I usually buy mine at Home Depot, they only sell the real stuff (Velcro®), alternatively a good sewing/fabric shop if there is one in your area. In the past I would check out Walmart but the ones around me have reduced their "notions" department down to 2 square feet of pegboard.
i have attached 2" wide velcro from Walmart under the gunwales and to waterproof nylon fabric for custom home made spray covers on voyageur and C4 canoes for the Yukon River races. I used contact cement to hold it firmly to both carbon fiber and wood hulls, which obviously got very wet during use. it worked perfectly to hold the covers in place for more than one race in multiple years
Second using Dual-Lock, mostly because unlike hook & loop Velcro Dual-lock uses harder mushroom caps that snap together on either surface, and that mushroom cap design accumulates less debris over time and is easier to clean.
We have both Velcro and Dual-lock on some outfitting stuff, spray covers, paddle straps, etc, but none of those applications are in the bilge, where they are constantly wet and where dirt, leaf matter, spider webs and etc tend to accumulate. Even used above the bilge Velcro gathers gunk, especially on the snaring hook side.
Dual-lock, including some experiments. The experimental Dual-lock was self adhesive, and the pieces attached to the live-outside trash can lids are still firmly attached two years later.
Stripperguy, I recall that you attach a movable solo bucket seat to composite floor rails using 3M Dual Lock. I'm thinking of using it for a movable wooden solo seat on wooden rails -- strips of it on the "slider" rails and a patch of it on each of the four corners of the seat rails. This would...
But the larger issue is how to attach the Velcro or Dual-lock to the pad. If using minicel or sleeping pad foam I doubt the self adhesive stuff will adhere well over time, and if it does stay stuck might tear minicel off when the pad is removed.
I have minicel and ensolite pad scraps in the shop, as well as Velcro and Dual-lock; might be worth another experiment.
“One option would be to sew a cover for the pad and attach the velcro to that”
I expect that will prove true. An experiment is underway.
I have scraps of minicel, ensolite pad, exercise flooring and a DIY vinyl covered seat pad available, and have attached self-adhesive pieces of Dual-lock to each. Best adhesive practices, surfaces clean, Dual-lock self-adhesive stuck and clamped firmly for the night; from past testing I know the super-adhesive on Dual-lock takes a day to fully set.
Tomorrow I’ll press the Dual-Locked test pieces onto another strip of Dual-lock, one still firmly adhered to a garbage can lid from past experiments a couple years ago, and see what happens when I pull them apart.
My suspicion is that they will not separate cleanly; either the adhesive will pull free of the foam, or the super-stick weatherproof Dual-lock adhesive will rip some of the foam off with it. Except on the vinyl covered pad, where I think the Dual-lock with stay stuck.
One possible solution, without using Dual-lock or Velcro, might be to use puzzle-edged exercise flooring, and contact cement the removable edge puzzle strips some distance below the inwales, then lock a couple pieces of exercise flooring puzzle-edged together in that span. The thin, glued in puzzle-edge strips would remain in place, but larger puzzle edge slabs be easily removed.
(Puzzle edges there cut off to give me a large square of exercise foam)
A removable puzzle-edge attached pad would be better in out-of-canoe camp use as well, without Velcro or Dual-lock picking up hair, dirt and debris when used on the ground/in the tent.
FWIW in the Stripperguy thread experiment I goo’ed up Velcro and Dual Lock and
“The Velcro did not sponge off very well. At all; I finally resorted to blasting it with a hose trying to dislodge the little bits of sponge stuck to the hook side. With only minor success”. Simply sponged off the Dual-Lock came easily clean and crud free.
To be experimentally thorough I attached Dual-lock to both the flat and embossed side of the exercise flooring test piece. The embossed side is more durable than the unembossed side, and much more durable than minicel or ensolite foam, better for boot gouging resistance when used as a heel pad, probably the same over time for dog claws.