double layer hammocks
Chattin with WBG in another thread about heavier weight fabrics is what spawned this thread!!! That and the fact that there seem to be a several other heavy weight hikers about who have some questions about what to do when they are near the recommended weight limit on the materials that are commonly used to DIY a hammock.
The good Mister Speers uses Supplex to make his 350lbs+ hammocks, in the thread about the Taslan it was revealed that Hennessey makes his hammocks from that material. What WBG advised me of in those threads, is that those materials are mildly "grabby". That is to say they arent slick like nylon, so your clothes wont slide over them. His suggestion was that if I am concerned over the weight, to make a double hammock. This was not the first time this had been suggested to me, so I wanted to learn more about it, & have a couple questions.
1) With a double hammock, do I need to sew the 2 layers together all the way around? I ask because I read JJs bible to all things hammock & all things DIY (http://www.tothewoods.net/HomemadeGe...erHammock.html) where he made his version of Risks zhammock. I was afraid to rely on something like that, figuring that it really doesnt double the strength, just adds a pocket.
2) Would you use 1.9 on both layers? Two layers of a lighter weight nylon? One layer of 1.9 & a second layer of something lighter?
3) A more general question... does the double rolled, & double sewn hem do more than just keep the edges from fraying, & make it more presentable? I realize that hemming is necessary to prevent the fraying.
There were more questions when I started this post... but they have fled!!! ARGH!
for me a double layer hammock is any hammock where both layers are structural. if only one takes the load,it is not a double layer hammock. the jrb bridge for instance is not a double layer hammock, the second layer is not structural, but simply a pad pocket sewn to the structural layer.
since both layers take the load you can use thinner fabric than you would with a single layer. for instance, if you normally use a single layer of 1.9, using 2 layers of 1.1 would be about the same strength. two layers of 1.1 = 2.2 oz/yd, so it should be just a tad bit heavier/stronger than the single layer 1.9
actually, by my calcs, a double layer 1.1 should be slightly lighter than a single 1.9 with a 1.1 oz pad pocket attached. and the double 1.1 would be stronger at 2.2 oz/yd.
for an end gathered hammock, making a double layer would mean simply that both ends of both pieces are whipped/whatever into the hammocks suspension points. the sides are irrelevant with regard to structural matters.
double layer hammocks can't be beat for using a pad, ccf or inflatable. the pad is sandwiched between the layers which keeps it still and flattens out any buckeling that would otherwise occur, and ripstop is much more comfy than foam. it is the way to go if using a pad.
as for stitching the sides, i would recommend sewing one side shut, then on the other side, sew half shut, and leave the other half open (about 4-5'). this is obviously where you insert the pad. i personally have decided on using a 3mm zipper here. it is nice to have some kind of closure, and velcro is a pain. 5' of 3mm zipper weighs~1/2 oz. i think it is worth it as i have tried both and the zippered version just seemed alot nicer and easier to use.
as for figuring strength, just add the weights of the layers. 1.1 + 1.1= 2.2
i believe the nylon taffeta my hammock bliss used was between 2.5 and 3.0 oz/yd. the eno's and trecklights are probably the same. a double 1.1/1.9 would probably be in this range if not probably a little heavier/stronger.
some have suggested making the outer layer longer to make up for the thickness of the pad. i have never done this and do not think it is necessary. nylon is quite stretchy, and both layers seem to get loaded regardless of my using say my ba air core pad between them. i can tell this because both layers get pulled tight lengthwise when i get in. this is due to the moderate stretch of the nylon fabric. if both layers were not getting loaded, the bottom layer would be the only one to get pulled tight. i made a double layer out of polyester once, which doesn't stretch, and that is exactly what happened. the inner layer remained somewhat loose with the ba air core in there, this was b/c of the lack of stretch, the bottom layer took almost all the load leaving the inner layer loose. as long as nylon is used, this should not be a concern and differential lengths are probably not needed.
