C-Forum

I've been asked to look at fixing up 7 or 8 canoes (one may be a little far gone) for a local school - these are whitewater boats (most are Mohawk XL 15s) and they are candidates for grunch pads. They have the vinyl worn off on the right places and the beginnings of the kinds of cracks that will make the ends go soft, but nothing catastrophic yet.

So... don't think of this so much as taking another whack at a terminally ill horse, but as checking on the latest thinking on the treatment for said horse (is that metaphor mangled enough?) -

• West systems + kevlar felt
  West Systems + S glass
  G-Flex + another fabric
  ABS sheet (reviewing posts here, including some of my own, I'd consider using 1" strips + ABS cement)
  Kydex
  Rec Repair kit
  ???

Considerations -

• cost
  ease (i'm doing this on 7 boats *)
  temperatures (curing temps, cooler weather)...

Have at it ...

(*- the worst boat already *has* them - its in bad shape because it looks like it fell off the trailer at highway speed...)

I know what I wouldn't try--the ABS. Too hard to form around a curve. Perhaps that's why you're thinking the 1" strips. Still sounds too difficult.

Putting fiberglass or kevlar right where the canoe smacks rocks (in less than capable hands) never seems to work that well. You just end up having to repair it. I used a Rec Repair skid plate on one canoe and was and am still impressed with how tough that is. It's formable with a hair dryer or heat gun and glues well with g/flex. I have to admit my skid plate with it was far from beautiful though, but then I didn't try to hard to make it pretty. I did hear from one person who said they had a poor experience with Rec Repair in terms of the material itself degrading, but I haven't had that happen.

I'm sure others will have better advice on materials and more experience.

A Harmony kevlar felt grunch pad kit costs about $100. I am about to call Sweets to get an idea of how much resin / felt I would need for 7 boats to see what buying raw materials will cost. I'm not excited about the "rigid" repair, but G-flex looks like it would be expensive.

Rec Repair (now "Gemini Materials" - http://geminimaterials.com/patch-n-protect/skid-plates" onclick="window.open(this.href);return false; ) appears to be a peel and stick application. Did you augment that with G-flex or is that a new feature? A kit of these can be found for $105 - if the peel and stick is viable, that wins on labor.

I've had success with ABS repair, but, yeah, getting it to conform to the curves at the end of the boat is challenging. [See previous discussion here about use of heat and solvents...]

If you can get Kevlar felt and good resin at an acceptable price, I would go with that. It's a fairly fast way to get it done.

I can do layered S-glass skid pads that will outperform and outlast Kevlar felt, but it certainly takes longer.

I got prices from Sweets (thanks Jennifer!) on felt and resin (West systems 105) - assuming a quart of resin would be enough for 7 boats, the cost per boat could be under $20. Including the cost of the pumps. Kevlar felt + resin pulled into the lead, even with extra labor... The mark up on the Harmony kit is crazy!

At the time I used the Rec Repair, the skid plates did not have their own adhesive. That's why I went with g/flex. I did use a Rec Repair patch one time that had self adhesive and it really stuck to the Royalex. Might still be on there--I'm not sure because I sold the boat. It's interesting that Gemini lists polyethylene as one of the materials its skid plates will stick to.

Scott,
I think that 7 kevlar felt pads will require more than 1 qt of resin.

MarPro is a great marine epoxy at 1/2 the cost of west system. although my new go to for bomb proofing my canoe is G-Flex. i like the thickened g-flex it wets into kevlar felt just fine.

7 boats times 2 kevlar pads each... We looked at the West Systems coverage specs :

http://www.westsystem.com/ss/coating-quantity" onclick="window.open(this.href);return false;

A quart is supposed to give you about 100 SF on a porous surface. I'm looking at a little over a square yard of felt, call it 10 SF. I can see how wetting out felt could be more, but how much more? What do you think?

If I go with a gallon, it more than doubles my resin expense ($57 -> $135), but I'm still looking at less than $30/boat material cost. I don't typically use a lot of resin - I threw my last batch out after it sat on the shelf for 5+ years and I assumed it had gone bad... I'd hate to throw away a whole bunch later if I overbuy significantly...

With my limited experiences with Kevlar felt, it will keep taking as much resin as you throw at it. Obviously it does eventually reach the point of saturation.
Perhaps Dynel instead? Keeps soaking up resin too, though not as much.

I have done, and am doing something very similar to what you are entertaining, fixing up a fleet of around 16 livery canoes used for trips by a local nature society. Some of these boats are worn through at the stems into the foam core of the ABS.

I use G Flex and Dynel cloth. I don't particularly like the thick Kevlar felt and I feel that it soaks up too much expensive resin for the amount of strength gained. Although I always use G Flex epoxy to wet out the cloth initially, sometimes I will use conventional West Systems epoxy, or a mixture of West 105 resin and 206 hardener with G Flex for subsequent epoxy applications to fill the weave of the cloth. You can certainly use S 'glass or E 'glass, but I find that one has to use about 3 layers of 6 oz/yd fiberglass to get an abrasion plate as thick as a single layer of 5 oz yd Dynel cloth. The Dynel does soak up considerably more resin than a layer of fiberglass cloth of similar weight, but not nearly so much as Kevlar felt does.

