what causes yoyo motion while drysuit diving?

[stepfen]

Hello,

As I was trying a drysuit (did my 5 first ever drysuit dives with it) I noticed that while frog kicking my body was kind of yo-yo i.e. my head/torso moved up and down with every kick.
To get an idea of what I mean see from 8:30 in this video:
Ok, in that video this guy (among other things) is using his hands and as a result the yoyo motion is even more extreme, but I use it just to give you an idea of what I mean.

In my case, the motion is much smaller overall but I can still feel it. Generally, my hands stay still (either slightly extended forward, or wrapped around my torso) while I am fining. My weighting and trim is quite good but maybe not 100% yet (need more dives to get it there). I never had this problem with wetsuits (or at least I can't remember having it).

Any ideas what is causing this and how to avoid it?
I just got my new drysuit which has much better fit than the one I was trying (that one was huge on me) and going to be diving with it soon, so any help is welcome.

BTW although I am just an average diver I can see a lot of very wrong things going on in that video - please don't focus on these.

Thanks

 

[happy-diver]

First off you have to get into some relaxation techniques and learn how to breathe man.

 

[BlueTrin]

On the video the person is not stable at the time you gave. His trim keeps changing. If you are not stable and flat when finning you will fin upwards or downwards.

It takes usually a bit longer than 5 dives to get used to a drysuit. The air bubble in a drysuit is quite big compared to a BCD so you have to be very proactive when managing buoyancy with your lungs in a drysuit.

 

[dlofting]

It's hard to say exactly but what you've describing is usually caused by buoyancy changes.....breathing deeply?.....possibly you're moving a bit vertically when you kick? You do have another "air pocket" with a drysuit which is subject to depth changes. You may have been shallower than you usually dive, which causes a greater buoyancy change with depth change.

 

[admikar]

Depends on whether you are doing frog or modified frog kick. In video you posted, fins are above diver's body, which will introduce torque force, causing his head/upper body to pivot down on kick. Also, people worry too much of air going into trousers/boots and tend to maintain slightly body up position, which then force them to change direction of finning away from body axis, which will then again introduce torque force.

 

[rob.mwpropane]

99% of issues with drysuit end up being more practice required. It's just a new task your body isn't used to.

Personally it probably took 15 or 20 dives before I felt pretty comfortable, and I'm always tweaking how I dive. Some get it in 3, some in 30..

In the beginning I was adding too much air to the suit. You can always ask around for tips and tricks, but in the end it's usually just more practice needed.

 

[Lorenzoid]

Just to be clear, the video you posted is someone else, not you?

The person's frog kick is poor, so it's difficult to tell how much of that yo-yo-ing is due to poor kicking technique as opposed to a trim (weighting) problem. I would add that being able to hover motionless in horizontal trim is a good skill to master early on. If you can hover in horizontal trim, then adding forward propulsion should help zero in on the problem. Some trim weights may need to be added to balance you in horizontal trim. When I got my first drysuit, the first thing I did (or my instructor had me do) was plant myself above a platform and make sure I could stay there without rising or falling or pitching forward or backward.

 

[Shabaday]

I also thought the fin kick was poor...at first I wasn't even sure what the kick was??

 

[ginti]

Hi @stepfen, I don't believe the issue you posted is related to the drysuit. I think it has more to do with a good trim, ith arms positioning and kicking technique.

(1) trim here is borderline (or above the border) for tech diving activities; there are no references, but I believe the diver is more inclined than 20°, probably around 30°; not that bad, but not sufficient if you want to master the frog kick.
(2) arms are moving a lot; not only do the movements introduce some forces, but they also reflect that the diver is not very well balanced (again, with respect to what I consider a tech standard)
(3) the diver is kicking way too fast, probably to counterbalance the instability and the trim

So, for you, these are my suggestions:
{A} be sure that you are as flat as possible (<15°)
{B} be sure that you are very stable; how to check it? While in the middle of a swim, stop finning and moving; if you go up/down, you need to adjust your buoyancy; if you rotate, you need to move your ballast or to change your arms & legs positioning
{C} then, improve the technique; ideally, you should kick, wait for some seconds (3?), and then do another kick. There are a lot of details about the technique to discuss, but you better do it with an instructor

 

[VanHandyman]

It was a complete game changer for me when I stopped using my BCD for buoyancy and started using my drysuit instead. Managing two different sources for buoyancy is confusing and very difficult to manage.