DIY Tarp Shape

[Lance M]

Newton:

How did you go about sewing the netting to the canopy to avoid the raw edges?

First sew a hem into the netting edge, then attach to the fly.

Sewing the hem:

Attaching walls/floor to fly:

Have you weighed it? 24.2 oz with Triptease tie-outs.

Brian:

Here's a bit more info. The angle of the 'beak' point pictured above is about 90 degrees. Yours will vary depending on the shape of the main panel and how steep you pitch the sides, length of the 'hypotenuse', etc.

[Tohru Ohnuki]

I'm also a fan of the side entry tarp, I really like this design that is sadly not in production:
Brawny Tarp

Here are some myog notes on the design:
Forum Index » BPL Product Support » Brawny Tarp Dimensions

I'm in the process of designing something similar with cat curves…

[John Donewar]

Lance,

Thanks

Party On,

Newton

[Rob Hubbard]

Been thinking that a new tarp and bivy is next on my MYOG list. I've been messing around with a few ideas and Newton brought this thread back to my attention. Lance what are your thoughts on the design in the pic below? How do the dimensions relate to yours? Any thoughts from others. The beak would have a zip in it. A tarp tent may be the bug season solution I'm looking for rather than a bivy and tarp combo.

[Jerry Adams]

Is there enough head room? Can you get in and out? If it's raining, can you do some things like heat up some food?

What are the sides and ends? If it's not real breathable you'll have a lot of condensation.

[Ron Moak]

The tent as describe and made by Lance is a modified Bilgy Tent. It's been around since the late 90's and was designed by Bill Gurwell. Some history of the tent can be found at http://mysite.ncnetwork.net/resp320s/history.htm.

You can purchase paterns at:

Seattle Fabrics: http://www.seattlefabrics.com/bilgy.html
Quest Outfitters: http://www.questoutfitters.com

I do like the beak a bit better than the Bilgy model.

Ron

[John Donewar]

Rob,

Jerry makes a good point.

"Is there enough head room?"

Notice the extended trekking pole in the front of Lance's tent and the height of the front entrance.

Ideally, I'd like to be able to sit up and change clothes etc.

Party On,

Newton

[Jerry Adams]

Rig up a prototype with string on the ridge lines, or plastic, and try it out to see how big it needs to be

When I've had 40 inches from ground to peak, I found that it was marginal. Having a single pole makes it worse – it's hard to get in and out around the pole. But, that did work.

Right now I have two poles, 60 inches, "A" shape, so the peak is about 50 inches, that is spacious, perhaps unnecesarily high.

[Rob Hubbard]

Newton and Jerry
That example is a drawing of it in 'storm mode'. At that height I thought I would get doable head room and maintain a 4 inch gap between ground and tarp edge on the sides to help ventilation. With a 45 degree angle running from tarp edge to ground, simulating driving rain, the rain lands 4 inches shy of the floor. That seemed adequate though I could be wrong.

Any other time my set up height would be nearer 50 inches. I have begun making a simple plastic mockup to check it out. I'm a visual 3D type of information processor and learner so that's always vital for me on a project like this one.

[John G]

Is there an advantage to sewing the bug net to the tarp 12-18" in from the edge ? Wouldn't sewing the bug net to the edge of the tarp eliminate a seam that could leak and create more elbow room &/or gear storage space ?

[Bob Bankhead]

J.G.

For the same reason that roofs have overhangs rather than ending flush at the outside wall.

Rain sheeting off the roof (or tent fabric) drips onto the ground, not down the wall (or mesh, which acts as a wick). You can get a very wet floor that way.

[Rob Hubbard]

What are the sides and ends? If it's not real breathable you'll have a lot of condensation.

Sorry Jerry missed this yesterday when replying via my phone. It would be netting so there should be very breathable. I'm far to indecisive when it comes to these sorts of things because I think deep down I'm looking for that mythical shelter that does everything and will work in every season.

[John G]

I wrote:
Is there an advantage to sewing the bug net to the tarp 12-18" in from the edge ? Wouldn't sewing the bug net to the edge of the tarp eliminate a seam that could leak and create more elbow room &/or gear storage space ?

