Trip Reports, News & Mountain Conditions for the Sierra Nevada » tents

The best snow wall construction to eliminate drifting on the leeward side

admin — Tue, 25 Oct 2011 08:00:42 +0000

Sometimes a basic snow wall is not sufficient to keep the elements at bay. The wind can drop spindrift on the leeward side thus burying the tents. Is there a solution in the way we can construct snow walls that would make them more efficient?

I asked this question on the Worldwide Expedition professional group on LinkedIn

Hastily erected snow walls

Last year on the Patagonian Icecap we built snow walls as normal. In high winds spindrift gets dumped on the leeward side when the wind hits irregularities in the surface ie snow walls. This gave another problem in that we had good snow walls but the tents behind them got buried! Do you think there is any way the shape or construction of the wall can be improved to eliminate this occurrence? I ask this as I am heading for a rematch in Patagonia in November 2011!

Thanks to the respondents and their excellent suggestions.

Damien Gildea • Richard, I had this problem once at high camp on Vinson. A 3-day storm blew in a lot of new snow and half-buried our VE25, needing lots of digging and a broken pole. I think it might help if you build the wall not so flat to the wind, with more of a V shape, or a U shape, so that the wind blows around the wall more, taking the snow with it, rather than just hitting it flat and dumping its load on your tent. I think it’s also good to make the wall at least as high as the tent, not the same or lower.

Stuart Remensnyder • no doubt shape is a huge factor along with height but something we had good luck with on Denali was a second lower wall in front of the main wall. The biggest mistake we made was taking over and abandoned “dug-in” site which filled in rapidly and we had to dig out in the am from drift snow only. from then on we always set up on a level the same as the main snowpack. good luck in November!

Tim Vogel • I like Stuarts method it tends to help with less snow behind the wall by lessening the eddy foot print (kayak talk) also try tapering the wall back to improve the flow over the wall.

Simon Garrod • Hi Richard, I would agree with the comments so far. I tend to make walls as aerodynamic as possible so the wind flows around them and is therefore less likely to lose momentum and dump snow. I therefore make them curved rather than straight and also back fill the windward (front face) to make an angled slope. This potentially creates less buffeting and hopefully keeps the snow moving. It also reduces the risk of scouring between the snow blocks with prolonged stays and reduces the risk of blocks being blown off and hitting the tent. I had this happen once in a 80 knot plus blow and it ended up breaking my tent partners ribs. My philosophy with walls is that I would rather shovel than have my tent destroyed by the wind, even if they can be a pain to build and maintain! A different tack would be to build lower walls and double pole the tents – just a thought.

Werner Berger • My three climbs on Denali concur fully with the comments made by Simon Garrod. V-shaped walls with packed snow on the windward side, angling to the top and about 6″ to 12″ higher than the tent allows the snow to fly over and get dumped on the downwind side of the tent.

Dave Hartman BS EMTP I/C • I would suggest that you review some basic concepts. First, and foremost, any time you change the velocity of wind, you alter it’s ability to carry snow. The deflection upwards creates a vacuum behind the wall. This causes an eddy which tends to rotate. This causes it to drop it’s velocity i.e. load. This is why you get cornices. It’s also why airplane wings ice up.

The reason the windward side is always cleaner is that the velocity increase can carry more,, thus “scrubs” the ground clean.

I’m not too certain that you can shelter a site and still not have it fill in with drift. Having said that, think about natural areas that are sheltered, and at the same time not drifted. If you can maintain the wind velocity over your site and not create turbulence on the lee you’ll be cleaner. (that’s why an igloo doesn’t accumulate very much). Either a secondary wall on the leeward side to maintain the wind velocity, or positioning your site directly before a negative slope change might work.

I would think combining Werner an Simon’s method of a smooth angled windward wall,, then a secondary leeward structure to minimize turbulence will work best.

Interesting problem! I’ll do some playing around and let the group know what I find. I’m teaching a mountaineering SAR class next month. I’ll turn my students loose on it and see what they come up with. Thanks!!

