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 Post subject: Royalex repairs - Cracks
PostPosted: August 25th, 2014, 6:23 pm 
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My trusty Swift Raven that has suffered much abuse since I acquired it a few years ago has finally cracked under the pressure of said abuse.

During my recent expedition involving dragging upstream through Class III/IV rapids including a partial pin, the scrapes and gouges in the bottom of the hull turned into actual cracks which grew slightly as the days passed. There is also a single small crack on the inside which may have been there previously.

I'd like to make it structurally as robust as possible, cosmetics are unimportant. I think it still has a future as a "light tripper"

Ease of repair is important, instructions for dummies appreciated.

Overview
Attachment:
raven1.jpg


Main area of cracks
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raven2.jpg


Close up showing most of the cracks
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raven3.jpg


Detail of individual cracks
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raven4.jpg

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raven5.jpg

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raven6.jpg

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raven7.jpg


Inside, crack starts under the centre D Ring, it's only about 1 inch / 3 cm plus whatever extends under the D Ring patch, the debris in the crack is sand.
Attachment:
raven8.jpg


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PostPosted: August 25th, 2014, 9:18 pm 
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If this is a Royalex boat, then a wide area of ABS has been exposed to UV for some time. You have less ABS to work with (Thinning by scraping) and what you have is seriously weakened.

I can imagine doing a broad three layer concentric S-glass patch on the outside, or E glass if you're cheap and lazy. The cracks that go through should be patched and reinforced from inside, usually with Kevlar.

You aren't going to end up with more than 50% impact strength than you had from the beginning, and the boat boat will weigh more. But if the patches are done right, the hull will be tolerably stiff.

Have I talked to you about my buys on the used boat market?


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PostPosted: August 26th, 2014, 7:00 am 
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Recep:
I don't think this canoe owes you anything.
Sorry, but with that many fractures in the hull, I would send it to the dump and not risk your life further by using it on either rapids or flat water.


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PostPosted: August 26th, 2014, 7:56 am 
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We patched the bottom of a friend’s OT Appalachian that had similar wear on the bottom, although it had no cracks in the ABS layers.

It that repair we cut pieces of cloth (he used Dynel) and epoxied them to the bottom. We ended up using three pieces of cloth, not to layer them but to place them adjacent to each other and overlapped a bit. We had laid out a single diamond shaped < >piece of Dynel as a dry test, but found that the weave would not upset and lay flat. (Note: we did not cut the cloth on the bias, which would have helped).

For your Raven I would fill all of the cracks and splits first, using Gflex epoxy.

That is a big piece (or pieces) of cloth, S-glass or dynel or whatever you choose to use and would be an expensive fix using Gflex, so probably West System 105/206 or other epoxy resins. If you have Gflex remaining you can mix it into 105/205 is any ratio for added strength. You can also add some blue pigment into the resin mix so that the repairs are somewhat alike color-wise.

It would be worth the sanding elimination and weight savings/epoxy distribution to use peel ply over the entire epoxied cloth area.

Discussion of cloth preferences for this kind of repair is another matter. If you often drag the hull Dynel might be preferable to glass for its abrasion resistance. In addition Dynel does not fray as badly as glass when cut, especially if shaped on the bias.

If the canoe sees a lot of sun exposure on the bottom I’d wait a few weeks, wash the hull thoroughly and spray paint the epoxy for UV protection. If you pigmented the cloth/epoxy blue and spray paint it blue the inevitable scraps in the paint won’t show as badly.

Whatever cloth/epoxy you use this kind of massive repair is going to add significant weight and the Royalex may be at the end of its useful life. While I would trust the repairs for a trip on mild waters or near road/rescue I’d be leery of taking it on a long trip anywhere remote.

If you decide to patch it using cloth and epoxy send me a PM and I’ll reply with some, as you put it, instructions for dummies (ie, taping and papering the hull to catch drips and dribbles, mixing small batches of epoxy so it doesn’t cook off in the pot while you are brushing it on, etc)


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PostPosted: August 26th, 2014, 9:28 am 
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I don't think Swift made the Raven in anything other than Royalex.

I agree with ezwater. The white colored area of the hull bottom is where the outer layer of blue colored vinyl has been worn off. You have undoubtedly thinned the outer solid stratum of the ABS under the center where your weight has caused the boat to hang going over rocky shelves and such. The thinned ABS has now cracked through into the foam core.

A reasonable repair may cost up to a couple to few hundred dollars USD. You will a few yards of fiberglass cloth and perhaps a little aramid (Kevlar) cloth for the interior, as well as epoxy. I prefer using West System's G Flex epoxy for repairs on Royalex boats as the cured epoxy is somewhat more elastic, better matching the compliance of the Royalex especially on the hull bottom. Some have reported good results using conventional epoxy for Royalex repairs, however. You might need as much as 32 ounces of G Flex (16 oz each of resin and hardener) to complete the repair. I would also get some colloidal silica powder (cab-o-sil) as a thickening agent.

