Summary - Short Version

Here's the short scoop. No matter who you talk to, or what you may hear, Souris River's Kevlar is stronger than Souris River's Duralite, period. The order of strength between the layups is as follows (from strongest to weakest): Kevlar, Carbon Tec, Duralite. The strength difference between all three of Souris River's layups is miniscule for ordinary use as a canoe. If you had to hang from a rope made from Souris River's layups and your life depended on it's strength, you would choose Kevlar first, Carbon Tec second and Duralite third. If you had to hang from a rope made of Duralite or another canoe builder's Kevlar layup, you would choose the Duralite.

All Souris River Canoe cloth layups are stronger by far than all other canoe companie's cloth layups because of the way Souris River puts them together. All Souris Rivers can flex when necessary which minimizes damage to the hull because of the epoxy resin and unique rib system. All Souris Rivers are made with the same flexible, heat-cured, epoxy resin and unique flexible rib system. No other major canoe builder uses this type of resin, or building process. Most other manufacturers use vinylester resin. Unless they've had the tar kicked out of them by rough outfitting customers, Souris River Canoes do not oilcan (flex underneath when a wave passes by). They generally only flex under duress and tend to slide over of an obstacle ending up with just a scratch. Regarding speed, Souris Rivers will keep right up with other kevlar canoes and are generally more stable, easier to turn and MUCH tougher. This is a summary of the article below. If you have more time, you can read about how the confusion about Kevlar and Duralite began.

The Beginnings of Confusion - the Long Story

After two years of selling, renting, and using Souris River Canoes in the Ely, MN area and the rock-laden Boundary Waters Canoe Area, Red Rock was satisfied that these were the best cloth-layup canoes built on the planet. We were confident in the canoe and decided to sell them to outfitters for their own rental programs.

Most every outfitter had experience with one major builder of kevlar canoes and every outfitter I talked to had horror stories about those kevlar canoes coming back destroyed after just a single trip out in many instances. Holes, cuts, tears, and cracked foam-cores in the bottoms were common in a lot of kevlar canoes. The outfitters needed to rent super-light kevlar canoes as customers demanded them, but they hated the fragility of kevlar canoes as they knew them. Most resolved themselves to hiring an unskilled highschool kid to smear goo on the afflicted part of the damaged kevlar canoes to make them stop leaking so they could rent them out again. It is very common for outfitters to use a old-technology kevlar canoes for about 1-1.5 seasons and then search for a buyer. They turn over those particular kevlar canoes because they look like heck after just three months of rentals. Cracks along the foam core line in the chines of the canoes, broken down kevlar along the gunwales at the center of the canoe, loose seats where the rivets are pulling out of the foam, pinhole seepages, lot's of patches, etc. Knowing these problems and after having rented out Sawyer Canoes which were built with the pretty much the same resin and vacuum bagged, foam-core, technology that all those other companies use, we at Red Rock paid really close attention to Souris Rivers in rentals. We found that they were not only easier to paddle and control on the water, they held up beautifully in rugged terrain. We found NO cracks from running over or against the occasional rock or log even after the canoes were rented for extended canoe trips. With this knowledge under our belt, we approached the outfitters to try Souris River Canoes.

New Canoe for Outfitters

The outfitters were gun-shy. Based on their limited experiences with only one brand of kevlar canoes, they concluded that ALL kevlar was fragile and all kevlar canoes are tippy. So, with skepticism, some of them bought low numbers of Souris River Canoes - in Duralite only - because it was cheaper than kevlar and not too much heavier. When they put the Souris River Duralites next to all of their other kevlar canoes made by other companies, the Souris Rivers Duralites outlasted those other-brand kevlar canoes hands down. Soon everybody was talking about how much stronger Duralite was than kevlar and that's how that bit of misinformation began. The outfitters themselves were comparing apples to oranges. They were comparing Epoxy-resin, Duralite, Souris River canoes to vinylester resin, kevlar canoes, foam core canoes made by a different manufacturer. They are entirely different animals although both happen to be canoes. From that point, many outfitters would only consider Duralite because they concluded that all kevlar canoes are the same - meaning "fragile and delicate". One cannot believe the contortions we went thru to clarify this misunderstanding that spread like wildfire. Souris River Canoes in general are more durable than other cloth layup canoes and a Souris River kevlar canoe would do far better than other-make kevlar canoes as well. There are distinctive reasons for this being so.

