lightest water proof Bivy bag

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ianfitz
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lightest water proof Bivy bag

Post by ianfitz » Sun Jan 04, 2015 9:13 pm

with racing in mind I've been thinking about this for a while now and reckon it should be possible to make one under 200g that is breathable and reasonably robust.

using this on the top - http://www.extremtextil.de/catalog/2-5- ... :1977.html

and this on the bottom - http://www.extremtextil.de/catalog/Cube ... :1144.html

possibly a small strip of this over the opening with some cord to tie it out the way when not in use - http://www.extremtextil.de/catalog/Mosq ... :1565.html


thinking c. 2m long 55cm wide at foot end and 75cm wide at shoulders gives 2 x 0.65 = 1.3m2 for top and bottom

so 49g x 1.4 = 69
and 80g x 1.2 = 96
plus 17g x 0.2 = 4g
makes 169g plus a bit extra for thread seam sealer and a small zip, plus the mesh to keep the wing death at bay if you're feeling flash! thinking of using the black diamond twilight as a pattern its a 'climber style' bivy where the zip goes across at about face level, you have c.45cm above that to put a rucksack or what ever in there. There's plenty of space for a neoair so maybe a 'race bivy' could be a bit smaller as no need for such luxuries! TBH i could go shorter than 2m maybe 1.85 which would bring it down to 157g. Then again the extra 12g would make quite a difference to the amount of usable space in there!

Although I'm posting this in the MYOG forum it will actually be my dear old mum who I'm hoping to persuade to sew this for me (mainly as she is a retired pro seamstress and I'm am, shall we say, less talented with a sewing machine) so really its the first post in the new GYMTMYG get your mum to make your gear!

I think it would cost about a fair bit in materials as there would be a lot of wastage just making one. Anyone else fancy an experimental super light UK made bivy??
Last edited by ianfitz on Mon Jan 05, 2015 2:12 am, edited 1 time in total.
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Zippy
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Re: lightest water proof Bivy bag

Post by Zippy » Sun Jan 04, 2015 10:30 pm

Ooh maybe, depending on cost and providing your mum makes me one too. Have in my head something like £30 as interest level...

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Mike
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Re: lightest water proof Bivy bag

Post by Mike » Sun Jan 04, 2015 10:52 pm

I could potentially be interesed in this but I'd imagine the cost will be a lot more than 30 quid due to the cost of the material. Keep us posted ian :wink:

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Zippy
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Re: lightest water proof Bivy bag

Post by Zippy » Sun Jan 04, 2015 11:01 pm

Yetiman wrote:I could potentially be interesed in this but I'd imagine the cost will be a lot more than 30 quid due to the cost of the material. Keep us posted ian :wink:
Ah, I might have skimmed specs on a small screen and my eyes saw a factor of 10 smaller number than reality :oops:

ianfitz
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Re: lightest water proof Bivy bag

Post by ianfitz » Mon Jan 05, 2015 8:42 pm

ianfitz wrote:with racing in mind I've been thinking about this for a while now and reckon it should be possible to make one under 200g that is breathable and reasonably robust.

using this on the top - http://www.extremtextil.de/catalog/2-5- ... :1977.html

and this on the bottom - http://www.extremtextil.de/catalog/Cube ... :1144.html

possibly a small strip of this over the opening with some cord to tie it out the way when not in use - http://www.extremtextil.de/catalog/Mosq ... :1565.html


thinking c. 2m long 55cm wide at foot end and 75cm wide at shoulders gives 2 x 0.65 = 1.3m2 for top and bottom

so 49g x 1.4 = 69
and 80g x 1.2 = 96
plus 17g x 0.2 = 4g
makes 169g plus a bit extra for thread seam sealer and a small zip, plus the mesh to keep the wing death at bay if you're feeling flash! thinking of using the black diamond twilight as a pattern its a 'climber style' bivy where the zip goes across at about face level, you have c.45cm above that to put a rucksack or what ever in there. There's plenty of space for a neoair so maybe a 'race bivy' could be a bit smaller as no need for such luxuries! TBH i could go shorter than 2m maybe 1.85 which would bring it down to 157g. Then again the extra 12g would make quite a difference to the amount of usable space in there!

