I run into a problem with glueing anchor patches in my Royalex hull. I use vynabond, and follow the following procedure:
1) light sand the hull at traced location of the anchor patch
2) dedust and wipe hull and patch with aceton
3) let the aceton vaporise
4) apply 2 thin coats of vynabond to hull and patch, and let glue dry in between each coat for approx 10 minutes
5) reheat with hair drier
6) apply the anchor patch

I'm now half way with glueing all anchors, but for some unclear reason two of the anchor patches did not bond...
one patch I noticed already during first contact that the glue only partly bond... half of the patch just didn't seem to be willing to bond/stick... I had to tear off the anchor patch off the hull, partly detroying the anchor patch. Another patch was glued yesterday, and when i loaded the patch this eveneing I could just peel it off very easily without damage... again glue didn't bond. the other patches seem fine... I can pull realy hard without any movement.

What could have been the problem...?

only thing I can think of is that the drying time has been too long. 10 minutes for each coat... 2 layers glue on hull, 2 layers on patch.

Should I allow only a brief drying time of say 3-5 minutes in stead of 10 minutes?

Any other idea's/suggestions/solutions?

When I use vynalbond I reheat the glue as soon as it's dry and use a heat gun rather than a hair dryer on both the hull and the patch then apply right way while both surfaces are still warm. Perhaps your hair dryer isn't warming the surfaces enough.

Its temperature sensitive..are you above 50 degrees F?

http://www.plastidip.com/docs/vyna_bond.pdf

No mention of heat gun though paddlers in the know do use them.

The brochure says reapply a thin layer.

Also mentions MEK as thinner which is nasty.

The acetone can leave fumes that are heavier than air and will sit on the Bottom of the canoe. Use a fan and make sure you disperse the fumes before applying the vynabond.

I had the same problem with varnish not hardening. It is the most pronounced when the canoe has significant tumblehome

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I like canoes

Acetone and Vynabond fumes will never cause a problem. There won't be enough to inhibit drying. It's the liquid that poses a risk, if it gets through the vinyl to the ABS.

I have never used a heat blower or heat source, and my patches have lasted ten years. Then, like bamboo, they "die" and fall loose. Not only those that I applied, but those applied to a boat I bought used. Very mysterious. I now use G-flex epoxy for all critical patches and fittings.

On reflection, I think your patch-pulling-loose problem was due to your use of acetone as a cleaner. While you waited for the acetone to dry, the problem is that acetone goes into and through vinyl very easily. So the surface of the vinyl hull coating and the surface of the patch were already softened by the acetone when you swung into your Vynabond application. The combination of a little pre-weakening by the acetone, followed by the (necessary) attack on the vinyl surfaces by the Vynabond solvent, was too much. Some of your patches held, some did not.

I have to recommend against getting acetone anywhere near Royalex. A small, slow leak from an acetone can I had put aside in a Royalex boat, after using the acetone on a composite boat, resulted in the acetone going through the vinyl, disrupting the inner ABS, bubbling up the foam, and softening the outer ABS. Acetone is just too penetrating and softening to be around Royalex.

Use rubbing alcohol instead. It is more than effective as a surface cleaner after you have sanded the vinyl hull skin and the patch.

I always sand the bottom of the patch as well. While Ez is correct that acetone will soften plastics, you shouldn't be using so much that it is a problem. I also think that you may be not heating he Vynabond enough to make a difference. When I use it, I let the first coat dry, then wet again to reactivate and apply the before the second coat has dried. Other adhesives would be G Flex, or Scotch 3532, the latter a very very strong adhesive I've used in composite and Royalex boats. Unlike Vynabond, however, 3532 cannot be removed by heating. Once its on, it will stay for ever. Another cleaner to use besides acetone or alcohol is ammonia, perhaps in a 60% solution with water. It cleans well and evaporates, but you will definitely need a respirator with the correct filters.

Yeah, Erich, I have a 3532 scratch repair on the chine of my Royalex ww boat that has lasted over ten years. It does not seem to have chalked at all from UV exposure.