Kevlar is Kevlar

To understand the differences between Souris River's durability vs. other brands of canoes, you'll need to know some details. First of all, kevlar is kevlar as it pertains to canoe construction. It all pretty much comes in string form on a big roll and is purchased from DuPont by various weavers around the world who weave it into cloth fabrics that are used in everything from bullet-proof vests to canoes to fishing rods to bike tires and stuff that I haven't even heard of yet. Varying thicknesses, different weaves, and variations in the kevlar itself make it suitable for different applications but for all effects and purposes, the kevlar cloth used in a  Mad River, Bell, Wenonah, Sawyer, Nova Craft, Old Town,  etc., is the same as the kevlar cloth in a Souris River which is Kevlar 49. That's why you see decals that say Kevlar 49 on canoes. Kevlar 49 is not the model of the canoe. Kevlar 28 in used in bulletproof vests. These are examples of slightly different formulations and weaves of the same overall material called kevlar.

As a fiber, kevlar is incredibly strong, and extremely lightweight. Just a few sheets of kevlar will equal many sheets of fiberglass in strength. You can't cut the stuff with ordinary scissors, either. It was invented way back in 1966 by a Stephanie Kwolek an R & D scientist for DuPont who had a great interest in liquid crystalline polymers = aramid fibers. In 1971, the name Kevlar was trademarked by DuPont and Stephanie's invention has since become one of the most well-known, famous, fibers ever used.

Hull Shape and Speed

When it comes to portaging weight, fiberglass canoes are generally floating boat anchors while kevlar canoes are relative feathers. With regards to Duralite or Kevlar, neither cloth dictates how a canoe will handle on the water. Many of our customers want to feel what Kevlar (or Duralite) feels like on the water in the same model canoe. There's no difference. The cloth only affects the weight and appearance of the canoe. The hull shape of the canoe is what determines how the canoe will move through the water regarding speed, stability, turning and tracking. You might notice in various canoe brochures references to Jensen hulls or Yost hulls or Krozier hulls, etc. These designers build the hull in a shape designed for a specific purpose. Then the canoe is built by the manufacturer who in turn pays a royalty to the hull designer for using his design. In Souris River's case, all the Queticos, Wilderness 18's, and Tranquility solo were designed by Keith Robinson of Souris River. If you like the way that Souris River handles, you can chalk it up to Keith's brilliance as a canoe designer and manufacturer, not the fabric from which the canoe is made.

The Resin is the Key

Because kevlar (or Duralite, or fiberglass, etc.) is a cloth, you can form it into all sorts of shapes (very similar to fiberglass) by soaking it in resin and allowing it to cure. Canoe builders and tons of other watercraft industries build with kevlar cloth, fiberglass cloth, and variations of the two. Souris River uses kevlar but followed a different path in resin. Unlike the all other canoe builders, Souris River uses epoxy resin in all of their canoes. Resin is of critical importance and maybe one of the most overlooked factors in determining how tough a material (in this case, a canoe) will be. That's what holds the canoe together in the shape of a canoe otherwise it would just be a pile of cloth. Unfortunately, you can't tell which resin was used just by looking at cured resin. Cured, epoxy resin, looks a lot like cured vinylester resin. But you can smell the difference when you are around new canoes. New vinylester resin canoes smell like styrofoam because they thin the resin out (to make it easier to apply and squeegee through cloth fibers) with liquid styrene which pretty much consists of melted beer coolers from a layman's perspective. Freshly cured epoxy resin has a distinctively different odor which is hard for me to describe but it's definitely not melted beer coolers. Better still, to determine if the canoe is made with epoxy resin or vinylester resin, look at the logo. If it says Souris River Canoes on it, it's epoxy resin. Any other namebrand and it will be vinylester or worse yet, polyester resin (really cheap stuff!).

Different Resins and Building Processes

The epoxy resin used by Souris River is not your run-of-the-mill resin that you can buy at any hardware store. Hardware store resin (in the little tubes in 2 parts) has additives to make it viscuous (runny) at room temperature. That's so ordinary folks can use the stuff more easily. Souris River's epoxy resin comes in a more pure form with no additive so it needs to be heated up to flow. Then after it's applied to the cloth in the canoe mold, it must be baked in a big oven to cure. This baking process is what causes the epoxy resin to bond so hard to the kevlar fibers. Other companies who use vinylester resin, simply wet out the cloth in a female mold and allow the canoe to cure overnight after vacuum bagging it. Vacuum bagging is a process which allows the builder to sandwich a sheet of styrofoam into the bottom of the canoe between two sheets of cloth. The air is then sucked out of the bag with the canoe inside. This results in external air pressure pushing down really hard and sandwiching the foam between the resin-wetted cloth layers. It's a interesting process, but it limits the amount of hand work that can be performed once the canoe is in the bag. That's why sometimes you'll see ridges or lines of resin on top of the foam-core (the plastic had a wrinkle in it), or excessive resin built-up with air-bubbles in the inside corners surrounding the foam-core and its various ribs that run vertically up the side of that particular canoe. That styrofoam (foam-core) keeps the bottom rigid while paddling the canoe and results in racing efficiency. Without some sort of stiffener like the foam-core in place, the canoe bottom would flop up and down as waves passed under the canoe.

