What’s wrong about redrock is that
he structures his presentation to claim that the way others build canoes is totally wrong, while Souris River does things totally right.
If the Souris River canoe designs were as good as what one can get from Wenonah and Bell, Souris would be in a very good position with their construction. But there is no absolutely right answer. I personally do not like a canoe with a bunch of separate ribs in the bottom, forming little water pools, and full of stress risers. I don’t like flat bottomed canoes. Those two points are more than enough to steer me to canoe makers who know how to design a hull.
he is like
The Mike Holmes of canoes. Always telling me what’s wrong.
Ryan L.
Ribs end at chines
on Souris as well - as I can see on their photos. The flex of the sides along chine line that one poster noticed to happen mostly in the bow - could this be eliminated by adding a short deck in the bow? I’ve been thinking of making deck anyway.
No, Mike Holmes would come to your
boat and tear it apart.
That’s one guy I hope never to see at my door.
I’m no engineer
I cannot explain why using physics equations, but simply what, based on several Souris River boats I have used.
The flexing seems to happen along the length of the chine, and only in the mid-section, not near the ends. This, I believe, is caused because the ribs are covered with rectangular bits of fabric, with square edges, that form a neat line along the chine.
I’ve been told that Souris is now lengthening the rib-cover to extend a bit further up the side. This would certainly eliminate the problem.
Truth be told, the “problem” is only noticeable after a decade of constant outfitter use, so while it is a weak link in the chain, it is a very strong chain.
Further, and I think Souris can pass off some of the blame since it is we, as a canoe-buying public, that keep demanding the manufactures create ever lighter canoes. I would much rather have a 55lb canoe that is tough, stiff, and performs well than a 35lb canoe that I need to baby. To that end, I would prefer a Souris River Canoe that came with an additional 5lbs in the skittle and 4lbs in the trim to make everything a bit more substantial. I have a Hellman in Duratuff that feels really solid.
Could it be gelcoat
cracks, rather than Kevlar cracks? Kevlar is much more flexible than gelcoat. When Kevlar flexes more than gelcoat’s limit of elasticity, gelcoat cracks.
1 Like
whats funny
– Last Updated: Jun-30-11 8:21 PM EST –
Is when I notice this flex problem in my new to me sawyer, I remember thinking that I would buy a souris river boat next time and I won't have this problem because there is no foam core. So now you guys are telling me that this happens any way. So I'm going to just paddle my boats till they fall apart and then put them back together.
Ryan L.
definately
Just in the gelcoat for now.
Ryan L.
You might not notice it
as I don’t when the boat is laden for a long trip…as we run whitewater sometimes…and its shallow we appreciate the flex.
We have a Wilderness 18 and frankly its most susceptible to damage during transport. VIA rail threw ours down the embankment at a bush stop.
Souris has
no single foam core. Instead, they have multiple foam ribs. Those foam ribs end on chines, and this is where it cracks, as I understand. When they extend the ribs up onto the sides, it will be a better boat.
And they have
I understand they have extended the ribs in later editions. Also, when I say “cracks”, we are talking about stress lines that develop after many years of hard use. These are still usable, still waterproof, just a visible line that if left for another few years may develop into a deformation.
I agree with the “paddle it 'till it breaks” sentiment, as all canoes will fail in some way eventually. Most of the good ones, in normal use, will last at least one lifetime.
Sawyer
which is “Superior Sawyer” IIRC - when I look at specs, it is just a little lighter than comparable Wenonah models in Kevlar - say, 43lbs vs 40 lbs; and it’s heavier than comparable Swift. Doesn’t sound like too light layup. It must be the flexibility of Kevlar that causes gel coat cracking. There isn’t much need in gelcoat on Kevlar, IMHO.
other quality builders will disagree
I have with one exception always traveled beyond the Boundary Waters with gel coated kevlar.
