Tarp seam

[plodder]

I'm missing something. Saw stuff relating to placement of seams in silny tarps. Ties vs grommets also. Clue me in before I waste a Grant.

[SGT Rock]

If your tarp has a seam anywhere but on the very edge, you'll want to get some silicone and seal it to prevent water from getting through. Most sil-nylon tarps do not come seam sealed. As to Grommets and tie outs, some tarps have metal grommets which sometimes pull out under high stress, so most folks use fabric tie outs instead when getting a good sil-nylon tarp.

Hope that gives you the info you need to buy the right one for you.

[peter_pan]

Read the thread on 8x10 tarps on Sgt Rocks www.hikinghq.net . Also read the Tarp article on the Jacks R Better site www.jacksrbetter.com .

If your ridge line does not have a seam you will never get the ideal pitch over a hammock.

[Youngblood]

...If your ridge line does not have a seam you will never get the ideal pitch over a hammock.Peter Pan,

I have seen you say this before, but have not understood the reasoning behind it. I have used 8x10 rectangular tarps a few times and have had them with the seam on the 10 foot length and also with the seam on the 8 foot length. I used both when hammock camping with the 10 foot length as the ridgeline and don't recall the sag being particularly different. My understanding is the sag has to do with the stretch characteristics of the fabric and that silnylon is an orthogonal woven fabric that has about the same stretch characteristics along either orthogonal axis. Why do you feel so strongly that the seam on the ridgeline affects the pitch when using a flat tarp in an A-frame pitch over a hammock? You do realize that the asym Hennessy tarps have their ridgeline at a bias (or an angle) to the orthogonal weave of the silnylon?

Youngblood

[peter_pan]

Youngblood,

Yes, I realize the HH fly, when hung diagonally, as normal, is on the bias as oppossed to normal tread weave and stretch.

My belief and experience is that unseamed tarps ( stock HH Fly) and tarps where the seam does not run along the ridge line will not hold the sharp ridge without extreme tension. Tensioning to this level put stress on the least supported part of the center seam for possible seam failure. It is virtually impossible to achieve for those tieing to the hammock ropes. But most importantly there will occur excess material in the center. This is what cause the puddling, sagging and flapping that many report and are always seeking solutions too. Some might argue that if staked down with multiple guys and a steep angle this can be avoided. To some extent it certainly helps. But now there are extra lines, pegs and time involved.

You and I have been part of many threads discussing catenary cuts on ridgelines: how to do it, how much drop along the curve, how to measure how to cut, sew etc. In fact, we have both made tarps and shelters with this technique. They work...in the designed pitch range... while giving up traditional flat tarp versitility. Having now made in excess of 25 tarps, 8x10, 8x8 ( traditional and diagonal seamed), three with catenary cut ridges; my experience is that tarps with seams on the ridgeline of the intended pitch out perform those without such a ridge seam in every case...Further, I have found that tarps which have the outer corners inboard of a line perpendicular to the ridgeline end point ( Mac Cat, diamonds, and JRB 8x8 with diagonal seam) readily and routinely pull down into near catenary curves with routine staking and stresses. This makes them, as some like to describe, "hummers not flappers".

Also consider the truth in this old adage. Those who do not learn the lessons of history are doomed to repeat them...As a historical interpreter and professional flint knapper,I have gone to many pre 1840 rondeveous...these are tent cities, as large as 5000 tents, standing a week or more at a time in often bad weather. Yes, they are mostly cotton. They are mostly "A" or baker design, they all have ridgeline seams...Those that use ridge poles,hold there shape for years and pitch taut in all designe directions...Those without ridge poles, pick up a natural cat curve and pitch tightly also... There drawback is that they seem more prone to material failure due to the weight of wet cotton as it ages over time. This is not an issue for silnyl. But the lesson of design are.