Although I'm posting this in the MYOG forum it will actually be my dear old mum who I'm hoping to persuade to sew this for me (mainly as she is a retired pro seamstress and I'm am, shall we say, less talented with a sewing machine) so really its the first post in the new GYMTMYG get your mum to make your gear!

I think it would cost about a fair bit in materials as there would be a lot of wastage just making one. Anyone else fancy an experimental super light UK made bivy??

Just realised that the cuben on the bottom of my borah bivy is the 19g and not 49g so in fact

so 19g x 1.4 = 27
and 80g x 1.2 = 96
plus 17g x 0.2 = 4g

Is 127!
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Scattamah
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Re: lightest water proof Bivy bag

Post by Scattamah » Fri Mar 13, 2015 7:44 pm

@Ianfitz...any further movement on this idea? Would make a good piece for my summer kit.

Greetz

S.

ianfitz
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Re: lightest water proof Bivy bag

Post by ianfitz » Fri Mar 13, 2015 7:48 pm

Sorry no timescales as yet. She's busy with other sewing currently and as she's meant to be retired I don't want to hassle her.

Will get some cheaper fabrics first to work up a prototype.
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Scattamah
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Re: lightest water proof Bivy bag

Post by Scattamah » Fri Mar 13, 2015 7:54 pm

No worries. Ta for the update.

Greetz

S.
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Alpinum
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Re: lightest water proof Bivy bag

Post by Alpinum » Tue Apr 21, 2015 10:33 pm

Been pondering over the same idea with the same top fabric but instead of a Cuben floor I'd (or better will) go for a Chikara floor.

Chikara rip stop nylon weighs 42 g/sqm, is double PU coated, much cheaper than Cuben and will take tons of abuse. Other good thing about it, it's dead easy to sew and work with.

u02sgb
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Re: lightest water proof Bivy bag

Post by u02sgb » Thu Apr 23, 2015 1:56 pm

My Oookworks inner for my Trailstar has a Chikara floor and I can vouch for it's effectiveness. Pretty tough and not slidey like Silnylon.

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adjustablewench
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Re: lightest water proof Bivy bag

Post by adjustablewench » Mon Apr 27, 2015 8:29 pm

Hadn't heard of the chikara - so had a look. Sounds good and is used by kite makers so you get loads of pretty colours :grin:

http://ripstopshop.co.uk/PBSCCatalog.asp?CatID=1751977
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Zippy
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Re: lightest water proof Bivy bag

Post by Zippy » Mon Apr 27, 2015 10:41 pm

u02sgb wrote: slidey like Silnylon.
That's the one bad thing I have to say about my borah bivvy!

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Mart
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Re: lightest water proof Bivy bag

Post by Mart » Wed Apr 29, 2015 4:43 pm

Zippy wrote:
u02sgb wrote: slidey like Silnylon.
That's the one bad thing I have to say about my borah bivvy!
Im with Zippy on the slippiness
2924 miles per Gallon

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TheBrownDog
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Re: lightest water proof Bivy bag

Post by TheBrownDog » Wed Apr 29, 2015 6:29 pm

Mart wrote:
Zippy wrote:
u02sgb wrote: slidey like Silnylon.
That's the one bad thing I have to say about my borah bivvy!
Im with Zippy on the slippiness
I'll add my voice to that but I found that a tyvek groundsheet keeps it in place.
I'm just stepping outside ...

ianfitz
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Re: lightest water proof Bivy bag

Post by ianfitz » Mon May 04, 2015 10:55 pm

These are on now! I've not ordered any materials yet but will do in the next couple of weeks. Mum wants to stitch up a practice one using cheaper materials first. Fair enough!

Planning on using the Black Diamond Twilight Bivy http://eu.blackdiamondequipment.com/en/ ... AALL1.html as a rough pattern, although will go to around 200cm long as don't need loads of extra space in the head end.

Will have 25g Cuben on the base, a 'water proof' zip and bug netting. Final design is still TBC but will be focussed on being as light as possible throughout the bag.

My guestimate is that it will be around the 180g mark, I'm unsure how much extra weight the thread will add. I think that is at least 100g lighter than any fully waterproof bag I've seen for sale elsewhere. the waterproof fabric is breathable to 15,000 while the alpkit hunka is 10,000, I've always found that to be a pretty decent bag in use.

