What material for dry bag?

[Ultra Magnus]

I intend to make a couple of dry bags- one for the handlebars to strap to a sling, and another for use as a seat bag.

I have some silnylon scraps I can practice on (manipulating the fabric through the sewing machine to make a flat felled seam on a sack sounds tough) but I don't think silnylon is durable enough to last, nor is it water proof enough.  I don't have any intentions of going rafting or canoeing, but don't want my gear to get soaked if I get caught in a rain storm.  I have some dyneema, but I think that's a bit excessive (at $24/yd) for a dry sack.

Any suggestions as how to finish the bottom of the sack would also be appreciated.  So far I've been making all of my stuff sacks with squared out bottoms and french seams to hide the fabric edges.  I don't know how a squared out bottom would translate to a dry bag with a flat felled seam.  Maybe it would be ok..  I dunno.  then the last part would be seam sealing...

anyway- thanks,
BM

[12wheels]

You can order heat sealable fabric from a number of sources if you want to skip the difficult sewing.  Seattle Fabrics has several different weight fabrics and can provide an article from Sea Kayaker with the instructions.
http://www.seattlefabrics.com/nylons.html#heat sealable 30 Denier Ripstop

I've made some round bottom models for my own use from 400 denier ripstop pack cloth with a heavy urethane coating.  Felled seams are overkill, just sew around the base perimeter two or three times and seam seal it with a silicon caulk/white gas(3 to 1)  mix.

[Ultra Magnus]

thanks for the suggestions...  I tried a prototype in silnylon last night and it turned out kind of crappy.  I'll probably cut it up and reclaim the material for sutff sacks or something... 

I've the done math and figured in the frustration factor, and as cheap as dry bags are to purchase, it's just not worth the hassle.  MYOG projects only make sense to me if they are stupid easy to make or offer a significant saving in money.  Like buying $100 of materials to make a tent that would cost $300 - $400- yeah, the myog tent maybe crappier but that much savings is way worth it.  Alcohol stoves are a no brainer, being essentially free. 

So anyway, I'll pass on this one and just buy something...

Thanks again,
BM

[chrisx]

If I get more heat sealable fabric in Seattle, I will buy the thicker stuff.  The thinner stuff did not hold up to heavy rain.  After shivering in my wet bag for an hour, I remembered the emergency blanket I carried unused all those miles.  It worked.

Somewhere in these pages someone made a ( seat bag sling? )  A devise to make a ready made dry bag into a seat bag.  Maybe I will try that next time.

[Eric]

OWF and Rockywoods also have the heat seal at way better prices than seattle fabrics. That place always seems to be a ripoff. I found the 400d was too heavy to seal with the iron I had. I've used the light taffeta on big trips and it holds up fine inside something else. the 200d oxford is fine for all around use. Don't sew it at all, just heat and pressure. Test by filling up with air and hit any thin spots with the iron. Making an "inside" pattern so the seam allowance is all that is showing makes the ironing step much easier and you can get a crisp edge.

Magnus.. you're missing the point a bit, with making these bags you can make them exactly to fit what you want, not some generic 10L size. Like long and skinny to fit inside frame bags for example, and they are cheaper and quite easy once you get it figured out.

[chrisx]

Wholesale price is $3 a yard,
Seattle Textile Company
3434 2nd Ave S
Seattle, WA 98134
district: Seattle
(206) 233-0595
instead of $15 a yard at Seattle Fabric.
They will sell to the public.  They sell by the roll only, and these are big rolls.
If you have $3,000 to spend call them.  Who wants to find 15 people with $200 to spend on fabric.