Finally, the only reason to make 8x10 with the center seam on 8 foot length is to save material, minor sewing time and money. False saving IMHO for those who intend to primarily pitch it on the 10 length in an "A" variant.

Pan

[Youngblood]

Peter Pan,

This is an interesting subject.

I was talking about an 8x10 flat rectangular tarp and whether the ridgeline being on the 10 foot length or the 8 foot length effected the sag when it is pitched as an A-frame with a 10 foot length. I would like to leave out tarps of other cuts for this discussion. If I understood what you said, you mentioned extreme tension and possible seam failure as the reason one worked better than the other? I assume that you are referring to the stress being applied parallel to the seam versus orthogonal to the seam. With identical tieout points, I'm having a hard time seeing that... all the tieout points need pretty good tension if you are going to stretch the tarp enough to reduce the sag. And like you mentioned, to get more of the sag out you need some tieouts on the sides of the tarp, towards the center... and when you do this with enough tension, the ridgeline will take on a catenary shape. But this only occurs on flat tarps when enough tension is applied to actually stretch the material slightly-- this puts stress orthogonal to the seam when the seam is on the 10 foot length. I guess what I am seeing is that when you put tension on the tarp to reduce the sag, you are going to put tension on the seam from all kinds of directions and I don't see the seam direction having a bearing on sag unless seam failure, or the threat or it, limits how much stress you put on the tarp.

Do you know of these seams failing? I haven't heard of that but I'm not a tarp manufacturer. The failures that I've heard are with grommets pulling out or tieouts failing if they aren't adequately re-inforced and I suspect that some of these failures occur because of guylines becoming slack during the night and the resulting forces when wind gusts cause huge dynamic loading on the slack line.

Youngblood

[peter_pan]

Youngblood, etal,

First, I believe we say the same thing for the most part. Point, if you were to pick either of your 8x10s for a couple week section hike. I bet you would pick the one with the center seam on the 10 foot length? Am I right? ;)

As too the stress issues...I agree with you a rip-out is almost unheard of assuming 100 % poly thread, and it not being deployed as a near flat wind screen in gale force winds....That said, many here are deciding on designs for do it yourself projects...to that end, we have again been party to discussions of the strength issues of flat feld seams, french flat feld and modified "flat felds" of various design. My only point is that to make an 8x10 with the seam on the 8 foot length, ie pitched "across the waist" of a hammocker it must be drawn very tight to take out the ridge flop/slack. At least it is tighter and more stressed than necessary for a 8x10 with a ridge line seam.

[Youngblood]

Peter Pan,

I guess at this point we will just have to agree to disagree. ;) ... I still don't see the tensioning difference. Maybe when we see each other again we can better see each other's point of view and come to an agreement.

As far as which tarp I would carry? It would be one with a catenary curve on the ridgeline, so yes it would have the seam on the ridgeline... but that is primarily because I need the ridgeline seam to implement the catenary curve. But the advantage of a catenary ridgeline is another discussion.

Sure is a lot more to tarps than I realized when Dorathy Hanson at Mountain Crossings suggested that I use one on my 2000 thru-hike. I believe I now know enough about them to be dangerous but hopefully have enough sense to realize that there is still a lot about them that I don't know. Everytime after I make one with the catenary curves, I look back and rethink the flat-felled seam and rolled hem issue... sewing on a curve that wants to fight you every inch of the way with slippery silnylon can sure test your attitude and sewing skills... and I have no allusions about my lack of sewing skills.

Youngblood

[plodder]

OK. Follow that ridgeline stuff. Now clue me in as to the difference between a $56 tarp and $175 tarp.

[SGT Rock]

$175 tarps carry themselves and come with a heating and air conditioning unit.

[smokymtnsteve]

$175 tarps carry themselves and come with a heating and air conditioning unit.


up here in AK U get the special AK $175 tarp deal..no AC but a triple size heater.

