Linear polyethylene sleds(the roll up ones) are cheap and could be cut to shape for a semi-circular, semi rigid harness. You could cut slots and thread the webbing, rivet it or even gorilla tape it to the poly to keep it from dangling. It's got tons of other uses as a stiffener as well.


http://www.amazon.com/Paricon-Inc-611-Flying-Carpet/dp/B001Q8SLE2/ref=sr_1_1?ie=UTF8&qid=1391709800&sr=8-1&keywords=roll+up+sled

Another great Magiver idea.  It's possible to cut the thin wall of a plastic ice cream tub too.

Cheap, easy solution for keeping a dry bag away from your brake/shift levers. 1" pvc, cut down to 2" stubs, one end filed to snug up to the bar. I put hockey tape on the bar to keep them from sliding, as the bar I'm using has a very slippery finish.

Simple, effective + cheap = Brilliant!  I'm totally going to run with this idea.  I will apply camo tape to my handlebar and dip the ends of PVC in silicone to protect from long term abrasion OR apply a reinforcement patch to the part of my dry bag that touches the tube.  Cut grips are also brilliant.  Great ideas guys, keep em coming!

I had a look and your bag looks good.  I like how the 3 straps seem to give a sense of multiple useful compression points to seat post and seat rails.  Does it accomplish it's goal of being "relatively" immobile when ridden?  I've been brainstorming material for (with velcro cinching bag to post) the back of the velcro looping to grip the seatpost when sway is initiated from turning or tilting the bike.  Perhaps a silicone or similar grippy material could provide some sway relief in addition to compressing the bag to the actual aluminum seat post.  Cheers.

Cool, I may have to learn some pythagorean OR make measurements along the seatpost on a parallel to level ground plane every 2" or so to arrive at an acceptable bag capacity as determined by a stencil made from such measurements (a la troubleshoot/grind).  You did a nice job with your math skills, though I'm not sure I'm down for that kinda mathyness...Who knew that I could design awesome adventure gear that could actually improve my life with pythagorean  Math makes me short.  We'll see how mathy I feel once I've ordered my fabric yardage and the new sewing machine arrives.  I have ordered fabric samples from rockywoods - a few camo, different shades of green and black/grays that are waterproof, some being double WP coated denier, others xpac, silnylons, goretex and event materials (we're adventure nuts who refuse to be held back by all but lightning storms, dehydration and threat of hypothermia.  We cycle all winter in Ontario, including during freezing rain and some snow.  It teaches you just how important ventilation, waterproof materials and clothing layers, can be, for adapting to a changing climate, in conjunction with body heat levels.  I'll keep you posted on my bag plan/build progress, as I do have a camera and desire to share.

Hi there,  I'm wondering if anyone who has made a seatbag, has created a pattern for it, and would be so kind as to share their pattern.  HOPEFULLY something 6-10 liters in capacity as end result.  I'd be happy to share my experience building the bag as well, with pictures; to continue in the spirit of generosity.  

I'll be making one in the porcelain rocket, revelate design and Oveja Negra form for glorious bikepacking adventures; pauper style, low budget DIY (I work in a bike shop).  I already have a bunch of fabric samples on their way in varying waterproof xpac, sil-nylon, goretex, denier cordura in a few colors to help decide my order by the yard.  Webbing samples are on the way as well.  So will just need velcro, cording, webbing and buckles; pattern aside.  It will be waterproof and have a roll-top closure with a compression cord lock.

Thanks for sharing your experiences with me and you were right when saying rockywoods.com.  I'll be ordering some lightweight camo 70d cordura from owfinc dot com and using kevlar or ballistic nylon to add stiffness/reduce bag sway where needed (like a good pair of boxers)- worth checking out the site, as they offer even MORE options!

Starting with a frame bag and ending with a saddlebag and top tube bag, I'll post what I've done once I'm there, to share my experience with others.

If you think you'd want to take the bag off regularly or put different items in the harness, I'd look more into a harness.  If not, no need.

YES!!! That is exactly the kind of stuff I've been looking for. And the reason for trying this versus a stock bladder is a) I'm a huge weight weenie and b) I'm a little dude, so don't have much space to give up in my frame bag. If I actually use the full volume of the bottom corner of the bag, I can fit nearly 3L in the same space that I currently fit only 1L using stock bladders, which also happens to be almost 2/3's of my bag. And, I've got a tricky little idea for water treatment that is going to make getting and treating water take less time than filling a bladder at a faucet. I know it seems silly, but every time I stop for water and treatment its usually a 5-10 minute ordeal and with a little bit of doing, I think I can cut that down to a minute or so. Add that up over a week or more... Cause we're racing...right?

Yes, you would need measurements, heat-sealable food grade plastic and a hose, perhaps with a clip on it to go on your shirt, handlebar or frame etc.  Just buy plastic thick enough to limit punctures.  You may need silicone sealant at the joint from bag to hose.  I saw a post from one guy who ran a strong wire from one downtube waterbottle bolt hole to another on his seattube.  He did this to support the bladder from getting in the way of pedalling feet and footrub.  The water wants to spread the bag out and move around as you move your bike.

Awesome!  Are those both TI bike frames?   I just can't tell if that is a silicone nylon or cuben fiber with cordura or not...  How has the bag held up?

Looks like your hard work paid off!  I'll be doing something similar, but have chosen to go with heat sealable material for more waterproofness at the exchange of slightly higher weight than that of cordura.  How did you decide to attach the roll top bag to your bars?  Could you post a picture of it mounted?

Awesome job on the frame bag!  Your brake and shift cables work best with low friction, so you might try with velcro below the cables, as opposed to the weight of contents pulling down onto the cables.  Just my 2 cents from working on bikes at a bike shop.  Keep up the great work!

This looks awesome!  You've inspired me to explore sewing, the different materials available for a saddle bag I can take on marathon adventures.  I've seen some from Rocketfish and Revelate designs, but not quite custom!  I'm thinking a 1.9oz silicone coated 70d nylon because it's about 20 dollars less per yard, available in many colors (not just white) and will weigh negligibly more than cuben fiber.  Thank you very much for sharing your sewing experience with the online community, now I can order some cheap fabric to build a prototype and learn for myself.