# Diminshing vs Standard raft tubes



## nicho (Mar 18, 2009)

Deciding between diminishing tubes and standard tubes. Looking at two boats by NRS the E-160 and the E-161 Nez Perce. The latter has tubes that go from 21.5" to 18" at the bow and stern. NRS advertises that the diminishing tubes allow for "better visibility increased gear capacity and wave punching power." The E-160 has 22" tubes all the way around and is 5" wider at 7'7" compared to the Nez Perce at 7'2". Any pros/cons/experiences/info on the two styles to assist in the decision is appreciated.


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## synergyboater (Jan 5, 2008)

I have an Aire 156D which is primarily used as an oar boat on multiday trips. I picked up a small amount of room, but I also have a wetter ride. Overall, I prefer how diminishing tubes handle compared to standard. I feel that diminishing tubes are a bit quicker in relation to your pivot point, but at the end of the day I don't feel there is a huge difference. Marc


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## brandob9 (Jun 13, 2010)

I haven't had the opportunity to compare the two, but I will tell you that the E-160 that I have is a fairly dry ride with its 32" of kick. I'm sure that the E-161 will allow more water over the bow. I'll leave it to your judgement as to whether that is a good or bad thing. 

One that I have found that I really like with the E-160 is the ability to store nearly everything between the tubes. There is just so much cargo room beneath the hatches! The end result is that the boat comes out looking long and lean with a clean deck. 

The attached photo is from a lower salmon trip supporting 5 kayakers out of my boat, powering a few abnormal things: the bag on the bow I placed there to break waves, the kayak behind the cooler and the full everything bag. The young lady rowing doesn't come with the boat either - my own couldn't make this trip. 

_The bow is riding low here due to the 25gal of kegged beer under my butt!_


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## The Mogur (Mar 1, 2010)

I have rowed several thousand miles in the original Riken Cheyenne. My raft was the prototype, hand made for Dan Baxter and Vladimir Kovalik who originally came up with the tapered-tube design back in the mid-1980s.

This very raft was featured on the cover of the Jan/Feb 1986 issue of River Runner Magazine, and the accompanying article says that the "diminishing tube design allows for significantly more interior space and . . . helps the boat slice through waves rather than stalling on top of them." The article also quotes Kovalik saying that the raft looks like a fat inflatable kayak, and explains the pointed ends this way: "In a reversal, the more pointed the boat, the better it punches through the wave." 










The design was a direct outgrowth of the relatively new self-bailing raft idea, in that the tapered tubes would allow a lot more water to break over the front of the raft, and such a thing would be imponderable in a bucket boat. On my raft, the tubes tapered from 22 inches on the sides, down to 9 inches at the ends. The first production Cheyennes tapered only to 11 inches, and because the public thought even that was too radical, the dimension was increased again, to 15 inches, which is how most of the Cheyennes were built.

I met Vladimir (who spotted my raft and came over to ask how I liked it) during a trip down the Rogue River, and he told me that his idea was to make a raft that could do vertical or near vertical drops. That required a very sharp upturn in the floor, to keep the raft moving rather than stopping at the bottom of the drop. To get the maximum upturn on the bottom without changing the frontal profile, he tapered the tubes. The River Runner Magazine photo was taken at Hussom Falls on the White Salmon River, demonstrating how well the raft handles the near-vertical drop.

I personally never attempted anything like that, but I did find that the tapered design resisted stalling when run against big reversal waves, and it was far less affected by upstream winds. I considered both of these to be big advantages over conventional rafts. And I made full use of the extra load-carrying space in the raft. I liked the raft. I liked it a lot, and it was my primary personal raft for 25 years!










I now row a 16' Vanguard that has the same load capacity as the 15' Cheyenne, which I have given to my daughter, who rowed it down the Grand Canyon right behind me (shown here in Hells Canyon). In The Canyon, Cheyenne didn't perform as well as the more traditional rafts. The low bow allowed the massive waves to blast right over the boat. The V-Wave at Lava Falls blew my daughter right out of the raft. One other mishap occurred at Badger Creek Rapid, when she followed a less-experienced boater right over the pour-over boulder at the top of the rapid. The hole yawned as she went over, and going vertical, Cheyenne dived straight to the bottom. Then, like a kayaker doing an ender, the raft popped back up, the stern sailing downstream, and Cheyenne landed upside down. It was the damnedest think I've ever seen a raft do.

Still, on balance, I would have bought another tapered tube raft had I not run across such a great craigslist deal on my Vanguard. I love the Vanguard, but Cheyenne remains the best raft I've ever rowed.


