As discussed in Jack L's recent thread, to turn quickly & tightly canoeists use a bow rudder. One can plant the blade either vertically just beside the canoe (posting, either on or off side)or, in an almost horizontal position extended well out ahead of bow paddler.(cross bow rudder)
My question is which position deflects more water & is therefore more effective ? Assume angle of deflection(# of degrees off zero) is same in both cases & ignore which is easier to set or hold.
My 1st thought was since # of square inches of blade was same in both cases, the effects would be equal. Then I envisioned an extreme scenario w/ a 10 ft x 1 inch object held rigid in an oncoming current. Seems like the effects of same would be quite different depending on whether object was positioned horizontally or vertically.
Looking for guidance from those more "physically endowed" than I. Which blade position is more efficient ?
Thanx for help.
Watch…
Watch the bow rudder move at the end of this film…
Movie of Murray and Dave running Double Trouble
http://www.huntsvillecanoeclub.org/locust0405.html
Vertical vs. horizontal isn’t the issue.
The issue is leverage. The longer the lever, the greater the torque that's created which will cause an object to be twisted against some opposing force. In this case, the opposing force is water resistance that builds up against the hull if you try to rapidly change the orientation of the boat in the water. The length of the lever arm is the distance away from the boat's center that you plant the paddle. The farther from center (in this case, the farther toward or in front of the bow) that you plant the paddle, the greater the turning/spinning force that's applied to the boat, relative to the force you must apply with the paddle (and your arms). That's also why sweep strokes work better and better as you apply them farther and farther from the pivot point of the boat, and all turning strokes in general work better if you reach farther forward or farther back (or sometimes farther out from the gunwale, which still increases the distance between the paddle and the pivot point) depending on the stroke.
Short answer: The paddle will turn the boat more effectively (and with less effort) if you reach as far ahead of the bow as you can. I remember when I was a scrawny kid in Boy Scouts, and I weighed about 70 pounds. I wasn't strong enough to steer a big old Grumman loaded with two people plus camping gear in any conventional way, but when seated in the bow, I COULD pry the bow a few feet to the side in a single stroke to avoid a "last minute" obstacle by reaching way ahead of the boat, planting the paddle diagonally across the stem and holding it there, or better still, by prying (it was then up to the stern paddler to side-slip his end of the boat to keep us from broadsiding the obstacle!). That pry stroke worked for a wimp like me partly because a pry takes less effort than a regular stroke, but also because it maximized the distance between the paddle and the pivot point.
Couldn’t get it to work
the message said it won’t work with AOL media player.
JackL
I can’t answer your questions, but
I think your words,"physically endowed" comes into play.
My wife absolutely cannot hold the onside rudder, (post) at any angle for more than a second or two, but has no trouble holding the cross bow and angling it too.
JackL
cross bow rudder v. post
Jack:
That’s endowed w/ a knowledge of physics
Guideboatguy:
Thanx lots for detailed explanation. Experience showed that cross bow was more effective than posting near the hull (&, as Jack points out, much easier to hold against force of current also)Now I understand why