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Welcome! Ultralight backpacking is my passion, and keeping up on new technologies, gear, and techniques relevant to UL backpacking is what floats my boat. I'm always looking for the lightest, most functional gear to improve a lightweight or ultralight backpacking kit, and report my impressions and field testing results here. For hikers wanting to keep up on the latest and greatest ultralight backpacking gear, this is a good place to hang out. Also, there is a lot of information here (and on our informational website Southwest Ultralight Backpacking) on useful techniques and backcountry etiquette -- food for thought for hikers wanting to lighten their load and their impacts.

My goal for Ultralight Insights is to understand, test, and report on new technologies and gear of interest to lightweight and ultralight backpackers. It's a passion after all, so we just plain enjoy talking about it. I hope readers will add their own wisdom and comments, respond to my questions, ask their own questions, and correct me if I get something wrong. Happy hiking! Will

Sunday, August 3, 2014

GEAR REVIEW: Big Sky International Wisp 1P Tent (1-person, single-wall, trekking pole supported)



By Will Rietveld

Introduction

Big Sky International has been a leader in providing lightweight, roomy, and user-friendly tents for lightweight backpacking and camping. Notably they were one of the first companies to break the 3-pound barrier for a two-person double wall freestanding tent.

Until now, most Big Sky tents are designed with a lightweight pole set, typically in an X-pattern. But dedicated poles add a significant amount of weight – typically around 12 ounces or so – to the total weight of a tent. Utilizing trekking poles to support a shelter eliminates that weight, bringing the total weight down to impressive lightweight levels. Note that most trekking pole supported shelters are single wall, and this design only benefits hikers who normally use trekking poles.

The new Big Sky Wisp 1-person, single-wall, trekking pole supported tent will be available in several fabric options, three of them shown here. Tent weight varies with the fabric option chosen. Details below.

 

Description

The following photo tour provides information on most of the Wisp’s design elements and features. Photo series is of the Wisp with SuprSil SUL fabric option.

Top View. The Wisp 1P is supported by one vertical trekking pole set at 47 inches near the head end and a built-in 15-inch vertical strut at the foot end. There is an external entry vestibule (opposite side in photo) and an internal storage vestibule on the facing side.
Entry Side. The side entry is protected by a roomy vestibule.
Vestibule Open. One side of the vestibule ties back to provide lots of ventilation and views in good weather. A mesh wall with a large zippered entry door provides easy entry and bug protection. The internal gear storage vestibule is visible in the back. There is a mesh storage pocket inside to the right of the door.

Single Trekking Pole Support. The tent is supported by a single adjustable length trekking pole set at 47 inches located to the right of the entry door
Inside, Foot End. The floor measures 39 inches wide by 91 inches long (plus the storage vestibule), so this is a good tent for taller hikers. The foot end has a mesh vent. There is enough headroom to reach items at the foot of the tent.
Inside, Head End. The head end is roomy and has lots of headroom. There is room for gear storage in the internal vestibule to the sleeper’s right and behind her head, as well as the external vestibule. The blue rectangle is a groundsheet under the floor.

Outside, Head End. The head end has three steep panels in an asymmetrical design to achieve the desired features: large entry vestibule, steep sided head end for headroom, and interior gear vestibule.
Top Vent. There is a closable small high vent at the peak, which is a good feature to utilize the “chimney effect” for ventilation.

Back Side. The back side of the tent is solid fabric with two panels to create the internal storage vestibule.
Foot End.  The triangular foot end of the tent is supported by a vertical strut inside and secured with three guylines.

Perimeter Seam. Unlike many single wall tents, the Wisp does not have a mesh skirt around the perimeter. Rather, the sidewalls are sewn directly to the floor. All seams are bound for extra strength, and are sealed at the factory. According to their website, Big Sky tents do not require seam sealing by the user like silnylon tents from some manufacturers.

 

Fabric Options

I previously omitted details about the Wisp’s shell fabric because there are lots of options, five of them to be exact. Big Sky sells their tents ala carte, so you choose individual tent components from a list of options to create the configuration you want. Tent weights below do not include a trekking pole, storage sack, stakes, or guylines because those are options chosen by the buyer.

  1. 40 denier silicone/polyurethane coated ripstop nylon, with aluminum foot end strut – Available soon, XX ounces, about $149.95. This will be a budget version for Boy Scouts, etc. where price is an issue.
  2. SuprSil shell and floor, aluminum strut – SuprSil is similar in weight to regular 30 denier silnylon, but stronger. Available now, 20 ounces, $199.95.
  3. SuprSil-UL shell, SuprSil floor, aluminum strut – SuprSil UL is best described as a lighter weight of silnylon, about 20 denier. Available now, 18 ounces, $234.95.
  4. SuprSil-SUL shell, SuprSil UL floor, carbon fiber strut – SuprSil SUL is a still lighter version of silnylon, around 10 denier, and is not a ripstop like the others. Available now, 14 ounces, $339.95.
  5. Let-it-Por™ shell and floor, carbon fiber strut – Big Sky’s Let-it-Por shell is Cuben Fiber. Available soon, 10.6 ounces, $499.95.

 

Home Testing

Before heading out to the field, I wanted to evaluate several items so I could be as well prepared as possible. These included a good staking and guyline scenario for wind stability, need for a groundsheet, and a test of the tent’s weatherproofness.

