Yet another royalex repair thread

[Tripthenorth]

Hello all,

I recently became the proud owner of a Novacraft prospector 17 in the royalex layup. The canoe seems to be in decent enough shape except for a crack on one side of the hull.
The previous owner said that it was up on a rack outdoors and was blown off by strong winds hence the mishap.
I’m hoping for the knowledgeable folks on here to point me in the right direction on the right way to repair damaged royalex.
I have done smaller repair jobs on gouges and scratches using g flex epoxy on my other royalex ww canoe but have never tackled anything like this before.
I had seen a repair done on cold cracks using only g flex epoxy and was wondering if this would be a strong enough repair.

Thanks in advanced,
Tripthenorth

 

[pblanc]

For a big through and through crack like that I would apply both interior and exterior patches. Fiberglass will work for both. E fiberglass is cheaper but S fiberglass is stronger and more abrasion resistant. I would recommend plain-weave fiberglass cloth of 6 ounce/square yard weight.

I would start by completely unroofing the cracks inside and out by removing the green vinyl layer on the exterior, and the tan vinyl layer on the interior for a distance of at least one inch in all directions beyond the fractures in the solid ABS layers of the Royalex. Don't be surprised if the cracks in the ABS are more extensive than the breaks in the vinyl layers suggest.

Then gutter out the cracks inside and out at a 45 degree angle to the adjacent surface so that your bevels meet at the midpoint of the foam core layer. Fill in the cracks from both sides using G Flex moderately thickened by stirring some silica powder into the mixed epoxy. Apply more thickened epoxy as needed to completely fill the cracks on both sides. Once cured sand the epoxy so that the filled cracks are fair and flush with the adjacent hull.

Make your fiberglass patch big enough so that they overlap onto undamaged hull be about 2 inches in all directions. Use unthickened G Flex epoxy to wet out your patches. Apply an additional coat of epoxy to the exterior patch to fill the weave so that it is smooth and feather the edges of the patch.

After the repair paint over the patches on the interior and exterior to protect the epoxy from UV degradation.

 

[Glenn MacGrady]

Tripthenorth, welcome to site membership! Feel free to ask any questions and to post messages, photos and videos in our many forums. Please read Welcome to CanoeTripping and Site Rules! We look forward to your participation in our canoe community.

As to your damage, you've already gotten advice from one of our most experienced paddlers and repairers of Royalex canoes. It would be of great help to future canoeists in your situation if you would photograph and document your progress in this thread, inlcuding mistakes as well as successes. That's how we transmit our knowledge to future generations and one of the reasons folks come to this site.

 

[goonstroke]

Did it happen in winter? It would be hard to do that to royalex at room temperature.

G Flex on royalex/ABS is pretty amazing. I have a friend who shredded his Penobscot 17 in a whitewater wrap (say 6-8 linear feet of torn material). He put it back together with G Flex, good prep of the cracks as pblanc describes but not any cloth. It's survived several years as a floating Frankenstein. He didn't paint the outside so everyone can see the scars.

If you do the gold standard repair with fabric inside and out, protected from UV, it might outlive you.

 

[Tripthenorth]

Thank you for your prompt replies Pblanc and Goonstroke.

I do have some G Flex epoxy on hand but am missing the silica as a thickening agent. I’m ordering it on Amazon as we speak.

I was wondering if I could get by with just using G Flex epoxy, first with the thickening silica agent, then finish it off with just pure G Flex . I know I will be losing some structural integrity doing so and have seen such repairs online done on cold cracks and has held up fine.

Would this suffice for a canoe that will not see any WW use? This will solely be a flat water tripping canoe. The only concern would be the weight of gear loaded onto the canoe and if it would somehow place undue stress on the crack once it has been repaired.

Goonstroke, did your friend ever used his Penobscot 17 in WW after the repair was done?
Was the structural integrity still sound?

I will update the thread with progress pictures, once I have the required materials in.

Thanks again Pblanc and goonstroke for your wealth of knowledge and insights.

