Fin/ Skegs opinions

Anyone who has serious knowledge about fin/ skeg design and its relation to oc-1 performance, please post your expertise, all sacrcastic people, please spare me, mahalo.

Submitted by aaronlabuguen on Thu, 11/01/2007 - 8:51pm



That's almost exactly like saying, "Give me the most sarcastic answers you can. Please."


#1 Fri, 11/02/2007 - 4:58am


Don't know of any OC-1 with a skeg or a fin, but they do have rudders. I'd say contact any boat builder. Maybe contact Huki. They offer a wide variety of rudders with their boats, so maybe they know something. By the way, the sarcasm comment hurt my feelings.


#2 Fri, 11/02/2007 - 7:02am


I work with a guy that makes rudders for various canoes. What type of boat is it and are you looking for a flatwater rudder that won't catch any kelp or are you looking for a surf rudder.


#3 Fri, 11/02/2007 - 9:23am


I'm with Goto. Thats like saying "don't think of a naked fat guy eating a hot dog." First thing that comes to mind is a naked fat guy eating a hot dog. My hot dog...

I don't see how a rudder can improve/inhibit performance all that much. In my mind the only thing to consider is length. If its flat water, get the smallest rudder you can, in big surf you might want a longer rudder when your boat is teetering on waves.

Take steriods instead. That will definitely improve your paddling skill.

poops


#4 Fri, 11/02/2007 - 10:19am


From using various rudders on boats theres 2 main things that I can think of that affect the boat. How much kelp you can catch with the rudder and how much control you have in the surf. Swept back rudders don't catch much kelp kelp but suck in big surf. Straighter longer rudders give you more control in the surf but catch every piece of kelp that you go near. In smaller surf a swept back rudder usually works fine. It ultimately comes down to the paddler as it always does. If you can read swells etc and can surf well a swept back rudder isn't going to hinder you that much.


#5 Fri, 11/02/2007 - 10:50am


Poopoo, you have said some bad things in the past, but making a visual about a naked fat guy eating your hot dog?!!! That is just wrong.

Now to make a point, I think you are all kidding yourselves to think rudder design makes little difference in boat performance, It is obvious surfing you need a good long dagger style rudder to hold the water, and around kelp you need something that sheds, However a good design that is wide at the entry is going to slow you down. or if the release is not clean it will create drag. Imagine a 2x4 and drag it through the water. Now reshape that same 2x4 with a rounded leading edge and a feathered tail, It will move easier through the water. Now look at sail boats, There keel acts in many ways like our rudder, If it made little difference of how an object protruding into the water beneeth a hull, why is there so much secrecy and money put into the designs.
My prediction is the next biggest improvement in OC-1 design will be in the rudders. Could it be that the sucess of the Hurricane is not in the hull but the rudder design. Look at how clean and thin the design is compared to just about any other canoe.


#6 Fri, 11/02/2007 - 7:47pm


I agree with you ocean, the shape of a keel is very important. But the rudder to boat size ratio is much much smaller on a oneman. The shape is negligible. I mean you can't use a block of wood as a rudder but I think a rudder thats shaped a little bit different than another is not going to make a difference. Not enough to fret over at least.


#7 Fri, 11/02/2007 - 10:13pm


Au contraire, monsieur Poopoo!

I paddled two different one-mans during time trials this year: A Hurricane w/it's sleek, high-aspect surfing rudder, and a Viper w/a fatter, blob shaped rudder.

The Hurricane was faster HANDS DOWN, than the Viper because of that sweet-a$$ rudder!
Please don't try to tell my coach that the rudders had nothing to do with it - I think he gave me a break on the days I was in the Viper... (probably because of that dang rudder!)


#8 Sat, 11/03/2007 - 2:57pm


OK goto you got me on this one. You have SCIENTFIC FACT to support that a fatter blob-like rudder makes you slower. You have made me change my mind on this issue....

I'm super duper sure that its true because the viper should have been way faster than the hurricane.

BTW your a frickin man for doing a time trial in a viper.


