DIY backpacking gear - Tyvek bivy bag

Tyvek bivy bag in "sleep under the stars" mode

Bivy bag in "inclement weather" mode

Every time I go backpacking, I keep thinking - "What more can I do to lighten my load?".  Because I live in Southern California and many (most?) trails don't have reliable year-round water supplies, we're forced to take large (heavy!) supplies with us, so the more we can lighten the rest of our loads, the better.

This time out, I was after lightening my 4 lb. "shelter" (tent and footprint), using a DuPont™ Tyvek® sheet made into a bivy bag.

Advantages:

• Lighter - bivy bag and groundcloth is 1.5 lb., vs. 4 lb. for my 1-man backpacking tent & footprint.
• Warmer - because it's such a tight weave and is so close to you, it traps body heat much better than a tent.  Claims of an extra 5°-10° F are probably not unrealistic.
• More compact - folds up smaller than my 1-man tent and footprint.

Parts list:

My Tyvek was shipped in Tyvek!
(good for small scraps)

• 1 9'x12' Tyvek sheet (~ $25.99 on eBay), available from various sellers on eBay - this is the one I used and can highly recommend.  If you don't need a Tyvek groundcloth, you can get a 9'x8' sheet.
  
  Also, I used the standard "house wrap", mostly because that's what I saw more recommended by others.  But some use the Tyvek 1443R "soft structure", which is lighter softer and quieter, but more expensive and more difficult to find in the necessary size.  I was a bit concerned about its water resistance, since I plan to use this bivy by itself, without a tarp.  If you make one from this fabric, please let me know in a comment how it works for you...
• 1 roll Tyvek tape ($12.50 or so from eBay)
• 2 36" robe zippers ($2.99 each at Joann Fabric and Crafts).  You can use most any 36" zipper; this was the only one I could find locally.
• 1 5' length of 1/4" PEX pipe ($1.76 at Lowes)
• 1 2" piece of double-sided Velcro ($4.99 for 25 8" strips at Joann Fabric and Crafts)

My pattern
(click to enlarge)

Assembly Instructions:

1. Make yourself a pattern.  I used this (dimensions are in inches), but you'll probably want to change the dimensions to fit your bag, height and girth.  I'm 6'5" and have a very long bag, so I made mine using the full 9' length of the Tyvek.  If you're shorter, you can trim to make it smaller and save some weight.
2. Knead and/or wash the Tyvek to soften and quiet it.  There's differing opinions on the 'net as to whether it's better to soften the Tyvek before assembly or after.  I chose to soften first (both by kneading the dry material by hand for 10 minutes or so and then putting in a washing machine (with no detergent or fabric softener, water only!) for a full cycle.  This has no impact on its water resistance.  Note that doing this will "shrink" the Tyvek by a few inches in both directions, so if you plan to wash after assembly, be sure your pattern is upsized to accommodate this.  Mine shrank from 12' to 11' 4" and from 9' to 8'5" or so.
3. Using your pattern, mark your cut points on the Tyvek, using either a pencil or fine-point permanent marker.  A yardstick can help keep the lines straight.
4. Make your cuts.
5. Attach the vertical zipper.  Set your sewing machine to use the longest distance between stitches.  You'll need to cut a 3/8" slit on both sides at the end of both zipper cuts in order to fold back 3/8" of Tyvek.  This makes an opening for the zipper and allows you to sew through two layers of Tyvek, making a stronger attachment.  Take your time, this is probably the hardest step.



Zipper detail
(click to enlarge)

6. Attach the horizontal zipper.  If you got a single-sided zipper, like me, you'll want to attach this one with the pull tab on the inside of the bag, to make it easy to open from the inside.
7. Using the Tyvek tape, seal all of seams of the bag.  You can do it in most any order, I opted to tape the long vertical seam (above and below the vertical zipper) first, followed by the top and bottom of the bag.  I opted to put about 1/4" of Tyvek overlap on all of my seams (with the overlap coming from the top of the bag, to keep any rain out that might get under the tape).
8. If you want, turn the bag inside out and put a layer of Tyvek tape on the inside of all of the seams.  This will help strengthen the bag and keep the overlapped flaps from catching on anything inside the bag.
9. Get inside of the bivy with your gear and the PEX pipe.  Figure out where you want to put the pockets for the ends of the PEX pipe and where you want the Velcro strap.  Mark the locations with your pencil or marker.
10. Make pole pocket by taking a 1/2" x 1-1/2" piece of Tyvek and placing it vertically in the middle of a 3" piece of Tyvek tape. Place it centered over the mark you made in the previous step.  Repeat for the other side.
11. Cut off a piece of Tyvek tape 1/2" x 2".  Use it to attach the velcro strap to the marked position on the inside of the hood.
12. Cut the PEX pole as needed to fit inside of your bag.  I needed to trim about 6" off of mine - you may want more or less.

