Tarp Tensioners specs and additional tips for making them

[Hangs4Fun]

Well, I just had to make those tarp tensioners part deux from Jeffs site. I almost gave up trying to get the surgical tubing (sling shot replacement kit) over the bights. Thank goodness I decided to try and heat the rubber up in some boiling water (keep the rubber off the hot pan). Perhaps it's just that I'm new to hammocks and working with these materials, but since a lot of the stuff that is probably common sense to most of you seasoned hanger DIY'ers, I thought I would do a quick write up on how I made them and the tension pounds and weight. The main instructions are on Jeffs site: http://www.tothewoods.net/HomemadeGe...ensioner2.html, I am only trying to explain where I was hung up following his instructions and offer some tips that helped me finally make them.

TarpTensioner_all_done.jpg

STEP 1
Materials for one tensioner is pretty straight forward (though I ended up cutting about 9 inches from the 36 inchers)
- One ~5" piece of surgical tubing
- A ~36" section of cord
- Two ~9" pieces of small string. I used inner core from 550-cord.
my comments - I got the surgical tube from Walmart (cut from a sling shot my son was very upset I bought just to destroy). Walmart doesn't have the slingshot replacement kit any more though, you will have to pay for a slingshot (or order surgical tubing online).
36" ended up being a bit long, but ok to start with. I too used the inner core from 550 cord. At first I didn't know what that meant, until I went ahead took a piece apart to find 7 strands inside that pulled out very easily - PHEWY.

STEP2
I formed the bight with an overhand knot
my comments - I embarrassingly had to look up what a "bight" was.

STEP3
Put the cord inside the tube, and pull the tubing up over the knot about .5".
my comments - ummmm, at least Jeff didn't use the word "just". This is where my initial problems started. I couldn't get the cord down the tubing to save my life. I finally used a hanger and dipped the surgical tubing in boiling water for a minute. It still took some major maneuvering, "massaging" the tube towards the knot I was trying to get over while pulling the end with pliers. Be careful not to cut tubing with pliers, but be patient, it will eventually go over, you just have to keep working it

STEP4
Whip the tubing to the cord with the inner core. If it's oriented like this picture (on Jeffs site), make sure the whipping is to the right of the knot.
my comments - Again, I am such a noob on this stuff, I had to look up how to whip. Found this video that really helped https://www.youtube.com/watch?v=QWoUbQXD65A. Having the whipping on the other side of the knot to keep the tubing from coming of the knot made sense

Here's where I am at in 4 different stages
TarpTensioner_early_stage.jpg

STEP5
Roll the end of the tubing backwards over the whipping.
my comments - Because getting the tubing over the knot was no fun, I didn't roll enough the first time and had to remove the whipping, reheat the tubing and pull more tubing over the knot this time. If you don't get the tubing to be able to wrap back over the whipping and contact more tubing it will roll back off the whipping too easy.

You can see the whipping is done and I have enough tubing left to stretch over top.
TarpTensioner_almost_done.jpg

STEP6
Stretch the tube down the cord to see how far it will go, and mark the spot (just pinch it between your fingers). That's where the knot needs to be.
Tie another overhand knot, making sure the knot ends up at the place you marked. You should be left with something like this picture.
my comments - In the picture on Jeff's site, I didn't understand why the picture showed such a long cord against the tape measure since I couldn't stretch my 5" piece of surgical tubing more than a couple of inches. I ended up just going with it and sticking to the main thing he said instead of trying to achieve what he had in his photo. I guess the slings shots these days are just a little more powerful? The main thing to remember here, is you want to set an ending knot where what ever tubing you are using can go to.

