Plastic Sheet Question…

[W I S N E R !]

I know little about plastics…

Looking to build something custom sized but minimalist like this seat bag harness by Wayward Riders:

The patterning, cutting, and sewing of webbing is not an issue…but what sort of plastic at what thickness?

Thoughts appreciated!

[BlackHatGuy]

Why plastic? It seems to me you could use sil or poly or even DCF to build this (and I have some extra DCF if you want it).

[W I S N E R !]

Yes, sort of wondering same and working this out…

Main issue is containing/compressing the front end of the load so the backs of my legs aren’t hitting it. I figure some rigidity would help here?

As of right now, I’m using a drybag strapped to a rear rack. But the rear rack is overkill given I only need 10-20 liters of space and use it mostly for lighter gear.

I had a Revelate Terrapin and returned it. It was nice and all, but I’m not convinced it’s worth the money. It doesn’t seem to accomplish much that I can’t do with a drybag and a few straps directly to my seatpost/rails. And if I use a heavy drybag (like my SealLine Baja) it seems to provide the same amount of structure. I can use a strap to cinch in the front end down smaller so I’m not rubbing it.

But the 20L heavy drybag is 14oz. by itself. Thinking a plastic harness like pictured would allow a UL drybag and easily cut the weight of the system in half, if not more.

I’m close to just sticking with the heavy vinyl drybag and straps….

 

[BlackHatGuy]

If you want to use plastic, I’d think you could cut up a laundry detergent bottle, that should easily be thick enough for what you want and thin enough to work with. Plus if you cut it to include the brand that could look …. different, which could be kinda neat.

[W I S N E R !]

Yeah, I was thinking something similar…or maybe a storage bin lid.

[Bob Chiang]

If you don’t like the idea of detergent/milk bottle material, would a kitchen cutting mat provide large enough stock?  Otherwise, I have some plastic I rescued from a dumpster that I could send.  Sort of the same thickness as a manila folder, bright blue and resists tearing pretty well.

[W I S N E R !]

Thanks for the offer Bob. There’s a supplier near me I’m waiting to speak with… we’ll see.

Your gear is amazing by the way, top notch stuff.

[David Thomas]

HDPE detergent jugs are pretty sturdy but also light.
There are some pretty thin cutting boards available.
Another source of HDPE sheet are the roll-up snow sleds (Flying carpet / Flexible Flyer):

For $15-$20 (check the length, they vary from 36″ to 60″).  Then create and test a pattern from cardstock before transfering it to the HDPE.  I’d use shop shears / aviation snips to cut it.

If you tapered the sides down to a strap, you could do almost the whole thing from that single sheet without having to transition to the nylon straps in the first photo.

[Dave @ Oware]

If you know anyone who is a teacher– Cover of plastic binders.

I made a lightweight fabric crampon case and lined it with motor oil bottles cut open and washed. it has held up for 25 years.

I like the bleach bottle idea. get something with the curve already molded. Probably wrap the light web/grossgrain ribbon all the way around to avoid putting stress on just a slit. Maybe sew the plastic directly to the web or a whole a stuff sack of the right size?

 

Doug- I am still thinking about the propane bottle covers, wish there was a thin plastic bottle I knew of that was the same size that could fit inside a carrying sack?

[Iago Vazquez]

I built a seat and handlebar harness of a similar design. I used this https://www.amazon.com/dp/B0788MBV1R/ref=cm_sw_r_cp_apa_fabc_0sL7FbB00YK2D?_encoding=UTF8&psc=1

Best of luck, Craig!

[Jerry Adams]

Tap Plastics

[W I S N E R !]

Lots to go on here… thanks folks!

Got any pics of yours Iago?

[Nick Gatel]

Subconsciously Craig wants a 3D printer. He just doesn’t know that yet.

 

[W I S N E R !]

Ha, I actually have the next best thing Nick: A good friend with a 3D printer. They’re pretty amazing.

[Iago Vazquez]

Hi Craig,

Here are my pictures:

As you can see my slot work is very crude, sloppy. A rotary cutter (dremel?) would probably be better than the the drill bit I used to cut the strap slots. I only used it on a couple of day long gravel and road trips. Worked well. The bag is an Alpkit. As you can see if has plenty of loops to attach to the saddle on its own. So why the harness? Because I know from experience that even durable fabrics get chewed up by the seatpost and seatcollar much faster than I like.

Here is the handlebar harness. One of the straps was taken out. It kept dropping, so sufficent clearance to the top tire is paramount. Also, I am thinking that separate slots to attach the harness directly to the handlebar would be better. And then deal separately with the drybag, perhaps in a similar arrangement to what I have. This would make attaching and unattaching much easier than with my current version, which uses the same strap for the handlebar, harness and drybag.

 

[W I S N E R !]

Thanks for taking the time to put this up Iago, much appreciated!

[Michael B]

I’d think that unless you need some impact resistance, designing a similar shaped harness from 420D robic would be super tough and pretty easy to sew up.

[John S.]

I played around with making a holster with a plastic dinner mat from walmart. It works sorta but I dont know what type plastic and how it would last on a longer trip. I have not used it “in the field”.

[Iago Vazquez]

You are welcome, Craig. Please post pictures of final project if you can :)

[Craig B]

If you are still guessing about the thing in the OP, I would guess it’s about .04-.05″ thick Polypropylene, Polyethylene, or HDPE.  I used similar material in my hip belt for my back/front pack.  You probably don’t want to use a fabric, as it won’t offer any structure on its own, even heavy fabric.  For sources, McMaster-Carr is always an easy option.

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