Late D-ring patch failure

-- Last Updated: Jun-26-10 10:49 PM EST --

I've used Vynabond according to directions to install D-ring patches in my Royalex Mad River Synergy. These patches have held up under considerable strain and abuse over more than a decade. On one occasion I failed to dump extra air from the float bags, drove to 5500 feet on the Blue Ridge Parkway, left the car and boat in the sun, and returned to find the hull significantly distorted at both ends by the greatly expanded bags. This put tremendous tension on the D-ring patches below the wide ends of the bags. Subsequently both D-ring patches held during many hot miles across the US.

Yet both patches peeled loose spontaneously, one last year, and one this year, during a period when the boat was just sitting around unused. The tension on each patch must have been low, yet each peeled up from one edge near the end of the black strap that holds the D ring. Examination of the patches and the hull shows evidence that Vynabond distribution was even and neither excessive nor sparse.

Just to show that these carport failures were not due to my Vynabond technique, one of the large thigh strap patches in my used Mad River Guide failed spontaneously while the boat was just hanging in the carport. That patch was installed by the previous owner over 10 years ago. In the past I had put normal strain on the thigh strap without failure.

What this suggests is that a Vynabond D-ring patch may function under considerable stress for years, only to fail spontaneously when it is over ten years old. All three of these spontaneous, low stress patch failures were with patches over ten years old.


But the same two D-rings spontaneously peeled loose

Dick Cheney

– Last Updated: Jun-26-10 11:40 PM EST –

Hear tell he wuz spotted snoopin' around yer Guide lookin' fer "Terrist" House Wrens.


I’ve had vinyl patches come loose also
Usually happens when the patch and hull get thoroughly warm in the sun. I’ve had D-ring patches that secure air bag keeper straps come off under tension as you describe. I’ve also had D-rings that secure thigh straps fail if I stressed them too soon after they had thoroughly warmed up.

Sometimes I’ve simply taken the tension off, pushed the patch back down and it seemed to “re-bond”.

I’ve removed many vinyl patches from Royalex boats many years after they had been glued in with Vynabond, or a similar vinyl adhesive by carefully warming the patch with a heat gun. I think this is normal behavior for this adhesive. In fact, I like being able to remove patches for re-outfitting.

If a patch completely gives way, I generally just clean the patch and hull with acetone and glue it back down with vinyl adhesive and it seems to work fine.

Uncured rubber
Like most contact cements, I suspect that Vynabond is mostly uncured rubber distributed in a solvent.

Eventually the rubber is going to get a bit crusty and let go.

An old saying comes to mind:
“Entropy is winning.”