Yes please!
Doug, yes please on the link. I can use all the help I can get.
Waterbearer, what epoxy did you use on the dynel fabric? I hadn’t thought of peel ply. Does that make it so you don’t have to sand?
Do I need to fill in the cracks with gflex or gorilla glue or something before laying down the skid plate or can I just go right over?
Gflex
Is the epoxy I used on my Royalex canoes.
Using peel ply leaves you with a finely finished surface without sanding. The Dynel skid plates are much thinner than the thick Kevlar felt plates. I used only one layer of Dynel and it has held up very well, with no breaks in the plate, despite intense abuse on the upper Buffalo when we had very low water.
The cracks
I have thickened Gflex and filled cracks before applying the Dynel. It can be done in one step or two.
If two steps, put peel ply over your cracks patch and you’ll avoid having to sand the repair before adding the next layer of epoxy/Dynel. Peel ply prevents the amine blush of curing expoxy.
In brief
– Last Updated: Sep-08-15 11:49 AM EST –
Don't use Gorilla Glue. Don't use JB Weld. Don't use Kevlar felt. Don't use Keeleazy. There are better choices in every case.
Do use G Flex epoxy. Do use a thickening agent to fill cracks. I suggest colloidal silica powder (cab-o-sil).
Gutter out all cracks before filling to make sure epoxy gets fully down into the cracks and to provide a greater bonding area for the epoxy.
Flame oxidation of the ABS prior to application of G Flex is suggested by West Systems. This can be done with a propane torch. I would do it but be very careful to move the torch flame quickly to avoid overheating the hull. Sand the area of repair well to remove the colored acrylic layer of the Royalite or at least rough it up well.
Either S 'glass or Dynel are good for exterior repairs. S fiberglass will add a bit more strength than Dynel. Dynel has good abrasion resistance and is good for plates. Aramid (Kevlar) or S 'glass are good for interior repairs. I would cover the completed repairs with some type of paint for UV protection.
I would probably first repair all interior and exterior cracks with thickened G Flex, then cover the "soft" area on the hull interior with an aramid patch that overlaps the damaged area. Then you can choose whether or not you need to apply an external patch and/or abrasion plate.
I have just completed a fairly major repair job on an old Royalex Mad River ME. It so happens that this repair included guttering out and filling in cracks with thickened G Flex, applying internal Kevlar patches, a multi-layer S fiberglass external patch, and application of Dynel abrasion plates and a keel strip. I made a photo album on flickr of the repair process. The photo captions describe a lot of the particulars of the repair.
If you would like to look at the photos the album can be found using the link below. There are quite a few photos. If you have and questions feel free to send a private message.
http://www.flickr.com/photos/42020723@N02/sets/72157657942924708
NEW HULL
from Oak Orchard stabbed with forklift abt 1/8th" deep.
The stab goes to but not thru the black layer nor into the interior hull.
Question is Gflex, Gflex with filler, or a commercial Royalex Vinyl putty for sustaining hull surface flexability and energy absorbtion…not producing a hard solid spot.
If this possible.
https://picasaweb.google.com/102234459580640424681/HULL
Is there any visible interior damage?
It is sometimes difficult to assess the extent of damage to the ABS strata of the Royalex without first removing the vinyl. The vinyl material seems to be more elastic than the solid ABS strata. I have frequently seen cracks in the ABS under what appeared to be more or less intact vinyl.
The vinyl of ABS really contributes little or nothing to the overall strength and elasticity of Royalex. It does provide a convenient bonding layer for outfitting, a nicer color depth, and some abrasion protection, but most of all protection from UV degradation, which ABS is particularly susceptible to. The deformity of the hull certainly indicates that the foam core of the Royalex has been damaged and compressed, and I would not be surprised to find cracks in the outer solid stratum of ABS if not the interior one as well.
I would remove the outer vinyl from the damaged and depressed area. If there are any visible cracks, gutter them out and fill with G Flex thickened a bit with silica powder. Adding silica powder to the epoxy will make it a stronger “epoxy glue” and a better gap filler.
If the area of damage does not feel soft, filling the cracks might be sufficient to restore structural integrity. If you want to fill in and fair the depressed area for cosmetic reasons, I suppose you could use polyester auto body putty then paint over it. I would prefer to fill in the area using a concentric multi-layer fiberglass patch and unthickened G flex for greater strength.
G Flex has a lower Young’s modulus of elasticity than regular epoxies meaning it is more flexible when cured. I have applied Kevlar and fiberglass patches to quite a few Royalex canoes using G Flex and have not had any delaminate due to compiance mismatch. I have seen patches applied to Royalex boats with conventional epoxies delaminate.
