Saw this on another website and thought it might have applicability for front steering OC-2's that tend to breakaway on the ama side: http://www.surfskimod.blogspot.com
This angle of the shaft might help counteract the tug of the ama and prevent breakaways that sometimes occur with OC-1's also?
Submitted by koacanoe on Sun, 06/06/2010 - 3:05pm
I know some guys switch out the stock swept rudder on those skis with a bigger straight rudder for more control in the surf. Interesting concept though... I don't understand the desire for a downward force on the tail -- seems like you might even want it opposite of that, a lifting force to drop you into waves easier. Trim control seems like it might be fun.
#1 Sun, 06/06/2010 - 5:56pm
I asked that question on www.surfski.info :
I understand how your rudder works. What I don't get is why you would want the rudder to create a downward force.
I may be wrong but I would have angled the shaft the other way so that the rudder woult lift the stern of the ski.
Am I missing something ?
Johan van Blerck's answer :
Dean Jordaan's answer :
I'm still not convinced...
#2 Sat, 06/19/2010 - 1:46pm
This is an interesting topic but I dont really understand it, surely increasing the downward force (if possible by the rudder) will also decrease the speed , and useable speed is everything in downwind runs.
#3 Sat, 06/19/2010 - 8:07pm
I can see this working really well downwind. When you're bombing downwind speed isn't an issue when you're using a lot of rudder angle. The only time you're mashing the rudder (and trying not to broach) is when you're running across a wave rather than straight down, to preserve positioning high on the face and avoid burying the nose into the wave in front. The situations in which you need max speed is when you're chasing fast moving bump and making connections, generally you're going pretty straight at these times. Keizo's comment about wanting some tail lift when trying to drop in is valid, but I'm never using much rudder when trying to scratch over the "make or break" point on a fast bump. I think pulling the tail downward would help a lot in the situations where the ski wants to broach.
The most difficult conditions in which to maintain control and not spin out are 1. short interval waves like the boat wakes Johan did his testing in and 2. steep waves which you find in big wind conditions or over reefs/ shallow areas. Both scenarios create a lot of tail lift. In the short interval scenario, the boat doesn't fit between crests, nose presses in, tail lifts, boat spins out. As Johan reports, the PCR rudder let him hold the boat at a greater angle to the waves' direction of travel, increasing his control. In the big windy steep stuff, the boat's rocker doesn't fit the curve of the wave. What tends to happen when chasing these bumps is you pull over the ledge, then immediately your nose is pressing into the wave face about halfway down towards the trough. If you try to minimize this mid-face pearl by angling early, your tail spins around and you broach. A PCR could help you angle down the treacherous steep upper regions by locking your tail in.
Another way to think about it in terms of boat trim: We can all agree that boats with fuller bow sections work better in steep downwind than boats with low volume noses. We tend to attribute this to what's happening at the front of the boat, but think about the entire boat's trim- when that big volume nose starts to go underwater in the steep stuff, the buoyancy pushes up hard. This is going to squat the tail down and help preserve the effectiveness of the rudder. Same idea, when guys lean back to keep the nose up, they're also leaning back to keep the tail down. Tail lift is the last thing you want when your steering angle is your limiting factor.
#4 Sat, 06/19/2010 - 10:00pm
Been reading it again and thinking about it, and I still don't get it :
when surfing runs and trying not to broach, i don't only turn the rudder but I also angle the ski to keep control. For example if the bow of the ski is going left when broaching, i use the rudder to turn right and i angle to ski to the right, as a result the rudder is presnted in the water with such an angle that it creates an upward lift.
#5 Sun, 06/20/2010 - 12:34pm
Another thing with this is the touted downward force is only effective when rudder is "on" so to speak ... You gotta run the boat straight ( rudder "off" ) or paddle in a circle.
aloha,
pog
#6 Sun, 06/20/2010 - 2:51pm
Perhaps not having a rudder would eliminate this issue.
All joking aside, I know at one point the surfing world also dabbled with the ides of raking fins forward as well. Some fins were specifically designed to angle forward, while others were near vertical, and some were just turned around in the box to see what would happen. A few people (very few) thought it worked.
The end result: it provided good debate, but in most scenarios it created poorer performance. All of that said, surfboards are a totally different animal so I could be way off base. I do know a major advancement in surfboard fin design was canting the outside fins in a thruster while foiling only the outside of the fin. This in effect creates a wing that pulls the board into the water when it is turned on rail. as any surfer knows, you loose that rail you have set in the water and you go for a swim.
