What size tarp would be good to carry in your BOB? In my other thread a lot of folks said a tarp would be better than making a tent out of contractor bags, so I'm trying to see what's out there as far as sizes and brands.

Also, how do you rig your tarp?

On the home page there is a good article about different ways to rig a tarp.
http://www.equipped.org/tarp-shelters.htm
Tarps are pretty versatile. The polytarps are cheap enough but they are pretty bulky.
Mountain Equipment Co-op sells good light ones in silicone treated nylon.
A bit expensive for throwing over boats, cars, or patching roofs and windows, but great for backpackers to rig as a tent substitute.
You can likely find them for less money if you shop around. Just be sure to buy one that is big enough to actually shelter you, your people and your gear.
I like this one:
http://www.mec.ca/Products/product_detail.jsp?PRODUCT%3C%3Eprd_id=845524442505763&FOLDER%3C%3Efolder_id=2534374302702975&bmUID=1231466409108

10x12 seems to work for me.
But to each his own.
If you go with a tarp you need plenty of good cord with it.

I carry an 8x10 in mine. I bought it at Walmart and it came in a plastic wrap / packaging. It fits next to my back. I like it and it has served many different purposes so far. My wife has one in her pack worth every bit of the 1 lbs that it takes to lug it around.

Nylon tarps seem the best bang for the buck - REI has a standard one, so does Campmor, 8x10 or 9x10 seems a good size to get pulled out and used alot (~ 1 lb). My current tarp is the REI brand, but that's because I got it really cheap at one of REI's .83 sales a while back. Kelty makes a really nice tarp, don't know the weight or sizes but I seem to recall they are blue and white and they have alot of grommets along the side for tying down (ck REI website). Silnylon is even better, but pricey. The nylon tarp isn't too heavy to hike in a day or two.

I carry a 6 ft. x 8 ft. Ultralight Backpacking Tarp in my get-home-bag. Packs small, big enough for one to get out of the rain.

I have an Outdoor Products Polyurethane Coated 12' x 9.5' Nylon Tarp that I got from REI during their annual New Years Sale. It was 30% off, and I used some of my Store Credit to get it for less than half price.

I tied some 550 Paracord to the grommets and use those for stakes and lines rather than the grommets.

Here's a similar Tarp Setup to what I put up except I use a centerline tied to a tree if at all possible. If the link doesn't work go to www.youtube.com and search for "Etowah 8x10 Tarp Setup".

I plan on adding a mosquito net to this setup.

My BOB has an Oware 6' x 8' flat tarp, 9oz, and 8 MSR needle stakes, 3oz, and 50' of line to tie out. Total 12oz. It covers me, my gear and my dog. Cramped but dry.

http://www.owareusa.com/
http://www.rei.com/product/734484

I do a 6-ish by 9-ish. I would love to find a good, heavy duty tarp in the 7ish square with a metalized side thought.

There's always one step up from the contractor's bag, a Christmas tree bag. I just got two more for a buck in the after-holiday sales.

They're 72x90"; opened, they've got a 45" diameter, 7.5 feet long. Poke a hole in the closed end to accept a cord, tie the cord between two supports, and you've got a big bag to break the wind and keep off the rain and snow.

No, they're not perfect, not very heavy-duty, but they only weigh about 8 oz, the enclosure bag is 9x12x~1/4", and will sit quietly in the bottom of your bag until you need it.

Sue

Another poorman's tarp are the plastic covers used to ship mattreses.If you have a local retailer with a warehouse they will have rolls of new bags on hand. A smile, $5 and you have thick mil, opaque plastic twice the size of a double/queen.kingsize bed.
A tarp is a excellent item to pack against the back for comfort.
You will save valuable time if your tiedown knots are pre tied ( there IS a tensioning knot, or use the plastic attachments)and at least a few groundstakes.
Fire and tarps- make them easy and quick. Once inside and warm your brain can nitpick 'shortcomings.'

Poor man's tarp can also be:
A piece of Tyvek. Comes in 9' by 100' rolls so the sky is the limit on size. It is tough enough for several uses and makes a good ground sheet. Use a good quality sealing tape to patch holes and wear points and you can get three or four camping trips out of one piece demoting it as it wears to less critical jobs. Last duty as as rock shield under the ground sheet.