I am relatively new to hammocks myself, but after owning and using a Claytor double bottom hammock, I think I would always want a double bottom. The reason is the flexibility. If I use my underquilt and its really colder than the UQ will handle, I have the double bottom as a backup. I can stick in a pad or clothing or even dry leaves. I always carry a pad to set around the fire on anyway so I have it in case I need it. My experience with my first hammock, an HH, with pad on the inside broke me of ever using a pad inside again. I even had a Big Agnes pad and bag where the pad fits into a sleeve in the bag, and it was hard keeping it under me. I have experimented with my pad between the layers of my Claytor and wondered if I even needed an expensive UQ. In the end, I have to say I am glad for the UQ. It is so nice sleeping directly on the hammock.
Also, the weight limit given by the manufacturers, according to HH is conservative. They made me an Ultra Lite Backpacker, 200 LB recommended limit, with thicker rope and told me I would be fine at my 210 to 220 range.
Hope this helps a bit.
I made a double layer 1.9x1.9 with wally fabric. I really like it. I weigh about 260 and have no concerns about the strength. The pad retention is wonderful. I like WBG's suggestion to zipper or somehow close the opening for pad insertion. This way you can make the opening larger for easier pad placement but the pad can't get out. I think I might like using velcro and adding some type of velcro positioning device to my pad as a way of keeping it positioned inside the layers. For some reason mine seems to always end up in the center, even though I position it for diagonal sleeping. I love the way having the pad inside retains the slick nylon next to you. Makes repositioning yourself no problem. Trying to turn over on a pad or non slick hammock material is a real pain especially with fleece clothing.
I'm glad you brought that up. That was the first thing I noticed years ago when I used a two-layer hammock. I resorted to using small lines tied into the hammock knot, taping ribbon loops onto my pads, and using that to keep them from sliding to the center of the hammock before I got in or when I got out. Of course that is something else to mess with so you have to decide whether it is worth it or not.
Originally Posted by rstms
When I started hammocking a year and a half ago, I really hated the pad inside the hammock. I always felt like I was velcroed in position and couldn't move around easily.
I made my risk double layer to his directions and loved it. I used some fabric from the walmart $ bin. It's kind of sateen looking and not ripstop. After a few field tests, I found it rather cumbersome to load the pad into the pocket through the end spaces left unsewed for that purpose.
I finally just removed the stitching on one side of the hammock. This makes setup much easier. I haven't noticed any particular problems with the unsewed side getting confused. When I set up, I leave the diagonal corner sticking out a bit. This seems to help the self centering thing.
Miles of Smiles
Im a heavy hiker and hated all of the lighter weight limit hammocks around, so I decided to make my own. First, i have found that a single piece of 1.9 oz ripstop did hold my 280 lb body. in fact I used this hammock on my aborted thru-attempt. I then went to a risk style zhammock made of 2 pieces of 1.1 oz ripstop. it has held my overweight body ok, but I still felt a little uneasy about it. I also thought it was a little to short, so then I built my newest hammock. its a Risk zhammock made out of 1.9 oz rip as the inner layer and 1.1 oz rip as the outter layer and feel that this combo will hold my weight just fine.
Thanks for all the comments guys, I really appreciate it! Ghost (or anyone else who made a zhammock clone) did you follow Risks instructions as given for sewing?
I have made 1 double layer hammock from the $1 fabric bin- ripstop but not coated - in sewing the two together I left only an opening centered on 1 side, about 2.5 or 3 feet long- once I had to get inside of it -head and arms-to arrange the blanket I was testing; friends nearby said it looked like I was being eaten....(Aggh! beware the hammock monster!!)
Betsy- still learning!
Fortuituously, I am just finishing a double (triple) layered bridge hammock.
Layer 1 is thin fleece. It is interfaced and hemmed to Layer2 which is polyester liner material. Together these form a basic open-ended bridge hammock that provides structural support and is warm and fluffy against the skin.
Layer 3 is cheap thin fashion camo material, formed into a lidded hammock sock that fits over the structural hammock. It is formed of four parts. There is a main section that wraps around the structural hammock contacting only at the edges. There is a void between the two layers upto 4 inches in the middle. The second part is a zip-on roof and the last two are velcro'd on end caps.
Layer 1 therefore is for feel and warmth.
Layer 2 is for strength and to reduce stretch.
Layer 3 is to block wind.