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What is the best choice for material for the outside patch on royalex? I have been talking to Sweet Composite and they have several different materials and by the time I finished reading their info page I was more lost then when I started.

Depends on the damage, how big and where on the boat

Although repairs to ABS boats can be successfully done with conventional epoxy, such as West Systems 105 resin and 205-206 hardener, I prefer using West System's G Flex epoxy on ABS. It bonds more strongly to plastic and is less stiff when fully cured which at least theoretically results in less of a compliance mismatch with the adjacent and underlying, rather flexible Royalex. G Flex can also be mixed in small volumes 1:1 by eye, which results in less wastage when very small batches need to be mixed to fill and fair small holes and voids. It seems to be less allergenic than West 105/205-206 but is more expensive.

If you have erosion into the foam core of the Royalex I would fill it in using epoxy thickened with colloidal silica powder (cab-o-sil). You probably will need to use multiple applications to completely fill the void and you may need to overfill the void a bit, then sand it down fair with the adjacent hull. I have found that G Flex wet sands quite well, even when moderately thickened with colloidal silica. G Flex wets out cloth up to 6 oz/yd weight just fine, but it is more viscous than conventional epoxies and takes a bit longer to work into the cloth. I have only wetted out one layer of cloth at a time when using it. Use unthickened epoxy to wet out cloth.

For exterior patches I would probably use 6 oz/yd fiberglass. S 'glass is stronger than E 'glass, but more expensive. You could use 4 oz/yd fiberglass if you are applying multiple layers. An alternative is Dynel. Dynel soaks up more resin than fiberglass and does not impart as much strength as fiberglass cloth of comparable weight, but it does provide quite a bit of abrasion resistance which might be desirable for a repair at the stems, along a sharp chine, or under the pedestal.

I see no reason to consider using either aramid (Kevlar) or carbon for an exterior repair on a Royalex boat. Carbon is too expensive and too stiff, much stiffer than ABS which would create a stress riser at the edge of the patch. Aramid fuzzes up when abraded, is more expensive than fiberglass, is harder to cut, and isn't as good for use on the hull exterior anyway. Polyester might be a possibility, but I have no experience with it.

Sweet composites style 6522 is the 4 oz/yd S 'glass that I use and style 6533 is the 6 oz/yd S 'glass. Style 1522 is 4 oz/yd E 'glass and style 3733 is the 6 oz/yd E 'glass. Style 90285 is a 5 oz/yd Dynel cloth.

Wow, that's a detailed set up.

I've been painting on ABS after mixing it with acetone. Seems to have worked on wear spots. It does come off a bit at a time. But it's easy enough to reapply. About six coats at a time.

Thoughts on the quick and dirty?

I have tried the ABS dissolved in acetone or MEK thing and gave up on it because it was not durable.

Actually it takes no longer to mix up small batches of G Flex and apply it to areas of wear or small divots than it does to apply multiple layers of dissolved ABS. True, it takes longer for the epoxy to cure than it does for the actone or MEK in the dissolved ABS mixture to flash off, but you can apply a subsequent coat of G Flex while the prior coat is still green.

When the OP referred to "materials" and Sweet Composites I assumed he was asking about repair fabrics. You can't wet out cloth with dissolved ABS.

I have found that for significant areas of damage it is generally better in the long run to take the time to do a good repair than doing a "quick" repair that doesn't last over and over again.

Obviously, there are many alternatives to epoxy. I know people who swear by Plexus (or Devcon Plastic Welder which is basically the same thing) and JB Weld (which I believe is an epoxy). I have heard of a few people thermal welding Royalex or bonding ABS plates over areas of severe damage. And there are many various forms of goop (plumber's goop, shoe goop, Bondo) that have been used as well as Gorilla Glue, Sikaflex, and other adhesives.

pblanc wrote: You can't wet out cloth with dissolved ABS.

Yes you can...




The mix has to be thin, but it works pretty well. Is it as sturdy as Gflex? Probably not. but it's also not$60 a quart.

This boat was pretty beat, cracked, and perforated, so it got to be the abs/acetone repair experiment. So far pleased with the results. I took it down Section III, and while I did manage to break it again, it broke somewhere other than where it was repaired. The repaired bits held up quite well, even with some pretty solid direct hits. (Pinned the heck out of it doing something stupid too.)

ABS sheet applied with ABS cement is good, especially for large flat areas - it is harder to get it to conform to curves, though some folks have softened it for that purpose through application of heat or solvent. My experience with the both is fair to poor.

I have used Gorilla glue injected into the voids on areas where the foam core is deteriorated and topped with ABS with good results.

I have used G-Flex with and without fabric - make sure you prep the surface by cleaning and roughing it thoroughly. I have had some pop off of vinyl that was left too smooth.

I have also had good luck with PC-7 (and PC-11, it's "marine" counterpart) - I applied a layer on the stems of a touring canoe where it had worn thin from abrasion (sand, occasional rock) and that lasted 12 years + with regular use.

For a serious repair, I wouldn't use G-flex over vinyl. I'd skim off the vinyl with a low angle chisel, flame the ABS, and apply the repair material with G-flex over that.

So far, in my attempts, skimming the vinyl off the ABS goes pretty fast. You have to be careful on concave surfaces not to let the chisel dig in.

I second that, G on ABS works better than on Vinyl. I used to make complicated laminations with an ABS sheet inset just like the original one but pure gflex with filler works so much faster. Open up the crack/area, bevel/round off/smooth edges to eliminate any stress points/crack entryways (existing cracks have to be stop-drilled to not continue on under new stress..), sand adjacent areas w/ 80 grit, fill with GFlex and cover up with some stiff film (acetal works, the stuff used for overhead projectors.. do you remember these, guys? ;D) that can be removed after the G has cured but keeps it in there, not running out.. tape down, wait 24 hrs, sand/scrape smooth (cabinet scrapers.. awesome tools! Always great for plastic). Then... paddle!

Cheers,

Jan

ps. the Gorilla glue is an excellent idea though.. it will just use any water that's in there to help cure it, foam up to provide a "new" foam core and bond to the old stuff very good.. I'll try that on a Viper11 I have sitting here to repair!

18oz roving fiberglass and Flexane 94 is the best stuff Ive ever used. Ive patched my Royalex
canoes for yrs. with the stuff, not pretty, but boy its tough.

Thank you !!!! I'm sanding off vinyl and will be doing repair job on ABS directly. Its relatively narrow dead down middle of bottom of hull about 24+"

Resurrecting this thread.

Time to work on my Bell Ocoee that's been down many a rocky river. The bottom has plenty of gouges (none into the foam but into the white) and there is a 2" crack under the pedestal. I'd like to put a protective layer of something that is durable but not heavy (ideally in red). Any new products or techniques in the past decade?