What's wrong with Split Fins??

[SkullDeformity]

Does this mean that there won't be a book of faq's on split fins anytime soon?

No, I'll have to put the book on hold while I work on my smoking mice experiment. Currently looking for an engineer to design tiny fins.

 

[WarmWaterDiver]

Hard money or cost-plus bid?

Is EPC possible? I didn't see the posting for bids.

 

[ffestpirate]

No, I'll have to put the book on hold while I work on my smoking mice experiment. Currently looking for an engineer to design tiny fins.

I've heard that split fins create a more favorable kick for technical mice.

 

[Splitlip]

I would not say there is anything wrong with split fins. I have a pair of Apollo Bio Fins and love them. They are fast (= more power out for the same power in as a paddle) and work very well in currents. They are not as intuitive to use as paddles however and not as precise.
The siltting complaint is really not an issue unless you are in a confined space or some really funky places , but paddles will silt as well unless you use alternative kicks (modified frog ex.). Those kicks seem to perform better with paddles. It is not the fin that silts, but rather the kick or diver.
With splits you have to consciencely modify the kick to a tight flutter and they do take a cycle or 2 to get going.
People will tell you go for Jets. Jets have their place, but are not the best for typical open water reef dives. They are short, stiff and heavy. Great for pushing a diver with lots of gear in tight places.
Having said all that, as you are a new diver, I would reccommend a good paddle such as the Mares Avanti Quattro. I also like the USD original blades not the Blades II, but they are no longer made. Little or no "learning curve"
As time goes on you will eventually have more than 1 set of fins. I just recommend you start with the paddle, but not Jets or a clone.
I have 2 pairs of Jets, a pair of USD blades and the Splits. (I have also wned and used "hinged fins" and the Cressi Garas's. Not for me, but others love them.)
The fin I use is determined by the dive I plan.
EDIT: Almost forgot. Whatever you decide, try the fins on with the boot you wll be using for fit and confort. Although trim is more a function of your body, weighting and distribution, the buoyancy of different fins might be something you want to consider.
And there are a lot of people on the board who are going to make recommendations without basis in fact because they want to be seen as a member of the "tribe".

 

[BKP]

Here is the response I got from my engineer friend at Duke. Ok, so he's actually my brother. He attached three studies in pdf format which are too large for me to attach here, even compressed, unless someone who is more computer-savy can tell me how to do it. Two are in the 400-500 kb range and one is 700-800 kb. I personally only skimmed over the studies but his email below explains the gist of them.

Hi Lilla,
Here are a couple of papers I have handy. Split fins (with the split running the length of the fin) are inefficient. The split fins place the shed vorticity in the water in an orientation that serves no useful thrust purpose. BUT other fins are not much better. Most fins fall in the 8%-12% efficiency range.

Lilla, I'd still be very interested in reading the studies your brother/professor/engineer sent you. Please feel free (if you would) to send them to my e-mail at bkp@scubaboard.com

I've read a couple of papers on this (terminal curiosity), and your brother's would be the first to contend that circulation created by the split fin effectively dissipates with no thrust (I'd imagine the effect would be that of a bike rider on a spinner bike).

I'm sure all fins are inefficient to a degree (nature seems to have endowed the large, fast pelagics with the equivalent of the Force Fin -- kind've renders this argument moot).

However, all the arguments go out the window since it boils down to personal taste...

DIR will continue to advocate Jets,
Most LDS' will continue to endorse splits,
And Keith Richards will continue snorting anything that'll fit up his nose...

 

[Splitlip]

Here is the response I got from my engineer friend at Duke. Ok, so he's actually my brother. He attached three studies in pdf format which are too large for me to attach here, even compressed, unless someone who is more computer-savy can tell me how to do it. Two are in the 400-500 kb range and one is 700-800 kb. I personally only skimmed over the studies but his email below explains the gist of them.

Hi Lilla,
Here are a couple of papers I have handy. Split fins (with the split running the length of the fin) are inefficient. The split fins place the shed vorticity in the water in an orientation that serves no useful thrust purpose. BUT other fins are not much better. Most fins fall in the 8%-12% efficiency range.

Larry at ScubaToys has an interesting Q&A. See theis link.

http://www.scubatoys.com/store/joelarry/splitcurrent.asp

 

[ffestpirate]

Any results on the smoking, caffeine laden split fin mice yet?
Oh, and apparently purple fins will make them swim faster.

 

[The Kraken]

I know, I know, I should actually go out and dive, BUT . . .

It takes X amount of force to move X amount of mass through X distance with X resistance.

The energy/force to overcome the resistance and move a body a given distance through water remains the same, regardless of the type of fin one uses.

Following that logic, it will take the same amount of caloric consumption to generate that energy regardless of the type of fin one uses. Now, that caloric consumption will, of course, include the amount of gas consumed to generate that energy. So, all other things being equal, with a blade fin it takes one kick cycle and 2 breathing cycles . . . with the split fin it will take two kick cycles and one breathing cycle . . . .

But when it all comes down to the brass tacks . . . . ??????

Remove the human factor, set up a controlled environment and test parameters and then show me, given the wetted area of the fin, yadda, yadda, yadda, which of the two, if you can make one "equal" to the other BEFORE the test begins, is more efficient.

the K

 

[WarmWaterDiver]

No, I've evidently been barred from bidding. it would have been a sweet deal. I planned on bringing in JeffG as my primary subcontractor. Everyone knows in the same time span that elapsed between Jet fins being put on the market and split fins being offered for sale, computers have shrunk to a fraction of their former size and gained orders of magnitude in power, so we could just do the same with fins. Then either splits or jets could blow any current away, and the real money would be in having an exclusive on the mouse-to-human interface kit, which was the keystone of this scheme. And I'd get to just look important and beat on others about budget and schedule - the cushiest of jobs - Project Manager! And funding should be easy - anyone with a Y chromosome that can live on Hawaii gotta be LOADED, right?

Looks like I'll have to go back to workin' for 'da man' again tomorrow morning. Oh well, easy come, easy go.

 

[ffestpirate]

BTW....have there been any studies done to find out if DIR mice, laugh at non-DIR mice with full fins?