Hennessy Hammock Weathershield Questions

**headchange4u** · 12-05-2006, 15:18

I just bought a Nest and No Sniveller from JRB for use mainly with my HH AULB. My plan is to use both the No Snilveller and Nest together as an under quilt in extreme cold conditions and use my WM Apache 15 degree bag inside the hammock

After reading Michele's thread on JBR's bottom weather shield and Jeff's thread on his zippered travel pod I have thoughts of weather shields on my mind.

I wanted to make one from the same material Frogg Toggs are made of and after starting a thread on WB I found out they are made of micro porus polypropylene (MPP for short). I think this is the same stuff JRB uses for their weather shields. The stuff is breathable, waterproof, and very light. On the downside it is very fragile and tears easily. I found this stuff for sell at Outdoor Wilderness Fabrics under the name of Duravent described as:

Duravent is a patented 3 layer fabric with a micro porous film sandwiched between 2 layers of soft but tough Polypropylene.

They list it as weighing 3.2oz in the description. I am assuming that's per square yard. That seems kinda heavy to me for the Frogg Togg material. There were also suggestions of using Tyvek in the thread at WB. I also have some 1.1 oz silnylon in the collection of fabric I have amassed at home.

What would be the best choice of material for a weather shield? I like the idea of MPP but I don't want to go buy more material and spend more money if I don't have to. I'm not even sure if that's what I am looking for.

Silnylon would be my next choice. It would have the advantage of also being a wind blocking material which may help give a few degrees extra in cold weather protection but I am afraid of condensation issues between the Nest and the silnylon. Should I worry about this? Do I need a breathable fabric?

Tyvek is another option. I have a roll of the Tyvek for soft sided structure which is supposed to be breathable. It is also waterproof but I don't care for the stark white color so it's my last choice.

I also have some questions on the design of the weather shield (WS for short). When I first started thinking about it I wanted something like Jeff's travel pod which would encase the entire hammock. The HH's entry method seems like it would make a "pod" style WS a little hard to deal with and a hassle to get in and out of, especially when I may be dealing with 2 under quilts.

I think a 2 piece design would be best. A bottom section that is basically large enough to cover both quilts without interfering with the loft of the under quilt(s). I also want to make a top WS that goes on the outside of the hammock and covers the entire bug netting portion. The top WS would serve several purposes: I am thinking that enclosing the netting would give you an area inside the hammock that could be warmed up, like Jeff's travel pod, which would be helpful in cold weather as well as protecting from wind, rain, low fog that could get under the tarp, tarp condensation, etc.

I want to use silnylon for the top WS. I am hoping there won't be condensation issues.

With a 2 piece WS you would also have the advantage of only taking the pieces you need instead of having to carry a complete travel pod.

Having written a short novel above, I have to let you know that I have never used under quilt on my HH so there may be something I am missing or not thinking of. Suggestions and comment are encouraged.

**Just Jeff** · 12-05-2006, 15:39

1 - Don't completely encase the top of the hammock with sinlyon. Aside from condensation issues, I'd be worried about having enough oxygen to survive the night!

2 - Check out the HH SuperShelter pics...it's just like what you're talking about, using silnylon and a big opening in the top.

3 - I'd be leary of using silnylon under the quilts unless there was a good air gap. That way any condensation would be in the sil only, where you could wipe it out in the morning, and not in the quilts.

4 - If the duravent is 3.2oz/sqyd, it's much heavier than you need IMO. Try looking at the Teflon DWR or Momentum 90 at thru-hiker.com. It's spendier, but might be worth it, especially for the weight savings.

5 - Sounds like, for the bottom at least, it might be worth it to just buy the JRB WS. It's not that expensive and you know it fits with the underquilts. Then make a separate one for the top. Or maybe...make a Speer-type since you don't need the bug net in the winter.

6 - You're right about the zippered TravelPod not working on the HH. Maybe if you put a small zipper in the bottom, lined up with the HH entry slit.

Good luck on your project! We expect pics...

