Best fin for Drysuit diving?

[Jeff Toorish]

rising in the water would prove what exactly? any flat plate in a comparatively high density fluid (water to air) can create a large lift vector at low velocity, but in order to be useful would have to be in line with the divers body and thus propel the diver forward, not upward. Of course the key to attaining this lift vector is the angle of attack and flow across the planeform. This is exactly why every single scientific study done to date has shown "fins where successive trailing edge segments that progressed at 90 to the horizontal produce the most thrust during the power phase" as the significant angle of attack sets up the lift vector to propel the diver forward. The terms in the lift equation are density, speed, plane form area, and a term called CL. CL incorporates angle of attack and shape of the foil as well as many other factors.

Point being, yes, the foil properties can provide significant advantages at the low velocity. and yes, there are fin designs on the market that use this fact, as I have already stated. Hopefully, I have shed some light on this topic to JeffToorish.

To answer the OP, I see you are posting in a couple of threads with the same question worded differently. But you have yet to answer my questions to you so that I, and the remainder of the intelligent people on here can make a recommendation to you and actually back up are recommendations with something other than "it worked for me"

Listen, I don't need you to shed light on this topic for me. I fly airplanes, do you? In point of fact, you told me exactly nothing I did not already know.

I asked a question of someone who made a specific claim and I wanted to hear the answer from that person --not you. Are you, perhaps, one of those people who doesn't listen to others talking because you are too busy thinking about what you are going to say next? Just wondering.

And the questions you asked of the OP had already been asked--if you had read the entire thread you would have seen that. Believe it or not, you are not the only person on this board with knowledge.

Jeff

 

[meesier42]

I think we both agree that the wings on a plane however are a very different case than a pair of fins. Dragging someone behind a boat would give the same sort of foil proof of concept that the manufacturer's claim of "works like a plane" would be equivalent to.

A plane has wings but also has engines. The engines propel and the shape of the wings doesn't change much. In the case of the fins mentioned, if they were to work the same way a plane does (and as the person claims), the diver would have to put rockets on his back and let his fins merely act as pure foils.

Sure airplanes have engines, and the engine uses airfoils known as propellers and turbine blades at the correct AoA to generate airflow and therefore thrust. This is same application I am talking about.

Listen, I don't need you to shed light on this topic for me. I fly airplanes, do you? In point of fact, you told me exactly nothing I did not already know.

I asked a question of someone who made a specific claim and I wanted to hear the answer from that person --not you. Are you, perhaps, one of those people who doesn't listen to others talking because you are too busy thinking about what you are going to say next? Just wondering.

And the questions you asked of the OP had already been asked--if you had read the entire thread you would have seen that. Believe it or not, you are not the only person on this board with knowledge.

Jeff

to you I apologize, I was interested in debunking the bogus marketing claim. As for OP, we (ie the group) have asked the same questions more than once but yet, he has not answered them. I hoping to return this thread to the intended purpose and off the hijack angle that it has taken

 

[hecker-the-wrecker]

Bernoulli's principle works on the theory that AIR moving over an AIRFOIL takes longer to move over and around the top of an AIRFOIL than the bottom of an AIRFOIL. (The AIR over the AIRFOIL is compressed creating a pressure differential between the top and bottom of the AIRFOIL) This low pressure over the AIRFOIL creates lift. WATER is NONCOMPRESSIBLE in any way, shape or form. Bernoulli's principle does not apply to propultion created by scuba fins. (airframe and powerplant mechanic license #476-06-3382) Let the flaming begin......

 

[meesier42]

what??? are you kidding me, you honestly don't think that Bernoulli's Equation is valid for incompressible fluids as well as compressible fluids. go check your fluid dynamics books

 

[hecker-the-wrecker]

A fin will not generate lift under water. Neither will any other shape. (unless it is bouyant of course.) It needs a differential of pressure between the upper surface and lower surface to achieve this. Until water is compressable, there will be no differential in pressure.

 

[themagni]

Too much math - and I'm an Engineer. If you're breaking out the differential equations to determine laminar flow and hydrodynamics from first principles, you're overthinking the issue.

Just use whatever fins feel good, look good, and are within your price range. Everything else is just personal preference. You won't die unless you do something ridiculous like bifurcate your regular fins to make fake splits. Yes, that has happened, and yes, the guy died, and yes, he probably deserved it.

Force, splits, bio, jet, two licence plates strapped to your feet, etc. If it works for you, then it's a tolerable fin. I like my Force Fins because they let me use my biking muscles for diving. Other guys prefer the stiffer resistance of Twin Jets. It really doesn't matter all that much, and anyone who has a zealous preference for one fin over another (a finatic, if you will) won't give you any useful information. After all, they're using the only fins good enough for them.

Try out different fins, and don't focus too much on the price. You want to be thinking, "wow, check out that octopus," not, "stupid fins".

 

[hecker-the-wrecker]

He He He, I totally agree. I use expert zoom splits with my drysuit, exactly like the original poster, "Borg" had lost. Someone else said not to use them in an overhead enviroment. Maybe they could explain why? My backup fins are good old jet fins that are 40 years old. I do like both.