royalite repair question

Howdy y’all. I need some advice on repairing my canoe, an Esquif Avalon, made of Royalite. On a paddle last week I managed to put a big dent in the stern along the keel. The dent was about four inches long, perpendicular to the keel, a little bit aft of the rear seat. The dent popped out okay. No damage on the inside (except the crease marks where the dent was). On the outside, the hull feels soft and mushy on a roughly 8" x 4" strip right along the keel. Also, there’s a half inch crack perpendicular to the keel and a 2 inch crack along the keel inside the mushy area. I’m guessing the area is mushy because the foam got crushed when the hull dented.

Ordinarily when I get small punctures, I cut out a V-shape section, fill with Gorilla glue, and patch it with JB Weld. But if I did that with this, I’d be trying to rebuild the whole stern end of the keel with Gorilla glue or epoxy or whatever. Should I fill in the cracks as best I can and cover the whole area with an S-glass patch or a Kevlar skid plate? What would you experienced Royalite/Royalex repairers recommend?

Perhaps a skid plate
I once put a nasty dent in the bow of an Old Town Penobscot by running headlong into a rock. As luck would have it, it was right where a skid plate would normally go and I thought no deeper about it. I bought a skid plate kit and put one on each end. On the bow I needed to use a bit of filler to fair out the dent before I slapped on the skid plate. If your dent is “skid plate ready”, that is an option.

This is not the most sophisticated of repairs and others will probably chime in about the roughness and drag of the common kevlar felt skid plate kits. But UPS will bring the kit to the door in a few days (I bought minefrom Wenonah) and after that you’ll be done in a couple of hours.


skin repair
most of the stiffness of the hull is due to the shell layers taking the stress when seperated by the foam. The breaks in the shell are likely part of the softness. I have successfully stiffened the bottom of a royalite canoe by epoxying fiberglass ribs to the inside. I suspect you will need some glass or kevlar tape epoxied over the breaks in the shell to get the stiffnes back. maybe over a greater area. You can get kevlar tape also which will be much will cover less area and be much lighter if you are not looking for full skid plates as part of the fix.

Yeah, the canoe is probably a candidate for skid plates now. I was avoiding them for all the reasons everyone hates skid plates. That, and I suck at DIY projects that involve precision and/or marine grade epoxies. The Kevlar tape sounds like an interesting alternative. Additionally, any one tried Keel Easy? Looks like it might work for abrasion, but not the added stiffness I need.

Abrasion yes, stiffness no.

– Last Updated: Sep-07-15 12:31 PM EST –

I also had problems with the Keeleasy edges not wanting to stay stuck in the body of the curved stem. I did the skids on my royalite with glass, and it's holding up very well - but mine were more for abrasion than hard impact.

Dynel fabric
Is what I have converted to for skid plates. Extremely abrasion resistant and using West system peel ply during the application will give you a finely textured finish.

Keel Easy and Dynal Skid Plates
I agree with Steve. I tried the Keel Easy on a MR boat and they add no structural advantage. I am a big fan of Dynal using West System and G-Flex mix. Have those on several of my boats and they are rock solid after beating the snot out of them on NH rocky rivers. I will never use those Kevlar kits. Just my point of view. I can send you a link to how I did mine if you are interested.


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?

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.

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.

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.