So maybe as Hiro says, all you really need to do is lean the hull to tilt the fin then steer a bit to get downforce if you really want it.
#7 Sun, 06/20/2010 - 3:20pm
Following on from past surfboard designs how would flyers (small triangular fins) mounted to the side of the tail work?
#8 Sun, 06/20/2010 - 9:01pm
Hiro- just to clarify, are you saying that the bow is swinging to the left, out of control, and to correct it you lean the boat to the right? Because in my experience and everyone else I've talked to about it we do the opposite. Lean the boat to the right, bow goes left. Lean left, bow goes right. works in flat water, waves, ski, canoe (non ama side), any displacement hull.
Pog- true that you would only get a downward force when the rudder is engaged. But isn't that the only time you need it to keep the tail locked in? Going downwind, if you're going straight, you don't want any downward force since you're likely trying to pull into a bump and traveling in the same direction in the swell. Downwind you're either pulling hard and traveling straight trying to catch something or you're surfing at an angle trying to stay high on the wave face, waiting for a gap to open up that you can convert that positioning back into speed.
jc9- We already use leaning, rudder, boat trim, steering strokes, and probably other stuff I haven't figured out yet to make the boat go where we want it to. The PCR if it works as it's inventor reports, would just expand that envelope of control. Probably would be more help to us hackers than to the pros. I don't spin out too often but I certainly am limited in the lines I can take because of my ability and the limits of my equipment.
Maybe it works as claimed, maybe not, but the theory is sound. I suppose we just need to try it to become believers. Two months ago, if someone (that wasn't Keizo) claimed he could make a sub-200 pound canoe that would surf the channel like nothing ever has before it, and change what we thought was possible for non-elite paddlers to accomplish downwind, and make that canoe for the same price as a 400 pound spec canoe, we would have naysayed. But after the Pa'a race, seeing the photos, hearing the OCP mafia's pornographic stories and "best ever" claims, we are all believers. The proof is in the pudding. Let's give Johan a chance. In fact, there are probably dozens of old Mako Milleniums floating around the backyards of Hawaii with those wimpy little ineffective stock rudders. I predict someone soon will chop one up and give it a whirl. If not me probably Pog he seems like a curious guy...
#9 Sun, 06/20/2010 - 9:45pm
Hope I didnt come across as too negative. I was just applying what little knowledge I have of surfboards to boat rudders. I honestly hope it works. Could be another design evolution in the making. Might even make me go back to paddling a ruddered boat again!
Also, much thanks for just calling us non-elite. You could have said much worse and it still would have been true!
#10 Sun, 06/20/2010 - 10:16pm
"Hiro- just to clarify, are you saying that the bow is swinging to the left, out of control, and to correct it you lean the boat to the right? Because in my experience and everyone else I’ve talked to about it we do the opposite. Lean the boat to the right, bow goes left. Lean left, bow goes right. works in flat water, waves, ski, canoe (non ama side), any displacement hull"
Ergophobe, the manouvere that Hiro describes is a basic whitewater technique if it is combined with a stroke like a high telemark where you hang out over the paddle on your right side, I've done something similar in the outrigger when the ama was in danger of going under and it allowed me to lift it up and track back to the right. Footstaps would of been handy then.
#11 Mon, 06/21/2010 - 2:08am
Just try it. Then we'll know. I'd try it... if you make me a boat with a PCR on it ;)
#12 Mon, 06/21/2010 - 8:28am
Ego,
NOT denying its potential effectiveness but it still bogs the boat down.
"you’re surfing at an angle trying to stay high on the wave face" ... Right, but at some point you gotta come off the rudder and then you "might" be on a higher line or in a worse one going slower. Guess a person would have to adapt to it.
A deeper, high aspect rudder is still a great thing as it holds the boat here right to the fingernail scratching edge.
The Art of Outrigger Canoe Paddling Vol. 2 .. ..There is a good sequence talking about Karel edging the hull.
aloha,
pog
#13 Mon, 06/21/2010 - 8:35am
So with PCR there is some extra bite on the water sometime when it may be a good thing, but being stuck with the tail bogging tendency all the time is a big price.
Something really smart tech would be a variable camber rudder shaft........but that sounds a bit like a hand held canoe steerer, blade which can make use of an infinite amount of angles and settings, with feedback to boot.
#14 Tue, 06/22/2010 - 10:23am