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Ann R. Thryft
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Re: The composite sled in a cold neighborhood.
Ann R. Thryft   4/12/2013 11:59:20 AM
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Chuck, hearing that from you makes me smile, since you live in Chicago. The coldest this Californian has ever been in was +19F (in California) and I found it kind of scary, even though properly dressed. I can't even imagine the -49F these guys are expected to encounter.

JimT@Future-Product-Innovations
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Re: A lot of hype
JimT@Future-Product-Innovations   4/10/2013 12:50:28 PM
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Icefield – I love your insights!  Having been born and raised in Detroit was plenty cold enough, so I relocated to Sunny Fort Lauderdale 30 years ago this month.  Your comment of "no big deal" to the residents of a village located north of the Arctic Circle is so unbelievably foreign to me. And your story of the pulka sled from 1960 also brought a smile.  Thanks for sharing details of a lifestyle half-a-world away.

Ann R. Thryft
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Re: A lot of hype
Ann R. Thryft   4/10/2013 12:18:32 PM
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icefield, thanks for the input about sled technologies. Regarding UHMW-PE, it's not hype so much as exposure; some of us who don't encounter skis or sleds regularly haven't heard of the material before or what it can do. The word "Pulka" was capitalized because it's the proper name of a product made by a company, and we gave the derivation from a common noun.



Ann R. Thryft
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Re: In the cold, or on the water, the stuff's amazing
Ann R. Thryft   4/10/2013 12:17:33 PM
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TJ, thanks for the added input on UHMW-PE. I'm totally impressed by this stuff.

icefield
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Bronze
Stiff vs flexible?
icefield   4/10/2013 3:57:56 AM
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Futher to my last message, it is interesting to comtemplate the different engineering philosphy behind a pulka and komatiks/dog sleds.

The former are designed to run at low speed behind a person, so they can be built as a hard stiff shell.

The latter must run at relatively high speed (dogs/snow machines) over very rough terrain (trails, pressure ridges, etc.) so they are designed to be quite flexible. Dog sleds and komatiks are invariably made of wood with the joints tied with rope. Both the strength members and the joints are therefore flexible. If you try to use fasteners, or welded metal for the frames, the sleds fall apart in no time (as many an early European Arctic explorer quickly learned - at least those who thought they knew better than the locals).

It is also easier to repair a sled that is essentially tied together - the repair kit is a spool of string (gut in the old days).

Elizabeth M
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Re: Good choice
Elizabeth M   4/10/2013 3:48:55 AM
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Thanks for the detailed description about that, William K. So I guess it could be done, if some clever designer was up to the challenge.

icefield
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Bronze
A lot of hype
icefield   4/10/2013 3:24:04 AM
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Perhaps there is some innovation in material here, but this does just seem like marketing hype. UHMW has been used on sled runners (e.g., dog sleds, Inuit komatiks, and pulkas) for decades. I own a fibreglass composite pulka with bamboo poles (a amazing material in its own right) that is at least 50 years old. My parents used it to pull me around as an infant in the 60's, and it was already a hand-me-down then. Carbon fibre would, of course, bring the weight down, but my point is that using composites and UHMW for pulkas is far from new.

Svalbard is a beautiful place, but I would not call it extreme. Then again, it's all relative compared to what you know. The island group is inhabited year-round, much like places in arctic Canada/Greenland/Russia/Alaska. It really is no big deal for the people who live there.

As for materials testing, I would think that pulling a 65kg sled behind a ploding person (4km/hr?) for 500km pales in comparison to a somewhat heavier dog sled running the Yukon Quest (1600km bouncing along at 10-15 km/hr). That might be a better promotion for Tikona.

As an aside, "pulka" is the generic Norwegian/Swedish word for a cargo sled (loaded with a child or other gear) that you pull behind you. No need to capitalize it.

TJ McDermott
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In the cold, or on the water, the stuff's amazing
TJ McDermott   4/9/2013 11:12:24 PM
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UHMW-PE is frankly amazing stuff.  It's the plastic of choice for many many packaging machinery manufacturers because of its inertness, low friction, and toughness.  Just about any food you purchase in the supermarket has probably touched UHMW-PE on its way to you.

This material also goes to sea - it can be processed into a fiber and woven into rope that many tugboat companies use for hawser winches - 8-inch circumference rope is quite pliable, soft, and light so it's very easy for deck-hands to manipulate compared to 2" steel cable.  It doesn't have to be carefully spooled onto the winch drum the way steel must be.  Its behavior at failure is much more benign than steel cable too.

Truly amazing material!

 

William K.
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Platinum
Re: Good choice
William K.   4/9/2013 10:37:06 PM
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Elizabeth, The HDPE would be good for a thin coating on skis, but real skis need to be quite a bit stiffer than that could be. Graphite fiber composite may already be in some skis, although it might be to brittle unless some special methods are used. Skis do need to flex a bit, although they could certainly have avariable and non-linear spring rate to provide improved survival along with good control. Quite a complex challenge indeed.

Charles Murray
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Re: The composite sled in a cold neighborhood.
Charles Murray   4/9/2013 7:25:30 PM
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I think you're right about it being an unpleasant place to visit, William K. I just checked on the Internet, and the temperature in Svalbard (which is where the location of Spitsbergen, I believe) is -2F right now. On Thursday, though, the temp will soar to 12F.  

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