C-Forum

Bless those double chines...

So I bought a Nitro last year that had pretty worn chines. In most places, the vinyl was totally gone. I studied up on the Legos and Acetone trick and did what I thought was a great job giving my boat a new lease on life. I even got the color matched nearly perfectly.

After a couple of trips, a 6 inch crack developed right under my Right knee along the first chine, about mid-boat. After I calmed down and called a friend well versed in repair, we applied what I hope is a pretty solid G-Flex repair.

We beveled out the crack drilled out the ends to keep it from spreading and drilled some holes around the crack and injected them to stop any further delamination from occurring.

The area in question was a bit soft to begin with, although the G-Flex did firm it up some. The opposite chine is in a similar state of flexibility as well, but no crack- yet. I'm putting in a bulkhead saddle, both because the strap system is annoying to me, but also to help give the boat a little more rigidity in the area too.

So, finally, the question: Should I put in some type of skid plate on the chine, or just leave the G-Flex repair as is? If I go for skid plates, what material do people think I should use? Kevlar or Glass? Felt or layered cloth?

I've got pictures of the boat in all it's stages I'll try to post in a couple days. I deeply appreciate any opinions or wisdom out there on the matter.

Hard to say what I would do for sure without seeing and feeling the boat, but the odds are I would run a "belt" of aramid (Kevlar) 5 oz/yd cloth (not felt) about 4-5" wide down the inside of both chines in the center cockpit area or wherever the hull feels soft. I suspect after doing that you would find that you had restored the rigidity to the hull. If not, I would run a strip of fiberglass (S 'glass preferable to E 'glass) down the outside of each chine. If the Royalex is cracked into the hull on the outside I would be sure that is completely filled in with epoxy and would be inclined to cover it with a layer of 'glass.

Yeah, I think it will take at least two, maybe three concentric layers of glass outside over the chine. The first and largest should be bias cut so that twice as many fibers cross the chine, at 45 degrees. Glass is the heaviest cloth for repair, so try for a rational balance.

The only anxiety I have about the suggestion to use Kevlar as inside reinforcement is that I have seen Kevlar fail on inside repairs where the stress may, at times, involve compression, or folding the chine on itself. Most outside blows to the chine would put the inside of the chine in tension, which is OK for Kevlar.

I haven't ever had opportunity to study a Nitro or a Blast that has experienced chine cracking. It occurs to me that another way to protect the hull from cracking might be to add some light thwarts and some minicell pedestal reinforcement of those thwarts to the bottom of the hull.

sweetcomposites.com sometimes has composite weaves (S-glass/carbon or Kevlar/carbon) that help in situations where unusual stresses are at work, but they are expensive.

Think it out carefully, because you don't want to spend a lot of money and effort, end up with a noticeably heavier boat, and then have the chines fail again.

By the way, if you were to use S-glass, then G-flex resin may not wet it out very easily. Warming might help, or you could use a more conventional resin.

Gluing ABS sheet to the outside of the chines might be something to consider.

I like doing the bulk of the repair on the hull's interior, especially when one is trying to restore rigidity, because one can use multiple lamina if necessary without the need for extensive fairing and without disturbing the contour of the hull's exterior. I have found that it is not always easy to determine how much the outer solid stratum of ABS of the Royalex has been thinned by abrasion once the vinyl is gone, just by looking. It is possible for it to become quite thin while still maintaining an intact appearance. I would press in with my thumb along any area of the outer chine that is missing vinyl. If the material indents with thumb pressure, you can assume that it has been seriously thinned. In that event, I would definitely add some cloth to the outer hull so as to prevent further abrasion from eroding into the foam core in short order. S 'glass (or carbon) would definitely be best for that.

I have applied aramid patches to repair cracks in the chine area to the interior of a number of Royalex hulls, and at least as of yet have observed no tendency for them to delaminate. I have generally preferred to use G Flex epoxy for repairs on Royalex boats, sometimes using G Flex for the initial wetting out of either aramid cloth or fiberglass, and then sometimes using West 105/206 or a mixture of that and G Flex for filling in the weave and/or fairing.

If you are applying cloth to the hull exterior I would definitely use fiberglass and not aramid as you cannot feather and fair aramid cloth by sanding. You could, of course, use fiberglass instead of aramid on the hull's interior but it will be a bit heavier.

I have used G Flex to wet out 5 oz/yd aramid cloth, both 4 and 6 oz/yd E 'glass, and the style 6522 (4 oz/yd) and style 6533 (6 oz/yd) S 'glass sold by Sweet Composites without any problems at all. I only wet out one layer of cloth at a time, however. After applying the wetting out coat of G Flex I do find that wafting a heat gun over the repair area does help "level" the epoxy (as well as accelerate the cure rate) but be careful not to overheat.

I have tried the ABS/acetone or ABS/MEK slather technique as well and did not achieve lasting durability with it.

