General Tarp Question

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11-02-2017, 13:11
tflaris

General Tarp Question

A Tarp is essentially an Isosceles’s triangle when looking at it mathematically. If I’m staking the corners close to the ground and if I’m using an 8.5’ wide x 11’ long Tarp and I raise the tarp roughly 125 cm or 4’ how much usable space would I have below?

I have done that math but it doesn’t really tell me how much viable/usable space there is.

Excluding reasons related to weather are there better angles (other than 45 degrees) to be considered when setting up a tarp that allows more floor space for 2 people?

Thanks in advance

TF

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11-02-2017, 13:21
tflaris

Quote:

Originally Posted by tflaris

A Tarp is essentially an Isosceles’s triangle when looking at it mathematically. If I’m staking the corners close to the ground and if I’m using an 8.5’ wide x 11’ long Tarp and I raise the tarp roughly 125 cm or 4’ how much usable space would I have below?

I have done that math but it doesn’t really tell me how much viable/usable space there is.

Excluding reasons related to weather are there better angles (other than 45 degrees) to be considered when setting up a tarp that allows more floor space for 2 people?

Thanks in advance

TF

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11-02-2017, 13:55
HooKooDooKu

Sort of difficult to answer the question without defining what is "usable space".

But some general comments...
1. I've never seen a tarp setup such that it's touching the ground. There is usually a certain amount of space between the edges and the ground.
2. A Tarp isn't an Isosceles triangle unless you decide to set it up that way. Tarps can also be setup to be all one sided (equivalent of a lean-to) as well has have the angle and lengths of each side of the triangle be different.
11-02-2017, 13:58
Alligator

Your example tarp is a rectangle. You could run your ridgeline so that it bisects either the short or long side. The lower you drop your ridgeline, the wider the base gets and that will factor into your floor space. Pull it all the way up and it wall hang like a towel. So if you make your angle shallower than 45 degrees (the angle at the ground level), it will widen out. You can create more space by lifting the ridgeline and using line to stake out your tarp--the tarp does not touch the ground. You will get some rain splash there but then the interior is taller. In your figure with the right isosceles triangle, the height is just over 3'. Tents seem to range upwards of about 40". I find that if I can't sit upright in a tent or tarp than I am uncomfortable.
11-02-2017, 14:19
Alligator

Quote:

Originally Posted by HooKooDooKu

Sort of difficult to answer the question without defining what is "usable space".

But some general comments...
1. I've never seen a tarp setup such that it's touching the ground. There is usually a certain amount of space between the edges and the ground.
2. A Tarp isn't an Isosceles triangle unless you decide to set it up that way. Tarps can also be setup to be all one sided (equivalent of a lean-to) as well has have the angle and lengths of each side of the triangle be different.

Flying V and pyramid configuration both have sides on the ground. I use the latter quite often, some folks like the flying V though. I'll throw up an A-frame if I don't expect a lot of rain and I am being lazy. It's faster than messing with the lines and I have a big tarp anyway. Pyramid shape has a shallow angle in the back for my size tarp and poles. It helps to have a pullout of some kind on the back side to create usable space.
11-02-2017, 16:06
Feral Bill

With a tarp that size you will have more than enough. I like the flying V for on the ground, or a ridge on the diagonal for hammocking.
11-03-2017, 01:02
Alligator

A regular sheet of paper is 8.5 " x 11". If your tarp is actually 8.5' x 11' you could easily make a few models out of paper. Before I bought my first tarp I folded a bunch of paper to get an idea of dimensions. My plan was for an 8'x10' tarp, so I cut a little paper off first.
11-03-2017, 10:45
Slo-go'en

Quote:

Originally Posted by Alligator

A regular sheet of paper is 8.5 " x 11". If your tarp is actually 8.5' x 11' you could easily make a few models out of paper. Before I bought my first tarp I folded a bunch of paper to get an idea of dimensions. My plan was for an 8'x10' tarp, so I cut a little paper off first.

I was also going to suggest this. But go one step farther. Get a doll with articulated waist and arms so you can sit it up and move the arms around. Then make a tarp model to scale. Now you can see how well you fit under it. Then get a fan and spray bottle to simulate a rain storm with strong wind to see how well you'd stay dry under it.
11-03-2017, 11:19
HooKooDooKu

Why bother with dolls... just go buy cheap blue tarp and someplace like WalMart and practice in the real world. You could start with an oversized tarp, say 12x12, and trim it down to the size you expect to use.
11-03-2017, 11:28
Alligator

Quote:

Originally Posted by Slo-go'en

I was also going to suggest this. But go one step farther. Get a doll with articulated waist and arms so you can sit it up and move the arms around. Then make a tarp model to scale. Now you can see how well you fit under it. Then get a fan and spray bottle to simulate a rain storm with strong wind to see how well you'd stay dry under it.

Is your implication there that one can't stay dry with a tarp? In particular the example size given in this thread?
11-03-2017, 14:13
Slo-go'en

Quote:

Originally Posted by Alligator

Is your implication there that one can't stay dry with a tarp? In particular the example size given in this thread?

Yes, you will get wet.

8.5 foot wide means you only have 4.25 feet on either side of the apex. If you make the apex 4 feet and have the sides at a 45 degree angle to the vertical center line, the edges of the tarp will be about 1.5 feet off the ground. The width of the area under the tarp will be about 6 feet. Assuming you take up 3 feet, that only leaves 1.5 feet on either side of you. Major splash problems.

If you keep the 4 foot headroom and bring the edges of the tarp close to the ground, now you only have about 3 feet of coverage under the tarp and that is pretty narrow. Still going to have splash problems.

I would want a tarp at least 10 x 12 to ensure good coverage. I'd also want a bug bivy at the least, which helps mitigate the coverage problems of using a tarp.
11-03-2017, 15:30
Alligator

You might get wet with it pitched as an A-frame in a driving rain. Pitched with the sides down leaves 11 ft open on both ends, which is 2 ft per side considering a 7 ft middle. Pitched pyramid configuration-not going to get wet. Enough room for one sleeping pad with an 8x10' tarp to avoid getting wet. I've sat reading paper books in my T-rest chair many times during downpours. Tarp was 8x10.
11-03-2017, 17:45
tflaris

So would I get better results a-framing the 11’ side (wide) and have the Tarp length be 8.5’

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11-03-2017, 17:49
cmoulder

Quote:

Originally Posted by tflaris

So would I get better results a-framing the 11’ side (wide) and have the Tarp length be 8.5’

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Until the wind changes direction. :D
A better approach might be to use an EE Recon bivy or the new MLD Bug Bivy 2 which are splash resistant.
11-03-2017, 17:52
tflaris

Quote:

Originally Posted by cmoulder

Until the wind changes direction. :D
A better approach might be to use an EE Recon bivy or the new MLD Bug Bivy 2 which are splash resistant.

Awesome. I’ve looked at the EE Recon but with the weight of a Light tarp and the bivy the weight is very close to a ZPacks Tent.

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11-03-2017, 18:00
cmoulder

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Quote:

Originally Posted by tflaris

Awesome. I’ve looked at the EE Recon but with the weight of a Light tarp and the bivy the weight is very close to a ZPacks Tent.

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Exactly. Add it all together and for the same weight you coulda had a Solplex! :D

This is why I like the Hex solo tarp... much more resistant to blowing rain with changing wind direction. Use with bivy or without. Use bivy alone when it's buggy but there's no chance rain. Sleep on top of the bivy like a ground sheet when there's rain and it's warm but no bugs. Very flexible that way.

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11-04-2017, 01:00
Alligator

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