Extreme Dolfinism

[Canetoad Films]

I have taken this fin (affectionally known in Hawaii as the Ronofin) past 50m deep in the ocean, and I spent a morning knocking out 100yd swims in the local pool and found that it is comparable in performance to my Waterway Glide. Comparable but very different. But it doesn't take long to get the feel of it and use it to your advantage.

I was excited with it because of its performance was right up there, and the design was so different. Who knows how far this fin will go as its dynamics are continued to be researched.

Regarding nature's designs, the closest thing I can see to the usual monofin design in nature is the dugong (Aust.) or manatee. Perhaps that is good. We probably are shaped a bit more like them than a dolphin, some of us for sure. However, we are quite different in physical design to most of the aquatic mammals, and hence despite copying the various natural designs, the true test of a fin is in the actual testing.

Having used the Ronofin only 4 times, I will probably choose it as my next fin. I am not saying I would retire my Glide, but who knows after I have had one for a while. I have had the Glide for nearly 3 years now and love it.

This fin will surprise you. You think you need a big surface to push a big amount of water... well, I did. This fin changes that concept.

 

[REVAN]

Ron, the shoes are mounted to the fins with the heels about 1 to 2cm wider than the toes. Is this the way they should be?

The amount of toe-in is really just a function of how you mount the shoe to the frame. On Connor's fin there are small tabs that fit into groves in the soles of the shoes that suggests a particular alignment for the shoe. In the end, I decided to do away with that feature for the X-20 and used a different cross-brace design that is better looking and more flexible to shoe alignment so that people can easily align it however they want.

Ron

PS - Please keep in mind that Connor's fin was alpha-class prototype hardware. In the end, the design was a good enough piece of hardware to sell off, but there were several improvements made after working with his fin for over a year. This is one example. Also, I should mention, those tabs on Connor's fin could be easily filed off if he decides he wants to eliminate them.

 

[laminar]

Review Article should be out soon, Papa Smurf has the final draft.

 

[Fondueset]

Nice one Pete, send money.

 

[REVAN]

Link to Laminar's Review: The End of the Hyperfin? The DOL-Fin X-20 Review | DeeperBlue.com

The link should be useful for readers of this thread in the future when the article is no longer front page material and easy to find.

 

[laminar]

In response to the potential troll post on the article itself:

I did several dives to 30m a few months ago and surfaced with 10-12 kicks, depending on the volume of air in my lungs and ballast and what I ate in the morning (you know, extra propulsion).

Notice that in Azapa's video he creates a lot of drag with his upper body, probably as he's trying to feel stable on the ascent (is that why, Simon?)

You can reduce the number of strokes simply by reducing the number of strokes, if you know what I mean. Counting strokes becomes meaningless if you're trying to achieve a certain result.

Looks like I need to film some head to head swims, then.... but in a few months when I've got it dialled in.

On the weekend I did a 4km surface swim with the DOL-fin X-20 and kept up with a bunch of swimmers in triathlon suits, some had fins on. Underwater they had no chance of keeping up with me. The best position for speed and good propulsion on the surface from the fin was with my arms by my sides, face down, which I find quite difficult with a hyperfin (usually because of the buoyancy). Unexpected, but relaxing and effective.

 

[Fondueset]

That bit about the surface swim is quite telling. Good surface swimmers move along at a pretty good clip. Also - arms down is very good news. My star fin is the best I've used on the surface but I've never seriously considered trying it arms down. 10-12 seems about right for 30 - unless of course your are using the reverse flatulentronic photic sneeze boost.

Excellent review - btw. Perfectly tuned.

 

[Bill]

I wonder if it means anything after reading all the engineering shtuff that Ron writes about oscillating reynolds numbers and such but 10-12 kick cycles from 30 meters (horizontal or vertical) is about right for C4-30s too. On another note; has anyone seen any results of drag testing arms up compared to down?

 

[noa]

a big thanks to Pete for the review. fantastic work (or better say play) there.
as always i'm very interested in the surface swimming side of things as open water swims are a big part of what i do with my monofins.
how did it compare to a glide for that application ?
interesting you used your arms to the side. that is how i also swim on the surface. i don't use a frontal snorkel, perform five to six kicks and then use the momentum of the last one to bring my head up for a breath. feels a bit funny at first and there is a slight stall phase during the breath, but doing away with the snorkel feels quite liberating to me.
thanks for any info and keep enjoying the exploration...

 

[azapa]

Pete, if you notice on the way up (those tremendous amount of kicks) I was actually looking down at the fin often. It felt so cool, like my legs were just kicking nothing, I wanted to kick again and again. The dive was also about as hard as a 25m dynamic, so I was taking my time.

If it is a criticism of the fin, the strange lack of feedback one gets with regular fins (load up, release, load up..) makes it feel as if you are doing nothing. I would imagine a dive line out front would make it easier to perceive ones progress in the dive, and therefore, reassure that more kicks are unnecessary.

