minimum tarp size for bivvy-less camping

7 x 9 sounds right

Ditto, 7×9, but maybe taper the tail to 5 or 6 feet. Still flat for multi-pitch, but save an ounce.

yer i would recon a taper towards the rear to! this would work great!

I've slept fine under a 5×9 w/o bivy in a storm. But to keep the weather out the pitch has to be pretty low (i was using and A-frame)and is a big sacrifice to interior living space.

I've used a 5ft x 8ft but it had to be pitched very very low – earthworm friendly.

7ft x 9ft is more practical. I've used this in stormy condititions with a 2ft-tall pitch and it's been fine.

It's well worth considering shaped tarps – say taper at the back to 5ft. You save a chunk of weight without any real down-side.

I've move towards a single-skin tent. It weigh's less than a 7×9 tarp and is more storm-worthy.

Mike – What tent are your using that weighs less than a 7×9 tarp?

You could do a 9ft tarp that is 6ft at head and 4ft at foot for the same 3 yards as a 5×9, it will give a little more room where you need it and allow for more head room.

9x4x6 would be great but if you want it rectangular, 6×9 or 6×10.

Many thanks for the input guys. I like many I have spent time under a 5×8 without a bivvy in a storm, and it can be weather worthy, but not comfortable! I'll take on the suggestions to base it on a 7×9 but taper it, and do some pattern drawing based on that. I also take from David's suggestions that the length is actually the key factor in getting reliable full coverage.

Ronald,

it’s DIY. It broadly looks like DIY Ultralight tent.

It’s basically a tapered tarp with doors on each end. The tapering and the doors use no more fabric than a 7×9 tarp and of course gives good weather resistance.

I’ve recently tweaked it to add a dome on the front and change the back to be a beak. This increased the weight by 2oz but that weight was regained by using shorter internal rather than external poles.

It’s always worth remembering with Tarps that they do not have magic powers. They do however tend to use less and lighter fabric than a conventional store-bought tent. That’s all.

For example, I found that of that 9ft length I needed at least 1ft to give rain resistance to give some weather resistance at each end and yet if I put a beak on the tail end it would use less than 1ft of fabric and so was lighter. My 8ft tarp relied on this fact to save weight and width.

mike, your post has just blown open my debate about my next shelter project again…Ron Bell surprised me by bringing out exactly the shelter I had designed in my head as a solution to the bivvy-less camping problem:

http://www.mountainlaureldesigns.com/shop/product_info.php?cPath=35&products_id=76&osCsid=32d8dc46397d0f257a2661b9ac6e33ab

I've been shuffling back and forth between the idea of making a smaller, shaped shelter, or a largish flat tarp, or compromising on a beaked tarp Ray Way/Jay Ham stylee- as well as weather protection I'm keen to have quite a bit of headroom for comfort and sanity- I clearly need to think more about this!

How much interior room does your tarp-with-doors have?

Josepth,

broadly there is about 1-1.5ft of free space between the front doors and the top of your head (my groundsheet is 6ft7 long and 3ft wide tapering to 1.5ft) . There is about 6 dry inches down each side of the groudsheet where you lie. Internal height at the front is about 3ft when pitched normally.

Most designs can be broken down into triangles and rectangles which is then simple high-school math to work wtih.

7 x 9 sounds good if you plan to keep a simple rectangular tarp.

With large beaks, you can use a shorter ridge line. Imagine a 7 foot ridge, 9 foot sides and 1.5 foot beaks. Sketch it out and you will see what I mean.

If you want to get more radical, consider a 5 foot ridge with 8 or 9 foot sides and a pyramid (two triangles joined) at the rear and a long beak over the open front.

Shortening the ridge can reduce the yardage and weight – but will reduce the versatility and ventillation of a flat tarp.

Take this to its logical extreme and you get something like a Gatewood cape tent.

Thanks very much for your input folks- I have decided to make a 7X9 flat tarp, simply because I am at the beginning of my sewing appreniceship, and I would like to continue my apprenticeship in tarp craft-I've really enjoyed what I've done so far and would like to take it further.

I think the points about adding beaks and doors are very valid, and need exploring further when my sewing skills are up to more. If my experience with tents is anything to go by, I find shelters where the highest point is in the middle the most comfortable- think MSR Hubba. Translated into simple ultralight form, this makes me think of a small half pyramid, with doors that could be rolled away in fair weather. I think I will look in this direction if I start a shaped shelter project.

Mike, thanks for your feedback on your prototype- it's really good to have the benefit of your experience there- it's something I might have tried myself- if I do I'll make it taller!

