Hi, Jim,

That's the kind of report I've been looking for.

The split is designed to reduce the energy wasted pushing water up and down
with a flutter kick.

The frog kick is more like a oar pushing on the water, so your results were
inevitable.

Based on what David reports on using them in the Northwest, it seems that
the floppy split fins have a fairly narrow "power curve" and would need to
be matched to a particular rig and diver.  If the entanglement issue can be
resolved, a center vented fin with replaceable battens like the Wenoka
Reeflex might work out in some applications.

Jim, I hate to cut you out of a commission, but since I already have more
fins than shoes, I'll have to take a pass on your kind offer.  :)

Don

----- Original Message -----
From: Jim Holcomb <jimholcomb@x-*.co*>
To: Techdiver <Techdiver@aquanaut.com>
Sent: 05 August, 2001 21:47
Subject: Re: Split fins


> Split fins were made for people with a high air consumption rate diving on
> shallow reefs.  I tested a couple pairs of those things when they first
came
> out.  They allow for less work (meaning less air consumption) traveling
> around in a non-current type environment.  From a technical standpoint
they
> are useless.  Most cave/wreck divers use the frog kick. When I attempted
to
> use the frog kick with them I went absolutely nowhere (must be the physics
> of the design?)  With a standard open water flutter or modified flutter
you
> DO move with less effort but not as far - so is that less effort or not?
> But at twice the price I would be glad to sell you a pair <big grin>. Call
> me at the store. <another big grin>.
> Jim

> From: "Don Burke" <donburke56@ne*.ne*>
>
> > From: Joe Citelli <joe@po*.co*>
> >
> > > How could a fin with less surface area and rigidity possibly generate
> more
> > > thrust in the water than a fin with greater surface area and rigidity?
> >
> > If the smaller fin puts less water in the wrong direction, less surface
> area
> > is needed.
> >
> > If the flex in a fin causes more water to go straight back, the flex is
a
> > good thing.
> >
> > An extension of your argument is the use of a 4 by 8 sheet of plywood on
> > each foot.  Since that doesn't seem to work very well, perhaps the
> > hydrodynamic problem is a bit more involved than just surface area and
> > rigidity.
> >
> > > People like them because they are easy to kick with.
> >
> > Perhaps
> >
> > >  But you travel less distance.
> >
> > That isn't how I interpret the test results I have seen.
> >
> > >  Personally, I'd rather kick hard once to cover a given distance
> > > than kick easy three times.
> >
> > I doubt the ratio is that high.  In any case, isn't the figure of merit
> gas
> > consumption for distance traveled?
> >
> > > The manufacturers simply had nothing to sell so they made this up.
> >
> > Perhaps, although the test results do look encouraging.
> >
> > >  Funny how people that buy this kind of stuff typically keep going
back
> to
> > the
> > > stuff in their garage that works.
> >
> > I'm watching all of this.  They have my attention.  Perhaps one day
> they'll
> > get my money.
> >
> > The entanglement issue needs to be addressed.  I touch my line with a
fin
> at
> > least once a dive and don't need anything else to wrap the line around.
> >
> > I saw a fin with vents down the center in one of the magazines and
perhaps
> > that is the wave of the future.
> >
> > The best performers seem to have the blade bent downward in a sort of
> > "ballerina set."  It would not surprise me to find that much improvement
> > comes from that.
> >
> > Don Burke
> > Chesapeake, Virginia

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