Incidental expenses will include sandpaper, masking tape, solvents (such as denatured alcohol) vinyl gloves, and spray paint to cover you repair when done. If you follow through I think the boat will be usable but probably not as strong and definitely heavier.

I actually did a very similar repair on an old Dagger Encore whitewater canoe that had worn through the bottom ABS into the core using G Flex and E fiberglass (3 layers) and it has held up well.

Your smallest patch should be big enough to cover and overlap a bit any areas of thinned out ABS. If you invert the canoe and press in all over the bottom, the thinned areas will likely feel a bit "spongy". The other patches should be concentrically larger by a couple of inches and it is best orient your patches so that the fibers of all three run at different angles and do not align with each other.

Before applying any cloth I would smooth the bottom and fill any and all cracks. It is best if you gutter out any cracks with a V shaped tool to make a bigger bonding surface for your epoxy and to make certain epoxy completely fills any voids in the foam core. I would use epoxy thickened with silica powder to fill the cracks and fair in any depressed areas of hull so that your first layer of cloth lays flat and smooth. The cured epoxy can be sanded smooth.

For a mulit-layer patch it is best to do all three layers at once to get a good chemical bond between epoxy layers but time constraints don't always allow this. If so, try to apply the next layer while the epoxy of the preceding layer is still "green" or by the next morning. If the epoxy cures fully before the next layer is applied you will need to wash off any possible amine blush that might interfere with epoxy bonding.

If you want to feather the edges of your patches smooth by sanding, put the largest patch on first, then the next largest, then the smallest. You can then feather the edges of the smaller patches without sanding through the fibers of the larger ones. In order to get a smooth surface, you will need to fill the weave of the cloth which generally takes several epoxy applications. When you have finished the repair, wet sand the entire thing, clean it well, an spray paint it to protect the epoxy from UV degradation.

On the interior, you can probably remove the D ring patch assuming it was bonded in with vinyl adhesive. Warm the patch carefully with a hair drier or heat gun but don't get it too hot as it can deform the foam core of the Royalex. Once it is warm, get under an edge with a paint scraper or putty knife and carefully peel it off warming as necessary. You can usually bond the same patch down later with vinyl adhesive.

Gutter out the full length of the crack and fill the thickened epoxy as before. Apply an aramid or fiberglass patch that overlaps the ends of the crack by 2 inches or so.


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PostPosted: August 26th, 2014, 10:56 am 
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Pete pretty well detailed the best repair methodology and costs above. Straight G/flex and layered fiberglass patches would be the right way to fix it.

Is it worth a couple hundred dollars in materials and a couple of days in the shop?

The downside is the time and materials expense for a heavier Royalex hull that is still somewhat suspect. The upside is that if you’ve never done glass and epoxy work you’ll learn a lot and still have a canoe in the end.

A question for those who know more about layup schedules – if using both fiberglass and, say, kevlar in such a 3-layer patch what order? Smallest patch with kevlar, then glass/glass?


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PostPosted: August 26th, 2014, 12:07 pm 
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I don't use aramid for exterior patches unless it is completely covered by at least one layer of fiberglass. Aramid cannot be smoothed quite as well as fiberglass since the fibers fuzz up when abraded. You can, however, completely fill the weave of aramid cloth with epoxy and sand it pretty smooth since you are then sanding epoxy, rather than aramid. But you can't feather the patch edges as nicely. And aramid exposed on the hull exterior can become progressively abraded and fuzz up.

So if I did use aramid on the exterior of the hull, I would cover it with a larger fiberglass patch. But there really isn't much reason to do so, unless one were patching an all aramid hull. Fiberglass actually has a lower Young's modulus (is more elastic) than aramid so at least theoretically it can flex along with a Royalex hull bottom better.

Although aramid has a higher strength to weight ratio than fiberglass, fiberglass (especially S 'glass) virtually matches the tensile strength of aramid; it is just a bit heavier. But aramid does not like to be hit sideways. The compressive strength of aramid is only around 1/10th of its tensile strength and is much less than that of even E 'glass. So aramid makes sense for interior hull patches, especially on the hull bottom center, where stresses are going to push the hull bottom inward subjecting the aramid fibers to tension, but not so much sense for exterior patches where the hull might be subjected to significant sheer forces.


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PostPosted: August 26th, 2014, 12:09 pm 
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One more thing, or one first thing. Or, actually, two first things.

