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Tour Divide Gear: frame bag

April 3, 2010

This is the first in a series of posts about the bike I’ll be riding in this year’s Tour Divide, and the gear I’ll bring along.

Folks have been bike touring ever since the invention of the bicycle, but as the equipment and techniques of lightweight backpacking trickle over to biking, racks and panniers have become a thing of the past.  First of all, they’re quite heavy:  an Old Man Mountain rear rack and a pair of Ortleib panniers comes in at nearly 6 pounds…empty!

Within the last few years, inspired by the needs of bike racers in long distance events like the Iditarod Trail Invitational, two cottage entrepreneurs sprang into action.  Which of Epic Designs Alaska and Carousel Design Works first came up with the concept for the full frame bag I don’t know, but they both make a solid product.  Since I had made the tarptent and backpacks for our PCT hike, cranking out a frame bag seemed pretty simple.

Frame bag on my XL Niner Air9

I began by making a cardboard pattern for the main side panels.  Hot glue or tape together ~3″ strips of cardboard so that they fill the frame triangle, and then trace the shape onto a fresh piece of cardboard.  Add an additional 1/4″ all around.  Minus the 3/8″ seam allowance, that will make the finished bag 1/8″ undersized all around, allowing the velcro to adequately tension the bag.

Mark where you want the velcro straps to go, so that they don’t interfere with cables, bosses, or the front derailleur.

Draw a center line for where you want the zipper(s) to go.  Having trial sewn a short section of zipper and noted how much extra material I need to attach it, I then drew parallel lines to mark the top piece and bottom piece.  With my zipper foot, the two edges are 5/16″ from the center line.  The pattern for the zipper-top, zipper-bottom, and plain panel are all here.

Pattern for frame bag. Size equals triangle space plus 1/4" all around. Sewn with a 3/8" seam allowance, finished side panels are 1/8" undersized, allowing the velcro tabs to adequately tension the bag.

The size of the piece you’ll need for the middle depends on the width of your tubing.  The length will be “long”.  Sure, take an educated guess, but unless you’re practiced in turning corners accurately, its best to cut it overly long and trim when you’re sure what you need.  The width of mine is 1.5″ plus 3/8″ seam allowance = 2.25″.

The fabric I used was Dimension-Polyant VX-04, a sailcloth laminate of ripstop nylon, kevlar grid, and waterproof membrane.  I used this material for our PCT backpacks, which worked okay.  The lightweight surface nylon proved to be only moderately abrasion resistant, and the membrane incapable of surviving repeated flexing, so after about 4000 trail miles, those packs were retired.  Perhaps that’s good enough.  I figured that in ordinary use a frame bag wouldn’t be subject to those same threats and just used the material I had.  A half yard of fabric is probably enough, but its always wise to make your pattern first and anticipate some “operator error” in the first version.

Other parts all from Quest Outfitters:
Waterproof Uretek #5 coil zipper (Zipper tips)
1.5″ grosgrain tape
2″ velcro
1/4″ Landau foam pad or other thin foam
Gutterman thread

Assembly:
Step 1: Assemble zipper into side panel
One detail that isn’t obvious from the photo above is that the zipper tape doesn’t terminate in the down tube seam.  Zipper tape butts to 1.5″ grosgrain tape.  ~3″ piece of grosgrain terminates in seam; it can deal with an angled bend in a way that the zipper can’t.  The urethane impregnated “waterproof” zipper is sewn in backwards with the urethane layer facing out.  A zipper foot for sewing machine always helps make it look nice.

Step 2:  Sew velcro to side panels
Lightly sew velcro to side panels with a straight stitch.

Step 3:  Sew sides to middle
Secondly assemble sides to “middle” strip.  Start in the middle of one of the straight edges, leaving an inch or so of the middle unsewn at the end.  Once you’ve sewn 90% of both sides to the middle, close the middle loop, then finish the side seams.  Turn the whole thing right side out.

Step 4: Tack velcro
I zig zag tacked the velcro tabs through the seam allowance on the inside, which is easier to do.  It is more awkward to do, but it would be stronger to zig zag tack through the visible side.

Step 5: Insert foam
Thin foam on the inside along the down tube isn’t required, but it will avoid an annoying noise from your multi-tool or bottle of beer clanking against the frame.  For my bag, before assembly I added a layer of silnylon to the bottom part of the “middle”, where I inserted a piece of foam.  That’s a big annoying to do.  Alternatively sew to the middle prior to assembly a couple of grograin straps or small velcro bits.

Step 6:  Put on bike
Close the zipper and put the new frame bag on the bike.  If you want to overstuff the thing, ease up on the velcro tension so that you don’t overstress the zipper.  Trim off excess velcro, and ride!  My bag came in at 3.9 ounces.

Packed up after a night in the Green Mt. National Forest

Riding Class 4/VAST between Hortonville and Lake Ninevah

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12 Comments leave one →
  1. April 5, 2010 11:31 PM

    Your frame bag looks pretty sweet – very nice job!

  2. April 8, 2010 5:10 AM

    nice bags, thanks for the how-to..

  3. stephen permalink
    April 10, 2010 10:15 PM

    what are you using on the seatpost and bars? looks like you’ve got a good amount of room with minimal bag weight — nice stuff.

  4. April 11, 2010 7:23 PM

    For the seatpost I’m using a Carousel Design Works Escape Pod, which is bomber. For the bar, I’ll be making a bag to go there. I’ll get that in place for the new bike, since it will require longer/rerouted cables and brake lines.

  5. May 9, 2010 9:19 AM

    I’ll be nailing the pieces of my frame bag together today. Will you be making a new frame bag for TD? Is there any thing you’d change the 2nd time around? It has been very helpful to look at how you made this one.

    • May 9, 2010 9:38 AM

      I’ll probably be making another one…at least I got some more zipper and velcro, so I have the materials. My existing bag will probably fit just fine on the new Carver, but I may make another one that is a bit higher volume, since I’m not close to rubbing it with my knees/legs. A bit wider in back, flaring out in the front 1/3 where there is no leg interference even when out of the saddle…to mimic the flare on my gas tank (coming soon) and as wide as a downtube fender (proper or ghetto plastic).

      • May 9, 2010 2:32 PM

        Doesn’t the width of the frame tubing limit the width of the frame bag? Or will you artificially support the wider frame bag?

      • May 9, 2010 2:47 PM

        That’s exactly what I thought when I made my first one. The reality is that if the bag has a bunch of stuff in it, it becomes a relatively rigid lump that won’t sway into your legs at all. No artificial stiffener to support the wider bag (that’s my theory anyway). The only downside I see is that the zipper might be harder to one-hand open while riding since the zipper will be in less direct tension.

  6. March 30, 2013 9:08 AM

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  7. Mad Hatter permalink
    February 2, 2014 7:31 AM

    Very nice work. Just a technical note about the origins of the idea: The Swiss military used a very similar design (but reinforced and with the bottom corner cut away) from 1905 to not so long ago. Going to war on a singlespeed bike, that’s bikepacking to the max!

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