Just wondering if there really is a need to take a bivi bag when you are under a good covering of tarp and on tyvek?

Who takes a bivi bag too?
And who doesn't?

What are your pro's and cons of yes or now please?

I tend to take my TiGoat Kestrel if I'm using a full-sized tarp.* It adds a bit of wind resistance, adding to the warmth of my bag (which means I can get away with a lighter bag). It also has a midge net built in (handy for keeping ticks off too) and cuts the draughts I sometimes get when using my quilt and I'm restless.

So, that's three positives for the sake of a little weight.

OTOH I rarely take a groundsheet.


* My current preference is a micro-tarp and a waterproof bivvy bag

I do exactly as Colin says. I can think of a couple of occasions where the lightweight bivvy saved me from a proper soaking. Both times involved mist coming in off the sea.

Use tarp and no bivvy bag here. 'water resistant' sleeping bags have always been fine. Tarps are 10x8 or 9x7 though not those pocket handkerchief jobs.

Paradoxically I agree with everything Colin and Stu said though

I've used a tarp without a bivi bag plenty of times, but pretty much always use a bivy with a tarp now. Generally a borah bivy

I also find it gives me lots of versatility - I often use a bivy without a tarp if the weather is looking good or I'm using artificial cover (eg a porch)

Helps with wind blown spray, wind and bugs. Plus I find groundsheet a faff

I always use a bivy bag - either a splash-proof one with a midge net or a Hunka XL, depending on the conditions. I don’t use a tarp if the forecast is settled and dry. I will sometimes use a space blanket, or tyvek, as a groundsheet if it’s really wet or muddy.

I have a with-tarp bivi bag that's just a weather resistant cover. TerraNova Moonlight, 180g. I use it w/o a tarp when it's clear and not too cold. Will use the tarp w/o a bivi bag when it's warmer with no chance of condensation but in conditions like that I'm more likely to just bivi, no tarp.

Pretty much as Colin states and for the same reasons. The extra versatility as noted by Ben is also a factor.

Tarp and bivy (Borah Gear) still only come to 300g or so, not really worth worrying about.

I'll be quite honest and say it hasn't entered my head not to use a bivvy bag when using a tarp. I thought they went together like bullets and guns! I suppose if the weather looks fine with no rain/mist then its an obvious thing to leave at home.
Wil give it a go

Slugs, midges and ticks (and mozzies) = bivvy bag with mesh.
Did a couple of overnighters in '18 during the winter on a groundsheet and tarp only. OK if your not in amongst wet grass (it was frozen on both occasions) and its too cold for bugs n' slugs

I'll be quite honest and say it hasn't entered my head not to use a bivvy bag when using a tarp. I thought they went together like bullets and guns! I suppose if the weather looks fine with no rain/mist then its an obvious thing to leave at home.
Wil give it a go

Or leave the tarp at home?

Yeah, bivvy bag and no tarp. Much greater choice of locations.

Norm, where you on the Mull of Kintyre? ;-)

APF

Alexpalacefan wrote: ↑Sat May 15, 2021 2:18 pm Norm, where you on the Mull of Kintyre? ;-)

APF

I noticed that one too.

Fifth Beatle me

Bearbonesnorm wrote: ↑Sat May 15, 2021 11:05 am

I'll be quite honest and say it hasn't entered my head not to use a bivvy bag when using a tarp. I thought they went together like bullets and guns! I suppose if the weather looks fine with no rain/mist then its an obvious thing to leave at home.
Wil give it a go

Or leave the tarp at home?

Yeah done them ones a few times. Thing is, I don't tend to get much sleep as I end up staring at the stars most of the night

Oh gawd I'm obviously a rank amateur . I suppose I'm going to have to start paying more attention to these "what boil-in-the-bag should I get?" threads from now on. I'm doomed.

RIP wrote: ↑Sat May 15, 2021 6:30 pm Oh gawd I'm obviously a rank amateur .

I think you're what statisticians call an outlier*, and not just when it comes to bivi bags

*Trying not to break the glass of my house whilst typing this

sean_iow wrote: ↑Sat May 15, 2021 6:42 pm

RIP wrote: ↑Sat May 15, 2021 6:30 pm Oh gawd I'm obviously a rank amateur .

I think you're what statisticians call an outlier*, and not just when it comes to bivi bags

*Trying not to break the glass of my house whilst typing this

Ah well Sean, that's an interesting rabbit hole to disappear down. By chance Mrs P is a statistician and we have just had a robust conversation about your observation.

She said "outliers can arise due to fraudulent behaviour, human error, instrument error or simply through natural deviations". I asked if I was a result of one, several, or all of those. She gave me a Mrs Perrin #3 Look.

So, er, about these boil-in-the-bags. I gather it's possible to obtain one that will fit a wide winter sleeping bag and a mat, is impervious to sharp ground-based objects, is waterproof, is windproof, is breathable, is camo coloured, and weighs under 200g? Just what I'm after, so I'm all ears!

You've kind of described a Borah there Reg but just not quite

Bearbonesnorm wrote: ↑Sat May 15, 2021 9:04 pm You've kind of described a Borah there Reg but just not quite

What's the not-quite bit? Or rather instead of one not-quite feature, is it that all features are very slightly not-quite? . (*)

(*) the waterproofness bit I guess

When I window shopped yonks ago I was entertained by the Kestrel and indeed the Borah cuben at 125g-ish.

In the end I decided not-quite was not quite worth it .

PS. As an aside, I'd like to see some hard facts rather than anecdote about how much, or not, bags/quilts are affected by breezes/wind. Of course this depends on the fabric - my 'ultrashells' claim 'total' windblock for example, as well as water-resistance. Maybe I need to book a session in a wind-tunnel with my bag and a thermometer inside it, plus a variety of bivvy bags.

So JC, have the agony aunts affected or changed your thoughts so far?

Bivvy bag and no tarp tonight

RIP wrote: ↑Sat May 15, 2021 10:15 pm So JC, have the agony aunts affected or changed your thoughts so far?

Not really, I'll take both as I did before.
I was just wondering if some did it without the bivi bag and if so did they die or not?

The ones that died didn't respond.