minimum tarp size?

[kobold]

i have a 11.5 x 4.3 ft piece of cuben fiber, is 4.3 ft wide enough for a summer mini tarp to use with a bivy sack (dont flame me ), or should i cut it in half and glue the two pieces together to get a 5.7 x 8.5 ft tarp? i would like to go with just the 4.3 ft wide option so i can maybe have some leftover material for a kilt or smaller items.
the bivy sack is waterproof everywhere but the head area, there is a mozzie net, so water can seep in (msr ac-bivy). so i want to protect mostly my head, my pack and hopefully a small kitchen area from the rain.

[TheDudeAbides]

I just ordered a 4.3 x 9 tarp from MLD. I have yet to use it but my intentions are to use it with a bivy.

[kitsapcowboy]

i have a 11.5 x 4.3 ft piece of cuben fiber, is 4.3 ft wide enough for a summer mini tarp to use with a bivy sack (dont flame me ), or should i cut it in half and glue the two pieces together to get a 5.7 x 8.5 ft tarp?

Neither. Keep it full-width and trim the ends at oblique parallels to make a sub 4-ounce parallelogram asym tarp, like the one Zpacks makes, only longer...



I would pick a lay direction and make a parallelogram-shaped 0.51 oz Cuben Fiber asym tarp with a width (i.e., height perpendicular to the long sides) of approximately 52" and a long diagonal of of approximately 139", necessitating a long side (down the selvage edges) of about 115".

https://www.calculatorsoup.com/calcu...h&action=solve



Answer:
A = C = 74.3575 °
B = D = 105.642 °
a = 54 in
b = 115 in
p = 113.102 in
q = 139.606 in
h = 52 in
P = 338 in
K = 5980 in2

(You can always adjust the cutbacks (oblique short sides) to place the tie-out corners where they will provide you with ideal coverage for your personal lay in the hammock.)

You should be able to make a finished tarp somewhere between 100 and 150 grams, depending upon your hardware and assembly techniques.

[Otter1]

Don't do the Asym for ground use.

Is the bivy waterproof? (I don't recommend any such bivies except for Myles Gear's for this anyway - waterproof bivies aren't breathable enough) If not waterproof you will get wet in a tarp that narrow unless you pitch it almost all the way to the ground. Now that is not a problem if you don't mind slithering under the tarp and contorting to get into you bivy.

I prefer breathable bug bivies (NOT waterproof) with a bigger tarp. 8.5' is enough if you're careful (and not very tall) so I would go with your cut & tape method. For me, though, it's still not enough tarp to be comfortable. I hate crawling thru mud, then changing while on top of bivy so I keep my quilt clean.

[kitsapcowboy]

Don't do the Asym for ground use...

To be clear, I wasn't suggesting that the OP use an asym tarp for ground use; rather, given that the piece of DCF cited is almost the perfect size for an ultralight hammock application, my suggestion was to make a parallelogram tarp for hanging and find another solution for the bivvy. The nice thing about ground tarps is that they are frequently small in total area relative to hammock tarps; thus, the absolute weight savings you get from using Dyneema Fiber is often quite small even though the relative weight savings remains approximately the same for a given design. If you're spending the big money for DCF, I think it's nice to get the most bang for your buck.

Regarding ground use, while I'm fairly fit and lithe for my age, I have found in the past using a plain Jane 5-foot wide rectangle tarp in an A-frame configuration for field-expedient weather protection to be a real drag on an overnight, generally only choosing that configuration when the site or available ancillary gear mandated it; I wouldn't design anything purpose-built at a 52" width and expect it to keep me very dry in the same configuration under similar circumstances. Five feet wide is about as slim as is practical, although, as is common knowledge, it will allow you a few decent pitches, some of which are more efficient and practical than an A-frame. For me, that's another argument against a one-piece (seamless) ground tarp application for the run of DCF cited in the OP. My $0.02...

[kobold]

wow, thanks, this is tempting actually, when i also consider what otter1 wrote... must sleep on it

[kitsapcowboy]

wow, thanks, this is tempting actually, when i also consider what otter1 wrote... must sleep on it

Otter is smart and definitely knows, as has been proven here many times with helpful advice. I don't disagree with anything Otter said. I'm just offering another alternative for your consideration. Hang your own hang, to be sure...even if it's on the ground. Good luck.

[kobold]

they claim the bivy is both waterproof and breathable, but i just bought it and have no experience. but what you say makes a lot of sense re the pitching height and size. i have a small tarp to try this whole idea out with. when i think about it, i might be getting too old for too much slithering and contorting. :-))

[kobold]

I just ordered a 4.3 x 9 tarp from MLD. I have yet to use it but my intentions are to use it with a bivy.

sweet! hope it will work well.

[Monkeyboy42]

they claim the bivy is both waterproof and breathable, but i just bought it and have no experience. but what you say makes a lot of sense re the pitching height and size. i have a small tarp to try this whole idea out with. when i think about it, i might be getting too old for too much slithering and contorting. :-))

You might to try this question over at the backpackinglight forums. They are the experts on this kind of set up.

Good luck!