Velcro strap
holding PEX pole
(click to enlarge)

PEX pipe inserted
into pole pocket
(click to enlarge)

OpenSprinkler Pi - smart sprinkler timer review

Due to the ongoing California drought, I decided to upgrade my old Toro sprinkler timer.  Some of the things that I wanted out of a new unit included:

• Weather "smarts" - ie. the ability to lengthen watering during the hot months, shorten it during the winter and turn it off completely when it's raining (or will rain in the next day or two).
• Logging capability - I want to see how much water I'm using on my lawn (our department of water & power bills sewer charges based on how much water is consumed - which isn't ideal if 75% of your water usage goes into your landscaping and not down the drain.
• Remote control - the ability to view and control the system from afar, preferably using a web- or smartphone-based system.

 With these requirements, run-of-the-mill sprinkler timers from your local hardware store are out of the question.  The only commercial offerings are "smart" units, aka Weather-based Irrigation controllers.  The good thing is that many qualify for rebates.  The bad thing is that all that I could find are ridiculously expensive - starting at well over $200 and going up from there.  And most didn't satisfy one or more of my other requirements above.

The OpenSprinkler Pi controller

What to do?  I'm a tinkerer and a Linux aficionado, so I starting thinking - is there a way to make a Linux-based sprinkler contoller?  After some Googling, I came across the OpenSprinkler project.  A great idea, but Arduino-based.  I have no experience or expertise in Arduino systems.  But wait - the same guy now has OpenSprinkler Pi - a Raspberry Pi-based version.  Perfect!  He even has users who had written a number of programs to control the system in various ways - using your SmartPhone, using Google Calendar, using the web, and more.

So I ordered the parts:  The OpenSprinkler Pi 1.4 kit, a Raspberry Pi model A and a tiny USB WiFi dongle.  Total cost was around $150.00 Everything showed up within a couple of weeks and I set about assembling the unit.

Assembly: 

Quite quick.  Everything necessary is included - no soldering required.  Just mount the Raspberry Pi on the OpenSprinkler board with the included screws.  Then attach the WiFi dongle to the USB port.  I reused the power supply from my old Toro controller, which saved a few dollars.

A pleasant surprise when I received the OpenSprinkler Pi kit was that Ray had thoughtfully included a MicroSD-to-SD card adapter that allowed a MicroSD card to be used without having to cut the OpenSprinkler Pi case.

That said, I personally am not a fan of his new "one-size-fits-all" case.  Basically, he custom-designed a case for his original OpenSprinkler (Arduino-based) system.  It's great for that, but then he decided to shoehorn the Pi-based version to that case.  In order to make everything fit, he redesigned the PC board so that the Pi mounted at an odd angle.  But all of the connections were in different places, so few of the holes in the case are used for their original purposes. And because there's no display on the Pi-based system, the prominent display slot used on the Arduino-based system is covered with a piece of adhesive-based white paper.  It works fine, it just doesn't feel professional, and isn't something I'm proud to show to others who might be interested.

Testing:

Ray recommends testing the power output on the OpenSprinkler Pi board before attaching the Raspberry Pi to it.  I did so using a Volt/Ohmmeter (VOM) of mine and it tested fine with the Toro power supply.

I downloaded the software image from Ray's website and put it onto an 8 GB MicroSD card that I had laying around.  I decided to use Rich Zimmerman's excellent sprinklers_pi program, which seemed to be the most feature-complete and also provided a way to use the information from my personal weather station on Weather Underground to adjust watering times.  Cool!

One small issue I ran into:  Rich designed his software to designate Zone 1 as a pump controller (for those on wells).  So if you're not using a pump controller, you should leave Zone 1 unused.  If you have 8 zones to control, there's a workaround.

Operation:

Sprinklers_pi graph example

It works, and works well.  I'm able to see graphs showing how much time each zone is turned on, I can control the system via a web interface from home or away, I can choose to use Internet-supplied weather information to adjust my watering schedules (or not), and I can parse the sprinklers_pi log
files to keep track of how much time each zone is being watered.  Now I just have to figure out how many Gallons Per Minute (GPM) each zone uses, and I should be able to determine how much water is going into my lawn each month.


All in all, I'm satisfied with my new smart system, even if it didn't qualify for a rebate...   ;-)  I just hope he decides to redesign his case into a true all-in-one solution for all of his OpenSprinkler options (Arduino, Pi and BeagleBoard).