Foam Core Problems and Souris River's Solution

Foam-cores crush, break and are limited in flexibility. They are made to be that way in an effort to maximize hull efficiency particularily in racing situations. Just about all the major-brand kevlar canoes made today come from "racing roots" and you can read about it in all of their ads. They say things about "top-end performance", "efficient paddling", "hull efficiency", and the like. Sure that's all great - who wouldn't want an efficient canoe? To achieve their hull efficiency, they rely on a a foam core bottom and other stiffeners that assure that the canoe is rigid and unflexing. From a racing standpoint, stiff and rigid is very desireable, but it does come with drawbacks for the more common paddler. There is a reason that hi-powered Chevrolette Corvettes aren't seen driving around in the winter in Ely, MN. Their highway tires and high-performance, stiff suspension with low ground clearance, and fiberglass body don't fare too well in -40 degree F below zero or even 20 above. Snow is also a problem and they also tend to get stuck on flat ground as their high speed transmissions spin the tires as they go nowhere on ice. High performance is cool, but it doesn't always fare as well in all situations and for all people. High perfomance hulls are great if you are racing but less fun to fish out of or sightsee from. Nonetheless, those other canoe builders still build in those unforgiving racing lines and tout the importance fo top-end speed. It's kind of like putting a soccer-mom in a Corvette in Ely in the wintertime when she really needed a more durable, frontwheel drive vehicle that is capable of hauling a load in all conditions and temperatures while moving at a good clip down the road.

Because the foam-core bottom of other-brand kevlar canoes is rigid and unmoving, when you land the canoe with two, 200 lb. paddlers and all of their gear on top of an underwater rock, you will usually cause a fair amount of damage to the bottom of a rigid foam-core canoe. It all depends on the sharpness of the rock, the amount of weight you are hauling and the speed that you are traveling. If you crash into an obstacle with the side of the foam-core canoe, the sides tend to flex and the edge of the foam core does not. Vinylester resin will flex to a point but becomes more brittle with age and is much more subject to micro-fracturing and decreased repairability. This is where foam-core canoes run into trouble with substantial tears and punctures.

Picture the canoe loaded wherein the foam core is just below the water's surface which occurs 99% of the time in a loaded canoe. Then slide the side (the part above water) of the canoe into the butt of a horizontal log sticking out from shore. To illustrate the results, visualize a truck pulling a trailer stacked six boxes high under a bridge that will allow only five boxes on a trailer to pass underneath it. The bridge represents the unmoving foam core, and the side of the canoe is represented by the sixth layer of boxes on the truck's trailer. The moveable, weaker, sixth layer of boxes (metaphorical side of canoe) shears off the trailer when it passes under the unmoveable bridge (metaphorical rigid foam core). If you're observant, you'll see lots of patches just above the foam core of these types of canoes. This type of damage is virtually non-existant in a Souris River due the lack of a foam core and the ability of the hull to flex.

A rigid foam core in a canoe is old racing canoe technology. It stemmed from making the canoe as stiff as possible for paddling efficiency in a race. All the strength of the paddlers moves the canoe forward with no flexing up and down which is wasted energy. For everyday use and Boundary Waters, this technology is has a serious flaw - it overlooks non-racers and encounters with obstacles. For this reason and others, Souris River does not vacuum bag a foam-core into the bottom for rigidity. Instead they hand-build a unique, flexible rib-system which holds the bottom down until an obstacle is encountered. It can then flex up or even sideways to absorb a side impact. Plus it can crawl over the obstacle which greatly inhibits the rock's ability to puncture, cut, dent or tear of the fabric. Repeated flexing is only possible in the long-run with SR's particular blend of epoxy resin. Vinylester resin will flex occasionally, but with repetition, it tends to break down rather quickly compared to epoxy resin.

Resins: Bonding OR Encapsulating

The difference between the way epoxy resin and vinylester resin work to hold onto kevlar fibers is one of the main reasons Souris River uses epoxy resin. Heat-cured, epoxy resin bonds with each and every fiber in the canoe after reaching the proper degree of heat-curing. Once cured, epoxy resin neither changes nor becomes brittle for the life of the canoe and to break one fiber, you need to break a whole bunch of fibers and that much harder to do.