Staking and Wind Stability. The Wisp is secured by seven stakes around the perimeter: three at the head end, three at the foot end, and one on the vestibule. Without any guylines, the tent is a bit topsy-turvy, meaning wind gusts can distort the canopy a lot. I tested different guyline configurations and found the combination shown works best to stabilize the tent. One guyline connects to two loops on the head end and the other connects to one loop on the back side. Adding extra guylines to the vestibule or foot end did not seem to make a difference. One vulnerability is the guyline attachments to tent seams, especially for the SuprSil SUL shell; it’s worrisome whether the ultra-thin fabric will withstand strong wind gusts without ripping out.
Floor Fabric. The SuprSil SUL version of the Wisp has a SuprSil UL floor, which is quite thin, as shown.

 

Initial Impressions



  • The Wisp sets up fast: simply stake out the perimeter, insert the trekking pole, stake the vestibule, and stake the guylines.
  • The tent is very ergonomic -- easy to enter and exit, easy to organize gear, and easy to reach everything.
  • With seven stakes around the perimeter, wind does not lift the tent floor up very much. Other tents with a floating bathtub floor can have a problem with floor lift. Also, the lack of a perimeter mesh skirt keeps wind from blowing through the tent.
  • As expected, adding two guylines to the head end provides good stability in moderate winds. I have not yet tested it in strong wind.
  • The thin floor of the ultralight versions of the Wisp needs to be tested in a variety of conditions. A floor this thin would seem to require more protection, so many users are likely to use a heavier groundsheet. That would negate the weight savings from the lighter fabrics in this tent. I have routinely used tents with a regular silnylon floor without a groundsheet, and have tested a tent with a thin mesh floor, with no problems. I will focus my field testing on the SuprSil SUL version to see how the thinner fabric holds up.
  • The Wisp stayed dry inside in light showers, but field testing is definitely needed to determine how storm worthy it is in heavy rain.
  • Condensation is another important item to evaluate in the field. The Wisp has minimal cross ventilation, so it’s possible that condensation will be a problem. Because of its one trekking pole support the back wall of the tent slopes sharply inward, so there may be a problem contacting condensation when sitting up in the tent.
  • At this time it appears that the Wisp with SuprSil UL fabric (18 ounces, $234.95) is the best balance of durability, lightweight, and cost. The SuprSil UL fabric option costs only $35 more than the basic SuprSil version, while the SuprSil SUL option costs $140 more, and the Cuben Fiber shell option costs $300 more.

 

Field Testing

I have tested the Wisp 1P on two overnight outings so far. The version I tested has the "Let-It-Por" shell and floor, which is Cuben Fiber. The weight is 10.7 ounces without stakes. On trip one, daytime temperatures were in the 70sF, the night was clear and calm, and the morning temperature was 41F. On the second outing daytime temperatures were in the 60sF, the night was again clear and calm, and the morning temperature was 29F. 

On both nights I left the zippered mesh entry door open all night and zipped the vestibule closed. Available sources of ventilation are a mesh panel at the foot end, the top vent, and the open mesh door. The vestibule has about a 6-inch gap around the bottom for ventilation.


I tested the Wisp 1P on two outings. This camp was in a mountain meadow at 8100 feet. The night was clear and calm with a 35 degree temperature drop.
 
On both nights I experienced a lot of condensation on the inside walls of the Wisp, as shown.
 
Because the back wall of the tent slopes sharply inward to the tents peak, which is at the other side of the tent, contact with the wet interior walls was unavoidable. The result was streaks of water running down the interior walls of the tent and puddling at the floor. The clothing I was wearing got wet in places, and my sleeping bag absorbed some water where it contacted the back wall of the tent.


This photo shows the angled back wall of the tent, which extends from the back of the tent completely over to the other side of the tent. Sitting on an air mattress, my head contacts the tent wall, and it is easy to contact the wall with my right shoulder and arm.

Tent condensation is normal on a clear, calm night with a large temperature drop. There is no air movement through the tent to exhaust moisture from a sleeper's breathing. Most tents remain dry inside if there is at least some air movement (a breeze) during the night, and it helps a lot to leave the mesh entry door open, if bugs are not a problem.

So, condensation is an unavoidable consequence of physics on a clear, calm night with a large temperature drop. To live with condensation, it helps a lot to have ample elbow room inside the tent so you don't contact the tent walls. That's where the problem lies with the Wisp; the back wall crowds you and you can't avoid getting wet.

The Big Sky International Wisp 1 has more condensation than many other tents I have tested, which means it needs more incoming ventilation. For air to enter at the foot end of the tent, it needs to go under the tent canopy which extends almost to the ground. Given the tent's complex geometry, it would be difficult to re-design it to eliminate the issues discussed here.

Also, as I pointed out in another post, it's easy to counter tent condensation with a simple piece of equipment -- a pack towel, wash cloth, or bandana to wipe the tent walls in the morning. A single-wall tent actually makes it easier to mop up condensation because the water is easily accessible on the inside walls. A double-wall tent develops condensation the same as a single-wall tent, only its on the inside of the fly where it is much less accessible.

4 comments:

  1. Thanks for this, I look forward to hearing more about it. I emailed Big Sky a couple weeks back but got no reply. I asked what weight of cuben they were using for the floor and fly - do you know? I also asked how they thought it would perform in warmer humid conditions.

    ReplyDelete
  2. Did Big Sky ever reply to your query? My concerns, also.

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    Replies
    1. they have not for me

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  3. Big Sky has not ever answered one of my questions. They sent out the wrong pieces to a 2 person tent and did not bother to reply making the tent totally useless.
    This site is picky on guests

    ReplyDelete