C-Forum

So on a casual 7-day trip down the San Juan, I loaned my Bell Ocoee out for a half day and it now has a 3" crack, roughly in the center between the knees. Not sure how he managed that on a class 1 section but I bought the boat used so probably just a matter of time.

Duct tape worked fine to finish the trip but I'd like a longer term solution. Not interested in putting a ton more money into this boat but would like to get a couple more multi-day trips in before it becomes a nice planting pot. So what are my low-cost repair options? The location makes it a flex point in the center of the flat bottom. On the inside, I'll have to deal with knee pads and a center attachment point for the lacing.

Cracked through, huh? Low cost options? You could epoxy a piece of ABS over the crack on the inside. I hate to see an ABS plate repair on the outside because, even if tapered carefully, it will cause the boat to "trip" sliding over rocks or ledges. Just a small point.... the edges of an ABS plate can be chamfered.

Here's what I'd do for a more costly repair. I would low-angle chisel the vinyl off the ABS, inside and outside, to clear an elliptical space. Then, using Kevlar on the inside, I would lay down a three layer patch using either West 105/205, or West G-flex. Largest patch should fill or just lie outside the area cleared of vinyl. Then the next smaller layer, then the smallest which should be cut to be a bit longer than the crack.

When cutting the patches, rotate the fiber orientation somewhat from one patch to the next.

On the outside you can use cheap, fresh E-glass, or S-glass if you want to hunt it up. Again, largest patch first. You can bag the patch with food wrap and tape slips for smoothness, or you can let it harden and feather the patch edges if you feel obsessive compulsive.

I didn't mention shoving adhesive between the ABS layers. I'm not sure it's necessary, do what you think best.

Let me know if you don't understand the reasons for any of this.

Oh, and I've done the San Juan run. Not many rapids but a good, swift current.

I would do something similar but if you are trying to keep the cost down, buying both fiberglass and aramid cloth is going to be costly, unless you already have them, of course.

You can buy a kit containing 4 oz of G Flex resin, 4 oz of hardener, some silica gel powder (Cab-o-sil) to thicken the epoxy for bonding, some mixing cups, a couple of dental syringes, and a couple of small spatulas. Jamestown Distributors and NRS sell them and it should be enough epoxy to fix a 3" long crack.

If the hull is cracked all the way through, I would definitely bond the crack before covering it with cloth. To do this you may need to gutter out the crack a bit. I would "terminate" the crack at both ends by drilling a hole a little wider than the crack all the way through right at the end of it. You might be able to get a bare hacksaw blade through it to use to widen it a bit, then round off the edges of the crack on the inside and outside with sandpaper. If you can't fit a hacksaw blade through, drill a series of closely spaced holes big enough to get it through. Wash out the cracked area with denatured or isopropyl alcohol and allow it to dry well. Then apply some clear packing tape to the outside of the hull to back up the crack and contain the epoxy.

Thicken mixed epoxy with silica gel to bond the crack. Mix the epoxy first, then keep adding small amounts of silica powder and stirring it in until the consistency is between catsup and mayonnaise consistency. Take the plunger out of one of the dental syringes and fill most of the barrel with the thickened epoxy, than reinsert the tip of the plunger. Invert the syringe and let the epoxy run down to the plunger and expel the air. Use the narrow, curved tip of the dental syringe to get the thickened epoxy down into the crack. You may have to wait and add a little more at a time as the epoxy settles into the core.

I would use cloth on the inside and outside but if money is tight you can use fiberglass on both sides. It won't be as strong as using aramid on the inside, but it will be strong enough. I have bonded fiberglass over Royalex with G Flex without first removing the vinyl layer(s) without any problems. Cover the patches with some Krylon Fusion spray paint (at least on the outside) to protect against UV exposure.

The G Flex kit with accessories runs about $30. One yard of 6 oz/yd fiberglass cloth (E 'glass) is about $7 and should be plenty to patch both inside and out. A can of Krylon costs about $5. Add a few incidental expenses like isopropyl alcohol, masking tape, sandpaper etc and you could do this repair for about $50 and the boat would be strong enough for more than just a couple more trips.

pblanc: " I have bonded fiberglass over Royalex with G Flex without first removing the vinyl layer(s) without any problems."

Normally that will be the case. But consider the Royalex layers as components in a composite layup. A vinyl layer will be inherently weaker than the ABS under it, and weaker than the FG and epoxy applied to it. Better to just skim off the vinyl and mate the glass/epoxy directly to the ABS.

That the vinyl layer skims off so easily, in a flexible lasagna noodle, shows what it is worth structurally. I personally think R-84 should have been used and developed more. Acrylic is a more logical composite layer in Royalex than vinyl.

ezwater wrote:That the vinyl layer skims off so easily, in a flexible lasagna noodle, shows what it is worth structurally. I personally think R-84 should have been used and developed more. Acrylic is a more logical composite layer in Royalex than vinyl.

Indeed, acrylic would be better... I can't help thinking that PTFE would be a good material for the skin, if only it wasn't so awfully hard to bond.