G-Flex 655, HDPE, and Hobie

Hi All, various sources on the internet indicate that G-Flex 655 will bond strongly to HDPE... the folks at West Marine, the technical support at West System, and two separate kayak repair shops all indicate the same. I just got off the phone with Hobie, and they indicated that G-Flex 655 (and all other epoxies) will not bond to HDPE.

I'm trying to patch a minor crack in a rear scupper, and am confused by the conflicting information. Does anyone have personal experience with G-Flex 655 applied to Hobies? FWIW, I intend to flame treat the plastic before applying the G-Flex.

I repaired my adventure hull with Gflex and fiberglass cloth. It has held up for almost 5 years now in all kinds of rough conditions. I drilled out the end of the crack and must have used 4 layers of fiberglass with copious Gflex on the inside. I put a couple layers on the outside to just to be safe.

I don't remember if I flame treated but definitely roughed up the surfaces with sandpaper.

It seems to bond pretty well in my experience!

If you can reach the spot and have a bit of room to maneuver, why wouldn't you weld it shut?

If you can reach the spot and have a bit of room to maneuver, why wouldn't you weld it shut?

I was originally thinking that I didn't have a whole lot of room to maneuver. When I first detected the crack, I had an xbar right over it, and I think that probably colored my assessment of how I could make a repair. Now that the kayak is in my apartment and I'm armed with a dental inspection mirror, I'm thinking that plastic welding is still an option.

On closer inspection, it seems that the hull may not be compromised (see picture). Something weird is definitely going on; I'm not sure if it's damage caused by the hobie scupper cart, or a manufacturing defect, or something else.

But, why is Hobie telling me that G-Flex won't work, when so many other resources are indicating that it will work? Is it a difference in terminology? My research indicates that Hobie supplied a 'fix kit' to mend cracked seat pegs, and that this 'fix kit' depended on epoxy. Here is one such post: http://www.newenglandkayakfishing.com/forum/index.php?threads/another-hobie-another-leak.13293/

The fact that Hobie endorsed a fix that used epoxy is odd, given the fact that tech support at Hobie told me that epoxy will not bind to Hobie kayaks.

I’m thinking hobie wants you to buy a new boat or hull instead of a product proven by others to bond to there boat! My $0.02 crack is kinda hard to see on my phone, is it separated or just offset plastic from the rotomold process?

My opinion:  Go with plastic welding on the scupper exterior surface.  Inside the hull, it wouldn't hurt to first do a plastic weld with the area that you can reach, then reinforce with any epoxy like GFlex.   My experience with any adherence for HDPE to repair cracks has been to use thermoplastic reflow of the HDPE (plastic welding) and any additional adhesives or supports like the Hobie repair kits for seat plugs will help reinforce the plastic weld.  When the crack failure is below the waterline, you will have to decide how much risk you want to take with your repair confidence.