**headchange4u** · 12-05-2006, 17:32

I checked out some pictures and comments of the HH SS over at Backpackgeartest.org. It was stated that the top cover, or Overcover, is said to be made of an non-waterproof material so breathablility seems to be the key attribute for a top cover. That nixs the silnylon.

The HH SS does have a silnylon bottom but they use a foam pad not down with a high loft. A WPB fabric would be best here. I will probably get a JRB WS for the bottom in the future. The JRB WS is rectangular in shape I think. I would like to make my own because I want to try one cut in a diamond shape that just fits the quilts to eliminate extra material and save weight.....and because I am a DIY junkie

.

The Duravents lists at 3.2oz for the 50" wide and 4.2oz for the 54" wide. The weight measurement may be in linear yard. That's still to heavy.

**ringtail-THFKAfood** · 12-05-2006, 17:34

You might be able to make an undercover out of a Gossamer Gear Spinnsheet. I intend to sew 4 grosgrain ribbons on each side so that it can be used as a dining fly.

I currently use a Spinnsheet attached with binder clips as an overcover. There is ventilation room on each end. It also can be attached low on the windward side and high enough on the alee side to still see out.

Not fancy, but it works and I was carrying the Spinsheet for a packing/unpacking staging area.

**Peter_pan** · 12-05-2006, 18:58

Headchange4u, et al,

Note that the Nest an NS you are talking about is the one of a kind 0.85 oz nylon with 800 down, baffled to 1.5, each quilt is sub 16 oz, that were exibited at TD 2004...they are like a wisps of air.... vulnerable to compression from any form of weather protector used below it... especially if used double for winter coverage... Make sure that anything you design is roomy enough...

Do not use any non breathable materials for a project of this nature.

BTW, JRB MPP is approx 1.75/sq yd... total wgt is 9.5 oz/per section.

Good luck with the project.

Pan

**headchange4u** · 12-05-2006, 20:06

Thanks for the info Pan. I knew that Duravent at OWF was way to heavy to be the same material you use for your WS of the same stuff that Frogg Toggs uses.

I will be sure to give my bottom cover plenty of room.

**headchange4u** · 12-13-2006, 00:05

I found some 1.9oz uncoated ripstop nylon at WalMart in a nice tan color. Since it's uncoated it's extremely breathable and sounds like it is similar to what is used on the HH SS system as a top cover I am going to use it to make a top cover. I am also thinking that 1.9oz is a little heavier fabric and may help retain more heat.

I plan on adding a vent hole in the top, right over where my head will be, like on the HH top cover.

Is there somewhere that I can get the dimensions on a HH ULBA, specifically the top area?

**Peter_pan** · 12-13-2006, 08:49

Measure the parallelagram bug net...add 6 inches all around.... fold and sew the corners in about 3 inches...hem it about 1 inch all around... run light shock cord thru the hem.... done ... it should cover nicely and wrap over the hammock edge by 3-4 inches... ropes and tie outs should match the corners...BEWARE... even with breathable material, this project will be a condesation trap.... There is a reason Tom H separated the halves and clearly states that the top is for desert winter conditions only.... but YMMV.

Pan

**headchange4u** · 12-13-2006, 10:19

You read my mind, Pan. I had planned on making the cover just as you described, sorta like Jeff's All-In-One cut for the shape of the hammock. I know condensation is going to be and issue but his cover would only be used in very cold conditions.

I also had the thought of not putting the hole in the top. Instead I would leave 3-4 inches of the netting exposed on the head and foot end of the cover. This may allow for some cross-ventilation which may help with condensation but if there is to much air flow it may defeat the purpose of the cover in the first place. Opinions?

**Just Jeff** · 12-13-2006, 10:29

Like everything else, using this will depend on conditions. I've had my whole body inside the Hammock Sock and not had any condensation problems, and Seuss made a WS like you're talking about for a Speer...just used ripstop instead of the bug net with the same Speer design. He said it works will and didn't mention condensation problems. But obviously, it's only appropriate under certain conditions. Though I think restricting it to desert winter is probably too much...I think Tom's first ones were made from sil, though. Maybe that's appropriate for a sil one.