[SGT Rock]

Steve, you need one of these: http://www.kifaru.net/paratipi.htm

[smokymtnsteve]

Steve, you need one of these: http://www.kifaru.net/paratipi.htm

or one of these

http://www.alaskatent.com/products/tents/arctic_oven.htm

[SGT Rock]

Mine was lighter :D

[smokymtnsteve]

I travel by dog sled when it is real cold so weight is not so much a factor.

come on up rock and let's do some backcountry dog sled travel...

we wont even carry a tent just stay in some old trapper shacks....I know where a few are. no permits, no fees, and no need to carry a cell phone..as there is no signal..however U will need to carry a gun preferably a 44 mag.

that's what we carry up here,,,,but don't tell any of my liberal friends :D

[peter_pan]

Youngblood,

Agreed. Hope to see you at Trail Days.

Now..... these guys have found some portable saunas....wonder if they come with cocktail waitresses...or waiters, special order for the ladies. :p

Regards,
Pan

[SGT Rock]

I travel by dog sled when it is real cold so weight is not so much a factor.

come on up rock and let's do some backcountry dog sled travel...

we wont even carry a tent just stay in some old trapper shacks....I know where a few are. no permits, no fees, and no need to carry a cell phone..as there is no signal..however U will need to carry a gun preferably a 44 mag.

that's what we carry up here,,,,but don't tell any of my liberal friends :D

How about a .308 and a .45 for a sidearm :D otherwise my wife won't approve of the spending, plus I would need a new sleeping bag, mine ain't rated for that stuff.

And for the weight, be nice to the puppies, they might appriciate the lower weight :D

[peter_pan]

Youngblood etal,

A point I've all but forgotten.. :datz .. One way to make the tarp without the ridge line seam perform better is to use a separate ridge cord strung tightly between the trees.... Of course the tarp will need ridge tie outs still to keep it from creeping towards center....An alternative to separate lines is put drop loops on the ridge cord about 6-8 inches out and tie snugly to the drop loops....This technique worked well for me for years when I used to use a "standard 8x10 with the 8 foot center seam"....The draw back to this approach is that the underside of the tarp wears on the ridge cord....no big deal if you only use it a couple of nights a year....Big deal IMHO if you are 100 plus nights a year hammocker...........The elimination of this cord (25 ' of 550 cord is about2.5 oz) saves some weight, saves wear, simplifies erection of the tarp....The elimination of this cord is another reason I prefer the 10 foot center seam construction model for hammock and general purpose use ( I agree with Youngblood's earlier post that for a single hiker an "A" on the 10 foot length provides better coverage than on the 8 foot length because the open ends are further from the protected center for any middle of the night wind changes or splash.)

Pan

[Youngblood]

Peter Pan,

Yeah, a lot of things come into to play when we think back on how things worked for us (in this case tarps). Sometimes we forget that we made small changes along the way that effected things in ways we had forgotten. You and I have probably tried so many different tarp combinations with different guying options that we may not be as sure of everything that we did in the past as we think we are. I know that there are many things that effect how taut a tarp can be setup... and also a few other things that effect how well it stays taut through out the night. I have a system I now use that I think works very well, but I still experiment a little bit to try and tweak it every now and then because it's not perfect... and heck, I sometimes like to try new things to keep my interest up.

How long has it been since you have tweaked your hammock tarp in some way? I had left mine alone for about a year... until yesterday, I pitched one of my three season tarps out back and changed how I used the shockcord... now I need to take a trip and see how that works.

Youngblood

[Youngblood]

OK. Follow that ridgeline stuff. Now clue me in as to the difference between a $56 tarp and $175 tarp.
I would have to look at specific tarps to see if I could spot the differences. Price difference could be because of many things-- like where they are made, number of tieouts (and where they are positioned), grommets or sewn on tieouts, tieout re-inforcement, if guylines are included (and what kind of guyline and are they attached), if stakes are included (and how many and what kind), whether it's seam sealed (if not is seam sealer provided), etc.

Youngblood