BUY A NEW BOAT !!!!!!! You will constantly be repairing some ragged out ZOMBIE BOAT that will get increasingly heavier. The time spent and materials bought make repairs on a boat like this silly. The Open Boat community, seems to take great pride in keeping worn out pieces of junk on the water, this seems to mostly affect the old codger variety of boater. There is no pride to be had in paddling a piece of crap. When a boat gets to the stage that yours seems to be cut it up, make a planter, horse trough, bathtub whatever out of it. Its days are done. Donate it to the local boyscouts. This is really a pretty cheap hobby, suck it up and tell the Wifey, ask permission of the Wifey, whatever it takes and buy a new boat. You will be much happier and you will be supporting the sport we all love.

pblanc, the inside problem with Kevlar patching of chines is more likely to be seen with Ocoee style boats. It isn't just delamination, I saw a Millbrook Defiant where pinching of chines caused by thumps to the center of the bow had actually caused Kevlar tearing. That's an unusual situation where patching might require use of S-glass. I may face that after I thump the bottom center of my Big Boy.

On sand-ability, CAP or polyester cloth accepts sanding somewhat better than Kevlar or nylon, and one might start an exterior patch with a layer of polyester, followed by glass.

Thanks all for the advice!! I finally got the photos: http://flic.kr/s/aHsjEcBE1x" onclick="window.open(this.href);return false;

Here's my new informed plan: Buy some 6oz/yard S 'glass and do Three layers using G/flex as the sole epoxy, doing the bias cut thing as was suggested.

After further analysis, the both chines are really soft, particularly in the middle where the most wear has been and will continue to be. This is also an area of the boat that I believe needs to remain somewhat flexible (different than soft), thus the reasoning for using only G/Flex instead of the harder resins. I took the simple G/flex repair out on the Nolichucky on Friday and it did very well. I had a minor direct hit to the repair spot and it didn't appear to have suffered and further damage and the repair job seemed to be solid.

Questions: Are there any good videos on this type of repair anywhere? I've found some ok ones, but nothing immediately relevant.

- When I do the 3 layers of glass on the outside, I should start with the largest layer on the surface of the chine and get smaller working my way out, right?

- Why not just lay on three layers of the same size?

- Is the 6oz/ Yard S 'glass to heavy? would 4oz/yard suffice? I'm willing to sacrifice a few more pounds for some peace of mind. Nitro doesn't win any awards for speed to begin with and I'm a pretty strong guy so I feel OK about the added weight.


Additionally: I think at least a contributing factor to the crack was that my LEGOS slurry was too thick when I applied it. I did some further archive searching and found a post advising to apply the slurry when it was on the thinner side. My buddy did a similar job on his Detonator and had a problem with it being too runny, so I think I over reacted. The crack may have happened anyway, but I think it's possible that the over-thickness of the slurry played a role. I still have a good amount of the slurry left and I think I may sand it back to the original ABS and re apply more thinner coats to try to fend off further cracking elsewhere.

Thanks again!

Adam

The reason for concentric patching is to avoid a sudden change in hull stiffness, which would result if you piled three patches of the same size on one another.

The reason for patching from largest layer to smallest is that the transition zones are out on the surface, where you can carefully hand sand them to ease the transition. Think about it: why would one want the edge of a smaller patch underneath a larger patch? One wants the fibers of the larger patch to be straight, flat, not taking a step-down over a smaller patch.

On bias cut, what you want to do is orient the patch fibers of subsequent layers so that they aren't quite parallel. That helps keep the patch from snapping along fiber lines. The first, largest patch should be bias cut. The second can be bias cut, but should be jogged a little when laid down so the fiber orientation differs. The third, smallest patch can be straight cut if you want.

The edges of the patches should not be parallel to the chine lines. The patches should be cut as ellipses or ovals so that their edges are not parallel to the chines.

Taken singly, these are picky details, but if you break all the "rules," you end up with an inferior patch.

I can see where G-flex would be an excellent fix for those chine cracks. The S-glass over the repairs will have a good foundation.

this reply is balanced with do whatever you need to do to paddle this year, but I would look at this nitro in two ways. How long do you need to get out of it and How long till you have about $1000 to buy a good used canoe or even new.

When I rebuilt Tommy's Creek and Destroy canoe I wanted to get a full year out of it. I patched it with 2 layers of glass and one of dynell on the outside. Let me point out that before I did this I ran the Detonator with not much more than Gorilla duct tape for a good 35 hard runs (that's a whole year of use for most people). I repaired the canoe because the chine was punching in at my knee pretty good on the Raymondskill's hackers falls in Pa and it was my first canoe.

1 quart of Gflex it about $50. The fabrics could be kept to about $25. I wouldn't worry about the purity of the canoe if you really have to fix it. put 3 layers over the soft chine and then tape the edges with gorilla tape and run that setup all year. Replace tape as needed. After my outside repairs to the Fullgnarlz detonator I couldn't tell the difference in performance, not that I really tried. I slammed it down Tallulah and the Green narrows and it held well. Eventually the soft chines did buckle enough that the patch delammed (seriously green narrows hits) a bit in two spots on one chine creating an in and out for water flow. It isn't any big deal and since then I just leave a little tape on the bottom. the patch still helps as a shield for the knee. On the stern where I drag the hades out of that canoe all the time where the vinyl is gone I keep tape to ware off. If you want to lay material down in the inside chines that could help your softness issues but your effort and costs rise.

