I am planning on making my own net bivy for use under a tarp. I am not interested in a bathtub floor. I do not want to use a groundsheet other then the bivy itself. Is 1.1 silnylon the lightest abrasive option?


Im making my gear with the pct in mind. So it would have to survive a few months of steady use. I would not mind having to patch with duct tape.

you could use 1.1 and it could work hassle free for a few months, maybe, but with 1.9 theres no question.

I'm not 100% sure duct tape will stick to silnylon.

You could try adding this coating to the 1.1, it may help increase the life.

http://jwbasecamp.com/Articles/Silnylon1/index.html#Description

That treatment adds some weight too, looks like about .75oz/yd so thats over 1.9 anyway, to me 1.9 is the no worries option.

Jeff....
The 1.1 is really going thin for a floor, perhaps the 1.35 would be more in line with what you need. Minute holes will self-seal slightly better with the 1.35. Duct tape can be stuck onto silnylon, but the usual method would be to stick a patch on using Silnet. (BTW... duct tape and Spinntex aren't really compatable, but a patch of Spinntex material can also be added to a Spinntex surface using Silnet.)

Edited by Quoddy on 02/21/2008 17:00:11 MST.

I think 1.1 and 1.35 are the same thing, just differing in number due to measuring weight before and after the silicone coating.

The 1.1/1.35 won't be completley waterproof under pressure. A 1.9 poly coat probably would be, but the finished weight would be around 2.5oz/yd. I would consider a 1.1 bottom and a polycryo ground sheet from gossamer gear. the polycryo sheet would be very waterproof and replaceable and help ease a lot of abrasion to the 1.1 nylon. If you duct tape both sides of the hole, it will stick to silnylon reasonably well.

Thanks for the info guys. Im considering the 1.1 because this is for a summertime bug bivy. At first my thinking is no water protection at all but then whats 1-2 more ounces to up the material to 1.9. Then add a 1" bathtub bottom for those just incase showers. Ah the decisions of light vs practical. Just trying to find that middle ground.

Now im gonna dig out a scrap of my sil and try some ductape patching.


thanks
Jeff

if you make it of the 1.1 and use the polycro you will probably be happy, and if you need more waterproofness and durability add the extra silicon coating. That should give you a best of both worlds option. if the light is too light THEN you can make it more durable.

I really dont want to carry poly ground sheet, its just something else to bring. Understanding that 1.3 is not going to stop any water wouldnt 1.9 be lighter then 1.3 and a poly sheet?

the 1.9 (70 D) with a light PU coating is 2.3 oz/yd according to oware. A heavy PU coating is 3.5 oz/yd. The Poly sheet from GG is .55 oz/yd and a total of 1.3 oz each. I have some 1.9 silnylon (probably about 2.2 after coating) from a few years ago, but oware doesn't have it anymore. It's rockin stuff though if another place has it. In the grand scheme of things, if carrying less items is more important than an ounce or two, go for the 1.9. If not, the GG is supposed to be good. Definitely post pics of your net bivy when you get it done

Personally, i use a 1.1 groundsheet from walmart $1 fabric- its so non-waterproof I can't use the awesome poncho I made from it for reliable rain gear! Being that careless is why my mom says I cant backpack with down things though.

David

Im interested in seeing the poncho you made. I was thinking of going the poncho route but a few things are keeping me away. 1-bushwhacking is not a good idea. 2-i love to fish and dont think fly fishing would be enjoyable in a poncho. 3-a main goal of mine is also peak bagging and other light mountaineering excursions. The weight savings over no rain gear is very intriguing but just not fezable for my activities. Maybe for the right trip or overnight summer trips it might be a great option for me.


I am in the middle of making a bivy right now. but as part of my new system im making I cant help but start thinking of the next thing on my list. In the sierras bugs are horrible at times(like anywhere im sure) but rain is usually a day time thing in the summer so a bug bivy doesnt really need a waterproof floor. But i was a scout and i like to be prepared.

Jeff, honestly as long as your somewhat carefull on what ground you sleep on (not in a hardpacked surface in the lowest lying area) you really shouldn't encounter any problems.
mike!

anyone know how to permanently attach no-see-um to poly???



If water was no issue. All that was needed was a fully enclosed net to lay in. Obviously the netting is to soft to be on the earth, but what would be the next best thing?

Sorry guys I just hate making something without weighing every option I can think of. If the weather is calling to be bad I would have my bivy with me anyway. The more I think about it the less I am inclined to make the floor waterproof.

Edited by JeffCadorin on 02/21/2008 21:29:30 MST.

http://www.backpackinglight.com/cgi-bin/backpackinglight/xdpy/forum_thread/9651/index.html?skip_to_post=75996#75996

i dont know how to make that link small like some other folks do, but thats the link to my poncho and some other stuff. Its a lot like a cheap featureless version of the MLD pro poncho. I'll still use it for summer even though it will probably leak in heavy rain as a shelter and keep me warm and wet as gear, but for $4 and 7oz what do you expect?

