about a mile (2 km) to the reservoir with a 100 yd (90 m) paddle across to the camp site.
Elevation about 6700 ft (2040 m).
Clear and hot with temperatures into the low 80s F (27 C) and down to 45 F (7 C) overnight.
Starting pack weight including packraft but not a ginormous tent (which I carried in my hand) or toddler (whom I only had to carry a little bit): 33 lb (15 kg).


Thermal Sheet on the packraft mattress.
I had some serious concerns about whether the Thermal Sheet would be adequate to its 50 F (10 C) temperature rating (as I mention in my Initial Report), let alone keep me warm on my Idaho trip where I expected even lower overnight temperatures.

What a surprise! All five nights of my trip had lows below the bag's rating, with the coldest night getting down to 37 F (3 C) - and I slept fine.

Of course my version of "fine" may differ from others'. I am a medium sleeper - colder than some, warmer than some. Fine for me means that I get some sleep. Light shivering is OK if I can sleep through it. Even short sessions of violent shivering are OK if I can warm up and then get back to sleep. I had light shivering on the cooler nights and used my secret weapon (the hooded Cocoon PRO 60 Parka) to add warmth when I had some heavy shivering. I needed to add the parka at about 43 F (6 C). I went to sleep with most of my clothing each night. My sleeping clothing consisted of lightweight long john bottoms and very light nylon pants, ankle height wool socks (I added insulated Integral Designs Hot Socks on cooler nights), a thin wool tank, thin wool long sleeve top, long sleeve sun shirt, 4 oz (113 g) wind jacket with hood, and a fleece hat under the hood. I also zipped the bivy hood up if I got cool.

I wouldn't normally carry long john bottoms, wool long sleeve top or insulated socks for the temperatures I was expecting. I did on this trip since I wanted to have dry camp clothing if I got soaked just before pulling into camp. These items definitely helped stretch my comfort range in the ULAP Thermal Sheet.

Still, I was surprised by my comfort since I had very minimal insulation between me and the ground. The first two nights I used a 29-inch (74 cm) foam pad (Gossamer Gear NightLight Torso) under my torso and my pack with thin foam backpanel under my legs. The last three nights I slept on my overturned packraft with the torso pad in combination with a foam PFD under my legs.

A bivy sack with waterproof bottom and breathable top added warmth but the tiny tarp I slept under on four nights probably did not. The nights were still and the air felt damp and chilly camped next to the river each night.

The third night I slept on the packraft under the open sky. The night was clear with a low of 41 F (5 C). Condensation had wet through my bivy sack by my middle of the night nature call and wet through the Thermal Sheet shell by morning. I was OK all night - just some light shivering.

The zipper tape is nice and stiff. I had no problems zipping and unzipping even around the curve at the top.

The top of the bag curves in above the shoulders which makes it difficult to impossible to stick an arm out the top of the bag without undoing the hook and loop fastener and unzipping the bag a bit. I often reach out to grab my water bottle or my watch to check the outside temperature. On this trip I needed to reach out to turn on my light so I could keep a salt hungry moose from licking my face (as had happened to the last person to camp at Broken Leg Creek).

This bag has a generous length for its specified 5' 10" (178 cm) maximum user height. I'm the maximum height and have plenty of length inside. I don't have to work overly hard on the shimmy-the-bag-up-shuffle to get the top opening up to my neck.

The Thermal Sheet is a very close fit. In some positions I had some down compression at my hips (44 in, 112 cm girth). I had room enough to wear the parka over my 44 in (112 cm) girth shoulders.

I, or rather my companions, used the Thermal Sheet as a quilt on an overnight trip to the Blue Ridge Reservoir to acquaint my two year old niece and an adult friend to backpacking. My niece looked to be warm and cozy under the Thermal Sheet for the first half of the night. At that point, my version of sleeping "fine" came into conflict with my friend's version. She woke me up saying she was shivering and miserable. I gave her the Thermal Sheet to layer under her quilt and my niece and I shared. My friend had a horrible night while my niece and I were "fine" with less down over us. Actually I can't speak for my niece and she can't speak for herself much yet, but she slept deeply, appearing to do much better than "fine." The temperature hovered around 45 F (7 C) all night.

In preparation for colder weather, I checked the fit of the Thermal Sheet inside a Western Mountaineering HighLite bag. The HighLite is known for a close fit itself, but the Thermal Sheet dimensions are about 3 in (8 cm) narrower. I can fit inside the two bags without significant down compression of the Thermal Sheet. There is little room to wear extra leg covering but enough room for a lightweight insulated parka.