This will cost you easy $100 with mask filters,gorilla tape,fabric, epoxy. The foam saddle will be about a Bun's worth at $150 delivered. My guess is that you will spend $300 on cracked Nitro materials that is worth $300-400. Put $100 into it with the cheap outside repair and sell it to a newbie for $300 in a year and save while you look for the used deal of the year. Good Luck.

PS or just tape that canoe chine with 3 layers of gorilla tape and forget about it for a year.

So I just ordered the goods from Sweetcomposits and the person I spoke with told me to start with the smallest patch on the inside and work my way out getting bigger each time. This is opposite of what yall are saying....yeah? While they seemed very knowledgeable about the materials, they didn't seem to have the boat repair experience that yall do....What's up here? Stick with the plan?

I went with the advice to go with Dynel on the outer layer since this is super high abrasion area.

And, yes, I'm beginning to see the wisdom of just saying F- it and buying a new boat. I just don't have that much cash. Additionally, I'm not going to be going kamikaze down wet rocks in this thing. I wonder if it's possible that some of the long time paddlers forget that not everybody is as nuts as them

I do appreciate the vast wealth of information that yall have so freely shared. As I've been doing more research I keep seeing posts by yall that go back for years and years. Thanks for your contribution to this wonderful way of life (notice I didn't say sport).

I'll keep posted as the processes continues.

There are other experienced boat builders who suggest doing the same. Technical manuals on composite repair from Placid Boatworks and Bell have the smallest going on first and I have seen videos on composite repair on youtube and elsewhere that suggest the same. I have done it both ways and found no difference in the results. Sometimes it is easiest to start with the largest patch and go progressively smaller and sometimes it is easier to do it the other way.

Charlie Walbridge maintained in "The Boatbuilder's Manual" that the largest patch should go on first and the smallest should go on the outside. What rationale did he give? Only the following statement: "The smallest piece goes on the outside; don't ask me why; it just seems to work". Not exactly hard science, that. If there was a difference in strength depending on whether the patches got progressively bigger or smaller, shouldn't the order be reversed when one is patching the inside of the hull as opposed to the outside? Yet, I have seen no one suggest doing that.

One technical bulletin from West Systems suggests putting the largest patch on first and then going smaller and they at least offer a cogent reason. If you are laying on multiple lamina at one time or if you apply multiple patches before feathering the edges, you will not be able to feather the underlying smaller patches without sanding through some of the fibers of the overlying larger patches. This is not an issue if you apply one patch at a time and feather the edge before applying a larger patch over it. In fact, by making the patches successively larger, one can feather the edges of each patch with zero chance of damaging any of the fibers of the other patches. I have discussed this issue with the tech support people at West Systems one of whom told me that they did tests comparing the strength of repairs using progressively larger versus progressively smaller patches and found no difference.

If one is patching an area of wear or a crack that has left a "divot" in the surface of the hull, or if one is patching a hole where you have "saucered out" the area surrounding the hole, I like to apply the smallest patch first. Successively larger patches will then fill in the void and build it back up to flush with the surrounding hull. The fibers of the last, largest patch will then be straighter than if you sunk this patch down into the void first.

In your application, I doubt it is going to make much difference either way and wouldn't worry about it. If you are going to use a three layer patch, I would cut two of them on the bias but at somewhat different angles so that you have the fibers of the patches going in as many different directions as possible.

You will get a stronger patch if you resin all layers at the same time. If you have to let each layer harden so you can feather the edge, then you have to remove amine blush, sand a bit, and finally you're expecting resin to bond to a "cold" resin surface.

If you're dealing with a "divot" so deep that you can't dish it out and bond the edges with the first, largest layer of a patch, then it may be best to pre-patch from the other side, or just to fill the divot with resin and build a smooth base for the patch.

I wonder if it was Davey, or Jennifer, or someone else at Sweetcomposites that advised smallest first. It may be the traveling racer's point of view. If you're in a hurry, possibly patching with Kevlar, and want a smooth result without having to sand the edges of three layers, then putting the smaller layers under the larger layers may same time.

On whether there is a difference, the question is whether valid and reliable tests have been done. But on theoretical considerations, it is clear that either largest-patch-first should be somewhat superior, or the methods should have equal effectiveness.

For me and my house, putting the largest patch down first on the surface of the boat means the longest, straightest fibers are where they belong.

since it sounds like you are easy on canoes anything you do to the chine to prevent wide open tearing of the crack will be enough to get a good solid year out of your Nitro (even for a bit of an abuser).... a little glass and or just gorilla tape will go a long way. The abs is UV sensitive so cover that abs up with tape where you don't see yellow vinyl or at least cover it when its racked not on the water.