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Ribs vs. Foam Core Floor

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Hey guys,

Curious what you’d go with if you could choose either foam ribs across the floor or a full foam core floor on the same canoe? Kevlar hand layup either way if that’s a factor. Thanks!
 
Below from another tread. Maybe foam ribs could be all right, but in my experience they were disaster.

I think the problem is from ribs only provide stiffness around the hull, but not along the hull.

Good luck with your purchase. And please let us know how it works out.
 
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My favorite canoe was a 17' Mohawk. It had sharp ends and a nice shallow arch bottom. But it was chopper gun fiberglass and kevlar cloth, without enough foam to stiffen it up. It needed a brace between the yoke and bottom or the hull would bubble up nearly to the gunwales. Plus some truly pathetic patches from the previous owners. But it was 55 lbs and very very cheap.

It was awesome. It was a disposable Kevlar tripping boat that paddled well. I never worried a second if the river was too low, too rocky, or if it might get stolen or confiscated. We just went.

Funny thing was we never destroyed it. I paddled it blissfully several years until the cheap chopper gun FG/kevlar finally got so flexy and leaky it had to be fixed. I wanted to fix it because I loved the shape so much. But just looking at it for five minutes, it was hopeless. Everything about that hull was trash buried underneath a chopper gun mess.

I stripped out the seats (great cane seats, nicely rounded frames) and yoke. Then it then went to the curb with a craigslist free notice.

My wife ask what I would do when nobody took it. I told her I'd have to cut it up to fit in a dumpster.

It was gone in 2 hours. Poor kid, I saw him struggling so I put the yoke back. I warned him it wasn't usable.

There's one for sale in GA, complete with an improvised yoke brace for the weak hull. Rubbish.

View attachment 134843
 
Full foam core layups are usually lighter, stiffer and more prone to damage in abusive situations than ribbed layups. If you like to run into rocks, a ribbed layup will probably better withstand the impact due to its more flexible layup. I've had a ribbed layup canoe for about 30 years (Clipper/Jensen WWIII) and it has been fine. The previous owner had cracked a rib, which was a simple repair. If you're dragging the canoe a lot, then ribbed layups will concentrate wear along the ribs, as the material between the ribs is more flexible. I didn't drag my boat, so it wasn't an issue. Nor did I have any concentrated wear along the ribs. The hull was stiff and never showed any flex which MrPoling mentioned. Clipper makes a higher quality canoe than Mohawk, with heavier layups than Wenonah. Additionally, I have a center-rib canoe (most flexible, for whitewater use) and a foam core canoe (Kevlar ultralight)--they are used for different purposes. A well made ribbed layup will do everything a foam core canoe can do, but there is a weight and stiffness penalty. Neither should oil can. Racing canoes, which require the ultimate in stiffness for paddling efficiency, almost exclusively use foam cores.

The quote by MrPoling doesn't mention any ribbed layup, so I'm not sure what his point is.
 
I'm quite fond of the durability of my Sourish River canoes, both rib designs. One bent quite a bit when it went over a dam fully loaded, and was fine. I don't believe the full foam core floor flexes so much without damage.
 
The image of the Mohawk shows ribs, with a a very thin foam strip along the middle. Without the full foam across the bottom it's too weak without additional fabric layers. Certainly Mohawk is not known for making the highest quality canoes, and that they chose to build one this way is part of the point.

I think BillConner has a point about the Souris River canoes. There's probably a lot of nuance around layups and their usages.
 
Hey guys,

Curious what you’d go with if you could choose either foam ribs across the floor or a full foam core floor on the same canoe? Kevlar hand layup either way if that’s a factor. Thanks!
It depends on how you're going to use the canoe. Mason provides some good details.

I have a Wenonah Odyssey 18.5 ft Kevlar tandem with foam ribs that was intended to be used on whitewater rivers and big lakes (often fully loaded) so they designed the hull to flex a bit when running big waves or absorbing an occasional rock bounce. It has worked just like it was supposed to in both those conditions. I also had a Wenonah Advantage 16.5 ft Kevlar solo cruiser with a foam floor that was intended to be used on flat water, traveling fast, where you wanted a stiff hull to maximize energy transfer. It worked just like it was supposed to.

Yellowcanoe mentions the layups that Dave Curtis offers, with no foam involved. I have three of his canoes (two Kevlar, one fiberglass) and they're all excellent boats. They do flex a bit when encountering waves, or beaver dam overflows, or bottoming out in shallow sections on a river, which is good in my opinion because that's how I use his canoes. But if I wanted a canoe that put my energy into going as fast as possible, I'd probably want a canoe with a foam core to minimize weight and maximize stiffness.

Edited: I will add that in my experience there's not a lot of difference if the canoe is well made and that any of the hull layups do just fine. I've taken my Advantage (not loaded down) over beaver dams and bumped along shallow streams without a problem and the Odyssey goes pretty darn fast if you want it to.
 
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My understanding is that any place on a fiberglass canoe hull where there is a rapid transition from a very stiff area (like a thick rib) to a very flexible area (like a thin skin) is at risk of becoming a 'facture zone' which is prone to cracks and other failures. This is why many high end manufacturers have avoided adding ribs to most of their fiberglass canoe hulls.