Sure gel is not structural but I have a eighteen year old kevlar gel coated boat with a few thousand miles with no bilge cracking. Oh it has no foam core either
no, its a sawyer
It is not the superior version. It is at least a few pounds lighter.
Ryan L.
A possible problem with Kevlar and
chines. I went to try a Millbrook that had marked chines through the bow region. It is a rather flat bottomed boat, S-glass outside and Kevlar inside.
I was surprised when the boat’s owner pointed out damage he had repaired to the inside of the front chines. The outside of the chines (S-glass) was less damaged, and the center of the boat’s underside was not broken. Why would Kevlar, reputedly an excellent “inside” cloth with very high strength in tension, have broken in the chines?
I then realised there is a gap in our thinking about strength in compression and strength in tension.
Usually, when a hull is distorted by outside forces, the highest forces on the outside are compression forces, and the highest forces inside are tension forces.
But suppose a flat bottomed canoe, with rather sharp chines, is struck hard from underneath, for example when slamming down while running a ledge. At the center of impact, the S-glass absorbs the fiber shortening, or compression, and the Kevlar absorbs the fiber lengthening, or tension.
But nearby, the Kevlar inside the chines is shortened and scrunched as the chines decrease in diameter. The S-glass on the outside of the chines is put under considerable tension, and may split. The Kevlar on the inside is scrunched, its resin matrix may be munched, and the Kevlar may break. Kevlar behaves very strangely when its fibers are forcibly shortened, or scrunched. It is where Kevlar performs least well.
I have seen chine splitting on several of my boats from ledge damage. There might be consequences for both boat building and for boat repairs. If an area is more likely to be folded by blows nearby, then that area might be reinforced inside by fabrics that have better compression strength, like carbon or glass. If toughness is needed but with better compression strength than Kevlar, Nylon and polyester are alternatives.
Similarly, while S-glass and carbon are excellent for most outside areas of a boat, areas like chines might need to be built, and repaired, with Kevlar, which can resist tension forces when inward distortion of the bottom of the hull causes the chines to fold.
Interesting
I’ve always been a bit puzzled thinking about where the compression and tension takes place. And I’ve been confused by the compression on the outside, tension on the inside explanation. In my mind I always pictured the chine flexing and it never quite made intuitive sense to me. Now I see I’m not alone. Thanks.
You know…coastal water = salt/fresh
mix…is slightly heavier than freshwater, hence a Royalex boat won’t feel as heavy as in freshwater…imho.
As long as it stays in water 
Weight in water doesn’t matter much - extra 20-30 lbs will increase the draft by a negligible amount. The problem is - most of us have to drag/tow their boats in and out of water every time, and this is when you feel the weight; most unfortunate (probably 50% or more) also have to cartop it.
Yes
That has always been my immediate thought when people say Kevlar belongs on the inside due to its tensile strength. It is simply not possible to create only an inward bend in a sheet of material, no matter what the shape. Any single inward bend must be accompanied by outward bends at more than one location. Of course, on a canoe, the sharpest bend is likely to be the inward bend at a point of impact, due to the nature of the cause, and because the counterbalancing outward bends occur at two or more locations, not just one, so they are apt to be less abrupt, and surely there is truth in the idea that Kevlar works best on the inside. I’m just saying it’s only common sense that putting Kevlar on the inside by necessity means that not all of the Kevlar is optimally located when the hull flexes.
Polyester is used
by Clipper as a mid-layer in 3-layer Kevlar layup - but only when there is a gel on top of it. At least, this is how I understood their explanations. When they build the hull in female mold from outside to inside, gel goes first, with Kevlar soaked in there. Then - reinforcing where needed, with Kevlar again. Then goes Polyester. Then Kevlar again. Then - foam core if the boat has it, and then Kevlar on top of the foam (this last Kevlar is the inner-most layer).
But their Ultralight Kevlar hulls are different - there is S-glass at the first layer (i.e. outside), no gel coat, and I am not sure if there is a Polyester in the middle.