#9 Sat, 11/03/2007 - 3:20pm


The rudder is to the canoe what the fin/skeg is to the surfboard. It is very important. For more on fin theory check out this site www.swaylocks.com and do a search on fin theory.
Im located in SoCal and have been bulding custom rudders for many years. Thay are all custom foiled, balsa cored, carbon skinned rudders with stainless shafts. Email me if interested.


#10 Fri, 11/09/2007 - 7:49pm


Way to segue from a meaningful post to a business add.

On another thought.

Surfboards are a bit different in that the fins are relied upon much more to create momentum, thrust, and turns via the rider shifting their body weight or pumping their legs. The difference between a potato chip 6'3" surfboard and a 20 foot long 25 pound boat that is driven by a paddle and not wave energy, is like comparing apples and oranges. This doesn't even take into consideration the ratio of fin surface area to wetted area of the hull. Perhaps tangerines and coxswains would be a better example.

Also, tons of the information on Swaylocks is interesting. But most of the studies quoted on there are testing fin actions in WIND tunnels. Although this can give a general idea of a fins interaction in a given medium, it by no means translates directly to water, which is many times more dense than air.

Unfortunately i do not own a wind tunnel for testing. So you won't be able to rent it out.


#11 Fri, 11/09/2007 - 8:17pm


DAMN! Look at the big brain on jc9_0!


#12 Fri, 11/09/2007 - 8:20pm


If you're strictly looking at drag as the parameter to optimize, you can pretty much consider the rudder as half an airplane wing. That being the case, induced drag (ie drag caused when you turn) is inversely proportional to the aspect ratio -- which basically means, the longer and skinner the better. Obviously there is a practical limit to this since a 4 foot long 1/2 inch wide rudder might not be so great.

It's also good to make a profile that creates an elliptic lift distribution. And you want to pick a good symmetrical foil.


#13 Fri, 11/09/2007 - 10:00pm


at last someone who knows what they are talking about. i just speak from my ass anyway...

all hail to RPI!!!!


#14 Fri, 11/09/2007 - 10:08pm


jc9_0, I have no idea where you get youre info, but swaylocks is primarily homebuilders (thats not to say they arent experts). The idea that most fins are tested in wind tunnels is so absurd and such an ignorant statement you discredit yourself completely. For the record, I dont know of one fin manufacturer that would be stupid enough to test in a wind tunnel. Even a low speed wind tunnel moves air at 30+ miles per hour.....well beyond the speed of a surfboard. The reason a surfboard fin is a good example has to do with foil design, leading edge, aspect ration ( as mentioned by kiezo), flex, and other concepts that are there for your education if you get to the humble point of wanting to be knowledgable as opposed to controversial. Incidently, a rudder is just a fin when its in its neutral position. Therefore its desirable for it to be efficient as such. The trick is to create a "fin" that aslo acts as a steering mechanism without hindering the canoe. As mentioned before, this depends on the water conditions in which you paddle. Performance oriented board surfers are constantly tinkering with fin assemblies. As Oceanohana said, rudder design may be the next big performance breakthrough in OC1. The ability to change the location of rudder placement would be killer. Listen up builders!!!


#15 Sat, 11/10/2007 - 7:11am


Just use a rudderless boat. Then all problems of drag are solved and boat builders have no worries about rudder placement.


#16 Sat, 11/10/2007 - 8:03am


If someone would start building a frickin' rudderless boat, (besides Tiger's Teva Nui - what are there about 12 of those in the entire country?) then I would DEFINITELY start paddling one.

...anyone? ...anyone? Hello?


#17 Sat, 11/10/2007 - 8:35am


Most fins probably aren't tested in a wind tunnel, but data gathered from one could actually be made applicable to our application. What you look for to get valid data between testing and the real world is flow similarity, or mostly that the flows have similar Reynolds numbers. The viscosity and density is different between air and water, but by running the wind tunnel faster you could probably get a pretty similar Reynolds numbers. And I think at whatever speed that would be, the effects of compressibility of air would still be negligible -- which is great since we don't have that issue with water.