I doubt that there is any way to apply a Kevlar or fiberglass fabric patch without creating some stress riser at the edge of the patch, however.
new hull repair
a larger patch produces less stress riser on a specific area…that is each glass patch creates a riser with 3-4 patches lessening a negative effect ?
Royalex hulls are banged abt with many dents. Repairs are common or not ? I would guess not. But with this unrepaired fleet what becomes of these hulls with unrepaired cracked ABS ? I’m not reading of complaints.
Royalex whitewater boats
It is normal for Royalex boats to acquire dents and shallow creases with use. Most people leave these alone as they really don’t affect the structural integrity and repairs usually don’t result in a cosmetic improvement.
It is pretty common, however, for whitewater Royalex hulls to require repair for cracks, punctures, and wear through the solid ABS layer into the foam core. Royalex was sadly never all that abrasion resistant, and running boats over rocks and ledges often resulted in that type of damage. I know one paddler (a very aggressive one) who was going through three Royalex hulls a year.
larger patch not necessarily better
In order to achieve sufficient strength to repair a Royalex boat that has been completely holed it is generally necessary to use multiple layers of cloth.
The layers are made concentrically smaller or larger so that the edges are offset which makes for less of a stress riser at the patch edge than if they all lined up. It also allows the patches to be cut on differing biases so that the fibers run in as many different directions as possible which maximizes strength.
But when it comes to repairing Royalex boats, differential expansion of the hull material and the cured epoxy used for the patch has always been a potential problem. Sometimes a patch that has seemed secure for months or years will suddenly, completely delaminate and pop off, usually on the water on a very hot or cold day. G Flex epoxy has lessened the likelihood of this event since the cured epoxy better matches the compliance of ABS, but it has not eliminated it.
It is thought that using the smallest patch effective for the repair will minimize the the difference in expansion and contraction rates between the Royalex and the ABS which creates sheer stress on the patch/hull bond.
giving it a go
Thanks for all the suggests! I knew I’d find helpful ideas here. I picked up some g-flex and silica at the local West Marine and I’m going to try to repair those cracks with thickened g-flex. I like the idea of Dynel skid plates, so if the g-flex repair goes well, I’ll install the skid plate right over it. Fortunately for me, Sweet Composites it right up the road from me and I think I’ll have a chance to get over there in the next couple weeks to get the fabric and some peel ply.
Dougd - thanks so much for the link. Your blog is AWESOME! And extremely helpful for a canoe repair rookie. Love it. Your warning about using the bathroom with epoxy residue still on your hands is dually noted ;).
Sweet Composites
The folks at Sweet Composites are very helpful and they do sell Dynel fabric.
They also sell a nylon cloth that can be used as peel ply and I have used it as such. But it is not a treated fabric and if it is left on too long as the epoxy cures, it can be very difficult to peel off. As far as I know, that is the only “peel ply” that Sweet Composites sells.
If you plan to buy and use that I would talk to them and tell them exactly how you plan to use it so they could offer you advice on how long to leave it on.
Treated mold release fabrics are available from Jamestown Distributors and Express Composites of Minneapolis, MN.
Peel ply
If Sweet Composites is close, Chesapeake Light Craft in Annapolis isn’t too far away. They sell peel ply, they even mail it to you if you want to avoid the drive.
Haven’t seen DougDs blog, but one tip I learned is to cut the Dynel on a bias - that will minimize the fraying of ends
appreciate the advice
I’ll inspect and repair the first two stabs see what goes on in there and after
shipping Kevlar is not in order.
Two sheet metal patches are done with screws, plate and Gflex. Temperature and humidity, 86-96 and 70%.
Gflex giving more than enough time for locating , pinning, screwing and pop riveting of 10 holes in a complex shape. Maybe 12-15 minutes.
West regionalizes the mix ? No way did I expect that level of cooperation from the hardener.
Thanks
I saw that CLC has the West System peel ply. Is it better than the generic nylon that Sweet sells?
CLC is a bit further drive. But I was planning a trip out to Annapolis anyway to hit up Velo Orange for few bike parts, so maybe I’ll get the peel ply there. The same guy started both companies, incidentally.
repairs not going so well
I finally got around to taking a crack at this canoe repair (pun not intended). So far, not good. I was hoping to not mess with the interior, but when I was beveling out the crack, I slipped and went all the way the hull. I found that the foam core was indeed crushed under the cracked abs, so I went ahead and drimmeled out all the crushed and soft foam. But now I have a two inch long oval hole in the bottom of the canoe. Too big to slap a little g-flex in, so I think I’ll need to do an interior patch afterall. So should I:
a: tape some wax paper to the inside of the hole and layer up the g-flex on the exterior, then patch the interior with Dynell or glass?
or
b: put the Dynell/glass patch on the inside first, then do the g-flex patch on the outside?
