Carbon paddle strong enough for reentry?

I was wondering if there is any danger to a carbon paddle used under the deck bungies with a paddle float for reentry. For example, what if a forceful wave hit you broadside on the nonpaddle side? Wouldn’t that put a lot of pressure on the paddle, in addition to your body weight?

How does the strength of plastic, fiberglass, and carbon shafts compare?

Strength per se I would not worry about

– Last Updated: Jul-07-13 12:21 PM EST –

You can put far more stress on the paddle with a single, very strong stroke than that which is needed to push a paddle float below the surface. Among my Flickr photos is a shot of me putting a very noticeable curve into the shaft of a very stiff wooden canoe paddle, but I'd have no fear whatsoever of doing that exact same stroke in the same conditions with something like an ultra-light Zaveral. In the situation you describe, it's surely not the flexural strength of the paddle that you need to worry about, but perhaps you need to worry about whether the shaft can tolerate force being applied to a very tiny point of contact, where pushed against the hull of your boat (sort of like what happens if you let the screen door slam shut on a fishing pole - it is a completely different form of "strength" than what the nature of your question implies). Others here are bound to have some insight on this, but I can't imagine how the force applied to the paddle as a whole could be a problem, since the force will be limited to what the paddle float can apply from its end, and that's not all that much. Yes, the two opposing forces (boat hull and perimeter line) creating the lever action that pushes the float down are much closer together than your hands are when you put the paddle under the same kind of stress while paddling, but I doubt that that alone is enough to endanger the the shaft. Further, "getting hit by a wave" shouldn't put much torque on the boat. The boat-paddlefloat combination will just tilt as the wave goes by, but the forces shouldn't be affected much.

I have broken carbon and fiberglass
In my opinion composite paddles by their lightweight nature can be broken, that is why I always carry a spare. Having said that they are tougher than you would think and would probably be ok in most any re-entry situation. My wife uses a thinner diameter shaft paddle that seems very flexable (breakable) and she has never broken a paddle shaft.

On every occasion I have damaged a paddle I have done something stupid, usually involving rocks or other immovable objects.

Light weight paddles make any trip more enjoyable, I would not think of using a “bulletproof” paddle that is unbreakable, but heavy.

Buoyancy of paddle float
My paddle float has an air chamber on each side. It feels very buoyant, very hard to submerge, meaning it offers more resistance to the paddle, no?>

Paddle on shore entry
Apparently I’m not the only person who never places my paddle on the shore to stabilize the kayak for entry. I’ve heard of people breaking paddles doing this. That’s basically the same position as during reentry, except that the shore offers more resistance than a paddle float.

You can break them all
By putting too much weight on the middle of the paddle. The paddle float isn’t for supporting your body weight, the kayak does that, the paddle float is for providing one direction you can balance the kayak with 90% of your weight ON THE KAYAK.

There is nothing wrong
With using your paddle to stabilize onto the shore, the problem is using the paddle shaft as though it was the shore. Stabilizing is not the same thing as putting all your weight into the shaft.

With carbon paddles laid up with the
usual tubular weave matrix, another danger besides just totally exceeding the breaking strength, is that the resined matrix will be chipped or worn locally. Such local damage can make the shaft much more likely to break. It is a good idea to inspect carbon shafts for wear or knicks that interrupt the matrix. Such damage can be repaired.

Carbon matrix shafts should not be used for boarding, rubbed along gunwales or seam lines, etc., so that the matrix is not damaged in the first place. Resting a carbon shaft kayak paddle over a boat to re board is normally safe, because contact with the hull will not occur in one sharp, hard zone.

I protect the carbon shafts on my canoe paddles by having the paddle maker put 18 inches of shrink-down vinyl tubing over the most vulnerable zone. I don’t think that strategy is useful for kayak paddles.

More resistance than WHAT?

– Last Updated: Jul-07-13 5:39 PM EST –

I'm trying to approach this from an analytical perspective, and am attempting to see some relationship between the amount of force that can be applied to the paddle blade during abrupt maneuvers and that needed to simply submerge a paddle float. The mere fact that your float has two air chambers doesn't provide useful information because that's not quantitative. What one would need to know is how many pounds of force it takes to submerge the float. Just for the heck of it, I looked for the photo I was referring to...

... and then tried to estimate how much force it takes to bend that particular paddle that amount with the help of a spring scale. It looks like the force applied to the blade (I attached the scale to the center of the blade to give an overall average) was at least 20 pounds, and quite likely 25 or a little more. Certainly an ultra-light paddle could tolerate this much stress too and still have something in reserve (if it didn't, it'd be too easy to break during normal use, not just during abuse).

Anyway, as I mentioned, the whole stress-comparison issue is made more complicated by the fact that the points of force application on the shaft of the paddle are closer together when using a paddle float than when paddling, and the shaft length between the blade and the nearest point of force application to the shaft is much greater. So the best one can do is get a rough feel for comparing the two situations. That said, paying attention to those actual points of force application brings up another reason to doubt that the paddle shaft is stressed much. You see, holding a lever down by means of a tight line stretched horizontally across it is about the most inefficient method possible, and I think on a lot of boats you'd pry loose the perimeter-line anchors if you held the boat solidly while applying an upward (buoyant) force on the blade of 20 or 25 pounds (bear in mind that this is exactly the same, in terms of forces applied, as if the boat were tipped forcibly enough, with the paddle attached, that 20 or 25 pounds of flotation attached to the blade are pushed beneath the surface). I'm just being logical about this again, because this would result in hundreds of pounds of "lift" on the perimeter line and its anchors, and the resulting tension in the line would be several times greater still. I just don't believe these kinds of stresses occur during paddle-float use, and since I DO believe what I said before, that the boat won't undergo a strong twisting action simply due to being hit by a wave, I'm not coming up with any reason at all to expect what you do (if the boat did twist the way you imply, who'd have a strong enough brace to keep themselves upright in such conditions in the first place? In actual fact, when people brace it's because they have tilted beyond their natural balance point and they need to push themselves upright again lest they fall over the rest of the way, NOT because the boat itself is undergoing a strong twisting force that must be resisted).

That's a whole lot of talk, but it's an attempt to apply a logical method of looking at what the forces could be, and where are they would be applied. When I do that, I just can't imagine a way that the forces or stresses could end up being all that great.

More resistance than a single chamber
Thanks for your analysis. I was thinking of a twisting motion from a wave, but simply more downward pressure on the paddle.