Although I won't be encountering cold enough conditions to need the Western Mountaineering UltraLite with a Thermal Sheet inside, I checked the fit anyway. The UltraLite is listed as having the same interior dimensions as the HighLite and the fit of the Thermal Sheet inside it confirmed this.

In my in-home laboratory the Thermal Sheet (with just the bottom zipped) gives good coverage on top of the above bags - an option if more room is needed inside for extra clothing.


So far, I've been pleasantly surprised by the warmth of this bag!


I will continue to use the Thermal Sheet on all my backpacking trips. As the weather cools, I'll combine it with another bag or quilt. I will report my further findings in two months in my Long Term Report.



October 10 - 13, Wilderness of Rocks on Mt Lemmon near Tucson, Arizona
Rocky trails in forest and boulder fields.
Elevation 7400 - 9100 ft (2260 - 2770 m)
Clear with temperatures from the 80s down to 44 F (29 - 7 C) overnight.
Starting pack weight: 20 lb (9 kg).

November 12 - 15, Pisgah National Forest, Mount Mitchell area, North Carolina
Very rocky trails usually covered in dead fall foliage and sometimes flooded or muddy.
Elevation 2800 - 6600 ft (850 - 2000 m)
Cloudy and rainy with temperatures from the 50s (10 - 15 C) down to freezing.
Starting pack weight: 20 lb (9 kg).

November 30 - December 2, near Blue Ridge Reservoir in Coconino National Forest, north-central Arizona
Forest trails, waist deep stream crossing and two swim crossings.
Elevation about 6700 ft (2040 m)
Nearly constant rain with temperatures from the low 50s to high 30s F (11 - 3 C)
Starting pack weight: 20 lb (9 kg).


I used the Thermal Sheet inside a bivy sack and under a tarp in the Wilderness of Rocks in October. I was warm most of the third night (low 44 F, 7 C) except for a few times when my back and butt felt cool when I was on my side. I was very warm and cozy the second night with a low of 57 F (14 C). Interestingly, my back/butt were cold (rather than just cool) at times the first night with the same low temperature (44 F, 7 C) and camped in the same stream side location as the third night (and wearing the same layers). I've noticed before that my body seems to adjust to sleeping outside after a night or two on the ground.

I wore nylon hiking pants, ankle height wool socks and fleece socks, fleece hat, a thin long sleeved wool
top under a sun shirt with a lightweight puffy hooded jacket (Cocoon PRO 60 Parka) on top.

My trip in November to the North Carolina mountains was a nice change for me - I got rained on! I used the Thermal Sheet under a 2 inch plus (5 cm) thick down quilt (Jacks R Better No Sniveller) inside a lightweight bivy and under a tarp. I was expecting - and prepared for - lower temperatures than actually occurred. The extra down insulation saved me from a cold night when my camp site flooded and my tarp blew down.

My first two nights in North Carolina I slept very warm and cozy with a setup worthy of 20 F (-7 C) or lower with actual temperatures down to about 45 F (7 C). The system of fully zipped Thermal Sheet under an open quilt and inside a bivy sack worked great. It felt really warm and of course my movements were no more restricted than when using the Thermal Sheet alone. It did take a few minutes to arrange my sleeping pads, Thermal Sheet and quilt inside the bivy, but climbing in and out wasn't appreciably harder than when using the Thermal Sheet by itself.

The third night was a different environment with lots of rain and wind including periods of very hard rain and high wind gusts. After a few hours deep puddles formed near the head and one side of my bivy sack and at the foot end as well. Two stakes on my tarp blew out even with three rocks on top of each. The stakes were near my head so I reached out of my bivy sack and held the tarp to keep it from blowing away and for rain coverage for a few hours until the water started to seep through the floor of the bivy sack. The Thermal Sheet got wet near my head both inside and out where I was holding the tarp open for fresh air and occasionally reaching out to check the water level.

I moved my camp at about 1 am to a narrow flat spot squeezed between trees and an embankment. There was no room to put up the tarp so I laid it over me with my breathable rain coat over my head for the rest of the night. By morning, the Thermal Sheet was very wet at the head end inside and out and the shell was wet through almost everywhere. There was still some loft left though. The temperature had dropped steadily throughout the night. I stayed warm until 6 am at about 36 F (2 C). I added a thin synthetic insulated parka over my torso which kept me warm enough the last hour of the night.