A standard shower curtain works as a small tarp and, if sized right, as a useful rain cape.

Standard polyethylene sheeting, Visqueen is one brand, comes in black or clear and makes a good cover. The 4 mil stuff is okay for a couple of uses, a bit more if you patch any rough spots well with duct tape, but the 2 mil is pretty much one use only unless you get lucky. Black lasts longer in sunlight and doesn't act as a greenhouse. White, if you can find it, reflects a lot of heat and makes a decent sunshade on a sunny day.

Tightly woven nylons or Dacron, less subject to UV degradation, cloth can be coated with urethane to make your own tarps. Urethane coated and treated with silicone water repellent, Thompon's Water Seal is a favorite, it makes a tarp that sheds water well, lasts a long time and about half the cost of the commercial version.

I have both a 6x8' and a 10x12' silnylon tarp in my BOB. The 6x8 is for making a rain shelter while pausing from moving and the 10x12' is my shelter building tarp. it's big enough to build a shelter with a side or two if needed for weather protection of a sleeping/cooking area and big enough to be comfortable for several people if stuck in one spot for several days,
Back in my SAR days, I carried a 10x10 blue tarp on the out side of my pack. It was often used as a overnight personal shelter tarp for me and maybe a team mate (if needed) and as a team shelter if we had to hunker down or as a shelter while treating or packaging a patient.
I was picked on by team members until I used it as a 3 sided A-frame shelter one very cold and rainy 2 night training session while others used large trash bags. Those in the trash bag shelters were often wet and cold, while inside my tarp I was warm in my hand warmer heated 2 pound sleeping bag and dry. The 3 sided A-frame design also acted as a ground cloth and it was long enough for me to pull the ends in and basically close them off. During the day I opened the trap up and hung it on para-cord from trees as a team weather shelter.
Several others added 10X10' blue or the more expensive nylon tarps to their packs after that training.
As far as I am concerned, a large tarp in a requirement in a BOB bag.

Ditto on experiencing the tarp envy - they're great for setting up temporary relief from heat, cold, wet or wind. Kept an overheated Scout out of the sun for a couple hours, made a tarp believer there. More often its shelter from the abrupt downpour where you just don't wanta keep trudging along the muddy trail, stop, pitch a tarp, and watch the weather for a half hour instead. Best survival has us staying warm (not too warm) and dry, tarp helps with that.

In an emergency setting up a tarp has value beyond the shelter from sun and weather it provides. Set up a tarp and people think of it as a landmark. I have noticed that even if you have nothing more than a box of bandaids with a tarp it is an aid station. A tarp set up high enough to walk under, a table and makeshift seating pretty much puts you in charge of the scene. Try it some time. Don't be surprised when people start coming up and asking where you want them to set up.

People will naturally congregate around any such landmark and assume anyone who looks like they know what is going on is in charge. This can be a double edged sword. If you don't wish to be looked to as an authority don't put up a shelter or, at the very least, use a tarp in a subdued color and keep it low.

Six foot square, roughly the size of a standard rain poncho, is IMO about the minimum useful size if you want a lot of options. Rigged low you can sleep under it and have complete coverage if you sleep on the diagonal.

Eight foot square or over opens a lot of options and allows the simplest, swiftest and most foolproof of all shelters, the burrito roll. Simple as: spread tarp, lay on one edge, roll over making wrap tighter at foot than head. With practice you get complete coverage with all edges tucked under you even in hurricane winds, decent ventilation and end up with enough extra coverage at the head to pull in and shelter your pack. Total time: less than a minute.

Helps if you rig a light line from the foot inside so you can seal or loosen the foot end as need be. The burrito roll is a last resort but one that has saved my bacon when I was wet, exhausted, at the edge of hypothermia and there was no shelter anywhere nearby. Once your warm you can climb out and build a more substantial and comfortable shelter. Or not.

Eight by ten allows you to use it as a lean-to and ground cloth in one.

Twelve by twelve is about all one person can effectively use in my opinion and is pretty much the point of diminishing returns if your not setting up a base camp.