Stuart Remensnyder • Below is something technical on snow drifting with a number of interesting conclusions including:

“Scalemodel tests by Sherwood (1967a) in the NCEL wind duct have shown that the rate of drift accumulation around the types of at-grade polar buildings at present in use can be reduced by orienting them 45 degrees to the storm wind. These tests have also shown that buildings elevated on solid platforms 2 to 4 feet above the surrounding surface have much less drift than when directly on the surface.”

Dave – If would be great if you can all take some measurements and pics and report back to us!

here is the link to the download pubs.aina.ucalgary.ca/arctic/Arctic22-2-112.pdf

Snow Movement- Drift Control forSurface (At-Grade) Camps
N. S. STEHLEl
ABSTRACT. Snow movement in polar areas creates problems for surface (at-grade) camps,particularlyinareas of net annual snow accumulation. Snowdriftstudies, which were made over a 4-year period around a single unprotected building and around a cluster of buildings in an area of net annual snow accumulation on the Ross Ice Shelf near McMurdo Station, Antarctica, showed that at-grade camps will eventually becomecovered with drifting snow. Driftcontrol measures, however, can be used to increase the usefulness and life of such camps. The measures devel- oped cover proper building orientation and camp layout with respect to the major storm winds. In addition, mobile foundations may be used for buildings to facilitate camp moves when snowdrift becomes excessive.

Dave Hartman BS EMTP I/C • It’s funny,, the more you look at this, the more involved it becomes! I’m looking forward to seeing what my students come up with. Since they’re engineers I suspect they’ll beat it to death. We’ll take pictures and measurements. I wouldn’t be surprised to find there’s a master’s thesis in there somewhere! I’ll report back.

Richard Hartley • Any news on what the students have come up with Dave? I tried v shaped walls and a smaller windward pre wall on the Icecap a few weeks ago. Partly successful but still had some spindrift over the tents. Unfortunately, we were blessed by 3 days of unheard of (in Patagonia anyway) windless and sunny days so werent able to try out slightly differing alternatives. Too tired to take measurements, sorry getting old!

Tents for mountain use in the Sierra Nevada, Alps and Patagonia

admin — Wed, 04 Nov 2009 04:32:27 +0000

A review of the tents we currently use and recommend for year round mountain use in the Sierra Nevada, Alps and Patagonia.

A recent clear out and repair of our tent stocks has made me re-evaluate which tents we use for which location and mountain activity. Basically we recommend high quality tents from well known makes such as Terra Nova, Bibler (now part of Black Diamond) and Hilleberg. Yes, I know there are many other fine tent makers out there, but I can only comment on what has worked for us over the past 10 years as mountain guides.

We don’t compromise for the sake of cost. This is false economy! We always go for the best quality, even though it will invariably be a higher price than competitors. I have a simple way of looking at this. You may end up paying €100 more but if you get 100 better quality nights in the mountains for 2 people then 50 cents a night extra per person is well worth it in my opinion. True?

So what do we recommend you use, when and where? All the tents below have similar characteristics ie. are quite expensive but well made with quality materials that have stood the test of time and use.

Summer Sierra Nevada, Spain (normally Jun until Oct incl)

NalloGTR

2 person lightweight tent

Hilleberg Nallo 2 GT
Weight: 2.6kg (1.3kg a person)
Typical cost: 440GBP
Manufacturers webpage and specification
Comments:

We have used our Nallo for many years. A large and roomy interior with a massive vestibule for storing rucksacks, cooking in, or for somewhere for the dogs to sleep! Well made and stable. Loads of headroom. Simple and quick to erect. We have had 2 poles snap in 8 years use, both on the same night on an incredibly gusty evening camping at Siete Lagunas en route to doing Los Tres Miles 3000m peak traverse. This was in late August so was unexpected!

