flipper design

General Discussion
1

I know Churchill fins have blade cut on bias to copy tail fins of sea creatures (see attached pics) BUT seems to me they might work better if used on opposite feet??? Put the most resistance where the most muscle is? Aligned with leg bones and “neutral” mechanics of joints? Engage the quads mo’ bettah?

If not, why I’d love to know? This is also applicable to anyone modifying a pair of UDT’s. Most of them I’ve seen have been cut square. Originally (also Duck Feet) have slight “diamond” shape with blades slightly longer down center of each.

Would love any comments and technical discussion.


2

The theory behind churchills actually has nothing to do with , say, whale fins or whatever. In fact, it’s meant to be a non-cramping design, as the additional pressure on the big toe was thought to cause cramps in non-fin users…which was everybody about the time the Churchills came out.

However… it’s a flawed theory. You can get leg cramps just fine with churchills, as with any others. It’s a matter of conditioning and stretching, especially for us old folks. Plus, maybe, technique.

Copying, say, a whale or a seal is kinda silly, 'cos we don’t have a very flexible and very strong back that goes just about all the way to our heels. They can use a wide, high aspect ratio finset on their after ends, they are built for it. We’re not.

Now, as to modifying duck feet - when ya think about it, how does a fin work? Well, they get used two ways ;

The first is a flutter kick, in the surface, thrashing away at the water. Kinda like the flutter kick pioneered by Duke Kahanomoku in the Olympics. But the reason he used it was to get the back half of his body up and paralell to his direction of travel. Lots less drag that way than with the ( roughly ) 15 to 30 degree incline that most swimmers of the day used. He blew his competition away.

But as to adding thrust - not much. Neither does the surface flutter kick with fins. It’s better than a surface flutter kick with bare feet, but that’s about all. It burns a lot of energy for not a helluva lot of thrust, especially during the 99% of the time when you’re not scratching for a wave and instead are just cruising back to the lineup.

The more powerful and more efficient deeper stroke - there’s where a larger, longer fin stands out. Why, for instance, the longer UDTs blow away the standard duck feet in use if you are kicking deeper and with your fins submerged at all times. You can cruise along without looking like you have an outboard motor set too shallow, use the strongest muscles in your body efficiently.

hope that’s of use

doc…the other one, ya know?

3

As for modifying UDTs; Greenough does it and some say if you weigh in under about 170 pounds its likely necessary. I weigh 130. Plan to try 'em first of course. I figure, if the flippers stay put and my body torques around and up and down, that’s a clue…

4

With the scarcity of UDTs (as alked about in other posts) I’m not about to mess with the design of mine. However, regular duck feet are reasonably priced and readily available, so I made some changes to those. Had no idea where I was headed-just went by what seemed right. For starters, kept the length but reduced the “ribs” to see what happened. I’ve been using them with no complaints. I wish those things were lighter.

5

Why not use your arms for paddling?

6

DrStrange,

A Strange thing happens when you wear Churchills on the “wrong” feet - your feet bang into each other when you kick! Did some testing in the pool. Made me realize that what appears to be almost a backward design actually was well thought out despite the fact that it copies nature.

Quote:

“The feet and legs of a human being were not designed by nature for swimming . . . and the use of my invention converts the feet into swimming members of correct hydrodynamic structure and design.”

— Owen Churchill

7

Well, they can help, but…

I used to have these kids come into the surf shop, looking for webbed gloves to use with their bodyboards and what have you. And then I’d ask The Question:

“Uhm, what kinda fins are ya using?”

“Awww, duuude” - which is a great way to get a thwack upside the head, calling me ‘dude’, I mean, what do I look like, the Lone F#c#ing Ranger or something? - " I don’t use fins, duude".

“So, Ace”, I’d answer, “Like, you walked in here on your hands? Think it through.”.

The thing is that give or take severe medical problems like being a paraplegic, your legs are much, much stronger than your arms and shoulders. They are built to carry you, propel you, the endurance and strength of your leg muscles is vastly better than your arms and shoulders. Even if you’ve got real strong arms and shoulders, your legs are stronger. We won’t even get into the exciting world of rotator cuff injuries. Suffice it to say that if ya can use your legs, you ought to .

And, being a sneaky low life kneeboarder, I use both. With the occasional webbed glove or two when my rather torn up shoulders let me. Which lets me alternate legs an arms (using both for that hard scratch for the sneaky set wave) and basicly stay in the water until i am tired of it, not just tired.

Guys on surfboards can’t use fins. Guys ( and ladies, grommets, what have ya) on kneeboards, paipos, bodyboards, handboards or plain old body surfing… they can. And if ya can, squandering that energy and strength with bad albeit stylish fin design is kinda silly.

So, then, the purpose of this wee discussion…

hope that’s of use

doc…

doc…

8

Let’s not forget the lowly mat rider. 50-75% inflated (how they are ridden most effectively), you paddle w/ your arms it pretty much buckles. It can be done. I did it yesterday after my legs got tired some, just cruising the lineup. But you’d not catch many waves that way.

9

hey Pete, what was it you did with the d/f’s?

I’ve given up on the blue/black udt’s that Greg / John M gave me at Big Sur. Soooo painfull. Should have bought those neo-fins! Have to persevere with the d/f’s I think, or get hydrosplits or similar [lots on ebay]

regards

[say hi to pat]

10

Maybe the kids don’t want to wear fins on their boogieboards because they actually kind of stand on them. Maybe it’s difficult to get that foot on there with a big fin on it? Of course this begs the question: if they want to stand/crouch on a board, why are they on a boogieboard and not a surfboard anyway?