Twin-Jet In Current

[deco_martini]

Does anyone know how the "X fins don't work in current" thing got started?

It seems like observer bias. I was once in a ripping current off North Carolina and my Slipstreams (some of the stiffest fins available) were useless. I had to pull myself hand over hand down the anchor line to get to the wreck.

The truth is, you can go X fast with a pair of fins on. Based on old studies, X is marginally the same with most fins depending on your own fitness. So lets say you are going to the left:

<-X

Now the current is flowing the right (represented by Y) at 3 knots (very strong).

-> Y

The following is for the learning impaired, to stay still in the 3 knot current, you have to be able to swim 3 knots in the opposite direction

<- swimming 3 knots
-> current 3 knots

Why do I mention this? It is near pointless to fin against a current strong enough to pull your mask off with any kind of fin. Switching from Atomic Splits (which I used on strong dives like Maracaibo in Cozumel) to Slipstreams for North Carolina did not turn me into a Superman who could fight against the current.

Not only would I have to do X many knots to stay still, you would have to do much more to actually make good headway against a current.

Now, divers do not have current-o-meters with them on dives. If a diver swims in splits on a rough dive and has a bad time of it because he flails against the current, then wears paddles against a current less intense and makes headway, he might assume the difference was the fins and not the current (surprise). Current is invisible to you. Fins are tangibles.

 

[DA Aquamaster]

Most divers are doing well to maintain 1 kt for a sustained period of time. In the short term, a fit diver can do 1.5 kts, but not much more and not for the whole dive.

Yet I have lost count of the number of divers claiming to make headway in 2-3 kt currents. Umm...No....the current was not as strong as you thought it was.

----

Having cut my teeth diving in the tail race of a hydro electric power plant (currents of 1-7 kts depending on the day, the specific location and the number of turbines running.) I found that really stiff fins like the original Mares Power Plana and Power Plana Graphite worked best with the long bladed XL Jet Fin coming in a close second.

That is not the case for everyone however as not everyone has the leg strenght to take advantage of a large, stiff fin. Several years diving there gave me really strong legs, so I remain biased toward fins I can take full advantage of. If you have stong leg muscles and can use a large, stiff fin to full advantage without cramping you will have excellent results. If your legs can't hack that, a split fin may give you better results in the same way you shift down with a bike to allow a faster kick cycle to make up for less brute leg strenght when going up a hill.

----

Technical diving adds another dimension. When you add the mass of 200 pounds or more of double tanks, stage bottles, deco bottles, can light, etc. with the increased drag of a dry suit, stage and deco bottles, doubles, etc, you need a lot more thrust than the average recreational diver, partcicularly when overcoming all that inertia to get you moving. I have yet to see a split fin do a good job of motivating a diver in that kind of configuration. At best you pedal like mad for several seconds before you start to inch forward. Its frustrating and you look like a dork.

To make it worse a frog kick or a modified frog kick are the primary kicks you will use in technical in order to prevent stirring up silt by ensuring you do not direct any water downward (as is common in a flutter kick) and most split fins frog kick very poorly. That is not surprising as split fins are after all designed more or less for a rapid kick cycle and that is about as far from a frog kick as you can get.

Then there is backing up. If anyone can back up in a pair of splits with doubles, a stage bottle and deco bottle, my hat is off to them. I have yet to see any one do it effectively.

So...in the end I agree with the idea that large and relatively stiff bladed fins are the best way to go when you need to apply a lot of thrust over a short period of time as is the case in strong currents and when accellerating to cruising speed in doubles and stages.

 

[krawdady]

What's funny is almost nothing gets people fired up on this board like the mention of split fins. I own numerous pairs of fins, both split fins and traditional and one of the pairs are twin jets. They are a little "soft" in a strong current so I usually wear blades or my atomic spilts which are great in a current. I can honestly say the Atomics are as good in a strong current as any other fin I've tried.

 

[FishOutUvH2O]

My guess, having used both the Twin-Jet and the Twin-Jet Max, is that the material of the Twin-Jet had more to do with the OP's issue than the split design. The Twin-Jet is a highly flexible fin and had a tendency to expend more of my kick energy on the flex than on propulsion (given the number of previous posters that said the same thing, I'm not being original). The Twin-Jet Max on the other hand is made of a much stiffer material and was able to handle current and hard kicking much better. The trade-off was that the Twin-Jet was considerably easier to kick with than the Twin-Jet Max.

. . . Then there is backing up. If anyone can back up in a pair of splits with doubles, a stage bottle and deco bottle, my hat is off to them. I have yet to see any one do it effectively.

I would love to prove you wrong on this. . . Unfortunately, I tried for most of an AL80 to do a back kick in my Twin-Jet Max's and failed miserably. Was it me or the fins? I don't know. I do know that I was able to back up in a pair of Jets just fine though.

 

[Splash-X]

yes, certain styles of fins work or fail to work best for specific things, stiff fins like turtles are quite good for tight space work were everything except speed is required, they suck in straight line speed and endurance that is required to overcome a stiff current. It has been shown time and time again, that moderately flexible fins are faster and better for endurance that stiff blades.

So then we do agree, different fins for different purposes? You said it yourself:

"certain styles of fins work or fail to work best for specific things"

Twin-Jet is a highly flexible fin and had a tendency to expend more of my kick energy on the flex than on propulsion

The Twin-Jet Max on the other hand is made of a much stiffer material and was able to handle current and hard kicking much better. The trade-off was that the Twin-Jet was considerably easier to kick with than the Twin-Jet Max.

It would also appear to me that someone else has come to the conclusion that different fins are made for different purposes.

There is no SINGLE fin that does everything the best. Know the conditions you will be diving in and select the gear that will best do the job. It applies to anything you do. Sure, tools X can do the job but tool Y was designed for the job in mind.

 

[DevonDiver]

If you want to out-pace your dive buddies, whilst wearing split-fins, then there is only one real option........

Get a pair in pink. You won't actually go faster, but they will be certain to let you swim ahead of the group....

 

[Headers]

I've had a couple of kind of paddles, both fairly soft and fairly stiff as well as a couple of different kinds of splits. I do find that the softer split twinjets don't do much for me and neither do paddes, honestly I just don't feel like i get propulsion out of them that is proportionate to the effort put into them. However my favorite all time fin is the Black Twin-Jet split. They are made from a stiffer material than the yellow, blue etc ones. I'm a guy with fairly beefy legs and I can kick hard enough in the yellow ones or the pair of split Tusas that I have that they basically bend double. Not so with the black one. I really like them for turning in tight places. I've been in ripping currents in them and have found that not only do i keep up, generally i'm at the front. If you're a strong swimmer with the legs to drive them they're an excellent fin.

 

[deco_martini]

My unscientific guess is that people working against a current might "feel" like they are doing better if they feel feedback from their fins. (obviously not in the case of DA who was a special situation diver).

 

[jlovold]

Just a tip: If you are struggling in a current, just hug the bottom or a wall, as the current usually is a lot weaker there. Which is another reason I like using frog-kicks, as I can get closer to the bottom.

 

[tboxcar]

As mentioned I don't go looking for current, but it seems to find me on occasion
I have been using the black Twin Jets for 4 or 5 years now, other fins were giving me cramps, and have not had that problem since using these.

Now as mentioned, I'm diving tropical conditions, no wetsuit (rash guard), and minimal weight. I have been with alot of experienced divers and have have never been in a position where others have left me behind. Although some give me a hard time about my split fins at times.

I agree with the one comment about 'what your legs can handle', strong legs can maybe handle a stiffer fin. I certainly don't think there junk though, and they are very maneuverable.