Hilleberg Akto

1 person lightweight tent

Hilleberg Akto
Weight: 1.5kg (1.5kg a person)
Typical cost: 330GBP
Manufacturers webpage and specification
Comments:

The Akto was my second foray into the 1 man tent sector. My first purchase being a Terra Nova Solar. This is much roomier and I like the large side entrance which is useful for storage and cooking. Strangely, there is only 1 centre pole. The front and back panels do take a bit of getting used to but once erected do function well. Not as stable as a Nallo in cross winds when the centre pole can bend alarmingly. Nevertheless a very light and roomy tent. Also just about suitable for 2 persons who know each other very well!

Jupiter bivvy

1 person hooped bivvy bag

Terra Nova Jupiter
Weight: 840g (840g a person)
Typical cost: 250GBP
Manufacturers webpage and specification
Comments:

I never got to grips with the old style bivvy bags. Sure they worked ok and were very light but the drawback for me was always the claustrophobic nature of the head covering. The advent of hooped bags changed that. One of the best around now is the Terra Nova Jupiter with a massive hooped section. Now you can while away the time reading or playing on your ipod! Terra Nova also do a Saturn bivvy which has a second smaller pole near the foot area. They are low to the ground so getting in and out can be a bit of a pain but they will never get blown over by the winds. Goretex outer ensures it is waterproof.

Winter Sierra Nevada, Spain (normally Nov until May incl)

Ultra Quasar

2 person alpine tent

Terra Nova Ultra Quasar
Weight: 3.3kg (1.75kg a person)
Typical cost: 450GBP (Offers now direct from Terra Nova at 350GBP!)
Manufacturers webpage and specification
Comments:

The Ultra Quasar is a lighter version of the bombproof Quasar (see below). You save 1.1kg and quite a few bucks over it’s expedition style neighbour. Everything else is the same. Great space for 2 (or maybe 3?). The double vestibules are perfect for storage or cooking on those dark winter nights. Ventilation options keep the inside dry on the coldest nights. As everything with Terra Nova, there is a genuine feel of quality about it. Perfect for winter mountaineering in the Sierra Nevada

Summer Alpine (normally June until Sep incl)

i-tent

2 person alpine tent

Bibler I-Tent
Weight: 2.2kg (1.1kg a person)
Typical cost: 500GBP
Manufacturers webpage and specification
Comments:

Single skin Goretex skin. Easy erection from inside even in a blizzard. High head space and narrow footprint for small ledges. Well made, strong and above all…..super light. At only 1.1kg a person, this is an incredible alpine tent. Perfect for 1 or 2 nights out in the high mountains. The only drawback is the lack of a vestibule which unfortunately is an optional add on at 119GBP, but well worth it. I also believe that if I had a choice again I would rather go for the slightly larger El Dorado tent they make. A must have for alpinists!

Patagonian Icefields (Nov and Dec)

Quasar

2 person expedition tent

Terra Nova Quasar
Weight: 4.3kg (2.15kg a person)
Typical cost: 450GBP
Manufacturers webpage and specification
Comments:

THE expedition tent. This is the one I have most confidence in. For taking the worst weather that the Patagonian Icecap can throw at you and never bat an eyelid! When the blizzard is howling outside you will know that there will be no epic story of survival against the odds looming. Spacious, 2 vestibules and strong. I remember once being hit by storm force winds high on Aconcagua (Camp Berlin, I believe). Other climbers were struggling to retain control, but the Quasars, lent to us for the expedition by those nice people at Terra Nova, stood the test. Recommended for expeditions to wild places.

Tents for China?

admin — Sun, 25 May 2008 18:44:41 +0000

Nothing really to do with Spain or the Blog really, but it might affect us.

Ive just heard that the Chinese are looking for tents for the victims and those displaced by the earthquake. All the tents that we buy as mountaineers these days seem to be made in ………………. China!!!!

Am I missing something here?

Isn't the answer to stop making the tents for us in the first place and concentrate all production efforts on the home front? Seems a little silly and a waste of transport money to be sending us requests to return tents that have already once made the journey from China to Europe!

Bet you can still get (and will get for many months to come) as many tents as you want in the outdoor supply shops though!