Bob replied:
For the same reason that roofs have overhangs rather than ending flush at the outside wall.
Rain sheeting off the roof (or tent fabric) drips onto the ground, not down the wall (or mesh, which acts as a wick). You can get a very wet floor that way.

Follow-up:
Oops. I should have clarified – the floor of the tent would be 8-12" in from the edge, so the edge of the roof would still overhang the floor. ie: the tent would be roughly pentagon-shaped instead of house-shaped.
Given this overhang, is there any advantage to sewing the bug net into a separate seam 12-18" in from the edge, rather than just sewing it to the edge of the roof and making the floor smaller than the roof line by 8-12" on each side ?

Thanks.

[Lance M]

Rob – Impressive 3D rendering!

Lance what are your thoughts on the design in the pic below? How do the dimensions relate to yours?

I agree with others that head room in 'storm mode' seems pretty low. The door height will be even lower, perhaps 24" or less. I settled on just lowering the outside edges for storm mode. It provides good head room and access, and still sheds wind quite well.

My dimensions (excluding the beak) are quite a bit larger than yours, as my original intent was a shelter for two.

Floor length: 84” Fly ridge length: 108”
Floor width, front: 60” Fly side length: 98.9”
Floor width, rear: 48” Fly front edge: 57”
Front wall ht: 45" Fly rear edge: 36.4”
Rear wall ht:23.5" Weight: 24 ounces

The walls tilt out 5 degrees.
There is a 6” 'rain shadow' beyond that.

What have you decided on for poles? Fixed poles through a grommet at each peak? Trekking poles, grip end up, under a reinforced peak? What method have you decided on for ridge guy lines? Guy lines from the pole tips to the ground or guylines from the beak to the ground or ? What method did you decide on for transitioning from a flat felled ridge seam to a butted beak zipper? I struggled with all of these issues.

Jerry's suggestion to rig up a prototype with string and plastic sounds like a good one. There are pictures of this somewhere in the BPL forums.

Let us know how it turns out.

Ron: Rest assured I received no cues from Bill Gurwell's Bilgy Tent but instead was inspired by the desire to combine, simplify and lighten the separate myog tarp and bug tent pictured below.

J.G. wrote:
Is there an advantage to sewing the bug net to the tarp 12-18" in from the edge ? Wouldn't sewing the bug net to the edge of the tarp eliminate a seam that could leak and create more elbow room &/or gear storage space ?

I agree that 12-18" seems excessive. I chose approximately 6 inches as a good balance between 'splash' protection, wasted space, and extra weight. I try to keep gear (and elbows) away from the tarp edges anyway, so I feel I'm not really giving up any usable space.

Adding a seam inboard from the fly edge was a concern to me also, but I found that whether the seam is at the fly edge or inboard from the edge, without proper seam sealing water can leak through the stitching onto the netting and then onto the floor. Moving the wall-to-fly seam inboard doesn't really create a new area to leak, it just moves it. The edge hem can be left unsealed.

Another concern I had about sewing the bug net to the edge was that slack netting could possibly fall outside the fly edge when the fly was lowered for storm mode. By sewing the netting inboard, I reduced that concern.

Hope this helps. My appologies for the delayed post.

[Jared Dilg]

Lance, thanks for the detailed post and all the photos. All very useful info!

I had a couple construction questions for you (or anyone with this experience).

When creating a catenary-cut flat-felled seam, did you have any problem with the finished seam not stretching flat under tension? I once made a cat-cut tarp like the one in the "5 Yards to UL" series but the resulting flat-felled seam would twist/contort under tension, making it much harder to properly apply seam sealer. I had offset the widths of the two pieces so that the finished seam would straddle the center-line of the tarp. Did you do the same? Any tips to aliviate this problem?

When attaching the netting skirt to the underside of the tarp, what was your technique to mark a symetric seam line (the white markers) that fit perfectly with the perimeter length of the mesh? With small piece projects I've pinned down the straight lengths and fudged the radius corners as I went. It's easy to do when you can hold both ends taut with your hands. I'm having trouble grasping the same on a larger project.