Either way, I’m going to finish up the repair with a Dynell skid plate, so I don’t think I’ll need an exterior patch over the g-flex.
My approach
Would be to start on the inside and work my way out using multiple layers of crisis crossing fabric I would use glass on the inside as a backing for thickened Gflex.
Hopefully Pblanc will chime in as he’s experienced with this stuff.
For holes in the canoe another product worth looking at is 3Ms marine adhesive sealant, sold in a caulk like tube-5200. About 20 years ago(before Gflex) I used it to fill a hole in my OT Tripper, which revealed itself as I was doing a Kevlar skid plate repair and, like you, my efforts punched a hole in the damaged area.
The 3M 5200 worked just fine. Had enough flex in it that it didn’t crack when the canoe was put to use on the water bouncing off rocks. I used glass as a backing on the inside for the sealant to bond to.
Today thickened Gflex, glass, and Dynel may be all you will need. Perhaps unnecessary to state, but whatever your choice it will be important that the added fabric overlaps onto the exiting hull at as many locations as you can so the hole doesn’t pop open.
thanks
Okay, that’s sort of what I was thinking. I’ll work inside out. I’d kind of like to minimize having to buy a bunch of different materials, so I’d probably rather use dynel for all the patching, but when I get over to Sweet Composites I’ll ask them about it.
Suggestion
I would use glass for all the structural part of the repair. I’m no fiberglass expert but it seems s-glass gets high marks from many folks for adding strength to your repair. I don’t think Dynel will do as good a job adding strength.
Dynel I would use on the outermost layer(s) as it is extremely abrasion resistant. With a fg/epoxy underlayment providing strength the Dynel will hold everything intact from abraiding away.
noted
thanks, I’ll keep that in mind.
a photo would help
– Last Updated: Sep-29-15 10:30 AM EST –
If I understand correctly, you now have a sizable void in the Royalite extending to the interior that is dished out toward the exterior.
If that is approximately correct and you have not already done so, I would bevel the intact Royalite at the edges of the void at a pretty shallow angle before doing anything. That might seem "wrong" because you are removing good material and making the exterior hole bigger, but it will provide a much bigger bonding surface for your epoxy and fabric, which will make for a stronger repair.
I agree with waterbearer that filling a sizable void with epoxy/fabric composite will be much stronger than using epoxy alone. Epoxy blended with silica powder is great for filling in small voids like cracks, but a big mass of cured epoxy unsupported by cloth is going to be more brittle than epoxy supported by cloth. I would also use fiberglass for this purpose in preference to Dynel, although Dynel will certainly work.
Dynel is an acrylic resin and its stand out characteristic is abrasion resistance, although it does have good tensile strength. It is best used as an exterior layer in an abrasion-prone location.
S fiberglass is considerably more expensive than regular (E) fiberglass but I think the improvement in tensile strength, compressive strength, and stiffness is worth the additional expense, especially since a yard of material should be fine for your repair. S 'glass also has pretty good abrasion resistance and works well for skid plates. The fibers do not swell in resin nearly as much as Dynel does, so a skid plate made of fiberglass will be much less thick than one made from Dynel cloth of similar weight. If you want a thicker plate you can just use two layers of 'glass.
I would fill in the dished-out external void using multiple layers of cloth as waterbearer suggested, orienting the fibers of the layers in different directions by cutting the patches on varying biases to the weave and warp of the fabric. Ideally try to apply each new layer while the epoxy of the preceding one is still "green" so as to maximize the chemical bond.
Each new layer should be concentrically slightly smaller, or larger than the preceding one. The number of layers will depend on the thickness of the Royalite. Some folks insist the first patch should be the biggest. I don't feel it makes any difference whether you go progressively larger or smaller with patches from a strength perspective, so I would do whatever seems easiest until the void is filled in.
If you have an interior split or hole, I would cover it with clear packing tape to avoid epoxy leak while patching the exterior, then deal with the interior after the exterior repair is done.
I prefer using aramid such as Kevlar 49 for interior patches but fiberglass will work just fine if you don't have any aramid cloth and don't want to buy a second type of fabric. If you have a through and through hole, I would cover it with an interior patch of at least one layer of cloth that overlaps the edges of your exterior repair by a couple of inches.
If you are interested in the varieties of different types of fabrics and their particular strengths, this webpage at Sweet Composites is helpful:
http://sweetcomposites.com/Fabric.html
also this:
http://www.christinedemerchant.com/carbon-kevlar-glass-comparison.html