I would start with the entire hull as clean as possible, inside and out, not just the epoxy and cloth areas alcohol wiped.

If you wash it with soap and water you may need to wait a week for the moisture inside the cracks to completely dry, but it is probably worth it. Then, after it is dry and not too long before starting the epoxy work, wipe the areas with alcohol.

Contaminates on the hull are the enemy of epoxy adhesion and I know where my wandering hands go on a canoe in the works; I don’t want to lean a hand on some dirty part of the canoe and then cross-contaminate the cloth or alcohol cleaned area.

Hanging on the shop wall in a place of dishonor I have a visual reminder to thoroughly clean the hull before laying glass and epoxy. We needed to reinforce the chines inside a Caribou sea kayak and did so with two layers of glass tape (2” and 4”). Those reinforcement patches were almost 3 feet long on the sharp chines on either side.

A year later when the owner (my shop partner) brought the Caribou back for a tune up he mentioned that one of the chine patches seemed to be coming loose at one end. I looked, it was, and when I gave the patch a gentle pull with my fingers the entire 3 foot long double layer patch came off cleanly.

How cleanly? He had written his name and contact number inside the hull where the patch was later installed and even the Sharpied contact info came off with the patch.

We had cleaned one side, but not the other. There was enough contaminate (I suspect aerosolization of past applications of silicon spray) on the unclean side that the patch came off with all the tenacity of a Post-it note.

Second, after alcohol wiping and before the epoxy work, it pays to tape and paper the hull around where the epoxy and cloth will go.

I can be sloppy with epoxy, so I am anal about how I tape and paper the hull. I box out the perimeter with painters tape, then tape sheets of newspaper half way up the painter’s tape with little pieces of tape, and then run another full perimeter circumnavigation of the area with masking tape, sealing the edge of the newspaper to the painters tape.

When I think any drips or dribbles have stopped running I pull the masking tape and the newspaper comes off with it, leaving just the painter’s tape in place. (It helps to leave fold-over on the tape ends). That leaves me with a clean epoxy line on the painter’s tape and when I’m sure the epoxy is no longer creeping I pull the painters tape for a nice, clean epoxy line.

Photos of the tape/paper and reveals towards the bottom of page 1 here:

http://www.canoetripping.net/forums/for ... ng-project


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PostPosted: August 26th, 2014, 2:41 pm 
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Yes, thoroughly cleaning the hull is important before trying to get anything to bond to it. Actually, before cleaning the hull, I would go over the bottom with sandpaper and make sure that any loose edges of the blue vinyl and removed and sanded down. If you can completely remove the vinyl from the area of the hull you need to cover with cloth, so much the better. This can be done by sanding, but it takes considerable work. Sometimes the vinyl can be peeled off with a sharp putty knife or wood chisel, but if the surface of the hull is irregular, it may not be easy to do this without gouging off a lot of the white ABS in which case I would just take off the loose stuff. G Flex does bond well to vinyl.

After sanding and removing any vinyl that will come off and guttering the cracks, wash the boat as Mike describes. Then when thoroughly dry clean with EtOH and you can fill in the cracks and fair in any low areas with thickened epoxy. You might need to make multiple epoxy applications with wet sanding in between to get the hull surface reasonably smooth. When you are satisfied, wash the hull again before laying on your cloth.

If you use G Flex and read the directions, you will find that West Systems indicates that prepping the hull using flame oxidation with a hand-held propane torch is "optional". While flame oxidation is essential for bonding to polyethylene, I have used G Flex on ABS with and without flame oxidation and gotten good bonds in both cases. If you flame treat the hull, keep the tip of the flame moving along the hull surface to avoid overheating the Royalex core.

When you are done I would simply paint the entire hull bottom up to a 4 inch waterline to cover both your repair and any areas of exposed ABS on the hull bottom.


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PostPosted: August 26th, 2014, 5:07 pm 
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That's a well-used boat! As mentioned, might be worth taking the money you'd put into a full repair and start looking for a used replacement.

That said, if you've been using it in this state, maybe the hull isn't too spongy or floppy and you can live with just filling the cracks, and skip all that messy, expensive, heavy work with epoxies & glass?... You could consider just filling the cracks, painting the hull, and moving on to see what light use you get out of it.

I'd carve out the cracks to clean them up into "V-s" and make sure you're getting out any rotten foam - which will give you an idea of how bad things are. A sanding/grinding bit on a power drill can be a good way to remove the cruddy ABS and clean out these cracks into the foam.

Assuming that goes OK with the sponginess you may uncover, you could just fill the cracks with a plastic repair putty. I've used some PC-## putties which were too brittle (i.e., not flexible like G-Flex), but I think they've got some new marine stuff now. JB Weld may have similar products. A current patch I've got that is holding uses the plastic repair putty from MEC, I'd use that again. Any of this should work if you're really just filling cracks. If the putty you choose is too brittle, it probably won't last for bigger areas though.