A couple of yards of Dynel cloth (5 oz/yd, 54" wide) would certainly be enough to do all the boats at both ends. Sweet Composites sells this for $9.60 per yard. I buy the G Flex in the 32 oz kits (16 oz of resin and 16 oz of hardener) which Sweet Composites sells for $58 per 32 oz (price has gone up). The price is comparable to buying a quart of West 105 resin and the appropriate volume of 206 hardener, but you don't need to buy pumps for the G Flex. You can mix up batches of G Flex of any volume 1:1 by eye.

I find that 32 oz of G Flex will do 5-6 boats, depending on the size of the abrasion plates. I have also had to rebuild stems on some of these boats when they were flattened and softened by abrasion or outright worn into the foam core, and G Flex is very good for that. So 32 oz of G Flex would not be enough to do all of the boats you are considering repairing. But you can also buy two 4 oz bottles of G Flex for $21 and there is a good chance that a total of 40 oz would do the job.

I also like to mix graphite powder in with the epoxy. Theoretically, this makes the abrasion plate slicker and more abrasion resistant. I find that the black color that results looks good on Royalex boats of just about any color, and it allows you to bypass spray painting the abrasion plate to protect the epoxy from long-term UV degradation. Sweet sells West graphite powder but you have to buy a minimum of 12 oz (more than you need) for $17. You might be able to find graphite powder cheaper at your local hardware store.

So if you can get by with 40 oz of G Flex you are looking at a total of around $115 for Dynel cloth, epoxy, and graphite powder, not counting shipping. Add in some incidental expenses for stuff like denatured or isopropyl alcohol to clean the hulls, masking tape, disposable gloves, and sandpaper and you are still looking at less than $25 per boat to fix 7 boats, which I think is pretty reasonable. Even if you had to buy a total of 64 oz of G Flex you are still looking at a cost of less than $30 per boat, not counting your time.

Not to hijack the thread, but I have a guestion about the graphite mix. I've been thinking of coating the bottom of a Royalex boat with a mixture of g/flex and graphite, Any suggestions on how much graphite to put in the g/flex?

pblanc- thanks for the input! I'm giving dynel some serious consideration and your experience with volumes is very useful. I think I'm close enough to give them a quote, but don't need to make a specific decision yet (provided they accept it).

milkman wrote:Not to hijack the thread, but I have a guestion about the graphite mix. I've been thinking of coating the bottom of a Royalex boat with a mixture of g/flex and graphite, Any suggestions on how much graphite to put in the g/flex?

I don't measure it quantitatively. I first mix the resin and hardener together thoroughly and then drop graphite powder in by scooping a bit out of the can at a time on the end of a stirring plastic spatula or popsickle stick. I stir each small scoop of graphite in before adding more and continue until the graphite powder makes the epoxy just a bit thicker.

For the initial application of epoxy to wet out the cloth I generally mix in a bit less graphite so that the mixture is less viscous and soaks into the cloth better, then mix in a progressively more graphite on subsequent epoxy applications. For Dynel cloth I generally use at least three epoxy applications (the initial one to wet out the cloth and two more) but if you want an absolutely smooth abrasion plate you can keep going until the weave of the cloth is completely full, wet sanding with water proof paper (around 220 grit) between applications. I don't think this is necessary for a livery or club boat. If you wet sand after the last application you will have a flat black plate. If you want it glossy, don't sand after the last application.

In my hands, this results in a deep black finish which is very opaque. Another advantage of the graphite powder mixed into the epoxy is that the abrasion plate will scratch black, unlike paint where the scratches clearly show the off-white cloth fibers.

If you were doing the entire bottom of a boat I would mix up multiple small batches of G Flex and in that event you might want to be at least semi-quantitative when you add the graphite to get a uniform depth of black color. If you kept the size of the epoxy batches roughly the same using the same mixing cup, you could just add in equal numbers of small scoops of graphite powder each time.

I recently picked up an old dagger encore that was gone to hades. The outside was worn off the bottom and was delaminated pretty bad. Most of the foam core was completely rotten. It was cracked through to the inside also.
I tore out all the rotten foam and bad pieces of royalex. Then I built back all the foam core with gorilla glue.
Then, I used ABS and acetone. And a good amount of it. I cut up a 2 ft by 2 1/2 in piece of ABS pipe and put it with a full can of acetone. It makes it more watery (or acetoney) then solid. I then start brushing on, in lots of thin layers with a day or so in between. After about 5 coats I added s-glass and more ABS goo. About 5 layers.
Did this on both the inside and outside. The thing is really strong now. Still doing a little more ABS goo. Then Im going to sand down and repaint.
So far, the ABS and acetone and Sglass has been really solid.
And its been fairly cheap.