On the other hand, room-temp cured, vinylester resin merely encapsulates each fiber. That means that a passing rock can pull out one fiber out of the resin and break it; and then another fiber, etc. The weakest link goes and the rest follow. Being only room-temp cured, vinylester resin continues to cure forever, meaning that it tends to get harder and more brittle all the time. When you go to repair an epoxy resin canoe five years down the road, you just get some new epoxy resin and apply it to the canoe. Unless the canoe is dirty, the new resin generally bonds right to that canoe with great strength. When you go to repair a vinylester resin canoe in five years or so, you apply new vinylester resin to the canoe with different, less predictable results. Unfortunately, the canoe's resin is no longer the same vinylester resin in that canoe you bought five years ago. The canoe's been aged and the patch you are putting on the canoe with fresh resin, may or may not hold because you are merging essentially two different resins now. Losing a patch doesn't always happen, but it can. Then there is what is referred to as "fish or alligator scaling". This condition occurs when new vinylester resin doesn't bond well with the older resin of the canoe. It to flakes or peels off like big fish scales. This makes a rough and bumpy surface that slows the canoe down in the water. We personally have seen several canoes that have had these problems with vinylester resin. Epoxy causes far less trouble in repair work and touchups.

Summary

A major contributor to a canoe's durability lies entirely with the resin used. Sure, Souris River has a whole bag of other innovative (and proprietary) techniques that they employ in constructing a tough, well-made, superlight canoe, but their use of their unique blend of epoxy resin is a big key factor. If the resin can't hold onto the cloth fibers, the fibers can be pulled out and individually broken instead of flexed when the canoe hits a sharp obstacle. Outfitters experienced the uncanny toughness of Souris River Duralites in rental situations and talked about it loudly. That's where the "Duralite is tougher than Kevlar" talk came from. The fact of the matter is that Duralite is actually a weaker cloth than Kevlar, but since so many outfitters concluded that all kevlar is weak based on their past experiences with other weaker canoe brands. As a result they initially gave Duralite a chance and concluded that all Souris River kevlars would share the same properties of the other brand, less advanced, kevlar canoes they were all using prior to Souris River Canoes.

Truth be told, regarding kevlar cloth, the outfitters were 100% correct. From a molecular standpoint, Souris River's kevlar cloth was pretty much the same as the other-brand kevlar cloth. The part outfitters and laypeople always miss is the type of resin the canoe manufacturer used to hold all those kevlar fibers together in the shape of a canoe. Epoxy resin is substantially superior to vinylester resin. Go ahead and do the research right on the web. It's also harder to work with initially (during the actual canoe-building phase) for reasons I won't go into here. In the canoe industry, everybody knows about the difficulty of working with epoxy resin and this is a large reason you don't see any other epoxy resin canoes out there in the Boundary Waters or the rest of the canoe world.. Another reason for major canoe builders using inferior vinylester resin is shear economics. It's much cheaper (one third the price of epoxy) and much easier to work with initially than epoxy. No baking required, no extra heat used in the wetting out, less mold problems, etc. No additional R & D for vinylester resin builders because they all build them about the same way using similar, old-fashioned techniques.

So why not make flexible rib system canoes using vinylester resin? Therein lies the rub: Vinylester resin doesn't do well when flexed repeatedly. It lets go of the fibers. Epoxy resin doesn't let go of the fibers without a real fight. So, in order to change the foam structure of their canoes to allow them to flex when they need to flex, the other-brand canoe makers need to change their resin system. To do this, they need to rebuild their entire factory. So far, two of the three better-known canoe manufacturers have attempted to build canoes with epoxy resin. Didn't go too well. They both abandoned attempting to use epoxy resin entirely. The mere fact that they decided to try epoxy resin construction in 2003-4 is a telltale sign of a better building component. Otherwise, why would they even consider messing with it? For the shear adventure, or did Souris River rattle a few cages with a better canoe? Feel free to speculate on the indicators...

The resin and overall hull design of a canoe that can flex on demand, out of the way of obstacles is what makes Souris River's Duralites (and Kevlars and Carbon Tecs) so much better than those other-brand kevlar canoes. When comparing Souris River's durabilty to any other brand kevlar canoes, it's simple. Believe it or not, there is no comparison. Souris River Canoes are built better through a melding of resin, cloth, and design improvements. Souris River's unique design and construction techniques results in canoes that hold up much better and handle very nicely on the water. Of course, nothing is indestructible. You CAN poke a hole in a Souris River Canoe, but you generally have to work at it.