 

[baiyoke]

Firstly; nice review

Pete, if you notice on the way up (those tremendous amount of kicks) I was actually looking down at the fin often. It felt so cool, like my legs were just kicking nothing, I wanted to kick again and again. The dive was also about as hard as a 25m dynamic, so I was taking my time.

If it is a criticism of the fin, the strange lack of feedback one gets with regular fins (load up, release, load up..) makes it feel as if you are doing nothing. I would imagine a dive line out front would make it easier to perceive ones progress in the dive, and therefore, reassure that more kicks are unnecessary.

But what about sensations other than the "feet load-up". Maybe a focus on sounds of water flowing over the ears, or water over the fingers. That helps me, at least if my fingers are not padded with 8mm. I'm thinking it must be possible to develop sensitivity to other speed sensory cues.

By the way..... must...... have...... fin..... soon......

 

[REVAN]

...has anyone seen any results of drag testing arms up compared to down?

I've done rigid body drag measurements on myself. Arms overhead tucked and streamlined vs. arms at side with elbows tucked tightly along the side of the body (not spread out like in azapa's video). My data indicates that arms at side increases drag by about 25% over the classic streamline pose. Raising the head out of position to look forward costs another 25% drag penalty. It is reasonable to assume the drag increase is at least as much for looking down at the fin and maybe more. I'm not sure how much of a drag increment to expect for having elbows out away from the body but I'm sure it is substantial.

 

[laminar]

Quite right, Simon. You were transfixed by the strange thing on your feet. Because it doesn't look like it should work!

Once we give up the instinctive post-monofin desire for springiness and loading up the fin, you'll realize that the sensation of speed should now be the absence of drag, not that misleading feeling of exertion.

 

[Apneaddict]

I guess the sensation is closer to what a dolphin might feel, although their tails do flex a bit and I assume they can feel this "loading".

Note the picture of a beluga tail on the LHS - looks a LOT like my hyperfin with the large leading edge.



The Dol-Fin is a pure hydrofoil - more like a tuna tail or marlin tail.

 

[REVAN]

Wow! I just noticed this thread has over 500 posts to it.

You may not recognize it, but the beluga whale's tail is actually more similar to the DOL-Fin than a hyperfin.

The beluga's tail is angle controlled by the caudal peduncle and flies like a hydrofoil rather than flexing and releasing. The DOL-Fin is angle controlled by the fin's suspension system.

The beluga's tail has little or no sweep angle, but has raked fin tips (sweep varies somewhat within the species). The DOL-Fin also has no sweep, but with raked fin tips. The hyperfin is a deep delta wing, characterized by a high sweep angle and high taper ratio.

The differences between beluga tail and DOL-Fin are simply that the DOL-Fin approximates the elliptical plan-form of the beluga's tail with a rectangular section and a pseudo-elliptical tip section. This variation is done for manufacturing purposes. Also, the span (width) of the DOL-Fin has been stretched out to compensate for our high drag in the water compared to the much more streamline beluga.

It is interesting that the beluga was used as an example here, because I referenced it in my design phase specifically because it has a tail with no sweep angle (only taper) and was similar to my non-swept hydrofoil. Imagine stretching the beluga's tail (from the picture above on the right-hand-side) to twice the original span to compensate for drag, then thinning it to reduce the surface area because we are not as strong as the whale. It will start to look a lot like the X-20 or Orca fins.

 

[Mukiker]

Hi there,

I got my X20 two months ago. I use it for long distance surface swimming - or at least this is what I aim for

Areas I would like to share and discuss:
- X20 praise
- X20 surface swimming technique challenges, keen to hear recommendations
- navigation issues on a large see (offtopic, sorry)
- some fun with X20 at the end

 

[Mukiker]

>>> READ HERE IF YOU CONSIDER BUYING A MONOFIN <<<


Many people considering to buy a monofin will stumble upon this thread, read its few last pages and make a purchase decision based on impression they get. My case.


Pain: Buying a monofin is a difficult dilemma. Which model to choose? Which stiffness? What is best for the way I want to use it?


Solution: DOL-Fin X-20 removes this dilemma completely. Change a few screws in five minutes and you have a totally different monofin. X-20 provides you with a variety of options how to tweak its feel and performance.


Pain: You just went through the dilemma as mentioned above. You picked one particular monofin. The moment you open the package, you will fall into uncertainty if you chose the right model. This uncertainty will chase you night and day. You end up buying yet another monofin - just in case you did not choose right the first time.


Solution: The moment you unpack DOL-Fin X-20, you realize how many options it provides to you. You will love to have that many options to tweak the fin.


Pain: Monofins pricing spectrum is wide. Which price range to choose? Isn't it unreasonable to spend e.g. 1000 dollars for a fin? Wouldn't be a 100 dollar monofin good enough for me? How much more value do I get for a more expensive monofin?


Solution: DOL-Fin X-20 costs 850 USD. Expensive? Not really, it actually provides an amazing value for money because:
1 - You will not need to buy multiple monofins in order to accommodate various use cases.
2 - DOL-Fin X-20 will not wear, it is a solid build, most parts are made of metal, and all parts are easily replaceable.


