Do swim fins generate drag significantly ?

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zensuni
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Do swim fins generate drag significantly ?

Unread post by zensuni » Fri Jan 25, 2019 8:32 am

I was wondering, do swim fins generate drag significantly ?
I thought about that the other day, as I was riding a very small, weak wave. I was wearing asymetric fins, Churchill like model, oversized to balance the tick winter socks (short rider but XL fins). As I was riding I could feel the flippers dragging and slowing me down. I usually don't feel that on regular waves.
My theory is that maybe I had reached the minimal planing speed for the board, but not for the fins somewhat.

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Re: Do swim fins generate drag significantly ?

Unread post by Nels » Fri Jan 25, 2019 11:41 am

My unscientific observation: If it increases propulsion when kicking in the water, it increases drag when riding.

Options seem to include narrower profile fins like Duck Feet and Vipers, larger board to allow you to pull your feet out of water, or large enough board to arm paddle without fins.

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Re: Do swim fins generate drag significantly ?

Unread post by rodndtube » Thu Jan 31, 2019 9:21 am

Fins (and legs) in the water while riding can affect the entire drag range from none to complete stop. Often times you will need one's knees bent to keep the leg and fin out of the water which means you are planning on the board. Most fins & legs on an even plane behind you on a wave will create some drag, can aid in turning, etc. Some fins' top surfaces, the same ones in contact with the water while riding, can provide increased speed if part of your board's plane or create a rear flex while in the face of the wave and maintain or increase speed. My Vipers were good in not creating drag with correct placement in the wave, but my DaFin's do not. A little commentary is here:
https://mypaipoboards.org/flippers/flip ... vs._DaFins

Fins should be evaluated for each person needs and preference. No right answers for everyone because our feet and styles of riding vary so much.
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Re: Do swim fins generate drag significantly ?

Unread post by GeoffreyLevens » Thu Jan 31, 2019 10:11 am

Quick note on Viper fins fit. When I lived in Sonoma County in NorCal it was cold water all the time. I just bought up a size from that suggested by my shoe size and wore 5 mil booties in them. Perfect comfort and all the rest of the Viper benefits.

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Re: Do swim fins generate drag significantly ?

Unread post by rodndtube » Thu Jan 31, 2019 6:04 pm

Geoffrey, you are exactly right and that is the moral of the story... feet are so different. For me, sizing up to cold water fin socks were so tight they caused cramps.
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Re: Do swim fins generate drag significantly ?

Unread post by krusher74 » Sat May 18, 2019 2:50 am

I once wore a GoPro facing backward on my back to film into the wave behind me, one interesting part of the footage I caught was my fins, they were skipping across the water barely touching and my legs looked like jelly. So as anything would touching the water they will create some drag, but it thinks the human ability to only press them against the water hard if needed negates most drag there is hardly any if not needed.

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Re: Do swim fins generate drag significantly ?

Unread post by rodndtube » Sat May 18, 2019 8:28 am

I am 5'10", ride a 50 inch board. All my boards are basically 50 inches except for the wood Xylem which might be 48 inches. In some cases the swim fins are extended in the manner in which Krusher relates, in other times one might be plop into the wave during a turn. I don't think about it too much, just work on muscle memory, but am surprised at how often my knees are bent. For example, in these two photos:
RodSurf-2011-0125_TdlR_Drop_w600.jpg
RodSurf-2011-0125_TdlR_Drop_w600.jpg (114.83 KiB) Viewed 1234 times
RodSurf-2011-0116_TdlR_Cutback_HiRezCrop.jpg
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Re: Do swim fins generate drag significantly ?

Unread post by nomastomas » Fri Nov 01, 2019 2:04 am

zensuni wrote:
Fri Jan 25, 2019 8:32 am
My theory is that maybe I had reached the minimal planing speed for the board, but not for the fins somewhat.
The other day I was out on my G5 in barely 3ft surf. It was a very clean, dawn patrol session, and I was out because I was eager to try my new Duck Feet fins. There are times when I'm moving around the line-up that I pull the nose of my 49" board under my chest, stop kick paddling and simply arm paddle (you know, swim). I'm always surprised at how quickly and smoothly I can move through the water, at least for short periods of time, when doing this. What I noticed was that my feet were actually floating on the surface behind me as a moved through the water. This never happens when I'm just swimming without fins. If I stop kicking my feet, they just drop under water. Duck Feet fins are said to be buoyant, and the thought occurred to me that the combination of the buoyancy and the surface area of my fins was helping to keep my legs up on plane, and that this is what was giving me the enhanced glide through the water. (I once read that kicking helps to keep the swimmers body on plane more than it helps to propel the body)
I'm rarely aware of my feet when actually riding a wave, unless I'm purposely dragging a fin to stall, or instinctually sticking my leg in the face of a particularly steep section.
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Re: Do swim fins generate drag significantly ?

Unread post by GeoffreyLevens » Fri Nov 01, 2019 11:01 am

nomastomas wrote:
Fri Nov 01, 2019 2:04 am
There are times when I'm moving around the line-up that I pull the nose of my 49" board under my chest, stop kick paddling and simply arm paddle (you know, swim). I'm always surprised at how quickly and smoothly I can move through the water, at least for short periods of time, when doing this. What I noticed was that my feet were actually floating on the surface behind me as a moved through the water. This never happens when I'm just swimming without fins. If I stop kicking my feet, they just drop under water.
I noticed this when paddling kneeboards. But remember, if tail of board is even a very small amount past your hip joints it is taking some of the weight of your legs and also shortening the lever arm of legs to flippers. AND, it's been awhile so not sure of this, but I suspect that even if just short of the joint, by taking the weight of your hips and butt, it changes all the angles etc from there down and (your board) helps keep feet "floating"

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