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Tarp Size Rules of Thumb?
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John Julyan-Gudgeon
(Cyanide) - F

Locale: Red Deer, Alberta, Canada
Tarp Size Rules of Thumb? on 09/19/2011 19:27:22 MDT Print View

Hey all

I am crunching numbers and designing/redesigning a cuben tarp.

But, I must say I am having a hard time determining the size I will ultimately cut this tarp to.

The uses:

solo shelter for a 6'3" guy who uses a tyvek groundsheet and no bivy

Likes to sit up in the shelter when it is raining sideways.

Also:

would like the tarp to do double duty as a shelter for myself and my two children as they get older (say up to 12 yo before I replace the tarp). But, no need to sit up when the kids are with me.

Configurations:

typically A-frame with optional front and back beaks that seal the two ends.
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So, the natural conclusion I draw is:
106" wide (8'10") which is two widths of a standard bolt of cuben (54") losing an inch on either side for seams.

114" long (9'6") which is 3 feet longer than I am.

Likely to use two treking poles, but commonly a ridgeline cord between trees.

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So, does anyone's experience lead them to some pearls of wisdom or rules of thumb regarding what sizes are too large, or too small?

Thanks in advance.

Cheers

John

Edited by Cyanide on 09/19/2011 19:29:07 MDT.

Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: Tarp Size Rules of Thumb? on 09/28/2011 22:00:14 MDT Print View

John,

Can't comment on the 2 kids. But for me...

5' X 8' Poncho tarp requires a bivy for splash, etc.

8' 10' requires no bivy. Can sleep two people theoretically. But I almost never hike with company. I think this size would work for you.

John Julyan-Gudgeon
(Cyanide) - F

Locale: Red Deer, Alberta, Canada
Tarp size rules of thumb on 09/28/2011 23:03:36 MDT Print View

I actually did take the bulls by the horn and developed a way to objectively choose my tarp size.

Assumptions: pouring rain, hunkered down for the day waiting for weather to pass, thus tarp needs to be staked to ground.

I measured myself sitting up to see how high the roof would need to be for my head to not rub. Measured width of my head at that height off the ground, then width of shoulders and height off the ground. Then I measured myself laying down and how much space had to be over my face so I was clausterphobic, and width and height off shoulders for comfort. Then I plotted models of myself sitting at the midline of the tarp, and two of me sleeping on backs with enough space for a child in between. I did this all in sketchup. Then I mapped an A-frame over these figures.

All that said, I came up with 10 feet wide (almost exactly), 8 feet long (a bit more arbitrary -but I am making separate beaks).


Once I had those dimensions, I then went on to sketchup multiple pitches to see if everything was still possible: lower wider pitches to get 4 people in and taller pitches when it is just myself and maybe a companion.

Overall, for purposes of multi-person utility without getting too large to make unweildy for a single individual, all all things in between, 8X10 seemed to be the ideal go-to size.

Cheers

John

Eric Blumensaadt
(Danepacker) - MLife

Locale: Mojave Desert
Ideal size - and tie points on 09/30/2011 13:53:10 MDT Print View

I really like the tarp configuration depicted by Mike Clelland in the paperback "Lighten Up!" on the bottom of p. 13. That is one of the most stormproof setups I've ever used back in my tarping days.

But it requires what Mike labels as "quarter point" pullout loops sewn to the tarp at the proper locations. He has convienantly drawn a bird's eye view to show the pullout locations.

For a trial run I'm using an old urethane coated tarp to attatch tie-outs in the same pattern before getting a silnylon tarp with the same setup. As a dayhike leader I'll carry the silnylon tarp for emergencies. One pound is not too much to carry for a safety item for shade or rain protection for an injured hiker.

Oh, yeah, the size will be 10' X 10', as Mike describes.

Edited by Danepacker on 09/30/2011 13:55:34 MDT.

Ken K
(TheFatBoy) - F

Locale: St. Louis
Trial run on 09/30/2011 20:12:08 MDT Print View

Once you have a decent idea what size you'll need, I'd try a couple nights under a cheap blue tarp of those proportions. I'd hate to get $100 into a cuben tarp only to find I made it a foot too short.

Hamish McHamish
(El_Canyon) - M

Locale: USA
tarp size on 10/06/2011 13:10:38 MDT Print View

John, I'm going through the same process as you with very similar parameters. Similarly, I have determined that an 8x10 is just about perfect: a palatial overnight retreat for the soloist and a reasonable emergency shelter for 2 or 3 dayhikers waiting for a storm to pass. In cuben it is still light enough. A larger size or a heavier fabric begins to get on the heavy side to me. I'm sticking with 0.74 oz/yard cuben for now, I'm not sure if I can keep the 0.51 oz/yard stuff from getting thrashed.

One thing you might try is to cut a 3 mil polyethylene drop cloth to your selected size and set it up for real. Cost would be just a few bucks.

Andy F
(AndyF) - M

Locale: Midwest/Midatlantic
Re: Tarp Size Rules of Thumb? on 10/06/2011 15:04:24 MDT Print View

I have a 8.5 x 10.5' silnylon tarp. I don't think I'd want to try to fit more than 2 people under it in a blowing rainstorm. I think I'd go with a 10'x10' tarp for three people.

See the flat tarps section of this site for ideas about how many will fit under what size:

http://www.owareusa.com/