Ribs vs. Foam Core Floor

[scoutergriz]

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 actually find the opposite is true, I've seen far too many ribbed canoes crack right at the rib when hitting a rock because the hull between the ribs can flex more than the rib itself creating a pattern of weak or flexible spots between the ribs, while the ribs themselves are stronger and more rigid.
foamcore boats tend to have consistent strength and flexibility throughout- while they may scratch or gouge more, I find them hard to actually puncture the hull because that rock doesn't eventually hit a more rigid spot.

 

[Mason]

I actually find the opposite is true, I've seen far too many ribbed canoes crack right at the rib when hitting a rock because the hull between the ribs can flex more than the rib itself creating a pattern of weak or flexible spots between the ribs, while the ribs themselves are stronger and more rigid.
foamcore boats tend to have consistent strength and flexibility throughout- while they may scratch or gouge more, I find them hard to actually puncture the hull because that rock doesn't eventually hit a more rigid spot.

I can see your point, especially as I had a cracked rib in my Clipper. Wenonah marketed the cross rib layup as an intermediate between their whitewater-directed center rib and their foam core, with the stated goal of providing a more durable build than the foam core, while providing a less expensive option that weighed more. Personally, if I were to go with a rough-use boat, I'd avoid both ribs and foam cores. With my center rib solo, I've subjected it to a lot of rough use, and apart from dropping it on concrete from head height, it has held up well, though with a lot of spider cracking on its gel coat. But then it's also 40 years old, and I've paddled rocky Class III in it (you can hear the gel coat cracking as you slide over rocks!). If you're not dragging your boat or barreling into rocks, any of the layups should work (if made by a reputable manufacturer).

 

[billconner]

Curious if the ribs you speak of are like these in the Souris River canoes.

 

[Mason]

Curious if the ribs you speak of are like these in the Souris River canoes.

Pretty much. Hellman and Clipper in BC do the same thing. Looks like Wenonah dropped them.

 

[Jim Dodd]

If you are hand laying up a hull ? Getting the foam to take the shape of the hull ? Will be the biggest challenge. A vacuum bag system would be great. If you can accomplish that ? That would be my choice.

Ribs would be easier to fit, but I don't like how the full hull, isn't supported equally. I've seen from the bottom sides of hulls with ribs alone. The wear pattern is obviously different.

I chose Cedar strips, 1/8" thick, for most of my four composites. Actually my first was 1/4" thick. I soon discovered that was over kill.

I laid up a White water hull, for a friend. It ended up being quite expensive, using several layers of cloth, including Kevlar, S-glass, and a football of Carbon.
My latest has Kevlar and S-glass with a Cedar insert and partials in the stress areas,

There are a lot of options out there.

How you plan to use the hull will be a big factor.

 

[PaddleTime]

When you say epoxy, are you ruling out vinylester?

At this point I think so. Leaning that way as while I don’t feel great about the composition of either epoxy or vinylester, from what I’ve gathered so far it seems like there are some safer options out there in epoxy (when cured), compared to vinylester.

@Jim Dodd I wouldn’t be hand laying the hull (if I already had the mold ready I probably would give it a go!) but the manufacturer would be if I go that direction. But no vacuum bagging option. Mostly lakes or channels between lakes and maybe class 1 on some slow rivers. No intentional whitewater. BWCA-like or fishing on lakes mostly. That’s a nice looking canoe!

 

[stripperguy]

Not sure how I missed this discussion
Here’s a mostly finished composite with both full foam football and foam ribs.
How strong is it? Dunno, but I’ll find out this paddling season when I get it finished and in the water.
I can say this, the next one will be full foam core, sheer to sheer and bow to stern.

 

[stripperguy]

Was looking for this pic yesterday, this shows the football and ribs before they were stuck in place and glassed over.
Yeah, glass, 6 oz and the resin was pigmented black