STEP7
Pull the tube down over the knot, whip it, and roll it just like the first end. You're done!
my comments - again, at least he didn't use the words "just pull the tube down over the knot". Holy crap this was difficult, even after I heated up the tubing. I did find that using 2 pliers at once helped, I'm really beginning to think that not all surgical tubing is created equally (Jeff's was apparently MUCH more stretchy than what I was using. Though mine did end up being almost the exact same length unstretched, but I guess from last picture his tubing would allow the system to stretch over 10 inches.
Also attaching the other end to something solid was key, you need 3 hands here.
Here is the 2 plier technique ;-)
TarpTensioner_pull_over_last_knot.jpg

They ended up being 8.5" each
TarpTensioner_No_Resistance_8_5_Inches.jpg

Fully stretched they are 12.5" each for a total stretch of 4". I'm not sure that will be enough stretch, mainly because I don't know how much re-tensioning is needed overnight??
TarpTensioner_Max_Resistance_12_5_Inches.jpg

All in all, the 4 tarp tensioners weighed in at 42 grams (1.48 ounces)
TarpTensioner_weight_42grams.jpgTarpTensioner_weight_42grams.jpg

Now to see how many pounds of force there is when stretching these. There seemed to be 3 positions when I pulled them. The first was and abrupt end to the easy pull. The second was the where the tubing maxed out. The third was the stretch of the 550.

The easy pull ended at around 7 pounds of force:
TarpTensioner_1st_Resistance_7pounds.jpg

The tubing seemed to stretch out at around 11 pounds of force:
TarpTensioner_2nd_Resistance_11pounds.jpg

The 550 stretched a tad past that until there was no more stretch at 47 pounds of force at which point it was like a solid rope:
TarpTensioner_Max_Stretch_47pounds.jpg

Thanks to Jeff from tothewoods.net for the article. I will let you know how these work, I plan on setting up the hammock tomorrow night.

[AaronMB]

Great job, man. Thanks for taking the time to give us your rundown. I'm inspired to open up the slingshot bucket o' fun and make a few of these.

If 4" isn't enough play after your tarp starts sagging, you could always complement the tensioner with a length of cord that has a taut-line hitch, or something else adjustable so that as you run out of stretch in the tube, you can just take up slack with the taut-line, keeping your tensioner effective.

[Hangs4Fun]

Great idea.

I do like the amount of force I get out of these so maybe I will use them for the ridge line and male another set of 4 for the guy pines. I will find some stretchier stuff online this time though ;-)

[kerryandjane]

Thanks for the clear write up. I made a set a while back but stopped using them for some because I went down to zing-it which didn't hold a knot as well as the paracord I was using. They also broke down and lost the stretch after the first summer. I rely on the easily replaceable "clove hitched shockcord tarp tensioners" since. It's nice to know when the shock cord is maxed out instead of having the rope all hidden in surgical tubing. Anyway, the tubular tensioners look so much better in my opinion. Your post has got the brain juices going again. I'll have to try with smaller surgical tubing and something light.
I followed Jeff's instructions but instead of pulling the tubing over the length of straightened rope and knot.... I stuffed the rope and knot into the tubing. Maybe that's what Jeff meant anyway haha. Anyway Same result but a different route from what I thought. Was much simpler for me. Made the whole process a hell of a lot less finicky - more a perspective thing I guess.

Oh and to pull the cord through the tubing I used a strand of 550 inner which I clove hitched around the cord to pull through... I used a butter knife as a lever to pull it through. I thread the inner on a yarn needle and let gravity work it through.

The Jacks R Better - Self Tensioning Lines use Thera-band (cadilac of surgical tubing) which is supposed to be more flexible/durable/strong and handle being frozen better I believe.

Once again, thanks for the write up. Thanks for taking the time. I'll have to give it another crack.

[Scubahhh]

Great project and great post!

All I've done is tying shock cord into loops, and sticking them between the guy lines and tarp, connected on both ends with mitten hooks which will (I think) break before the tarp tears. That's DIY enough for me!

[wgiles]

You can get soft latex rubber tubing at McMaster-Carr supply company online. More importantly, you can get it in all sorts of sizes and in ultraviolet resistant black. The most common size that I have seen is 1/4" ID X 3/8" OD, 1/16" wall thickness. It strikes me that this is way too heavy for tarp tensioners. Does anyine remember what size tubing was furnished in the sling shot kits? I was thinking that something like 3/16" ID by 1/32" or 3/64" wall thickness would be more appropriate. If that ID is too small, there is 1/4" ID X 1/32" wall tubing available. I've used a lot of this kind of tubing for air pressure measurements in ductwork. The natural color tubing is well known for UV and Ozone damage. McMaster is a great source for all sorts of odds and ends. I just like to build up an order so I don't get killed on shipping.