Simple: clean up cracks, fill with repair puty, sand, paint (with plastics spray paint). Try that first and see whether you want to proceed with glassing!

I'd start with that and hope to end with that. But if I felt I had to add some stiffness/strength with some sort of glass (and when I say "glass", I don't know whether I should be meaning E-, S-, Kevlar, etc.), my next step would be to add a layer on the inside. An alternative to glassing the inside would be glueing in a thin sheet of ABS plastic, which should be easy to find at a plastics shop. Actually, that would be my 2nd step. If/when that came unglued, I'd then consider a laaer of glass inside. Personally, I doubt I'd ever get to a step that involved the multiple layers of glassing the outside! Too messy and too heavy.

On the inside cracks, I've gone from using putties to cleaning the cracks and just smearing in some Aquaseal. That's worked great.

Sigh, you remind me I've got some delaminating chines on my Ocoee that need to be dealt with.

Good luck! Pat.

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PostPosted: August 27th, 2014, 10:13 am 
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Recped, you surely now have a range of repair options presented. Somewhere in there lies the amount of time and money you want to put into a repair.

I would enjoy following the repairs as you go. Please post the results or work in progress.

It adds time to a repair to stop and write up progress (difficulties, successes) and take photos, but it can also be beneficial. Not just to folks following along, but to the repairs themselves.

Writing progress notes and taking photos helps slow my roll, and I know I’ve made most mistakes simply by working too fast or progressing to quickly to the next step before taking time to contemplate the needed prep work or coming best order of repair sequences.


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PostPosted: August 27th, 2014, 10:46 am 
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I had a similar, single crack appear in my Raven last summer. Owner abuse was certainly a factor, although I also implicate an overzealous pilot with a ratchet strap ("Herc strap") who actually managed to twist the hull while attaching it to the float struts. Apart from the crack, the hull material seemed in good shape - not soft or floppy. The crack didn't go through to the inside.

I cleaned it up and patched over it, using epoxy (West, I think) and two layers of light cloth. Then I just sanded it and spray painted it with Krylon plastic paint from Canadian Tire, for UV protection and to make it look better in photos. It may have added a couple of pounds to the boat, no more.

The patch has gone through a mild trip last fall and a fairly strenuous one this summer with no problems. I hope to get another decade out of it. Given the royalex situation, and the shortage of expedition type solo hulls available generally, and in Western Canada particularly, I don't see replacement as a good option right now.

-jmc


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PostPosted: August 30th, 2014, 1:01 pm 
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Thanks for the advice, suggestions and a bunch of laughs!

I'll post back when/if I decide to do something.

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PostPosted: August 30th, 2014, 5:27 pm 
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I avoid using G-flex for large S-glass patches because S-glass has very fine fibers and is reluctant to "wet out" unless a very thin resin is used, like West 105/205.

G-flex is not "best" for everything. It is best where one is attaching two (reluctant) objects or substances together, and where G-flex's advantage in flexibility can be of benefit.

For a lot of cloth repairs, s-glass or E glass with 105/205 resin will work as well or better than G-flex.


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PostPosted: August 31st, 2014, 7:35 am 
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I have used G Flex epoxy to wet out the plain weave S fiberglass sold by Sweet Composites in both 4 oz/sq yd (style 6522) and 6 oz/sq yd (style 6533) without any problems. In fact, I have not noted any significant difference when wetting out these cloths compared to plain weave E 'glass variants of the same weight. But I never try to wet out more than one layer at a time. Some satin weave S 'glass variants (which I have not used) have a reputation for being difficult to get the air out of when wetting out.

In comparison to West Systems conventional 105 resin (with whatever hardener) G Flex is considerably more viscous at any working temperature I have used it. It therefore takes a bit longer for the mixed epoxy to permeate the fibers of either S 'glass, E 'glass, or 5 oz/sq yd aramid. I have not found this to be a problem because it seems that at any given working temperature, G Flex has a bit longer pot life and working life than West 105 resin even when used with the 206 "slow hardener".

If one is having difficulty wetting out fabric with G Flex in cooler ambient temperatures, its viscosity can be reduced by wafting a heat gun carefully over the cloth after application of the epoxy. Placing a small space heater under the hull you are working on can also help. Needless to say, one must avoid overheating in either case.

It is also worth noting that G Flex epoxy can be mixed with West 105 resin and hardener in any proportion desired. Just stir the two together and apply. The properties of the mixed and cured epoxy will then be between those of G Flex and 105 epoxy and the exact properties will depend on the proportions mixed together.


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