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## climbdenali (Apr 2, 2006)

I'm a big fan of tapered tube boats that I've driven, including Riken Mohawks, Nez Perce, and Sotar SLs. They tend to pop through a wave rather than riding up the wave so much. In my experience they handle easier and turn quickly- ESPECIALLY the SL, which in addition to the tapered tubes, also has continuous rocker. They also really do provide a lot of room in the bow and stern otherwise filled by boat. Water over the bow will be increased, but that's never been a big problem for me. V-Wave at Lava is a devastating hit no matter what boat you're in.


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## Kendi (May 15, 2009)

I've gone over Husum Falls on the White Salmon several times (swam a couple of times too- lol). I've only done it in boats with diminished tubes so I can't speak to how it would compare to a round boat- but I do like the D tubes. Lots of splashy fun!


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## nicho (Mar 18, 2009)

Thanks for the great info everyone.


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## Kyle K (Dec 17, 2008)

Vladimir Kovalik is my father, so I got to be his guinea pig when it came to testing boats. I really like the tapered rafts. Like all things, they have their pros and cons. I think the previous posters hit all the points but here they are in short form:

Pros: 
More room in the ends than traditional designs (although this can be offset by less bouyancy; use the room to store bulky but light items). 
Handle steep drops very well.
Less wind resistance (yes, you can really feel it - especially on those long-mile canyon days).
Easier to pivot quickly in waves or chaotic water.

Cons:
Less bouyancy, as noted above.
Wetter ride, as waves can break over the bow. 

As for washing out the back of the boat, I've learned the hard way to build a nice little back rest out of personal bags directly behind my seat. This has two advantages
1. I can stay put, even in a big hit (V-waves for example). 
2. It makes for a great lounge when just floating. 

Note: Other than the back rest, I am a fan of keeping all gear as low as possible in the boat. Sooner or later you're going to flip* and the less stuff hanging off the upside down boat to entangle/smack people the better. 

* In the Canyon we used to say "There are only two kinds of guides; Those that have flipped and those that are going to."

Whatever raft you get, enjoy it! If you'd like to talk more pm me for phone number/email. 

Kyle


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## kazak4x4 (May 25, 2009)

My favorite topic. I have to put in my 2 cents!

I have been in the same "boat" a couple of years ago. I've ridden my old Riken Nez Perce for 4 years and learned everything about boating on that boat. It's a diminishing tubes boat going from 21 to 16 inches. I never experienced regular tubes boat and was used to a much wetter and more stable ride.

Then my wife gave me permission to upgrade the boat and the research has began! I've also found NRS Nez Perce and got super excited about getting. All my friends ride E160 regular tubes and all were telling me to go that route. I went ahead and rented E160 and took it down river. What I found right away is the bumpier ride. When the stern dropped into holes, I always felt a bump and a stop of momentum when the stern hit the bottom of the hole, then slowly the boat would rise up and over the wave. 

The ride in diminishing tubes is quite different. The stern usually goes under water at the bottom of the hole and due to less buoyancy in the front, it doesn't stop you as much as regular tubes. But what happens, is the stern drives through the wave and then the air pressure pops the stern out of the water (usually on top of the wave) and you ride over the wave smoothly. Aka punching the wave. 

This makes it much more wetter ride for the front passengers (Captain's shields is what I call em), but the ride is a lot more stable.

After my long research, I settled for Maravia Typhoon boat instead of NRS (if you want more info on this, PM me). It has 18" on the stern/bow instead of NRS's 16, but it still feels like a diminishing tubes ride, nice and smooth.

So obviously my vote would be is to go with diminishing, if you like that kinda thing.

Even though the guys above me probably have more experience than me, but I disagree about the buoyancy. The diminishing tube part is mostly out of the water most of the time. It only touches water when punching the waves. So the gear capacity sits on middle tubes, which are the same as a standard model (Well with Maravia, not NRS). 

Here is a link to my Maravia: Login | Facebook

And some pics of my diminishing tubes boats:
Maravia Typhoon 16' Custom Made




































And my old Riken Nez Perce 16'










Hope all this helps,

Alex


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## kazak4x4 (May 25, 2009)

Dug up my video from Westwater to show how diminishing tubes perform in bigger waves. Not GC waves, but class 3+

YouTube - Westwater 2,400 cfs low water. Colorado River

Look at 1:03, 2:33, 2:50 and 3:25


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## Kyle K (Dec 17, 2008)

Regarding bouyancy: (Note: I am not a physicist, although my dad is. Unfortunately he's out of the country so I can't contact him at the moment.) I think you're confusing displacement with volume. All other things being equal, a diminished tube raft has less volume (air in the tubes) than a non-diminished tube raft. The waterline of the raft determines the displacement of the volume of the raft on the water but it doesn't change the volume of air in the boat. Although I am sure there is a correlation between the two, unless there are extreme changes in how the boat displaces the water, the volume of air in the boat is the key determining factor of its bouyancy. 