I'm not totally sure on price but guess that £120 would be a maximum cost. Shout up if anyone is interested and I can order more fabric,
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Re: lightest water proof Bivy bag

Post by Ben98 » Mon May 04, 2015 11:16 pm

Ohh if I had the money! Sounds vaguely exciting, even if I've just got my new bivi in the post :-bd
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Re: lightest water proof Bivy bag

Post by Scattamah » Mon May 04, 2015 11:55 pm

Keep this design in mind as well - http://www.zpacks.com/shelter/bivy.shtml - seems they come in around the same weight you're looking at.

/me keeps one eye open on this thread for the proto...

Greetz

S.
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ianfitz
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Re: lightest water proof Bivy bag

Post by ianfitz » Tue May 05, 2015 12:01 am

Scattamah wrote:Keep this design in mind as well - http://www.zpacks.com/shelter/bivy.shtml - seems they come in around the same weight you're looking at.

/me keeps one eye open on this thread for the proto...

Greetz

S.
that does look good, although not fully water proof sounds like its designed to use with a tarp.
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Scattamah
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Re: lightest water proof Bivy bag

Post by Scattamah » Tue May 05, 2015 10:12 am

I would say you're spot on there. Switching out the pertex top layer for some of the very fine cuben (11.4g) might give it a bit more resistance to water. The only ingress point would then be the mesh.

This may have been thought of already - loops on the 4 corners to peg it down so folks that roll in the night don't turn it all over and end up with the lightweight top material rubbing/tearing on the ground.

Greetz

S.
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ianfitz
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Re: lightest water proof Bivy bag

Post by ianfitz » Tue Apr 19, 2016 10:01 pm

After having the fabric in the cupboard for quite a while and doing plenty of pondering, and a a fair chunk of forgetting, I sorted out a final design.

I just had the prototype from Mum in the post. Made out of old duvet covers and voile! it wider than I thought over the chest and waist, but actually happy with that as it is really roomy. I reckon I could actually get in wet, change and get into a bag out of the rain. Not too sure on final weight as there is a bit more material now. however I am thinking around 250g which for the size of it, with a stitched in midge net will be vaguely exciting.

Expecting the finished article early to mid may, depending on her other sewing commitments! report and photos to follow :-bd
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Re: lightest water proof Bivy bag

Post by Scattamah » Sat Apr 23, 2016 4:04 pm

So double the original weight but a lot more space...enough space to slide a Neoair Xlite in and still get decent loft with a down bag?

Greetz

S.
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ianfitz
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Re: lightest water proof Bivy bag

Post by ianfitz » Sat Apr 23, 2016 4:35 pm

Scattamah wrote:So double the original weight but a lot more space...enough space to slide a Neoair Xlite in and still get decent loft with a down bag?

Greetz

S.

Surprisingly huge. Near in there and I could get changed in there. Winter bag would be no problem at all.

I'm guessing 200-250 but time will tell :-bd
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ianfitz
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Re: lightest water proof Bivy bag

Post by ianfitz » Sat Apr 23, 2016 4:37 pm

Near = neoair. Can't see the edit button on the iPad im using at someone else's house
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Re: lightest water proof Bivy bag

Post by ianfitz » Tue May 10, 2016 8:29 pm

Post came today....

ImageCuban bivy by Ian Fitz, on Flickr

the whole thing, Decided in the end to go a little wider than originally planned. For winter lofting and also as it means that I can actually get changed in there!

ImageCuban bivy by Ian Fitz, on Flickr

the midge net, decided to add a zip at the base of this, adds a little weight but worth it...

Roll up roll up

ImageCuban bivy by Ian Fitz, on Flickr


The extra width and zip for the midge net have added a bit of weight but it is 261g on the digital scales. For a fully featured, and generously sized bivy I'm quite pleased with that weight. it does also need seam sealing which I'm guessing will add ~10g


Edit to say that the zip pulls are arranged so that I can leave the end bits open on both sides, the cuben flap will cover the gap to prevent rain getting in, there will be ventilation (especially as I'm a side sleeper) and the midge net can be used or not with the hood open or closed as its on a separte zip.
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Re: lightest water proof Bivy bag

Post by whitestone » Tue May 10, 2016 8:59 pm

Who made that Ian?
Better weight than wisdom, a traveller cannot carry

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