That was the last night of my trip, so I dried out the Thermal Sheet in a hotel room. It dried overnight and seems as good as new now.

The Thermal Sheet as a mummy liner.
I went back to the Blue Ridge Reservoir area of north-central Arizona at the end of November/beginning of December for three days to try some cold water swimming. It rained constantly starting the first night so, as a bonus, I was able to see how well my chosen clothing kept me warm in constant rain and also how it performed during the waist deep crossing of a flash flooding creek in addition to my planned test of swimming in my clothing.

The first day I hiked a short distance then swam about 50 yards (46 m) across the reservoir. I didn't wear clothes swimming since I was camping at the crossing and there would be no chance to walk my clothes dry. I did not get chilled from the swim and climbed into my bag that night with my body feeling normally warm. The complete cloud cover kept the night warmer than expected with a low of 43 F (6 C). I slept inside a tent with the Thermal Sheet lining a Western Mountaineering HighLite mummy sleeping bag (touted as a 40 F/4 C bag when I bought it). There was enough room that the Thermal Sheet lofted fully inside the mummy bag. I slept very warm and got a good night's sleep.

It rained steadily the second day as I hiked along a section of the Cabin Loop Trail. With fewer stops for snacks and rest during the day, and wearing damp clothing in the evening, I was feeling chilled by the time I climbed into bed. I'd pulled on thin synthetic insulated pants and a parka over my hiking clothes as soon as I shed my rain gear and entered my tent in the evening. I wore everything I had on to bed. The back and seat of my insulated pants were soaked through so I opened the Thermal Sheet and mummy bag and pulled them over me like a quilt to keep my wet pants from compromising the loft of the down bags. Midway through the night when my pants had dried from body heat and my chill was gone I zipped up both bags fully. I slept nice and warm with the bags in quilt and mummy mode. The temperature was 38 F (3 C) at 5 am when I got up to cook breakfast. It was still dark and raining after breakfast so I took a half hour nap with just the Thermal Sheet over me as a quilt. The temperature had dropped to 37 F (3 C) and I stayed warm.

Once it was light out I packed up, hiked a few miles, swam back across the reservoir in full hiking attire, then hot footed it the half mile (1 km) or so up to my car and blessed warmth. When I had packed up the Thermal Sheet at the campsite the shell was slightly damp in places from dragging in rain spatters and from condensation. I spread it out in the car and it quickly dried.


The Thermal Sheet is nicely constructed of quality materials but less than one-third of the total weight is down fill. In many cases there are warmer-for-the-weight options. The wrap around zipper is overkill. A three-quarter length zipper would save some ounces and still allow the Thermal Sheet to be used both as a quilt and as a mummy bag.

What I like:
Zipper tape prevents zipper snags.
Warmer than it looks.
Generous length for specified maximum 5' 10" (178 cm) user height.
Hoodless design means it can be used as a right-zip or left-zip bag.
Fit is close enough to layer inside a closely fitting mummy bag, yet wide enough to wear a thin, puffy jacket underneath with room for each layer to loft.
Tapered, rather than rectangular shape to save weight.

What I don't like:
Thermal efficiency - there is only 4.5 oz (128 g) of down in this 14.5 oz (411 g) bag.
Still don't like the color that much.
Full-length zipper adds unnecessary weight.


The Thermal Sheet will not be my first choice for future solo three-season backpacking trips. For trips where I want a quilt - in a hammock for example - I have a down quilt that weighs the same but has slightly more loft. For mummy bag trips I have a bag that weighs just 1.2 oz (34 g) more and is warmer with more loft and a hood.

The Thermal Sheet could be more of a contender for winter trips; not as a quilt over another bag (although it is wider unzipped than quilts I have, I haven't found extra width necessary for a quilt to stay in place over a mummy bag when both are inside a bivy), but as a liner bag. The Thermal Sheet has the exact right dimensions for my body build (shoulder girth 44 in/112 cm) to line a mummy bag. Its girth is small enough to fit inside close fitting mummy bags, but large enough for me to wear a thin insulated jacket inside.

Another type of trip where I might carry the Thermal Sheet is warm weather trips backpacking with my toddler niece. The Thermal Sheet is wide enough to cover both of us, where a typical quilt is not.

Thanks to BGT and MontBell for the opportunity to test the Thermal Sheet.

This report was created with the Report Writer Version 1. Copyright 2007. All rights reserved.

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