Looking for Seatbag patterns

[donnieboy]

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.

[Smo]

See my thread I just posted on the subject - I put up a pattern.  It's a complicated one, but it wasn't *too* difficult to sew.

[donnieboy]

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.