 

[pblanc]

Most epoxy manufacturers recommend thickening the mixed epoxy with silica powder to create an "epoxy glue" for filling cracks and for filleting. Presumably it increases bond strength.

Cold cracks are a bit different than cracks resulting from impacts. Cold cracks virtually always start at the gunwale so you always have the rigidity and strength of the gunwale supporting the repair. Cold cracks are also usually a simple, linear affair.

Cracks due to impacts often are accompanied by some crushing of the foam core as well as some degree of displacement of the fracture fragments. You often also don't have the support of the gunwale. In addition, impact damage often results in complex, stellar cracks with cracks oriented in multiple different directions.

Impact cracks are always going to be associated with greater loss of structural integrity than cold cracks.

Can you get away with just filling the cracks without supporting patches? Possibly. But it has been my practice to do a repair once and do it right. A quick and dirty repair virtually always makes doing a proper repair later more difficult.

 

[goonstroke]

...

Would this suffice for a canoe that will not see any WW use? This will solely be a flat water tripping canoe. The only concern would be the weight of gear loaded onto the canoe and if it would somehow place undue stress on the crack once it has been repaired.

Goonstroke, did your friend ever used his Penobscot 17 in WW after the repair was done?
Was the structural integrity still sound?
...

He does still use it for WW (local races are an opportunity to show off the scars!). I know he's had to "touch up" at least once, but it's taken some knocks without serious failure. That said, I don't think he'd tempt fate with a distant wilderness expedition in that canoe.

Your boat has a crack of much more manageable size, so a bombproof, one-and-done repair wouldn't add much weight. If you remove some vinyl on the inside that could serve as both surface prep and reconnaissance. If you see cracks that were hidden by the vinyl then you'll know to expand the repair area accordingly. I think if it were my boat I would add cloth at least on the inside, the epoxy has to go in somewhere and be shaped, why not add a strip of material? You can orient the boat so that gravity helps. Rolls of fiberglass in 3-6" widths are inexpensive and easy to find (at least E-glass).

Whatever you do make sure you gutter/bevel/chamfer the cracks as pblanc describes. If you do that then the cured GFlex material is shaped like a plug in cross section, so even if for some reason the bond fails it will still be mechanically held in place.

 

[Tripthenorth]

Wanted to provide you all an update on the repair. The repair supplies finally came in today, and as luck would have it, I managed to get off work early today.

I had I got to work on the section by first taping it off using masking tape. This would prevent any oopsies from happening, should they occur. I also wanted to make sure that I did not go over the repair area.



I then took off the thwart as it was in the way. This allowed for two things. First, it gave me better access for the repair on the inside. Secondly, by having it off the canoe now became less rigid and more pliable (the beauty of royalex ) which allowed me to push the crack back together somewhat flush.



At this point I had brought out the dremel tool and started working on beveling the edges and getting rid of loose material as well as any minor cracks that would compromise the structural integrity of the repair. Pblanc was right as when I started chipping away at the repair, the damage was much more extensive than what met the eye initially.

I had to get creative to separate the layers to start beveling so I ended up using two bits off the screwdriver which worked quite well.






This process took a little while as I wanted to only remove material that had to go.



This was the rotary kit I used from Amazon. Worked pretty well for costing only 10 bucks.



My little helper for the day


This was the end result of the dremel work.



I’m aware of the smaller crack running horizontally and will take care of that tomorrow.
I then mixed up some G Flex along with silica. This was first time using silica with G Flex and boy, is that stuff super fine and powdery. It was a bit tricky working with the silica outdoors (no shop or garage space) but made it work. I mixed it to the consistency I wanted and applied it to the crack.


In order to minimize sanding, I used a thick and sturdy sheet from a note pad and smoothed out the epoxy. A bondo squeegee would have also worked well.


Now just waiting on the overnight cure and will commence with sanding and laying down glass and regular unthickened G Flex

 

[Glenn MacGrady]

That looks like really good progress, TTN, with very informative pictorial documentation, which I'm positive will assist future repairers of Royalex canoes.

How did you prevent the epoxy mixture from flowing out of the "trenches" on that rounded curve of hull? I've applied it only on relatively flat spots.