Sometimes people write to ask me if they can design their own packraft and substitute a cheaper material in place of the TPU-coated fabrics used in the DIY Packraft kits.
The short answer is yes, though there is a reason why every major packraft manufacturer uses TPU-coated fabrics (even if they refer to it as a “PU” or “polyurethane” coating). Check out the Fabrics page for more on that.
At least one person has successfully made a DIY Packraft using PVC-coated fabric (from the old plans, no longer available). Another person used a plastic tarp and tape. I myself used plastic vapor barrier sheeting to build several prototypes (though I wouldn’t consider them seaworthy).
Before wasting money on a large amount of fabric that might not work, get a small sample of any material you’re considering and test it to make sure it performs the way you expect. Spend a few dollars on a DIY Packraft fabric sample pack so you have something to compare it to that you know will work.
Note that PU (polyurethane) and TPU (heat-sealable thermoplastic polyurethane) coated fabrics are not the same thing. TPU is sometimes referred to as “polyurethane,” but the reverse is not true. PU-coated fabrics cost much less because the PU coating is usually so thin that it isn’t even waterproof, let alone airtight. PU is not heat sealable in the way that TPU is. I am not aware of anyone who has successfully made a packraft out of PU-coated fabric, though I know at least one person has tried.
Also, if you buy a can of liquid polyurethane at your local hardware store and paint it onto some fabric, do not expect it to perform like a TPU-coated fabric. Yes, I know that some skin-on-frame boats are made this way; the important difference is that they do not have to fit into a backpack. If you fold and roll fabric that you have painted with polyurethane, even the most flexible PU paint will crack and flake away from the fabric. I have already tried it myself, so don’t waste your time and money.
At least one person has tried making a packraft from Dyneema Composite Fabric (a.k.a. “DCF”, formerly Cuben Fiber), but the seams did not hold up over time and it failed.
3 Comments
joseph cieslewicz · May 14, 2020 at 4:01 pm
Great job with your content by the way.
Just curious about attaching a TiZip zipper to a pvc drop stitch fabric (can it be heat sealed, what temp, if not what would be the best glue). It’s likely you have not played with this as I’ve not found any info here, but thought It’d ask.
Thanks!
jj
Matt (Admin) · May 15, 2020 at 9:57 am
Hi JJ, I haven’t tried it, but I’m pretty sure you won’t be able to heat seal those two together, but you can probably glue them. Again, I haven’t tried it, but I would test adhesives like HH-66, Stabond, or Clifton Urethane Adhesive – I think one of those will be your best bet. Cheers!
harald · May 16, 2020 at 10:21 am
There are many Polyurethane glues on the market that would allow you to glue a TIZIP Superseal zipper to a PVC fabric. There are however two problems you will need to solve along the way: a) TIZIP Superseal zippers are rated up to 700 mBar, but the required pressure of your drop stitch bladders is likely to be higher b) what do you want to put in a drop stich sandwich? A credit a card, maybe some crackers?- Just google pictures of drop stitch and you will be enlightened.