Ironically, birch bark canoes have the same problem. This issue was solved there by adding many ribs which are very close together with planking and other techniques to moderate the flex transition areas. This solution was carried over to wood and canvas canoes.

Another significant factor is how the canoe will be used as others have pointed out.

Benson
 
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My understanding is that any place on a fiberglass canoe hull where there is a rapid transition from a very stiff area (like a rib) to a very flexible area (like a thin skin) is at risk of becoming a 'facture zone' which is prone to cracks and other failures. This is why many high end manufacturers have avoided adding ribs to most of their fiberglass canoe hulls.
In the Kevlar Odyssey the cross ribs are fairly narrow and spaced regularly along the hull. You can also see where they used reinforcement layers at strategic places. Probably why it was a proven Kevlar layup. I did a quick look on the Wenonah website and it appears that they don't used cross-ribs in their Tuf-weave (fiberglass/polyester) layups anymore.
 
Depends what you want, what's available and how much it costs.

I have a solid foam core floor Nova Craft, which I suspect is lighter weight and less bottom-flexy than if it were built with foam ribs. I suspect ribs would give some additional structural strength to the chines and sides if they are thin. I also suspect ribbed floor would be more uncomfortable for the patellas of a kneeler. It also makes sense to me that the rib edges would be places that are subject to stress risers and eventual delamination or fracture.

Aesthetically, I don't think ribbed interiors look as nice as smooth floors or foam footballs.

And, finally, I'd prefer a no foam lamination over a foam lamination for any canoe other than something for the absolute lightest weight possible or racing. Your kilometerage may vary.
 
My understanding is that any place on a fiberglass canoe hull where there is a rapid transition from a very stiff area (like a rib) to a very flexible area (like a thin skin) is at risk of becoming a 'facture zone' which is prone to cracks and other failures.
Opposite of my experience and knowledge of the Souris River canoes. I wonder if their method of epoxy resins and hand laying affects this. I just know they are tough as heck. They are built for tripping and not built for racing. I think you'll find fewer failures of theirs percentage wise compared to the one piece foam rigid bottom.
 
The Odyssey was never built for a direct impact.
I have owned one for 32 years.
It hit a rock head on buried in a standing wave when we missed a portage
The diamond foam core floor fractured with seveeal perpendicular cracks and a couple of the ribs that extend from the floor did too
One alu thwart was severed by me hitting it.
The good part is that nothing on the outside cracked.
We were in Wabakimi ten days from civilization and continued the trip.
So the hull must have flexed and caused all the stress cracks
We epoxied the cracks from the inside as beat we could.
The boat is still useful but the bow slider seat jammed

It needs to go
 
The Odyssey was never built for a direct impact.
I have owned one for 32 years.
It hit a rock head on buried in a standing wave when we missed a portage.
My idea of a rock bounce and yours are quite different it appears. :)
Good to hear you weren't hurt and I'm impressed that the canoe held together enough to get you back home.
 
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And, finally, I'd prefer a no foam lamination over a foam lamination for any canoe other than something for the absolute lightest weight possible or racing.
I agree. After owning canoes with and without foam core hulls, I think I prefer the canoes without foam. It just feels like you don't have to watch out for them quite as much. But the foam floor never got in the way of my enjoyment of the canoe.
 
My idea of a rock bounce and yours are quite different it appears. :)
Good to hear you weren't hurt and I'm impressed that the canoe held together enough to get you back home.
Aand indeed it seems more flexible when empty but still we've used it for two week trips on Lake Superior
Loaded with gear its fine. Empty its 18.5 feet of maybe a bit more flex than you want
But wave $350 at me and come pick it up
That hit was early in its career and its done extended trips since. Handles the Allagash quite well in high water
 
Thanks everyone. Seems like both systems have their share of damage reports. Foam-less sounds really interesting…if the weight was alright…but I’m focusing on epoxy for now and I’m not seeing epoxy options out there with no foam at all.
 
I’d go full foam floor if I had to choose between the two. The full foam floor is a way more comfortable boat for the kids and dog to sit in but I wouldn’t take it anywhere too stressful like a fully loaded rock drag. That said my foam core Clipper Mac has seen a lot of wild rivers with very little damage, but is paddled with respect to its layup.
If I’m going somewhere super dirty, it’s in my Duraflex layup (have you checked this out?) or a plastic boat.

When you say epoxy, are you ruling out vinylester?
 
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If I’m going somewhere super dirty, it’s in my Duraflex layup (have you checked this out?) or a plastic boat.
I had a Clipper Prospector 17 in the Kevlar/Duraflex layup (no foam) and it took several good rock hits without batting an eye. Very tough layup, but it's 3.6 kg (8 lbs) heavier than the standard Kevlar layup. If I had to do it over again I would have gotten it without gelcoat, saving about 1.8 kg (4 lbs).
 
Swift has come out with the reincarnated WildFire and DragonFly
The latter is a downriver ww boat: carbon glass and Kevlar
 
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