Pain: There are many different monofins available. I don't want to end up with technologically old product.


Solution: DOL-Fin X-20 is a hot new product employing all of the latest science in efficient propulsion.


Pain: How do all the monofins rank in performance? What if I buy an expensive monofin and it will turn out that my monofin is an underperformer?


Solution: Make sure you only buy equipment which receives favorable expert reviews. You can find links to some expert reviews for DOL-Fin X-20 in previous pages of this thread. They are all very positive.


"Ok, are there any cons for the DOL-Fin X-20?"
Sure there are. Your wife will be jealous that you keep fooling with and tweaking your shiny new monofin. You will force your kids to swim with it. Their friends will be jealous that your kids can swim with that rocked science equipment.


So, dear readers, I do recommend DOL-Fin X-20. Please consider I am a standard paying customer. I only wanted to write this topic entry because I think DOL-Fin X-20 is a good product.


Thank you for reading.

 

[Mukiker]

Dear experts,


I am keen to hear your experience and recommendations for an optimal swimming style with X20 or any other monofin for long distances. I am also interested to learn how you set X20 for long distance surface swimming.


I swam 5 km lately with the following style:


Two kicks with X20, one hand stroke while the other hand stays stretched in front. Stroking hand returns back to front.


I changed my X20 for this style drastically, sorry Ron.


Please see photograph of my X20 setting:
https://plus.google.com/u/0/photos?tab=mq#photos/104284523567850693956/albums/5779619897042950017

1 - lever arm set to long for more power
2 - trim plates removed completely
3 - small plastic plate which provides resistance to suspension strap for downstroke has new holes drilled into it and it is shifted by 1 centimeter towards shoes.


These changes result in strong upstroke and a degraded - or better, demolished - downstroke.


Weird? My idea behind this is that human body is aimed:
- at accelleration rather than at decelleration
- at ascent uphill rather than at descent downhill
- at jump forward rather than at jump backward


When I used X20 with default factory setting, too much power required for downstroke was limiting me at my goal of long distance. Trim plates 5 and 7 emphasize the need for a powerfull downstroke even more.


I used my funky setting for quite some time and I also used it in 5 km swim. It worked great. If I had stronger hands or a more suitable hand stroke style, I could easily swim much more than just 5 km. My legs and body which works with the fin were totally ok after 5 km.


Before I got enough courage to discuss this setting with you here in this thread, I returned my X20 to factory setting. I was stunned how much faster I swam, how few strokes were necessary to progress, and how I almost hit my head against pool wall because I did not expect it to be there so soon.


But just after 300 meters or so, muscles doing downstroke were the first ones to report tiredness. I know, more training would deliver more power. I just feel that monofins are heavily biased towards propulsion by downstroke whereas my body has a lot of power for upstroke / acceleration / ascent / jump forward. This is an unfair statement for ronofins, which are revolutionary for propulsion by upstroke. Sorry for that


Here we go. My claim is that long distances require a relaxed downstroke and a powerful upstroke at the expense of less propulsion efficiency. Strong downstroke delivers amazing propulsion but kills people on long distances on surface with unlimited oxygen.


Your opinion?


Thanks for helping!

 

[neurodoc]

How long is the pool that you are swimming in for the video? and, what was your time for 5k? while swimming 5k in any form is an accomplishment, when you are talking about efficiency and such the speed is important to compare. It is hard to tell how fast you are swimming with no reference points.

 

[Mukiker]

Now imagine we agreed on an optimal setting for ronofins for long distance surface swimming with unlimited oxygen.


What about the optimal swimming STYLE? Long distance with monofins. Youtube says very little about this when I search for it.


What is your experience? Can you please share some videos about your style? Any other videos?


In my recent 5 km swim (sorry for bringing this up again), hands were the limiting factor. I could not keep my hands stretched forward for such a long time. Style with stretched hands looks nice on youtube when you and other folks swim it, it works fine in a pool, but it hurts after hours.


I am experimenting with a style in which hands spend more time next to the body:



As you can see, I almost drowned when reaching end of our small pool. Hmm.


One of contributors in this thread mentioned a 4 km swim with X20 with hands not stretched forward (apologies that I forgot the name of the person). What was your body undulation? Can you please share a video of such swimming style? I keep trying it but results are miserable.


Ron says that there is a 25% drag penalization for hands not being stretched. True for sure. But given that hands can not be stretched all the time when doing a long distance surface swim, what is the second best option? No hand strokes at all with a poor body undulation? I can't believe that.


I bothered Ron already asking if we is also manufacturing some hand paddles. He did not show much excitement for hand paddles


I must say, I feel very lonely with my preference for long distance swimming using a monofin of any kind. It seems that monofins equal limited access to oxygen, whether it is dynamic or diving. Why is that?


If you can share any experience or videos, I would greatly appreciate that.


Thank you!