[Hangs4Fun]

Thanks wgiles, I will definitely look into some of the smaller diameter tubing from them and make a variation of these tensioners with zing it's instead of 550 cord. At 10.5 grams each, the 550/slingshot version is too heavy. But I REALLY like how the tensioner is hidden inside the rubber and each end is a closed loop so you can do simple Larks head where you want to attach them.

However, for my Continuous Ridge line I just ordered from Dutch, I think I will use one of these 10.5 gram tensioners on the wasp side (adjustable side) of the CRL. This should keep the ridge of the tarp properly tensioned as these 550 tensioners seem to be more pounds of pressure than the standard double shock cord tensioners.

Bottom line though for my tie outs and pull outs, I will want light tensioners, that are also a nice package (without a lot of loops hanging around and such like the typical zing it based ones with a doubled piece of shock cord). I will also be looking to integrate the tie out and pull outs with the lineloc 3's (ladder lock, like a hinged lever; not the triangular looking line lock). I want the whole line to stay on the tarp attachment loop and just pull it and loop the end over my groundhog and then pull the zing it tight until the tensioner is stretched where I want it for conditions. The overall goal will be the weight of each tie out and pull out.

Thanks to that new continuous ridge line from Dutch, The entire adjustable ridgeline is only 19 grams with all attachments and adjustments. So I am shooting for some low weights on each tie out.

[Hangs4Fun]

So I just ordered 10 foot of the opaque black Super Soft Latex Rubber Tubing, 1/8" ID, 1/4" OD, 1/16" Wall Thickness from McMaster-Carr (10' was the shortest length).

I figure since my goal is to use the 1.75mm Zing-It as the inside tension stop, I wanted a little more than the 1.75mm cord, so it had room to compress as the tension is released. 1.75mm is 0.0689" (which is thicker than their smaller ID stuff the 1/16" ID which is at 0.0625"). They didn't have a 3/32" ID, so I jumped up to the 1/8" ID with 1/16" thickness. The theory there being the PSI strength is the same as 3/8" OD stuff wgiles mentioned is used. I won't know the tension strength until I make one.

But it should look pretty sweet with the black latex rubber over the yellow zing it with 2 closed loops out either end. I'm shooting for 4-5 grams a piece.

That will put each 8 foot tie out and pull out to 9.5 grams each with tensioner, zing it line and Lineloc 3 (using wooden stakes) or add in my mini groundhogs and the total with stakes is 19.3 grams. Below is a breakdown of what I'm building:
- 4.5 grams: 12" tensioner (18-24" stretched, for total tie length of up to 10')
- 1.0 grams: Linelocs 3 (http://dutchwaregear.com/linelocs-3.html)
- 4.0 grams: 8 foot of 1.75mm Zing Its
- 9.8 grams: MSR mini ground hog

[Hangs4Fun]

Dang, wouldn't you know it. That tubing was shipped same day. I got home this afternoon to find a box I wasn't expecting at the front of the farm. It turned out to be the tubing I just ordered from McMaster-Carr. So for $11, they same day shipped me with tax, 10' of that black super soft latex rubber tubing 1/8" ID, 1/4" OD, 1/16" wall thickness. Can not wait to get the 1.75mm Dyneema (I mean Zing It).

This stuff is awesome and looks to have a 3 to 1 stretch, yet decent strength.

[wgiles]

McMaster prices are generally competitive and their service is first rate. Another thing that I got from them that might be worth looking in to was some braided mason's cord, 2057T882. I got blaze orange, 0.058" OD and 150 lb breaking strength. It is hollow core and can be spliced like Zing-It or Amsteel Blue. I have made some whoopie slings and endless loops from it. The endless loops are for prussiks on ridgelines. The whoopie slings are for tieouts. This stuff is very small, so I use yarn needles for splicing. It will just barely fit through the eye of the largest needle. A locked brummel eye splice or endless loop seems to hold pretty well. I shoot for a 2" bury and don't try to taper the tail end.