Hydro dynamics. A discussion about rocker. - Mountain Buzz
 



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Old 06-01-2015   #1
 
Helena, Montana
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Hydro dynamics. A discussion about rocker.

Let me premise this discussion by stating that I am an amateur. So my impressions and experiences are of an amateur nature.
I do not want to turn this into a brand / model discussion so I’ll keep it to the design.

So I had the chance to demo two different boats last weekend. They were both very similar in tube size and diameter but one boat had a straight (flat) section on the bottom of the tubes and the other had continuous rocker. I rowed the continuous rocker the most. It seemed like the boats with a flat bottom were able to pick a line and run the big rapids with little to no effort to stay on the line they had picked. (but they were all more experienced boaters). My rockered tubes seemed to drift out of the line I picked and I had to work hard to keep it on the line I had picked (which means I had to row backward in the rapid which I didn’t want to do) . To make matters worse, when the boat would drift off line it seemed to drift toward holes and hazard in the rapids adding panic to my work. It almost seemed like I was magnetically drawn to hazards in the rapids.
Are these the views of an amateur that simply doesn’t know how to row or is there something to my impressions here? It seems like the more advanced boats have the continuous rocker but they were much more work. Or maybe there is an advantage to the rocker that I didn’t pick up. Thanks for any help.

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Old 06-01-2015   #2
 
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Belgrade, Montana
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Interesting observations. I think they're fairly accurate and that the pro is also the con (depends on the intended use, situation and experience).

I have owned both "classic" straight designs and rockered designs. I bought my new rockered boat specifically for it's ability (theoretical at the time of purchase) to move over the water with less work. I've found that the rockered hull is much more responsive, both in the spin as well as forward/backword moves. I think this response is what you noticed. The key distinction is it was specifically what I wanted! When I went looking for my new boat I wanted a boat that didn't "stick" to the water, I wanted one the slid over it. I row for fishing most of the time and I wanted an efficient back rower, that's pretty much how I row unless I'm on loaded over-nighters.

I've found the rockered hull to be an amazing tool and couldn't be happier with it for my uses. With that said it is very different. It's easy to overshoot eddy lines, seams, etc. and newbies (too it anyways) almost always do a lot of overcorrecting until they figure it out and get used to rowing it. The folks that do best with it are coming from drift boats, it moves much more like a hard boat than a rubber boat.

Why did you feel like you were pulled toward danger? My guess would be that you attribute a little too much to the boat and less to your level of experience. Experienced boaters are likely doing things you don't really notice to stay away from those hazards - often doing less is more but that takes confidence and experience to really know when to "let go" so-to-speak and let the river do the work. Some of it certainly is that as the boat is more responsive, it responds to the rivers input more too... That's the caveat - it's both easier to move and to get moved. Most folks that row mine pick it up quickly and in the end really like it.

If you get a chance to get back out into the rockered hull work hard on not over correcting, figure out how much energy you need to put in to move it where you want and how much it takes to stop it. You'll eventually find that you can keep it on line with very little work.

My guess is you were working to hard and over correcting - that was what felt like the gravitational pull of danger. Time and practice will cure that, no matter which boat design you run.
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Old 06-03-2015   #3
 
Helena, Montana
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Originally Posted by elkhaven View Post
Why did you feel like you were pulled toward danger? My guess would be that you attribute a little too much to the boat and less to your level of experience. Experienced boaters are likely doing things you don't really notice to stay away from those hazards - often doing less is more but that takes confidence and experience to really know when to "let go" so-to-speak and let the river do the work. Some of it certainly is that as the boat is more responsive, it responds to the rivers input more too... That's the caveat - it's both easier to move and to get moved. Most folks that row mine pick it up quickly and in the end really like it.

If you get a chance to get back out into the rockered hull work hard on not over correcting, figure out how much energy you need to put in to move it where you want and how much it takes to stop it. You'll eventually find that you can keep it on line with very little work.

My guess is you were working to hard and over correcting - that was what felt like the gravitational pull of danger. Time and practice will cure that, no matter which boat design you run
I'm sure I was over correcting to some degree. I ran the same run several times. The first time I was nervous as hell so it was worse, but I relaxed and tuned in a little better each time. I don't discount the newbie factor..but

Weather or not it was actually drifting towards hazards is a good question but there is no question the rockered boat was drifting off of the line I set up. I could see the difference in the boats ahead of me and the boaters behind me could see that my boat would not hold it's line as well. I think the rocker allows the boat to "surf" more so by nature it would drift from the higher parts of the river and drift or "surf" into the lower section. Not literally surf but overall effect would be the same. Maybe, I'm just theorizing here.