Also with regards to sweep mentioned further up the thread, a small sweep angle is probably a good thing and will probably fix any vibration issues. A large sweep will lower the lift slope, so you will need to turn the rudder more (creating lots more drag) to get the same amount of turning ability as before. If you need a visual for this, think about how a concord or the space shuttle lands -- they have a huge angle of attack to get the necessary lift and thus much more drag than a traditional plane at those speeds.

...but really, Kelly kind of has a good point.


#18 Sat, 11/10/2007 - 8:47am


Goto, the reason why you're faster on the Hurricane is because it's a much more forgiving craft for those w/ innefficient technique-just ask Kev. Maybe you two could compare top arm wave while you're at it.


#19 Sat, 11/10/2007 - 9:00am


So, I checked out swaylocks.com - pretty interesting. Didn't really find anything saying that people were testing, or NOT testing in wind tunnels.
Now, I'm not a rudder-maker, or boat-builder, or surfboard shaper, or wind tunnel operator, but if I were, I would advertise my business by contacting Keizo keizo@ocpaddler.com and helping him support this site, and not by posting for free on the forum.
You're probably wondering what I AM then. I am a professional observer. Yes, I observe things professionally. And when it comes to rudders, what I have observed is that one-man rudders don't really look like "fins". They look like - crazy enough - boat rudders.
When I first read aquafiend65's post about the rudder being a fin that should have the appropriate properties to turn your boat, that seemed to make sense to me. But, after thinking about it, I realized that of all the rudders I've tried, the best ones are the straight up and down ones, (rudder-shaped) and the crappiest are the ones all swept-back and fin-like. Even the tiny little flat-water "weedless" type suck. They're only good because you hardly need them. They can't turn worth a poop.
Then I remembered watching Luke's video here http://www.ocpaddler.com/2007video and at about 2:36-3:30 when you can see his whole body, (calm down ladies) watch how often he's pressing those pedals. It's obvious that the rudder's primary job is turning/control, not just being a "fin". The thing is actuated way more than it is neutral. So, now aquafiend's post does NOT make sense to me.
Aquafiend65, you have discredited yourself completely.


#20 Sat, 11/10/2007 - 9:20am


my apologies for the link to the tunnel tests being dead.

http://www.swaylocks.com/forum/gforum.cgi?do=post_view_flat;post=333000;...

Three things I've learned.

First. Live and learn, never speak your mind lest you be personally chopped down. Never use words like "most" or "never" in a conversation. (yes there is a contradiction there)

Secondly, dang, I need to be certified to fix carbon fiber boats... then there would only be two people in the whole world qualified to fix boats. (got to do my research, this is assuming no one else has gotten certified to fix boats)

Third. I'm up to my ears in all the lines of credit I've been issued since I bought my house. If anyone would like to take some of my credit for real cheap, PM me and we can work something out. (yes I know credit is different than debt)


#21 Sat, 11/10/2007 - 11:13am


Oh ye of little faith. Goto, nobody said all fins are swept back. It doesnt take a genius....does it?.....to see a rudder is a pivoting fin or a fin is a fixed rudder. If y'all would like to know more about the hydroynamics of fin/rudder foils, leading edges and such check out halcyon and blakestah's postings on swaylocks. Pure genius. The fact is that surfboards, and more recently sailboards, have a long history of fin evolution. You can ignore it if you like but I can assure you there is much knowledge there for the Outrigger builder/paddler. Check the last link.....just a fraction of what has been learned and concieved for surfboards. There will be a time when a paddler has a plethora of fins.

http://www.trueames.com/wind.html

http://www.finworksfins.com/wing.htm

http://www.finworksfins.com/waveBlade.htm

http://www.finworksfins.com/finCare.htm

http://www.hollowsurfboards.com/fins.htm (bottom section talks theory)

http://www.trueames.com/surf.html


#22 Sat, 11/10/2007 - 11:54am


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