question about square tarp set up diagonally over a hammock

[Big Dawg]

It seems when I look at square tarps (like Jacks r Better 8x8, or neo's 9x9 camo) that are set up over a hammock, the center dips, compared to the ends where they are tied off (to trees). Why wouldn't the ridgeline of the tarp be straight/taut, like a MacCat or Hennessy Hex fly,,,,,, & if the sag is natural, based on how a square fly is diagonally set up over a hammock, then does the sag in the center cause the tarp to be less taut? Also, based on previous posts, I assume it's best not to run a line under the tarp for a ridgeline, b/c the line could cause problems w/ the tarp, correct?

[Footslogger]

I've got the JRB 8 x 8 tarp and the seem is along the diagonal. I get a good tight pitch with very little, if any sag.

'Slogger

[peter_pan]

The JRB 8x8 does have a diagonal seam and is straight when tied taut between two trees... It is pulled down some because of the single side tie outs... properly pitched, it is taut without excessive downward force and ( as Footslogger states) has little sag....It remains reasonably taut throughout the night... If you want to ensure the material stretch of silnyl in the rain or under heavy dew situations does not reduce the taut pitch, try either the JRB line tensioners ( which have a 5 inch tension control for each line) or home made sling shot or shock cord tensioners .

Tarps with multiple side tie out ( Mac Cat, 8x10) distribute the down ward pull along a greater or multiple points of the ridgeline... and may appear to have less sag.

Pan

[neo]

my digital camo 9x9 tarp has a diagonal seam,it form a perfect cantenary ridge:cool: neo


http://www.whiteblaze.net/forum/vbg/showimage.php?i=9721&c=577

[rpettit]

my digital camo 9x9 tarp has a diagonal seam,it form a perfect cantenary ridge:cool: neo


http://www.whiteblaze.net/forum/vbg/showimage.php?i=9721&c=577

That's a true statement, so does mine.

[Just Jeff]

That "center dip" is what keeps the tarp from flapping. It's not sag, but an approximation of a catenary curve.

Running a line under this kind of tarp would:
1) cause the line to rub against the silnylon, causing a leak, and
2) raise the tarp's center, eliminating the advantages of the catenary, causing the extra material in the tarp to flap with the wind.

So either deal with the dip or get a different shape of tarp. It's not a big deal at all, especially in Hennessy. In an open-top hammock, I notice a difference in headroom between the MacCat and JRB. But then the JRB is lighter and quicker to setup (can't wait to see the MacCat Gen III, though).

I go back and forth between the JRB and MacCat depending on the trip, my mood, and which clothes I want to accessorize with.

[neo]

That "center dip" is what keeps the tarp from flapping. It's not sag, but an approximation of a catenary curve.

Running a line under this kind of tarp would:
1) cause the line to rub against the silnylon, causing a leak, and
2) raise the tarp's center, eliminating the advantages of the catenary, causing the extra material in the tarp to flap with the wind.

So either deal with the dip or get a different shape of tarp. It's not a big deal at all, especially in Hennessy. In an open-top hammock, I notice a difference in headroom between the MacCat and JRB. But then the JRB is lighter and quicker to setup (can't wait to see the MacCat Gen III, though).

I go back and forth between the JRB and MacCat depending on the trip, my mood, and which clothes I want to accessorize with.


you have a really awesome hammock hanging website jeff:cool: neo

[betic4lyf]

i flipped ahead in my math textbook, and it talked about catenary curves, and hanging string and all. they wher hyperbolic sines or cosines. it was the most putrid thing ever. bringin calculus, trig, and hyperbolic in one. i nearly wanted to burn the book

[Dobber]

Hey Neo,

Is that a homebrew "rigger belt" I see you wearing on your homepage and in the tarp pics?

I spent some time at Ft Benning, (even have the Airborne wings, but most of my time was in leg units) and the handcrafted belts were pretty much sought after by all.

I got one by trading time/use of a Humvee for a Armey Reserve rigger unit that didn't have military transport...Ahhh, the Army- the original barter system!:banana