I'm thinking 8'x10' would be my best option. I have either my daughter or my girlfriend with me a lot of the time I'm out in the woods. I picked up a cheap 8'x10' tarp at Walmart for $4.88 today to throw in there until I find a better one that I like.

What are good options in the 8'x10' size that have ties on the outside of the ridgeline and a decent number of grommets on the edges? I'd like to have the ridge paracord outside the tarp rather than underneath it. Also, how many/what kind of stakes do most of you keep with your tarp?

Home Depot has an 8x10 blue tarp that has "blanket material" (their description not mine) on the reverse side. Haven't had to use it yet, but I don't think I would rely on it as my only blanket.

Have any of you have success using recycled Billboards or misprints from that industry.

The most common locally used material is a reinforced vinyl in heavy weight (last time I checked it was 6oz or higher). It is UV resistant, it's tear resistant. Of course you may have a big Budweiser, KFC or Corona print on one side, but I have yet to figure how they are disposing of those materials. I used to work with smaller signage and I have always thought of that material as tougher than the FEMA/Wal-Mart Blue Tarp.

Got a link? Sounds interesting.

Nope, sorry. It seems like a cheap almost brushed paper or tyvek material laminated to the back of a regular blue tarp. Check HD as Lowe's didn't have them.

Well, I seem to have gotten it exactly backwards. Lowe's now has them and HD doesn't. It seems they have gotten smaller though.

Here is the Link.

8 x 10 blue tarp is SOP for any of our kits. They're so inexpensive and versital it's almost a sin to not include one.
With a blue tarp, duct tape, and zip ties you can fix just about anything in Alaska.....lol

I don't have this but out Scoutmaster does, and I consider it the Cadillac of non-silnylon tarps - 9x9 from Kelty http://www.rei.com/product/627834. If you look at the picture you see plenty of tie outs, they are all strong and reinforced, and the tarp itself is leakproof in the heaviest downpour. Three adults and a handful of Scouts passed a cold, wet evening comfortably underneath the larger size. $60 is not cheap, but it provides a lifetime of use. The REI brand tarp I carry is the same size with reinforced grommets, cheaper but no longer available apparently.

Most places we hike we don't need stakes to tie down our tarps, plenty of trees and root material. If you had to, use your hiking poles and a couple lightweight stakes.

i did not read every reply to your question but i would take the
largest tarp i could stuff into my BOB..i took an 8x10 tarp on a canoe trip many-many years ago with the idea that would sleep under the canoe with the tarp to compleat the shelter.i ended up using trash bags opened up to give myself more cover.

For you folks with silnylon and similar thinner materials...how well do they hold up to wear-and-tear? ...especially those of you using them as groundcloths?

i have a large Baker tent made from Silnylon and it's held up in very bad weather.it's sort of slippery so i never thought od using it for a ground cloth.i use a space blanket.

here is that shelter after a heavy storm.i woke to find a very bad thunderstorm sweeping across my camp on a open point on a lake.the shelter had pulled the stakes and was flapping and pulling on the main tie-outs.i cut the lines,pulled it down to cover the gear that was inside and put rocks and branches to hold it down and got back in my tent to get out of the driving rain.i took this photo later when things cleared and i was getting ready to set it back up..nothing ripped---

Check out tent "footprint" tarps. They are no too expensive and come with grommets, ties downs, etc.

I have one wrapped around an REI minimalist bivy with an REI Travel Sac inside, all covered by a Sea-to-Summit waterproof compression bag.

if anything I would like to trade up from my 7 x 7 tarp to at least 9 x 9.

For those of you that use a cheap blue tarp you might like what Tinny turns one into. This first video shows it done and the others are how to make it.

http://www.youtube.com/watch?v=0fXDcFfNwLs

http://www.youtube.com/watch?v=NnO4Nplk9m8
http://www.youtube.com/watch?v=3vRceEXBm3M
http://www.youtube.com/watch?v=hUHRFnJ7JJI
http://www.youtube.com/watch?v=lmWtZZvD22k

hope you enjoy!

But if you are looking for a lightweight tarp and are handy with a sewing machine there are many lightweight backpackers that make their own out of silnylon and some go as far as making a hammock to go with it. It is amazing what you can make very easily and cheap.