Foam insert for aiding structure and rigidity?

[flanagaj]

Hi,

Just curious as to what people are using to help with adding structure and form to their seat bags and bar bags.  I am just sourcing my fabric, but wonder what I can use so that the bag is not completly floppy.

Thanks

[AZTtripper]

Haven't seen anybody using anything. The bag starts small and tappers out once it's half full or so you can roll the end or add a bit more stuff either way with it packed and closed tight its solid. The post attachment is beefy and the rail straps suck it up tight under the seat.

My bar harness is just a plain sheet of fabric with a straps for the bars and then the main one holds the bag place. Then I use a long strap around the bars twice, around once on either side of the stem. That holds it snug to the bars then a lower strap on the harness goes down to under the crown this keeps it from flopping. Some of the harness's have a strap to the frame behind the head tube for the same purpose.

[trebor]

I use nothing for rigidity in a bar bag (roll closure style). Tightly packed contents give you structure.

Seat bags i put in a sheet of plastic from the post, down and under, and then about half the length of the bag. Stops flop even if packed poorly. I've made them without anything and if packed super tight, will work. But not everyone packs well, believe me.

Harness/sling style bar bags get an uber thin sheet of closed cell foam between two layers of fabric. This helps to stop flop while trying to load in the dry bag, nothing more.

[flanagaj]

closed cell foam between two layers of fabric. This helps to stop flop while trying to load in the dry bag, nothing more.

that is what I am after but unsure whether you buy it from a material shop or else where?

[trebor]

I get it from McMaster Carr or a local Foam Supply that happens to be a few miles from home.

McMaster's: http://www.mcmaster.com/#catalog/118/3563/=ikc3jy

I get the 1/16th sheet of Polyethelyne

I have also in a pinch, used craft foam from Michael's. They sell it in rolls. It's about the same thickness but not quite as tough.

[JReeves]

I've never used and foam in my kit, but I have used this stuff several times and it's super easy to work with, adds some structure and shape, and is light and easy sew, as the needle of the sewing machine will "find" the holes for the most part, and if not, then the material is soft enough that the needle will go right through it...  It's the mesh plastic cross-stitching type stuff, called Plastic Canvas.  It's available at Jo-Anne fabrics, or even Walmart for $1 or so a sheet, and comes in various sizes and thicknesses. 

http://shop.hobbylobby.com/needlework/plastic-canvas/plastic-canvas-sheets/

[bumbler]

My next project will be a handlebar harness, and I'm thinking of using some Reflectix to add rigidity. In cooler weather it could double as a sit-pad.

[Bill in Houston]

thin plastic cutting boards
coroplast - thin plastic that signs are made of

[jeremy11]

The only thin closed cell foam I've found is rather floppy, I've looked far and wide for a very stiff thin foam and haven't found anything available in small quantities.  I believe Cross Linked Polyethylene (XPE) is the stuff to look for.
Here's where I get my foam
http://www.seattlefabrics.com/neoprene.html#Closed Cell Foam

I've tried 1/8" closed cell foam in bar bag slings, top tube bags, and seat bags, and it seems unnecessary in each of them.  I do use this foam as padding along the bottom and stem panels on the top tube bag and for frame bags with padded tubes and tapered fronts, and in those applications it works well, but one thing it does not possess is stiffness.  If you want real stiffness and structure, look for high density polyethylene plastic (HDPE) I use 1/8" for seat bags and pannier framesheets and 1/16" for top tube bag side panels.  I've even used neoprene in place of foam in a pinch for padding and that works fine too.

[Turtle01]

I found some thin dense foam, 2 & 3 mm, that has some mild structure at Hobby Lobby.  It was in the kids craft area.

Just looked at it.  It's called Silly Winks Foam Sheets.  12" x 18" x 3mm is $0.99.  I'm going to make a front trunk bag using it for structure to go on a custom rack.  I'm slow on getting to things, so it might be a while. 

[bicyclehobo]

I have lately been eyeballing large plastic containers in the grocery store. Laundry detergent, bleach, 3 liter water bottles, really all types of bottles. They are rounded already and some of the conical tops look like they might be well suited to make an impromptu seat bag base harness. They are cheap, easily replaceable any time you were near a store and you could probably find one laying around in a closet at home.

[Trhoppe]

Use nothing for the handlebar bag, and use a couple of cheapo flip flops in my seat bag. I want to get out of the biking shoes at night to walk around and having the flip flips is nice AND provides rigidity. Win win

[ashleydaniel]

I don't understand, why people do this, and there are many comfortable seat bags available in the market,
one of my friends did this in front of me when he was going for a trip on his bike.