C-Forum

Up to a week or two ago, the ABS putty method of patching Royalex canoes had worked very well for me. The materials and process had been as follows :

*canoes rinsed clean, wiped with alcohol
*acetone from Ace Hardware
*mainly white ABS, some black mixed in more recent batches
*putty applied in the evening or in the morning - hadn't gotten too hot yet

However, the putty that I mixed up and applied starting about two weeks ago on one canoe in particular did not work out so well...

*canoes rinsed clean, wiped with alcohol
*acetone from K-Mart (different brand)
*mainly black ABS
*putty applied in the morning (it has been pretty hot lately)

The areas patched this time have turned out soft to the touch in places, not bonded well at all, and show lots of little bubbles. Some of this is visible in the pictures below. I was able to flake pieces off with my finger nail. I removed large areas with a sharp wood chisel altogether too easily... The underlying material seems fine (it's not soft), though a residue (sort of brown) remains in places.


[img]http://lh3.google.com/scott.broam/RoOcY ... 0_7557.JPG[/img]
link to larger picture
[img]http://lh3.google.com/scott.broam/RoOca ... 0_7558.JPG[/img]
link to larger picture

Is not all acetone the same? Should I switch to MEK? Did the overly hot, humid conditions affect how it dried? Could the black ABS matter?

I plan to remove all of this and sand off any remaining residue...

I believe that lots of thin layers is the answer. The ABS slurry dries by evaporation so if the outside of the layers dries first it traps the acetone or MEK inside. The trapped acetone keeps melting the boat and ABS so everything stays soft for a long time. I had this happen to me when I used a lot of slurry to fill a hole in my stern. I finally had to cut holes into the soft areas to let air in. A thin layer, being wetter, will melt the ABS on your boat faster for a better bond.

My Outrage is now about 20% black ABS pipe and it's still bouncing down creeks in grand style.

Jim

So, better to sand away the canoe's outer vinyl layer and bond the ABS paste to the ABS of the hull?

No matter if you use acetone or MEK?

PY.

I did a test in the stern of one boat without sanding away the vinyl and it has held up fine. Statisticly an invalid sample size, so your mileage may vary.

I got to agree with sanding the boat down and put on LOTS of thin layers until you have a really good base.

MEK is preferred, as it will actually dissolve the abs on the boat as well and will improve the bond - BUT Make sure you wear gloves and preferably a respirator - it is pretty nasty stuff

As previously stated, thin coats is best. You can probably put a few thin coats on, then go away for an hour, put a few more on - until you get it the way you want.

It may wind up a bit more brittle than the original, but you can always patch again and again.

black doesnt matter, i did my patching w/ all black... I couldnt find white! but will keep that in mind next time!

I've always sanded the vinyl to ensure ABS to ABS contact. I've also filled a major dent on my Probe 12II a couple of years ago, with a very thick past(ABS Acetone)... As mentionned here above not the best, took weeks to harden. It's now fine but I would not redo.

I beleive thin layers are best, sand / gring the vinyl and get dirty !

Good luck !

What you got there is refered to as solvent popping in the car painting trade. The material was applied too thick so that the outer surface dries faster than the under layers and traps the solvent that is flashing (evaporating off) therefore causing bubbles and poor adhesion. Thinner application is key as most here have recomended. I'm pretty sure MEK has a slower flash rate than acetone, so using MEK would probably help in hot weather applications cause the surface won't dry as fast.

Thanks for all the feedback - I'll go thinner and try MEK! I think I got away with what I thought was thin enough because it was cooler... SC in the summer time...

Do you use the ABS paste just to cover exposed areas of ABS and cracked vinyl, or do you also use it to fix soft spots? I'm wondering if it adds any structural rigidity. For instance, if you have an area about 8" x 18" on a chine where the ABS is getting soft, will adding the paste just build it up or does it actually add strength?

I had a fairly lengthy conversation with Mark Scriver one day about what to do with delamination - typically the hull will feel soft because the inner and outer layer are no longer tied together. To fix that he suggested drilling a pattern of holes from the outside (the worn side) , then injecting resin (or maybe a urethane glue, though the expansion may be an issue), then patching the outside with either a sheet of ABS or paste (depending on the degree of wear). I have done this to one boat (drilled, filled, patched with a sheet) and it felt solid when I was done.

Applying the paste alone has restored some rigidity where the flexibility appears to be due to the thinning of the outer layer alone.

Friend of mine sandwiched kevlar sheets with our ABS paste to improve structural integrity of larger delaminated area. Kevlar gives some structure to the paste.

Thin layer of ABS, Kevlar sheet. Leave to dry and apply ABS again.

I don't beleive he drilled holes(but if Mark said so...I would go there) but I think this would help alot in curing the ABS under the kevlar.

Plug those holes in the last ABS application.

Let us know how it turns out, we're all learning from this !

Tks

Drilling holes like Mark Scriver said is a good idea except that I would inject Gorilla glue instead of resin. The inside of the delamination almost always has water in it which doesn't mix well with resin. Gorilla glue on the other hand is activated by water and expands while curing, filling in the delaminated areas. I cover the holes with plastic wrap and place sand bags on top while the glue dries.

Jim

Jim Michaud wrote:Drilling holes like Mark Scriver said is a good idea except that I would inject Gorilla glue instead of resin. The inside of the delamination almost always has water in it which doesn't mix well with resin. Gorilla glue on the other hand is activated by water and expands while curing, filling in the delaminated areas. I cover the holes with plastic wrap and place sand bags on top while the glue dries.

Jim

That is exactly what I am planning to do to a boat, hopefully this weekend. I have some Gorilla glue (or rather Elmer's version of urethane glue) whereas my West Systems resin/hardener has apparently gone south...