May I take the rudder discussion in a new direction? (Sorry about that.) As background, I paddle without my rudder 95+% of the time. Would-be helpful kayakers I encounter are always pointing out to me that I've "forgotten" to lower it. Anyway, in the last several years Feathercraft and similar thin, tall surf rudders have become pretty standard, especially on single kayaks. My understanding of their advantages: 1) They submerge below surface turbulence to grip the "solid" water beneath. 2) They can retract fully onto the rear deck to avoid catching following seas when paddling, or following paddlers when portaging, or following cars when driving. 3) By being smaller, they have less drag than wider, shorter rudders. The case I've heard for wider rudders: 1) They offer more turning power for tighter turns, especially important in doubles where paddles are used more for propulsion than control. 2) They can be cranked to a greater "angle of attack" before they stall to cease being rudders and start being brakes. 3) By effectively increasing the waterline length of the hull, they create less drag than thin rudders (a direct contradiction of point 3 in the previous paragraph). I throw this out for discussion and comments (I'd be especially interested in John W's thoughts). Breathlessly awaiting being deluged by the fountain of knowledge that is PaddleWise. Philip Torrens "The opinions expressed in this posting are not necessarily those of my employer, or indeed, of any sentient being." **************************************** Mountain Equipment Co-op 1655 West 3rd Avenue, Vancouver, BC, Canada V6J 1K1 Tel: 640-732-1989 Fax: 604-731-6483 email: pid_at_mec.ca Visit our website at: http://www.mec.ca ***************************************** *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Philip wrote; (SNIP) > >Anyway, in the last several years Feathercraft and similar thin, tall surf >rudders have become pretty standard, especially on single kayaks. My >understanding of their advantages: >1) They submerge below surface turbulence to grip the "solid" water beneath. Surface effects do reduce effectiveness. I don't think turbulence is a significant problem with most sea kayaks that have fairly shallow slopes to the buttucks. The problem of air entrainment (ventilation) exists for both types and t would seem more logical to try to reduce this with baldes that have more area donw low and a ticker airfoil section (NACA 0009 is commonly used). >2) They can retract fully onto the rear deck to avoid catching following >seas when paddling, or following paddlers when portaging, or following cars >when driving. True and seems worthwhile to me. >3) By being smaller, they have less drag than wider, shorter rudders. Not sure why they are smaller. Seems to me that a low aspect ratio rudder could conceivably be smaller due to the greater turning moment generated. I think Dagger has a boat with a small low aspect ratio rudder (Sitka?) and from reports I have heard it works well. > >The case I've heard for wider rudders: >1) They offer more turning power for tighter turns, especially important in >doubles where paddles are used more for propulsion than control. Probably the case although I am puzzled by why tandems have to be so difficult to turn. >2) They can be cranked to a greater "angle of attack" before they stall to >cease being rudders and start being brakes. This depends upon the section shape and edge condition so much that I don't think it is a fair generalization. >3) By effectively increasing the waterline length of the hull, they create >less drag than thin rudders (a direct contradiction of point 3 in the >previous paragraph). Simply not true unless the rudder has unusually huge volume. I have not yet seen a rudder that had enough volume and was properly faired into the hull to do this. Even when the rudder is faired into the hull (ala Dagger) the flow around and over the edges disrupts the wavemaking. I think to get any effect one would have to have an effective seal between hull and rudder. I guess what I am saying is that ruddes on most kayaks are far from beingas good as they could be and that a propely designed rudder could serve the needs of tandem as well as solo boats. A nice simple treatment of this topic can be found in Ross Garrett's "The Symmetry of Sailing" Cheers, John Winters Redwing Designs Specialists in Human Powered Watercraft http://home.ican.net/~735769/ *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
On Thu, 2 Apr 1998, John Winters wrote: > >The case I've heard for wider rudders: > >1) They offer more turning power for tighter turns, especially important > in > >doubles where paddles are used more for propulsion than control. > > Probably the case although I am puzzled by why tandems have to be so > difficult to turn. How about the tandem doesn't tend to get leaned for carved turns and "most" pairs don't realize canoe style strokes, stationary draws and the like, would make the boat maneuverable. Could it also be both paddlers are closer to the center, negating the benefit of tandem canoeists who sit toward the ends (further from the center pivot point of the boat)? kirk waiting to be shot down ;-) *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