Imagine a beach ball with a 2lb. weight suspended inside, floating on water. If the beach ball was half inflated it would sink lower in the water than it would if it was fully inflated, even though the area of contact with the water would remain relatively the same. 

Any physics junkies out there want to corraborate or correct me on this?


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## Kyle K (Dec 17, 2008)

PS: Nice video! I ran Westwater for the first time this fall and really liked it, despite all the flatwater. Great little canyon!


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## kazak4x4 (May 25, 2009)

Well, the ball example you are comparing the air pressure on the outside of the ball. Full pressure vs low pressure. The pressure is what displaces the water. So taking that example to the boat, you can deflate a boat and it will sit lower in the water.

Regardless, I am probably wrong, either way I am loving my boat too much to care about the water displacement. As far as we all make it to take out in one piece it's all good!


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## Kyle K (Dec 17, 2008)

Good point. Maybe thinking of a smaller beach ball versus a larger one, or perhaps thinking of a kayak would be more illustrative: A kayak with lower volume but the same full shape will definitely sit lower in the water given the same paddler. 

Regardless, you're right! It's too much fun to run the river in anything than to get too worked up about the minutia! I hope to run something with you someday.


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## kazak4x4 (May 25, 2009)

Hey if your dad made Nez Perce, you are always welcome on my trips! I am sure we will have a lot to chat about.


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## swiftwater15 (Feb 23, 2009)

*displacement*

I'm not sure I understand the concept of riding lower. A floating object of a given weight will displace its equivalent weight in water. So a lower-volume boat, or a less-inflated inflatable, will generally sit in the water to the same depth, not lower, but less will be above water. So I am thinking that the volume difference makes a difference only when a portion of the craft is being forced under water - like sinking the low-volume stern of a squirt boat. The diminishing tubes would punch (some) waves that (some) larger tubes would ride over. Sotar legend cats with fat ends don't pencil in as much as my similar-sized ocelot when dropping over scary things.


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## blutzski (Mar 31, 2004)

If you have kids, consider the standard tubes. Our 2 and 3 year olds can stand comfortably in the front of my E-160, stay dry (on the class II we're doing now). and have a big bumper keeping them in the boat when they want to stand up front during the rapids. If you don't have young kids, go with the other advice. Of course, if I didn't have kids, I would go with a cat.


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## The Mogur (Mar 1, 2010)

Looking at the photos of the Maravia, the amount of taper is about the same as the later versions of the Riken rafts (Chenenne and Nez Perce, at least). I think that in most respects, the more extreme taper on the early versions (like mine) accentuated both the advantages and disadvantages. 

One disadvantage that hasn't been mentioned (maybe it affects only the most extreme tapered rafts) is that the ends of the raft are very springy. When using my Cheyenne as a paddle raft, I had to be always aware of the springines, lest I be launched from my seat. On the other hand, I sat closer to the water and thus had more paddling power to steer the raft.


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## kazak4x4 (May 25, 2009)

blutzski good point. Though my boy (I started him rafting at 4) always complains about not getting splashed enough. The trick about rafting with kids is to provide enough warmth and protection layers on them to keep them happy.

I got a dry and wet suit for my boy and he is always warm and always begs to get splashed by big waves. So the big bow shield would upset him even more.


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## noneuclidean (Aug 2, 2013)

Great thread.

I can relate to the pros and cons that go with the diminished tubes. Most of my runs in the canyons of the desert SW, the lower wind resistance is much appreciated.

I'm familiar with the SOTAR SL, NRS Nez Perce, Maravia Zephyr, and the AIRE D.

What are people's thoughts on the AIRE DD?


Sent from my iPhone using Mountain Buzz


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## tetoncounty (May 19, 2016)

I've owned a Maravia Diablo diminished tube raft for a few years now. Prior to that it was regular rafts.
This raft is more responsive, but wetter.
More turn-up at the bow. I have noticed that, with upstream wind, I have a harder time than other rafts.


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## jimr (Sep 8, 2007)

Have a 13' aire d sealed floor, so much better then the DRE boat I had. Plows through holes and waves, tracks amazing, very stable, great for low water, big water, fly fishing and class iv+. hell I Survived dowd chute at 9'. Diminished tubes... It's a no brainer. 


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