So here's a question to do with flat tarps- would you guys pitch a rectangular tarp with a lenghthwise centre seam in a half pyramid configuration, or would the stress across the centre seam be too much? If you reckon it'll be ok, I'll make sure there's a tie out in the middle of each long side (total three). If not, I'll put two tie outs on each long side instead of three.

all the best,
Joe

Joe,

to actually sew a 9' seam well is tricky. I still struggle to do it and the result is a little lack of tension in places.

The felled seam will be pretty tough whatever you do.

If you are using RipStop fabric then for a first tarp you could consider putting the seam in the other direction – sewing two 4.5×7 lengths together. 4.5 is the width of a typical roll of fabric and will reduce the size of the seam you need to do and give you a ridgeline that will be taught even if the flappiness moves elsewhere…

There are plenty of Sewing 101's out there but even so its always worth practicing with the actual fabric you are goihg to use.

I tend not to use pins (but I've done this quite a bit now) but its gonna be worth you using a few and pinning within the seam allowance for the first seam – these will be pinholes that never see daylight.

The other thing that's gonna be worth practicing is keeping the fabric undder tension as you sew. It helps to avoid wrinkles. For the first seam I hold either side of the fabric as far as I can reach along the seam-line. This creates fabric tension and helps me to sew a straight line (with no or very few pins).

For felling the seam I tend to hold the fabric flat and under tension either side of the needle.

Think of your first one as a training exercise. If at the end of the day it works then it's a success.

You can always sew extra bits onto it or chop it around at a later date.

On my most recent tarp i used a French seam for the ridge line. I was able to get a much better seam than my previous flat felled attempts. When sewing the "tube" down i sewed through all the layers with the tube being on bottom, this helped me get a much smoother seam than when i have done frenches with the tube on top.

Do you mean something like this?

or this (two operations)

1.
—!

It doesn't render in a proportional font.

This is what i mean
http://www.thru-hiker.com/workshop.asp?subcat=11&cid=16
but i top stich it with the tube on the bottom. With silnylon you can see through it and can always see the tension but it is out of your way and you can just pull apart the 2 layers of fabric and don't have to worry about the tube because it is being held in place

Here is a plan for a 6×9 foot tarp with an optional catenary cut ridge line.

This can be cut from 3 yds of 64" width silnylon. Besides the cut out for the catenary ridge, the only scraps left are two right triangles 6×21 inches. I have almost finished a tent based on this plan with screen ends and bottom.
This catenary curve ridgeline has a 2 1/2 inch sag. The measurements are symmetrical about the center 2.5 inch one. Your diagonal measurement might differ from mine if you have to lose a bit of fabric to square the ends. Whatever it comes out to, divide it by 10 and mark off 10 equal segments. I multipled the meaurements by 25.4 to convert to mm and used a millimeter ruler:
24, 42, 54, 61, 63.5, 61, 53, 42, 24 mm.
To connect the dots, I used a metal ruler on edge, bent it to follow the curve and then traced a section of the curve with a fabric marking pencil.

Robert

any chance to see some pics of this 6×9 cat tarp? How does the narrow foot end impact storm worthiness?

Tim,

Sorry for the long delay. I didn't see your question on page 2 of the thread. Here's a photo of the 6×9 tarp cut from the pattern I posted.

It has a bug net. The bottom is partly open. The net tucks under the ground cloth. It's not tall enough to sit up in, but it is plenty long enough for me and gear.

In a wind storm, I staked the foot end to the ground and left off the stakes at the corners of the skinny end. I folded the extra under and put it under my feet. (The unstaked corners meet under the tarp. These could be tied together for more security.) This changed the shape of the footprint from a trapezoid to a pentagon, sort of like home plate but skinny. The toe of my bag probably hit the roof, but it kept the blowing sand out. No rain experience yet, but this would be the pitch I would use if I expected a storm.

The silnylon was sold as 60" width but actually measured 64". Weight came to 14.5 oz (410 grams) with no-see-um net and 30 ft of guyline. Titanium stakes (10 with 2 spares), Tyvek bathtub groundcloth, and stuff sack added another 6 oz (170 grams).

Robert

Robert, looks like something I would make! :)
do you think the black will be a bit hot down in Texas?
nobody in his right mind would try that in AZ… you'd bake to death even in February.

Michael,

The black was leftover from another project. I definitely wouldn't try sleeping until noon under this kitty tarp in the summertime in Texas–you'd be Texas toast. Anyway, it's too hot for me to do much camping in Texas in the summertime no matter what color my tarp. I try to head for higher/cooler climes in the summertime.

Robert