I have never paddled a boat with a rudder but I am considering installing one on a canoe that I will be using in a ultra marathon next year.
I guess I don’t really completely understand the mechanics of the system. When no corrections are needed does a rudder just trail neutral in the water or would the paddler have to apply peddle control one way or the other all of the time? Is there something in the system that keeps the rudder straight when the boat isn’t being corrected? Just seems like the rudder would pull one way or the other if it wasn’t trailing straight behind the boat.
I am probably asking for pretty basic information here but like I said I have never used a rudder before.
thanks John R
Kayak rudder
Since you use your foot pegs when making a kayak stroke you have to keep pressure on the other peg or you would swing the rudder with every stroke.
If I take both feet off to stretch I don’t suddenly go into a spin, so I guess if your rig was balanced the rudder would trail neutrally behind but If you edge your boat the rudder would flop over to one side if you weren’t controlling the pegs.
Kayak rudders…
always have a position available where they are fully out of the water. So the trailing rudder thing when you don’t need it is not an issue. At least in any rudder system I have ever seen.
Don’t know how or if this would translate for mounting one on a canoe.
Some thoughts
1. If you didn’t need the use of the rudder, you simply raise it, using a cord that is attached to the system
2. If you leave it deployed in the water, you would have to keep your feet on the pedals or it is liable to move one way or the other
3. Unless you are in a very narrow canoe you will need your legs spread way apart or you would have to mount
the rails on some special stand-offs to get them close enough for you to reach the pedals. In which case they will just be in your way.
As one who paddles and races both canoes and kayaks, I suggest you put a lot of serious thought in it and take a hard look a rudder systems.
One last thought which might work: Install the rudder, with out rails and pedals, and have a tiller bar come from it to under your seat, extending all the way to in front of your bended legs. Then you could operate it hands free by using your legs
jack L
design
– Last Updated: Oct-14-15 12:32 PM EST –
In theory, a rudder should stay straight behind a boat going in a straight line if the center of the blade area is behind the pivot point.
In real life, the sterns of paddlecraft wiggle from side to side, and the rudder tries to align itself with the water flow created by the sideways movement. That can make matters worse, especially if there's friction in the rudder system. You can end up with the rudder slamming back and forth if you don't have your feet on the pegs.
It's good to have an easy means of pulling the rudder out of the water or locking it on centerline when you're not using it.
Aahhh
– Last Updated: Oct-14-15 1:26 PM EST –
Never thought about using a tiller bar, that's a good idea. I had been thinking gas pedal type peddles mounted on my foot brace bar. In that way I could control the rudder with my toes while keeping the arches or heals of my feet planted on the bar. Only reason for that design is that is all I have ever seen.
I have put quite a bit of thought into the rudder. I shyed away from adding one for the race this year but after 340 miles of battling sometimes ferocious headwinds and confused currents it just seemed that the amount of energy used on corrective strokes was excessive.
After day one I started to notice that all of the boats that were using rudders,(about 50% of the 400 boats) were having an easier go of it, they were able to put all of there effort into forward movement. After day three I decided I need to look into these rudder a little closer.
I have not decided to add the rudder yet, just researching and trying to decide how difficult a build would be and how a rudder actually works.
Thanks John R
Ok
That brings up the next question. If I do a rudder I would definitely want a kick up design. I understand the pull cord pulling the rudder up but what holds the rudder down when it is deployed??? Is there a second pull cord to deploy the rudder and keep it down? Maybe in a loop with the same cord raising and lowering the mechanism??? Ouch my head is starting to hurt.
Thanks John R
Get the Smartrack rear mount rudder
Assembly but not the footbraces, fabricate footbraces attached to your canoes footbrace. Keep it simple.
Flapping
– Last Updated: Oct-14-15 2:03 PM EST –
An unrestrained rudder in a neutral position will not always stay straight. It can be subject to deflection due to wiggling and off-axis velocity, as already mentioned. However, even if everything stays in line, vortex shedding can cause flapping - it's the same phenomenon that causes flags to flap or cables to vibrate in the wind.
I have seen rudder systems in kayaks that have bungee attached between the bulkhead and the backs of the pedals so that if you take your feet off the pedals, the rudder automatically returns to center.
I would adopt this system in a race situation whether I used pedals or a tiller bar. I have a tiller on one kayak, and it can be difficult to tell when it is centered - I've added a mark showing dead center, but an auto-center feature would be a big improvement.
There were some early drag estimates on kayak rudders that have been quoted many times -- that a deployed rudder adds 10% or more to the drag of a kayak. This always seemed questionable to me, based on the wetted surface area of a rudder vs the hull. In talking to some people involved, it seemed the rudders had not been fixed during the tow-tank testing, and I'm pretty sure the high drag numbers were due to flapping, although no one knew whether it was happening -- "we never thought to look..."
drag
– Last Updated: Oct-14-15 2:42 PM EST –
I don't have any idea if 10% is a good number, but drag from a rudder is probably significant to a racer. The only thing I have to suggest this is the (smaller than usual) swing keel in my sailboat. Going downwind, when I raise the keel into the hull, I typically gain as much as ~20% in speed - as measured by GPS. Never had the GPS on board to check it on either, but I easily perceived the same thing going on when lifting the thin daggerboard on my Sunfish, and also the very thin metal blade in my other sailing dinghy. I would definitely want to be able to raise a rudder when not needed on a paddlecraft.
