How Waterproof are Rucksack Covers?

[Teepee]

One or two people are coming out in favour of them now...

So which pack cover do you use Teepee?

A large Pod-sacs cover at the moment mate, I think I paid about £8 for it 2 years ago.

 

[Martin-123]

+1 on lining your pack with a bin bag or similar. However, it is also important to keep the pack itself dry. AS the material becomes saturated, it will gain weight - a lot of weight. I have'n't done an experiment, but I suspect that a 3 lb pack could become a 10 lb pack in short order. Easy enough to make a shaped pack cover with drawstring/elasticated sides out of 2 mil plastic.

Hi PDA, It took your comment several hours to cook inside my mind before I realised I should do the experiment!

I have photos but cannot upload them. I think because I'm a newbie. Can I upgrade myself somehow?

Anyway, the figures are, for 65L Karrimor Jaguar GR (with an sa back),

before: 2080g (4.6lb)

after a good 20 minutes in the shower (the bag, not me) (I could have gone on longer but I'm on a water meter), the sack was wetted out all over and the straps were too, but there were still patches of dry inside and I reckon the straps would have held more water if I'd been patient enough....
At the end I turned it upside down to empty out the water inside.

2473g (5.5lb)
an additional 393g (0.9lb) or 19%

So, roughly, 400g (1lb) or 20% heavier.

I'm more & more liking the idea (thanks Tiger and Limaed) of making one myself from rubble sacks. .... How hard can it be?

Mart.

There's no substitute for experience.

 

[PDA1]

@Martin123:
Thanks for doing the experiment. The results are by no means as dour as I expected. I think my expectations were based on 40 year old experiences in Wales/Lakes using cotton canvas bergens. I'm sure they increased by more than 1 lb. I guess that Nylon Cordura is a lot less absobent than cotton canvas.
Last weekend, I was using a lightweight nylon 18L daypack and it rained and drizzled all day SUnday. I was out in it nearly 10 hours. Everything in that bag was at least damp. For most of the contents that was no harm, but one ditty bag contained my down sweater, which is my emergency insulation layer. The down was definitely damp, not saturated, but any wetness on down is a disaster. Good job I didn't have an emergency! Worrying, because here in the New Hampshire White Mountains, it is not unknown for hikers to find out first hand, in July or August, why they are called the White Mountains I shall in future place the sweater ditty bag inside a ziplock and make a light plastic rain cover for the pack. A doctored shopping bag should be sufficient for that duty. I'm getting much more from this thread than I at first imagined.

 

[wizard]

Like others have said, put things in drybags or bin bags inside the pack. I carry a waterproof cover made by Sea-to-Summit and it will keep my pack mostly dry when walking. I mainly use it for covering the pack at camp when it is raining and I don't have room in my shelter for the pack. I've also used a large bin bag for this same purpose. A poncho over you and the pack is best but it is a pain on a windy day and some are not very long on the back when over a pack.
I have used a pack as floatation on some slot canyon trips where we had to swim some short sections. I had a bin bag inside and well tied up, nothing got wet in the pack.

 

[Limaed]

Those dry bags look the business but too heavy for my liking.

Re bivi "... will at some point wet out and leak" ... Am I showing my lack of experience here? Why would it leak if it's waterproof?

I can't remember exactly why Gore-Tex will leak but if you put water under pressure against it (as in sitting on a jacket or a stuffed rucksack) the pressure forces water
through. Additionally a Bivi-Bag is an expensive bit of kit (even a surplus one) that is being used not what its designed for. A liner / dry bag gets quite a bit of abuse and
abrasion from tent poles, stoves etc as we stuff things in. It would be quite easy to damage your Bivi in this way even if your careful.

I don't like covers as for me its all extra faff. I do agree with the fact they keep your bag dry, reduce abrasion and stop the bag absorbing water and increasing in weight.
I guess it comes down to personal preference and finding out what works for you.

 

[Martin-123]

The results are by no means as dour as I expected. I think my expectations were based on 40 year old experiences in Wales/Lakes using cotton canvas bergens. I'm sure they increased by more than 1 lb. I guess that Nylon Cordura is a lot less absobent than cotton canvas.

My pack was empty for this test. If it had been full there would have been a lot more absorbent material to soak up water. I'm sure a 10lb increase is possible, given a full pack and enough time in the rain.

 

[Martin-123]

I can't remember exactly why Gore-Tex will leak but if you put water under pressure against it (as in sitting on a jacket or a stuffed rucksack) the pressure forces water
through. Additionally a Bivi-Bag is an expensive bit of kit (even a surplus one) that is being used not what its designed for. A liner / dry bag gets quite a bit of abuse and
abrasion from tent poles, stoves etc as we stuff things in. It would be quite easy to damage your Bivi in this way even if your careful.

Good point, well made.