Split Fin Physics

[scubafanatic]

I doubt anyone knows for sure. Probably something cheap.

Probably those cheesy full-foot resort/rental style snorkel fins used in tropical locations....cheap kinda works unless the ' *hit hits the fan ', which most divers don't appreciate as the dangers/risks of diving are essentially ignored/glossed over in an effort to encourage dive/travel business.

 

[Eric Sedletzky]

Who knows for sure, but I have a strong hunch the most currently used fin in the world is a split fin. What brand exactly I don't know. Everytime I go diving, either on a boat, from shore, with the club, etc, I mostly see split fins.
I would say ten to one - for every paddle fin user there seem to be at least 10 split fin users.

At the Breakwater in Monterey on any given weekend when classes are in full swing there will be sometimes 200 people there, almost all of them are using split fins. I pay attention to gear people use, I don't know why but I do. Probably because I do some small time manufacturing myself.
Most of them are open water students, but that's what the dive shop has them use and that's what they end up buying.
When ever I go into any dive shop all I see is a full assortment and line up of split fins with maybe one or two paddle fins, sometimes no paddle fins at all.

I don't get out and travel much right now, but I would be half tempted to put $100 bucks on it that split fins are used in very large numbers at resorts and operations around the world, easily surpassing the 50% mark.
I obviously have no way to prove any of this so it's just a hunch.

 

[meesier42]

thus is the power of effective marketing.

 

[TN Traveler]

Not sure I agree that it is totally because of marketing. Remember, most members of ScubaBoard are fairly "die-hard" divers - which is a small percentage of the overall number of people who dive.

Most "average" divers are on vacation and just want an easy swim to look at the pretty fish and coral - they are not concerned with precise positioning or fighting currents - so all they want is something that makes it easy. There is no doubt, that split fins are easy to kick and make for little stress in finning. A slow flutter kick is easy and works well enough in the nice clear, warm water they are diving in. Plus you can get split fins for a very reasonable price and they work well when snorkeling as well as diving.

So, I can easily understand why they are very popular among the diving masses.

Are they the best?? Probably not if you are, like us, die-hards; but for the rest, they are just fine.
To try an convince them otherwise is an effort in futility!!

 

[John C. Ratliff]

Well, I have been in the water again to do testing, and was putting all the results onto an Excel spreadsheet. I then went to download a Microsoft update to my Excel 2004 for the Mac so that I could save XLX files, and it hung the computer. I had to shut it off, and it would not start, so my main computer has been down for almost a week now. I'll give you impressions rather than numbers with this post.

I swam the Scubapro SeaWing against my homemade scoop fins, and also against the Force Fin (yes, that's the 25 year old original model). To my surprise, they were all fairly close to each other. I was again swimming a dolphin kick, 50 yards timed. The other surprise is that these fins, which were my open water fins with an open heel, were a few seconds slower than the initial swims (which I posted earlier). Those initial swims, as you will remember were made using the some fin with three modifications, blade, split and scoop. All these full foot fins out-performed my open heel fins. I have a feeling that the wet suit sock I used provided significant drag, which would slow down the fins.

On a later trip to the pool, I swam with the split fin, my scoop fin and the Force Fin. Again, this Force Fin may not represent the Force Fins presently being made (many different designs, I see from the website), but I liked the split fin and the scoop fin better. I simply do like having an upstroke. There may be some difference between the scoop design and the split design, but it is not noticeable when swimming them.

TN Traveler, I would have to disagree about the blade fin being superior to splits for die-hards; the physics shows that the water is better directed using splits (or scoop) than using a blade for the flutter kick. What you describe as precision positioning, using the frog kick or sculling with fins, is successful with blades, but it can easily be accomplished with split fins or scoop fins too. It's just a matter of getting used to it. With all new things, there is an adjustment period (which is why I am withholding my judgments on Force Fins). This may be the main problem with splits for those used to blades.

SeaRat

 

[TN Traveler]

SeaRat

I do not disagree that it is possible to achieve precision positioning with splits - I did it with my Bio-fins for quite awhile - I have just found it is easier with blades. To be honest, the best fins I have found to date that almost do it all are the Tan Delta Excellerating Force Fins - they feel as efficient as a split, but can provide precision positioning like a blade. Of course to achieve the best of both worlds you need to adjust the wings on them to match what you are trying to do.

I just got a pair of Force Fin Splits (Foil Force) and the new "Hockey Fin - both of which seem to have elements that you have identified as being important to fin performance. I have not had the chance to test either, but I will be trying them both out on a trip in May and will post my impressions (probably on the FF Forum). This is not the place to discuss the characteristics of these fins - but why don't you take Bob Evans up on his offer to let you test these - I would be interested in your experience/evaluation.

I am a engineer/scientist and like your methodology - probably as close to an unbiased test as possible. By the way - try the Force Fins with Comfort Inserts instead of socks - it will eliminate the drag and give you a better comparison.

This has been a great thread - hope we can keep it going without individual prejudices influencing the rational discussions.

 

[redacted]

To be honest, the best fins I have found to date that do it all are the Tan Delta Excellerating Force Fins - they feel as efficient as a split, but can provide precision positioning like a blade. Of course to achieve the best of both worlds you need to adjust the wings on them to match what you are trying to do..

Well, they better do it all and then some: Excellerating Force Fin Tan Delta - The Snappiest: Force Fin

 

[TN Traveler]

AWAP - please take your hang ups on costs to another thread. This thread has evolved into a discussion about fin PERFORMANCE!!

I realize people will make their decision on what fins to buy based on their own "cost/performance" formula. That is their decision and I would never question the choice they make. If you are happy with your "K-Mart" fins because they give you all the performance you need/want for the $$$ you want to spend - I'm happy for you!!

But let's let this thread continue on a purely fin performance basis without trying to bring $$$$ into the discussion.

 

[lmorin]

............. All these full foot fins out-performed my open heel fins. I have a feeling that the wet suit sock I used provided significant drag, which would slow down the fins. ..............

SeaRat

SeaRat, I have been curious about the higher performance of full foots. One common difference between full foots and open heels is that many open heels have an empty space around the toe pocket on the underside of the fin. The full foots tend to have a smooth upper and lower profile around the foot pocket. The empty space would be a major source of drag and consequent inefficiency. Of course, the open heels also generally have more protruding pieces of stuff associated with the heel strap. These will also cause greater drag. I'd like to know 1) which open heels do not have that empty space and whether they tend to perform better; and 2) which full foots have an equivalent empty space and whether they tend to perform worse.

 

[Kern]

TN Traveler, I'd like to see this thread go back to the physics of split fines. As there seems to be little to no data to base such a discussion on, that seems unlikely. If however its fine for the thread to evolve into subjective assessments of fin performance, I think its just as valid for it to evolve in any other direction any other member would like to discus. I really don't see why someones opinion on a fins performance per dollar, is any less valid than their opinion on the performance alone.