I am about to start a tour on my Brompton folding bike with the Brompton bag on the front and standard hiking backpack rigged to the rear with bungee cords. This setup works except that I don't have a rain cover for the backpack. I was going to use trash bags but that will get expensive and seems wasteful, and I can't justify spending $30 on a simple rain cover.

Any suggestions for waterproofing my bag when necessary?

[And since someone will ask ... I almost bought a used set of Ortlieb front panniers which would have fit on my rear rack, but the backpack works better because I can wear it when my bike is folded.]

Trash bags...It will not rain everyday.

If you can't afford trash bags, then I guess you should get used to wet gear.

Actually, if you can't afford $30 for a rain cover, how can you afford to tour? Food may cost $30 a day, or more. Maybe you should work and save until you can afford to tour.

Tyvek, it's the material you see covering houses under construction. I bet if you politely asked a contractor they'd just give you a piece.

In the camping section at WalMart they have inexpensive rain covers for backpacks. They are probably not the best quality, but may be adequate for your needs. Another option would be to fashion a cover out of an inexpensive rain poncho and some Gorilla Tape. Perhaps a heavier plastic bag would be more durable and reusable that a trash can liner.

I too am wondering just what kind of touring you will be doing on a budget so tight. I'm all for self-sufficient, minimalist, living off the land type of travel, but you need to have some kind of budget for supplies, repairs, emergencies, etc.

There are back pack rain covers, and there are portage packs.. Its a Dry bag with shoulder straps.
Canoeists use them because the gear stays dry when you capsize, and the straps let you wear the pack
and carry the Boat upside down on your shoulders..
[there is a Carry Thwart rail at the balance point on canoes]

Trash bags on the inside... time honored method of keeping items dry in a leaky pack.

Aaron

Say what?

Best method I've found is to pack a large white trash compactor bag and use it inside the pack. I store my insulation and paper (and electronics if I have any) in it on wet days and everything else gets wet. The white bag is nice to find stuff in on a dark day. One bag has lasted me many years. It's easy to patch with duct tape if you get a hole. I check it routinely.

Yup.

You said you were going to use bunges to hold the pack to the rack. A good bump can make things move around and if your bunges are not tight enough, could be a problem. Some nylon straps that don't stretch like bunges may be better. Or, use the bunges with a nylon strap as a redundancy.

That is a great idea! Especially since I have a bunch of trash compactor bags . .. which we never actually use in our trash compactor. They are tough, and as you say, white makes it easy to find stuff. Pet peeve of mine is that for some reason the inside of camera bags are always black - makes it difficult to find anything.

Trash compactor bag.....good and strong.

TransitGeek, you might take a look at this video that Russ made to show how he and Laura attached their backpacks to carry them on the rear racks of their Bromptons when they toured. https://pathlesspedaled.com/2011/07/v...-on-bromptons/

I use the bags inside approach. But if you want to make one, just get a piece of ripstop or silnylon and elasticize the edge like a shower cap. If you can run a sewing machine that is a pretty easy build.