The Cold Crack Project

[dougd]

OK, I know I mentioned this before, might have been another hull though. An 04 MR Explorer with what I thought were 9 cold cracks and then turned into 13 by the time I was done. This is the 3rd hull I've fixed with CC's and is now the last, never ever again! Number one I think it's next to impossible to make a clean fix without leaving what I call a scar. Yeah maybe some paint but I'm not keeping this and know where it's going so cosmetics in this case in not an issue but if it was.,.. Even using Peel Ply and a roller to smooth the cloth and resin out I still have some sanding to do on all the patches. Now, I did try out one thing and will keep this in my box of tricks for down the road. I thickened up resin to more than peanut butter consistency and then put peel ply right over that and smoothed it out. Had to do it where old patches where and I could get it knocked down with a sander due to it's location. It worked well. Now one thing I should mention is that on stands a couple of the cracks spread which I haven't seen before so I had to put it on the floor and then tied the carry loops from bow to stern to pull it together to stop the continued cracking.

So, with all that being said I again have to wonder about why this boat would cold crack to much? Talking to a few people the common theme seemed to be the year it was made and if I'm correct it was when MR sold and got moved to NC and then SC where, as I've been told, there were problems with the ovens as well as the workers at one point. I have had several, still do one, royalex hulls with never a problem with CC's. Don't know, it's a head scratcher! A few pics included.

dougd

 

[alsg]

I don't own anything Royalex and I haven't heard of this issue before. When these cold cracks develop, do they always start at the hole where the gunnels were attached? And more towards the ends than the centers?

Gunnels expanding/contracting at a different rate than the hull?

 

[recped]

Talking to a few people the common theme seemed to be the year it was made

dougd

My Explorer (ash gunnels) was made in 1992 (might have been 1991), I have never done anything like loosening the gunnel screws, it's been stored in an attached garage, never experienced a cold crack and being in Southern Ontario it's been through many cycles of cold/not so cold.

Besides manufacturing issues at Mad River anecdotal stories about variations in the production of the Royalex sheets themselves may mean that some sheets were not up to snuff. Add to that, in 2000 Spartech took over Royalex manufacturing from Uniroyal so raw sheets made after 2000 may have issues that older sheets did not (although I'm pretty sure I heard of the cold crack issue before 2000).

 

[pblanc]

It is a widely-held opinion among whitewater open boaters that the durability of Royalex generally took something of a nosedive around 2000. This may in part have been due to the take-over of production by Spartech, but I have also read that changes in the manufacturing process mandated by OHSA requirements played a role. Also partly due to complaints about the weight of Royalex boats manufacturers speced lighter sheet for their models. Due to the decreasing demand for canoes resulting from the increasing popularity of kayaks, makers also did not order and store a lot of sheet in advance of production, so that the hulls were molded out of Royalex that was still "green" and not fully cured.

But cold cracks most definitely occurred back in the !970s, 80s, and 90s. The party line is that they are due to differential contraction of wood versus plastic. Royalex does very definitely expand and contract with changes in temperature. But this does not explain why some boats stored in very cold conditions without special precautions seem to be relatively immune to cold cracks where others are more susceptible.

G Flex works well for repair of cold cracks in Royalex hulls. Sometimes the crack needs to be widened a bit to allow epoxy to fully penetrate. This can be done with a hacksaw blade and is especially easy to do if the gunwales are removed. Beveling the edges of the crack to 45 degrees on both sides greatly increases the bonding surface for the epoxy. I thicken the G Flex moderately with colloidal silica powder. If you want a nice cosmetic result, sand the outside of the crack flush after filling it in with epoxy and paint with a color that matches the hull. If a patch is felt necessary, I apply it to the inside of the hull only.

Although hulls can crack anywhere from impact, the "cold cracks" that I have seen all originate at a gunwale screw hole near the sheer line, then extend more or less vertically down the hull as in Doug's photos. None of the cold cracks that I have repaired have propagated or recurred.

 

[Canotrouge]

Good job!! I fixed lots and lots of cold cracks ver the years, and I'm about to fix a lot more in the next year!! I have a mad river guide that got given to me with hugely long cold cracks and lots of them.... And two cents have contacted me to fix there boats.... I hate fixing them, but I hate seeing boat going to the dump!

 

[pblanc]

This article describes repair of 58 cold cracks in a single, wood-gunwaled Royalex canoe using G Flex epoxy:

http://www.epoxyworks.com/index.php/repairing-a-royalex-canoe-with-gflex-epoxy/

 

[dougd]

Canotrouge, yes, I hate fixing them too! As I said in the OP never again, I swear, yeah, I really swear never again. Good luck on your projects! The Guide is a nice hull!

Peter, I read that article a while back on my second round of fixing them. The MR Eclipse I did with CC's never leaked or split any further after I was done and I rode that boat fairly hard before I sold it. Thanks for posting that.

dougd

 

[Canotrouge]

This article describes repair of 58 cold cracks in a single, wood-gunwaled Royalex canoe using G Flex epoxy:

http://www.epoxyworks.com/index.php/repairing-a-royalex-canoe-with-gflex-epoxy/

I pretty much follow that procedure and so far it worked great!! I did a Dagger Caption with lots of them and paddled that boat quite hard since the repair and non of them have failed!