> >3) By effectively increasing the waterline length of the hull, they create > >less drag than thin rudders (a direct contradiction of point 3 in the > >previous paragraph). > > Simply not true unless the rudder has unusually huge volume. I have not yet > seen a rudder that had enough volume and was properly faired into the hull > to do this. Even when the rudder is faired into the hull (ala Dagger) the > flow around and over the edges disrupts the wavemaking. I think to get any > effect one would have to have an effective seal between hull and rudder. I have seen in marathons a couple of home designed/made touring kayaks where the rudder was the articulated last 50 cm or so of the stern, tapering from 10 cm to 0 cm over that lenght, and completely fair with the lines of the hull. They looked very sleek and this case would be an effective part of the LWL. The appearance paddling astern of such boats was bizarre (or maybe it was the delerium of fatigue after a day of racing), as the rudder corrections wiggled the stern and made it look as though the kayak was swimming through the water. -- jim *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
> Phillip Torrens pecked: > Anyway, in the last several years Feathercraft and similar thin, tall surf > rudders have become pretty standard, especially on single kayaks. Has anyone tried using a windsurfing fin for a rudder? If so how did it work? I had exchanged email with Alex Ferguson about this but don't know if he tried it. Before I drilled a hole in one of my windsurfing fins I thought I would check... I would love to get rid of the slab of aluminum plate pretending to be a rudder on my surf ski. kirk *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
I did have a rudder on my surfski made for me by Mark Edman from a windsurfing fin. It worked very well until the shaft broke after I had hit it on rocks a few times (the collisions bent the shaft and I weakened it by bending it back). Couldn't get him to do it again after the first one broke, and it's not the kind of work I would do myself. Of course, windsurf fins come in all shapes and sizes. ---------- > From: Kirk Olsen <kolsen_at_imagelan.com> > To: paddlewise_at_lists.intelenet.net > Subject: Re: [Paddlewise] Rudder types? > Date: Thursday, April 02, 1998 1:02 PM > > > Phillip Torrens pecked: > > Anyway, in the last several years Feathercraft and similar thin, tall surf > > rudders have become pretty standard, especially on single kayaks. > > Has anyone tried using a windsurfing fin for a rudder? If so how did it > work? I had exchanged email with Alex Ferguson about this but don't know > if he tried it. > > Before I drilled a hole in one of my windsurfing fins I thought I would > check... I would love to get rid of the slab of aluminum plate pretending > to be a rudder on my surf ski. > > kirk > *************************************************************************** > PaddleWise Paddling Mailing List > Submissions: paddlewise_at_lists.intelenet.net > Subscriptions: paddlewise-request_at_lists.intelenet.net > Website: http://www.gasp-seakayak.net/paddlewise/ > *************************************************************************** *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Kirk wrote; (SNIP) > >How about the tandem doesn't tend to get leaned for carved turns and "most" >pairs don't realize canoe style strokes, stationary draws and the like, >would make the boat maneuverable. Could it also be both paddlers are >closer to the center, negating the benefit of tandem canoeists who sit >toward the ends (further from the center pivot point of the boat)? All of the above. :-) True enough about the strokes (at least from my observation). Interestingly I know a couple who paddle freestyle canoes who have a tandem and complain about the steering. Maybe rudders destroy strokes. :-) I feel Dr. Inverbon will have a comment on this. This paddler positioning was the focus of discussion some time back. If I recall I was the only one advocating putting paddlers in the ends of the boat ALA canoe and making boats shorter ALA tandem canoe. I didn't win any converts but I did build a prototype and the response has been unanimously good. So maybe I wasn't completely off base. If it gets built (seems to be a lot of time between ideas and production here in Canada) we will see if it is worth anything. Cheers, John Winters Redwing Designs Specialists in Human Powered Watercraft http://home.ican.net/~735769/ *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
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