Ozark - I haven't paid much attention to kayak rudders, but my kick-up rudder on the sailboat has a gas strut that holds it down unless it hits something solid - or I pull the lanyard to raise it. Same thing can be done with springs or bungees. The old Sunfish dinghy used a long spring.
Keeping the rudder down
– Last Updated: Oct-14-15 5:38 PM EST –
All the systems that I have seen have a mechanism at the top to affirmatively get the rudder into the water. Exactly how firmly in terms of pressure varies by the system, but for the most part they all expect gravity to do its job.
(Later add - mine had a spring near the top as described by Jack below. I haven't seen enough of them to know if they all have springs.)
I have never persoanlly seen one that set anything holding the rudder at the bottom - all the mechanics are at the top. Otherwise it'd be pretty complicated to get it up out of the water.
Interesting points
I have a feeling there may an additional speed effect going on in sailboats, which are operating in a higher speed regime than a paddle craft.
If I flip down a rudder in any of my kayaks, I don’t feel a noticeable decrease in glide, for example. Both have fairly good airfoil cross sections which no doubt help minimize drag.
Yes
I agree that drag will be created by the rudder, especially when it is being used to make a correction. I have to think though that lots of corrective strokes also cause a big lose of forward momentum
Both in terms of the drag created by the corrective stroke its self and also because of the lose of a good solid forward stroke every time the stearn paddler has to make a corrective stroke instead.
Lots of good insights, that’s why I brought the question to this forum. Keep it coming.
John R
The Smart track rudder uses…
a spring loaded system to keep it down.
When you pull it up you just put the pull rope in a keeper cleat.
Take the rope out of the keeper and let it go, and the spring snaps the rudder down and keeps it there.
I have a love/hate relationship with them. - Sooner or later, the spring will break.
If you installed one for your race you shouldn’t have to worry about it breaking.
If you paddle thousands of miles a year, you’ll need to keep spare parts on hand
Jack L
In my opinion:
The small amount of drag from a rudder is far better than a zillion wasted correction strokes.
Ask any kayak or surf ski racer
Jack L
Yes, Snap Back To Center Rudders
Have been in use by Aussie Surf LifeSavers for at least over 25 years when I first saw them at the Molokai Kayak Race. Of course, they are mostly used in under stern rudder systems. Eliminates snaking and keeps the boat pointing straight, especially on a wave, when you put the hammer down pumping your legs. Instead of just passing through the eyelet fitting, the bungee is simply knotted off at the eyelet and pulls the rudder peddle back, so you don’t have to use your foot to center the rudder after a steering correction. Some surfskis have a cam to prevent oversteering and prevent the rudder from locking up. Now a days, I notice quite a few solo outriggers (OC-1) have snap back rudders with the bungee now located at the stern and attached to the cable flange on top of the rudder shaft.
Higher speed?
Not so much. Downwind in a slight breeze we can easily be talking about speeds in the 2-4 mph range. Lift the keel, and the acceleration is obvious and measurable by GPS. And this, with a pretty low aspect foil.
Only way to really know is to measure it. For sure, the rudder will induce drag if not centered and correction strokes may negate any advantage of leaving it up. But that’s going to be specific to the boat and rudder. Measure it and find out.
DeadLastJohnnyO, is that you?
– Last Updated: Oct-15-15 10:18 AM EST –
yes, for the mr340 a rudder is highly advisable.
I don't have one on my canoes, but I intend to add one to my solo for wave riding. In general, you have to keep your feet on the pedals and make minor corrective strokes or it will get pulled one way or the other.
One thing you could do is extend a post (a small aluminum bar or rod) towards the front of the canoe a few inches, then attach a bungee cord to it, so the rudder would be pulled straight when not under direction of the pedals.
Similarly, you could mount a V shaped bungee cord to the sides of the rudder mount and adjust where the center point is. That would also pull it back to center.
Edit: Clyde describes exactly what i was thinking of.
Whoops
…when I said speed I meant dimensionless speed, i.e. Reynolds number, occupational hazard I guess. I think you’re right that vessel specifics are likely more important than the generalities I have been talking about.
Check that other forum
Some guys that used to post here have been adding rudders to canoes and written a good amount of how-to, with photos. They don’t post here much anymore. It is posted in the canoetripping forums, so you might want to try your inquiries over there.
I’ll just say of course you want to control the rudder with your feet. A tiller isn’t going to help much unless you grow an extra arm to control it while you paddle.
~~Chip