I wouldn't recommend sewing to polycryo b/c it is 'disposable'. If you aren't looking for total waterproof, 1.1 sil is a great overall choice. spinnaker groundsheets from GG will be slightly lighter and weaker, the poly is lighter and lots weaker. A 'waterproof' fabric will also resist dirt better.

At the risk of going against the grain I don't think SilNylon is a good choice for a floor - it is far too slippery.

I've tended to use 2oz PU Ripstop which is not slippery and resists abrasion well. The only thing is that it is only casually waterproof.

It can also be repaired easily.

I'm currently looking at 4oz PU nylon for a base. It's a lot less fragile but obviously a fair bit heavier and a lot more waterproof and puncture-proof.

If you are planning to take some sort of groundsheet to protect your silnylon floor then consider whether just using a heavier-duty fabric would be a better choice.

My current 2oz bathtub floor weighs in at around 150g and is a nice size for one. I'm going to make a 4oz version which is going to be a little smaller. It'll probably weigh in at 200-250g.

The Silnylon I use in the Uk weighs in at around 60gsm and the 2oz PU-coated ripstop weighs in around 55gsm.

For something like the PCT - where your groundsheet is going to see a lot of wear it's worth considering if weight is the ultimate consideration.

You could also consider making 2-or-3 so that if one failed your resupply box carried a spare. You could also consider making a light and a heavy version so that the rougher areas of the trail could warrant a heavier version.

When I've been sleeping in very rocky grassless terrain I've taken on a groundsheet based on 6oz Nylon. It's "heavy" but small and bombproof and protected my thermarest quite nicely.

I've been and checked weights and dimensions.

The 2oz one is 2.05m x 90cm tapering to 55cm with 7cm sidewalls tapering to 5cm. It weights 159g incl. case

The 4oz-PU pne is 2m x 80cm tapering to 55cm with 6cm side-walls. It weighs in at 267g and will be both tough-enough and waterproof.

For stony and boggy ground that extra 100g is to me worth the weight. I've made it a little smaller so that it uses a little less fabric. Since I'm 6ft it's about as small as I can go and still have a bit of elbow room for wet ground.

That exta 100g means that I am less reliant on site choice as well. Sometimes nature can be cruel - especially after sunset...

Edited by ArchNemesis on 02/22/2008 11:43:47 MST.

1.3 silnylon floors are very common on the pct. I used one every night, no groundsheet, and it finished like new. 1.3 is not completely waterproof under pressure but the only times I've seen it leaking through were over a puddle or on snow. Wet ground/grass/duff is not enough to make it leak, in my experience. It's slippery stuff but sleeping pads are not and they stick reasonably well. You'd rather find a flat spot though.

My floor will only be slightly bigger then my 20x78 BA pad. If I put like 6 dots of silicone on the bottom of my pad would this not stop any sliding issues?

put the dots on the ground sheet, it won't mess up your pad and will work with any pad you use on it, or if you loan it out. And yes the dots should increase the friction and keep your pad from sliding all over.

Edited by MarshLaw303 on 02/22/2008 15:09:25 MST.

Tim. I was thinking about putting them on the pad since i would be carrying both bivys(normal and net) sometimes and always the pad. If they are on the pad I can just use it in any bivy or tent I use.

Dots (or lines) on the pad will work on any tent-floor or ground cloth. You might put dots/lines under shoulder and hip areas to get the most weight pressing the Silnet onto the Silnylon.

Since I've some Silnylon lying around (60gsm/1.7oz) I've made up a Silnylon bathtub groundsheet.

One thing that I have done is machine a pocket near the foot end of groundsheet. The pocket is about 30cm/1ft deep with 1cm sidewalls and is a simple patch-pocket made of 2oz PU Nylon. A Foam mat slides into the pocket and so has nowhere it can go.

I'll also put a few spots of silnet further up.

The total weight of the g/s including pocket and stuff sack was 123g/5oz. The pocket added 12g.

The g/s was 2.05m x 77cm x 52cm with 4cm side-walls.

The next trip to uneven sloping ground will see how it fares. It's passed the wet-garden-lawn-and-elbow test at least.

[After 2 latte's I realised 120g was a camera so worth fighting for....]

Edited by ArchNemesis on 02/24/2008 13:57:07 MST.

What pad etc. are you using under you? Most pads are waterproof, so a little water pushing through a bivy
bottom or ground sheet is not an issue. I have done
a lot of trips in the desert and high sierra with a
full length pad only. Course I wasn't dealing with a lot
of mud. Arrange your your kit around your pad so you don't
slide off in the night.