Also two other things your post reminded me of... the rockered boat did not move forward or back as well but would spin on a dime. I mean it would spin with almost no effort. It was good when I needed to quickly spin the boat to put the front into a large wave, but at the same time it was easily spun by the river. I did notice that it took more effort to row foreword or back so it was a lot of work to keep some foreword momentum in the rapids.

I'm not sure what to think yet. Yes I'm a newb, but there were some things I'm sure of. It was a lot of effort to build momentum and stay on line while it spun and drifed easily. I always thought the continuous rocker was a big advantage in big WW but I need to prictice more.
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Old 06-03-2015   #4
 
Bayfield, Colorado
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How was your front to rear trim. If you were trimmed back heavy even a little bit the current wants to grab the heaviest part of the boat and pull it down stream. Can you say swap ends. I have followed some really good boaters and it seems that they maintain a line with almost no effort on the sticks but when I look at their boats in a flat section they always are trimmed nose heavy. I rigged my cat that way this spring and after a few runs I dont want to ever run it ass heavy again. Part of your experience may have due to over correction, been there done that, but from my experience trim means a lot.
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Old 06-04-2015   #5
 
Helena, Montana
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It's funny you should say that. I've always set my center of gravity at the center of the boat or at least as close to center as I could get. Two weeks ago a group of VERY experienced boaters let me tag along and a few of them test boat for AIRE. It was obvious that they knew their stuff and I learned from them that all boats are supposed to have the center of gravity JUST BARELY to the front of center. In the rockered experience mentioned, I was trimmed just barely foreward of center and always will be from now on. It's funny that I've never heard that before but now I know.
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Old 06-04-2015   #6
 
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Hi

In addtion to how rocker effects the handling, there may be another issue going on here....

It has been my experience that the boat often tends to go where the eye is looking......by this I mean, if you look at that rock, instead of the path around, you hit tend to hit the rock....

Being somewhat new to this game, this may be an issue for you.

Scott
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Old 06-04-2015   #7
 
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Originally Posted by elkhaven View Post
.... My guess would be that you attribute a little too much to the boat and less to your level of experience. Experienced boaters are likely doing things you don't really notice to stay away from those hazards - often doing less is more but that takes confidence and experience to really know when to "let go" so-to-speak and let the river do the work. Some of it certainly is that as the boat is more responsive, it responds to the rivers input more too... That's the caveat - it's both easier to move and to get moved. Most folks that row mine pick it up quickly and in the end really like it.

[deleted for brevity]

My guess is you were working to hard and over correcting - that was what felt like the gravitational pull of danger. Time and practice will cure that, no matter which boat design you run.

I think elkhaven probably hit the nail on the head with these statements.


When I first started out piloting my own raft I could not keep up with my Uncle in his aire jag at all. I felt like I would hit all the lines the same and eventually just attributed it to the difference in boats (mine is a roundboat, his a cat).


As I continued growing and learning I started noticing small little subtleties in his technique and small differences in the lines, slightly different angle of approach, the orientation of his boat while dropping in or even just being a few inches one side or the other. These small diferences in boatmanship make a big differences in performance. Now Keeping up is no issue at all...in fact If I really exploit my raft's handling strengths, I have to wait on him!


I have a friend now, new on the oars and raft but has been on the river his whole life otherwise. He's got great instincts but it's the subtleties he's missing out on when he comes off line and bumps a rock. It's hard to explain to him but you kinda start percieving the minutia of a specific current and you learn how to exploit that in your favor.


Watching someone it's hard to percieve, it my just be a dip of the oarblade for a second or the position of the bow while entering a rapid. You'll learn as you go and eventually you'll likely develop a preference.
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Old 06-04-2015   #8
 
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Well said 2Kanzam. The set up angles, feathered strokes, using pillows above and adjacent to rocks, current breaks, etc are so hard to see other folks use, even if you're in the boat with them. My suspicion is most folks do a lot subconciosly and don't really realize how much they actually use the river.

I found that in the wind I can "auto ferry" my boat all the way across the river simply by setting an angle and holding an oar in the water to maintain the angle. The other day in a downstream wind (they do happen, occasionally) I ferried back and forth across the lower Madison 4 times without ever taking a stroke. Mind you they took some distance to accomplish but the difference directions of the two forces acted just like me rowing. It works in up river winds too.
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