Sideslipping Physics

Several weeks ago we had a weathercocking thread, which begat links to the peripatetic pivot point, which begat a monster thread on paddle physics, which begat deletions, which begat much heat and a few photons of light.

At the end of that thread there were posts on sideslipping that got me thinking. OK, confused.

One poster asked whether the movement of the lateral center of resistance accounts for a sideslip where you place the blade ahead of you and then have to slice-draw it backwards toward your body position as the canoe slows. That sounded right to me in terms of my sideslipping technique in flatwater current and in terms of moving LCOR theory.

Then, a couple of other posters said that a sideslip is executed by a static blade placement next to the hip with an open-angled blade face, which you then move forward when the boat slows. That also sounded right to me, as that is how I would sideslip in whitewater when Tablesaw Rock suddenly pops up 20 feet ahead of the bow.

This all now seemed somewhat contradictory to me.

The next time I was on the water I was at the Adirondack Freestyle Symposium, and I watched how the instructors sideslipped. They used the static blade at the hip technique. Some used a vertical paddle right near the gunwale; others used a vertical paddle held at arm’s length. They would go into prolonged sideslipping glides.

Still somewhat puzzled, I found myself on glass one evening in my Lotus Caper, so I could observe my water trails. Yes, I could sideslip like the instructors. But I could also sideslip with the forward paddle placement, slice-drawing diagonally backwards to my hip. Then, I could continue the sideslip glide with an open-faced static paddle at my hip, squeezing out some last forward glide by moving the open-faced paddle slightly forward.

My tentative conclusion is that the static blade placement at the hip generates a sideways force vector but also a slowing down force vector, which is why I instinctively use it when sudden rocks appear in front of me in whitewater. However, in general, I naturally tend not to take strokes that slow the boat (reverse sweeps, wedges, jams, open face rudders) when in flatwater and most of the time in whitewater, too.

Hence, I think the forward placed draw sideslip slows the boat less because the blade remains parallel to the current as it is drawn diagonally back to the hip. The sideslip is effected by the drawing force of the parallel blade, rather than the ruddering force of the static hip placement. However, the draw sideslip can’t be prolonged once you have drawn back to your hip, which doesn’t take long.

To the extent anyone cares, does any of this make sense?

Even if I am correct about the dynamics of these two sideslipping moves, I can’t explain them in terms of the moving lateral center of resistance. However, as I recall, carldelo is seeking a grant from the Naval Warfare Lab to write a book that clears up all the slithy toves of this canoeing jabberwocky while we, in ignorant bliss, gyre and gimble in the wabe. .

Being quite old-fashioned and positively over-the-hill, I use side-slips in whitewater all the time utilizing (on the onside) a static or “hanging draw” at the hip. I welcome the small loss in momentum because any time I am side-slipping it gives me more time to move laterally to avoid whatever it is I want to avoid.

In this instance, one does have to bring the blade forward parallel to the keel line of the boat as it slows to avoid yawing. I can’t explain why this is so, but I know it to be so, having done it thousands of times.

It sounds like the other technique that you are describing is an active stroke which is a combination of a diagonal draw and a “pitch” stroke done at or forward of the pivot point.

Lotus Caper has a much different
inwater hull shape. than probably all of the other boats at AFS.

That elongated center section is probably less sensitive to paddle placement. Most people in a more traditional shape canoe get an unwanted static bow draw wnen placing the paddle too far forward.

When you do a forward on side slide slip to your paddle is the point that the paddle is equidistant from the curve back to the stems forward of your hips? It seems that that middle point would be optimum but as my recall of the seat was limited to “wow an elegant slider” I cant comment further.

We try to remember to tell learners that they have to fiddle with their own boat since no two are really alike. There are different “sweet” spots.

