I've read this through twice & still don't quite understand what you're trying to achieve here.

You're going to laminate large/long lengths of fabric that need to be in one piece? And the laminator can't accommodate thick seams? I'm inclined to say try the web tape, it should hold to moderate tension as long as it's fused well to begin with.

How many rolls are you needing to laminate? Is this going to change the time on the job? (Assuming it's a pay job). and are you going to seam up lots of rolls? You're going to have some humungous rolls of fabric, may need to fuse as you go, or just fuse 2 at a time, if possible. I'd be leery of unrolling and rolling onto another bolt, it's very hard to keep the fabric straight when you re-roll (at least for me it is, and I've used elec. rolling machines). Good luck, post back w/more info if you haven't finished the job.

Yes, we laminate fabric that can be on rolls from 50 to 300 yds. of fabric. On those, we generally don't need to splice. On others, the fabric pieces can be anywhere from 4 to 30 yards long, and the short ones won't go through our equipment without a leader attached to each end. Well, they'll go through, but they'll be scrap when we're done, as we can't keep tension on the fabric and the film will wrinkle up. Every time the machine hits a bump (seam) or end of the fabric, the film that's being laminated breaks, making a mess and causing us to stop and restart.
We can rewind rolls if necessary, as our equipment has electric eyes that shift the roll left or right to keep one edge perfectly straight. If we can splice on a scrap fabric leader at the beginning, splice together the shorter pieces, and add a leader at the end, the whole thing will go through the machine in one motion, resulting in a good quality surface with (hopefully) no film breaks, and it will save on stops and starts, which cost us time.
There are "traveling head" sewing machines with large throats that move on a rail of sorts as they sew, with the rolls of fabric staying stationary. They cost around $50k.
I haven't had a chance to try the fusible tape yet, but will try it and report back.
Thanks for replying.

holy moly you've got sot some bux in your equipment! Thanks for clarifying...Hopefully the web tape will help, that way you're not continually breaking the film & resetting the laminator. Your traveling head machines sounds similar to large quilting heads to me, roving around on rails, and quite costly too.

The only other thing I can think of is some kind of chain stitch machine, not sure if there are models that can just lay on top & not underneath as well (ie no throat plate).

The more I think about this, I'm sure there's an industrial machine out there that would do what you want...I used to run a fabric store & we had tons of ROT (rolled on tubes) fabrics that were pieced w/some kind of chain stitch in the middle of the bolt, but I can't recall exactly how bulky those joins were so you'd have to see the thickness created & decide if it would work w/your laminator....

Ok found it! Now my memory is coming back. I love google! We called them zippers & they are not uncommon. The 2 pieces were butted together, usually didn't overlap but the join was thready, IIRC they used heavier gauge thread for it. Not nec. stronger but thicker, def a chanistitch. I can't find an example of an industrial zipper machine tho, it just takes me to clothing/deco zipper inserting machines not the stitch.

Alternatively, you may have to set aside short bolts and have someone handsew/baste during off peak times, will def add to production costs tho.

Man do those elec eyes sound nice for re-rolling tubes!

Here is a link that might be useful: response #5