Thanks

[Jerry Adams]

Regarding offsetting the flat felled seam at the top:

I use a 1/2 inch seam allowance, folded over twice, so the flat felled seam is 1/4 inch.

I try to center the pole and tie-outs on the center of the flat felled seam, so theoretically, one side of the tarp is 1/4 inch wider than the other side, but you'll never notice it.

Regarding twisting and contorting under load:

One problem is if you don't lay out both pieces perfectly parallel to the grain of the fabric (edge of the fabric as woven). You can have either the edge of the tarp or the ridgeline (before catenary cut) parallel to the grain.

Another problem is if you don't make both pieces a perfectly smooth curve. Sometimes I'll have a place that's a little inside or outside of the perfect catenary curve and I can see it when I pitch it.

You have to measure as perfectly as possible.

[Lance M]

Jared –

When creating a catenary-cut flat-felled seam, did you have any problem with the finished seam not stretching flat under tension?

Sometimes yes, but not to the extent that it interferes with seam sealing. I center the seam like you do as described in a previous post.

There are a couple of things you can try to help keep the seam flat.
1. After the first stitch line, pin the folded seam down. You don’t have to pin in advance from end to end, but at least several pins and a couple of feet ahead of the presser foot. If the fabric does stretch and bunch, you’ll see it and can make adjustments.
2. Use a wide presser foot on the sewing machine and adjust it side-to-side for best coverage of the seam.
3. Sew the seam under a bit of tension.
4. Use a narrower seam like Jerry does.

When attaching the netting skirt to the underside of the tarp, what was your technique to mark a symetric seam line (the white markers) that fit perfectly with the perimeter length of the mesh?

I’ve been using CAD software and have full sized patterns printed at the (expensive) local print shop. The patterns have alignment marks on the corresponding pieces.

Here is an alignment mark on the mesh wall pattern. Chalk doesn’t work well on mesh, so I snip the fabric to mark it

You can see an alignment snip mark through the mesh hem here:

Fly pattern cut to expose alignment template:

Alignment marks transferred to fly fabric:

Hope this helps,

-Lance

[David Drake]

I've been following this thread and just made a mock-up of the tarp described by Jerry and the OP. I like the simplicity of it versus the more shaped, side-entry shelter I've been designing on another thread.

I'd like to pitch it supported by two hiking poles in an a-frame at the peak, pole tips down. Looking for a good, lightweight method to attach poles together, as it seems somewhat unstable otherwise. A poster on my other thread had made an aluminum widget that looked interesting, but a bit heavier and more complex than I had in mind:

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=47007&skip_to_post=420512#420512

Here's pics so far (still need to sew a cat. curve in the ridge and beak):

[Jerry Adams]

This won't work for you because I use Easton poles rather than trekking pole, but anyway:

Made a loop out of aluminum flashing. Holes for pole tips to fit into. Holes to use 1/4 inch bolt to attach to tent. About 1/2 ounce.

[David Drake]

Finished two shaped tarps more or less designed like those discussed in this thread. Cat cuts on the ridges, and the edge of the beak. Using poles in a-frame for support.

Just got back from three night in Hells Canyon/Seven Devils, and they performed well–saw a little rain and wind, plus pitched one night in the dark. Need to add zipper for easier access, but weight for tarp + guylines in 30d silnylon 2ds (from Backwoods Daydreamer) is only 9.5 oz.

Here's a pic from a site near Bernard Creek, overlooking the Snake:

[Eric Blumensaadt]

The OP initially asked for an all-purpose tarp. That means a rectangular tarp with maybe a catenary cut doen the middle.

Take a look at Don Ladiogin's book "Lighten Up" with illustrations by Mike Clelland.
On P. 13 there's a great drawing of what looks like a 9' X 10' tarp set up in a real bomb-proof configuration. As you can see it has ties down the middle as well as on the perimeter. I've use this setup back in my tarping days even in winter and it works well.

BTW, the example shown of a 24 oz. tarp reminds me that my former TT Contrail only weighed 24 oz. Why make a tarp when you can get an even better setup at the same weight?
(Disclaimer: I sold the Contrail and now own a 28 oz. TT Moment for it's great design advantages.)

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