UKC

I suspect that tenacious Tape is a rebranded product and is available elsewhere in much longer lengths at a fraction of the price per metre.

Anyone know what it is called and where to purchase it? 

Never used tenacious tape but spinnaker tape works really well.

https://www.tcschandlery.co.uk/mobile/psp-spinnaker-repair-tape/p8306?gclid...

Tenacious tape is pretty rubbish. It cracks easily and doesn’t last more than a couple of wash.

Betrafol tape is far a better option. 

It is green though. 

https://www.luchtdichtshop.nl/luchtdichte-tapes-en-banden/binnenzijde/op-fo...

Must be different stuff to mine, which is kind of self adhesive black nylon fabric. 

That looks like the stuff and at less than half the price. Some groovy colours too. 

I found proper spinnaker tape rubbish on goretex. Just peeled off really quickly. 

My tenacious tape repairs have lasted about 6 years, same length of time as duct tape repairs on the same trousers. Perhaps you got a dodgy batch? Provided you clean the area to remove the dwp, cut the corners off your patch and apply it with heat then pretty much any tape will work. If you try and stick it onto a water repellant finish, leave sharp  edges to peel or put it on in the cold nothing will work.