Yes as the momentum is dribbled from the sideslip I find I have to move it forward too…

However on my second glass of wine…I am too fuzzy brained to think more about this…:slight_smile:

2 types
Glen you might have been seeing two different types of sideslips among several. One is done at arms length away from the hull, about at the hip, open angle, and is known as an “onside sideslip” because it moves the hull to the onside. Another type which you seem to describe is an “offside sideslip” in which the blade is placed more forward against the hull and at a closed angle of attack. This as one might surmise moves the hull to the offside. All sideslips require placing the blade in an exact “sweet spot” which is a learned placement as it can vary with speed, payload, trim, etc.BTW sideslips can be somewhat extended by moving the blade forward or back as momentum slows. HTH. BTW there are forward onside SS, forward offside ss, reverse onside ss, reverse offside ss, cross bow onside ss, cross bow offside ss, ad infinitum, get the picture?


my take
Never been in a canoe, but do side slips in a kayak.

You are correct to observe that there are two force vectors - one is slowing you down, other is moving your boat sideways. Since you paddle is not on axis of boat you will also have torque created by slowing force.

So - you move sideways, slow down and yaw at the same time. LCOR is a function of speed, it will change its location as you slow down as well, you will have to adjust paddle placement to compensate.

Anyways - distance of paddle from the boat - key to efficient maneuver is vertical blade - force projections, again. I notice that in my boat the closer paddle is to the boat, the more vertical it becomes, or rather it is easier to make paddle vertical if I place it closer to the boat. Further away - paddle blade is more off the vertical. Additionally, if the paddle blade is further away, there will be more torque causing yaw, for which you have to compensate further slowing down.

Now, how much you actually gain from placing blade close to the hull is a mystery to me :wink:

Also, some people vary angle of attack of blade depending on speed, usually opening the blade up as they slow down; but that depends quite a bit of purpose of maneuver.

Close is Vertical

– Last Updated: Jul-29-09 11:58 AM EST –

The reason for planting drawing, ~ behind hip, and prying, ~ at knee, sideslips close to the boat is, that we can have a vertical paddleshaft.

This eliminates diagonal flow off the paddleblade and makes the placement consistently repeatable. Diagonal paddleshafts require monkeying around to find the precise placement, which usually means we're torquing the paddlecraft and scrubbing off speed.

Canoe voodoo
I don’t understand these ‘canoe’ objects of which you speak - I’ll assume they’re similar to kayaks. And I can neither confirm nor deny any gray funding that may or may not be in place for small-craft, stealth-based, non-powered maneuvering studies.

Seriously, your analysis of the two different draw strokes seems correct. The static canted blade obviously gives a direct drag component due to its orientation, so will cause deceleration. The parallel blade drawn to the boat minimizes drag, but is less effective due to the short stroke length. All of this is independent of where the COLR happens to be.

More stuff

– Last Updated: Jul-29-09 5:52 PM EST –

Canoes are paddlecraft for those with beautiful knees, not seen much anymore as the overuse of high fructose corn syrup has introduced a genetic mutation towards ugly knees that must be decked over for public decency.

Sideslips, prying and drawing are static paddle blade placements that move the hull diagonally through the water without yaw. Except...

OK, a small initiation, a little draw before a drawing sideslip or a little pushaway before a prying sideslip will yield more diagonal movement. Boats need to be told where they're going next.

So will lifting the side of opposition by heeling away from the hull movement, but heeling, [improperly "edging" for those with compromised patellas], complicate exact blade placement and probably change the Rotational Center / Loci Of All Forces / whatever we're calling it today.

Interestingly, straight keeled hulls sideslip more easily than highly rockered ones - they require less precision in blade placement. And heeling, as above not only lets water flow diagonally under the hull more easily but also increases effective rocker.

So it goes

Speaking of sideslipping…
Over the 4th of July weekend I had the pleasure of escorting Arkay, his bride and daughter down the Middle Yough. FWalburg (Frank) was along as well. Neither Barb nor April had paddled a lick of whitewater, but were both skilled at showboating…errr…freestyle paddling. I assured them that balance and boat control would get them through Class II WW, and sure enough they both finished the run high and dry with smiles on their faces. At the takeout I was tickled to see April scull and sideslip her solo canoe over to the bank. Just like downtown.


Ah, so it’s not just me.
Thanks Charlie. As much as I love the way my Supernova maneuvers, it does seem more sluggish than my other boats when it comes to side-slipping. I wasn’t sure if it was due to the boat being so much heavier than my others, or perhaps the fact that the center of the hull sits deeper in the water, or something else related to rocker. Anyway, now I know I’m not imaginining things.