How to make air-tight seam in coated nylon or plastic tarp?

[PeteCress]

Think of a 3'-wide pillow that needs to hold 2-3 PSI.

I have access to a sewing machine, but not to the elecronic fabric welding tool that the pros use.

Tried hot-melt glue and it held for a bit before blowing out.

Tried sewing a re-enforcing seam over the glue line, but the glue jammed up the sewing machine.

Currently trying the green goop they use to seal bike tube leaks ("Slime") by attempting to get it to seep into a straight stitch.  It slowed the leakage, but not enough.

Does anybody know of a method?  

I wonder if my approach might be wrong and I need tb thinking in terms of an air-tight bladder inside...but that begs the obvious question.... maybe a weather balloon....

For those whom "3'-wide pillow" does not satisfy, here is The Real Deal:  

Unfortunately the original HoverDisks are no longer available and the Mylar knockoffs lack the needed durability and rigidity.

 

[tomdiving]

how about tyvek or similar material?

[PeteCress]

10 hours ago, tomdiving said:

how about tyvek or similar material?

But other materials also beg the "Airtight Seam" question.

[tomdiving]

https://www.amazon.com/3M-4950-Heavy-Duty-Mounting/dp/B007Y7GHYK/ref=sr_1_11?crid=30W92P1JOMLPD&keywords=3m+strongest+two+sided+tape&qid=1658274186&sprefix=3m+strongest+two+sided+tape%2Caps%2C80&sr=8-11

or similar. there are many types of 2 sided tapes, even for fabric, which may answer your first question. if i'm not mistaken, revolution kites are taped before they're sewn. if the tape width exceeds the stitching width, it should be airtight.

if your prior method of sewing your material was satisfactory to you, you could try "shoefix glue" instead of the tire tube goop. it's a flexible superglue and is the only thing i have found to get my teva sandals to stay together when the dissimilar materials from the sole and midsole separate.

https://www.amazon.com/Shoe-Fix-Shoe-Glue-Instant-Professional/dp/B01G8D69FW

 

i have turned 2 line foil kites into 4 line kites by simply using that glue to put tabs on the trailing edge of the kites to attach brake bridle lines to. i have a little hq symphony pro 1.8 that is now a 4 line kite and it's been out in 50mph winds without the tabs separating from the kite.

[PeteCress]

Thanks.

I just pulled the trigger on the 3M tape.

Now we'll see if my sewing machine can handle the stuff.... -)

 

I feel your pain on the Tevas.  After a mere 20+ years mine had started to disintegrate to the point where my daughter shamed me into buying a new pair.

But you know what?  It looks like the damn accountants have been messing with the design. The new ones, although superficially the same, are harder to get on/off bc some genius saved 3 cents worth of material...