Research papers on fin performance

[psparks]

After noticing a number of threads about fin performance and questions about actual data, I did some research and identified a number of pertinent research articles.

The Rubicon Foundation has an excellent repository here. And searching for 'fins' produces quite a few good papers, particularly those by Pendergast, et al

Search

Of particular interest is the finding that splits, vents, and troughs are not effective. Also that most of the propulsive force comes from the 'power' stroke and the recovery stroke is often drag-producing.

Also, of historical interest is this one by the US Navy in 1957, which identified the Voit Viking fin as the most suitable:

Fischer, "Comparative Evaluation of Swim Fins"

 

[David Wilson]

Thanks for bringing this body of research to everybody's attention.

Also, of historical interest is this one by the US Navy in 1957, which identified the Voit Viking fin as the most suitable:

Fischer, "Comparative Evaluation of Swim Fins"

I have a print copy of Fischer's report, which I ordered and obtained twenty years ago from the Navy Experimental Diving Unit library. I'm a big fan of this publication, not least because it's written in plain English without skimping on the quantitative data, while many researchers seem to write just with their PhD supervisors in mind rather than explain their findings to an intelligent lay audience. The report is also worth a read because it was the first to define the criteria by which swim fins could be compared, not only for performance but also for fit. It also set standards for measuring fin dimensions, weight and stiffness and complained about manufacturers' vagueness when it came to stipulating the materials used to construct the fins, even at a time when most fins were made of the same material; See 2.3:
Terms used by manufacturers to describe materials used include: 1. pure rubber gum 2. gum rubber 3. live rubber 4. synthetic rubber 5. hard rubber 6. moulded rubber. The actual significance of these terms is ill-defined.

Plus ça change, plus c'est la même chose... Modern fin manufacturers still seldom provide information about the exact internal dimensions of foot pockets so that people can order correctly-sized fins online, and they can be still just as uniformative when it comes to the fin material; I've seen the term "space-age materials" used to describe some indeterminate plastic used in fin construction, which certainly leaves me little the wiser.

 

[Bob Evans]

psparks

I can't believe this thread you started. For the past 2 hours, while driving home from the South Bay of Los Angeles, I was ranting and raving to Susanne about how it is time to post on the Internet the research files we have, including un-redacted copies of the earlier studies by Pendergast. We obtained these through a Freedom of Information Act request to the Department of Naval Research. These earlier studies, at the request for the Dept. of Naval Research, included the Force Fin, which rebound characteristics overcome the drag characteristic of other fins on the recovery stroke. That is what Force Fins are about. It was always curious to me, why in later studies Pendergast referenced the fact that fins required the Force Fin characteristics to perform optimally, but did not include the Force Fins in those later tests.

 

[REVAN]

How many divers really care about how their fins perform? I consider myself rare in that I actually do care. Nothing out there met my performance standards and I started making my own diving fins.

I think that since all the scuba fins commonly available work so poorly, there is no real public awareness of what truly good propulsion can feel like. As a result, scuba divers seem to be willing to spend a tone of cash on everything but the fins. I get the impression that what most divers want is a fin that is inexpensive and provides a strong feeling of resistance while providing some propulsion. The actual thrust to effort ratio achieved is usually not a priority.