Perfecting Buoyancy and Trim

[rmills]

Also don't buy into the pervasive theme that "natural trim" musty be perfectly horizontal.

That's good because I have limited mobility in my neck and if I'm truly horizontal and I can't see too far in front of me.

 

[Badger7]

Not sure you'd need "bouyant" fins to get a noticeable change in trim either, just "not so negative". Did you mention what you are using for fins? I didn't see anything mentioned above. I've always been very happy with my trim in warm water diving, salt or freshwater. I don't need any weight with a thinner wetsuit and an aluminum plate either in freshwater (pool in my case), and only 6-8 pounds of lead in saltwater.

I did have some significant trim issues when diving colder freshwater, especially with thicker exposure protection, drysuit in particular. Doesn't directly translate to your situation except this - moving a little bit of weight around between plate position and the cam bands didn't help, and moving the tank up further in the cam bands didn't help drastically either. For me, what made the biggest difference in trim was switching from Apeks RK3HD fins (-240g combined bouyancy in freshwater) to regular Apeks RK3 fins (neutral in freshwater), and switching my flashlight to a heavier one that uses 4 18650 cells. That was it, tank position back to centered on the wing, and nice natural horizontal trim with the heavier flashlight and lighter fins. I suppose that makes sense, as the farther a weight change is from center of gravity, the longer the lever action.

Point being, see if you can borrow some lighter fins and carry a flashlight and you might like the result?

 

[rmills]

Not sure you'd need "bouyant" fins to get a noticeable change in trim either, just "not so negative". Did you mention what you are using for fins? I didn't see anything mentioned above. I've always been very happy with my trim in warm water diving, salt or freshwater. I don't need any weight with a thinner wetsuit and an aluminum plate either in freshwater (pool in my case), and only 6-8 pounds of lead in saltwater.

I did have some significant trim issues when diving colder freshwater, especially with thicker exposure protection, drysuit in particular. Doesn't directly translate to your situation except this - moving a little bit of weight around between plate position and the cam bands didn't help, and moving the tank up further in the cam bands didn't help drastically either. For me, what made the biggest difference in trim was switching from Apeks RK3HD fins (-420g combined bouyancy in freshwater) to regular Apeks RK3 fins (neutral in freshwater), and switching my flashlight to a heavier one that uses 4 18650 cells. That was it, tank position back to centered on the wing, and nice natural horizontal trim with the heavier flashlight and lighter fins. I suppose that makes sense, as the farther a weight change is from center of gravity, the longer the lever action.

Point being, see if you can borrow some lighter fins and carry a flashlight and you might like the result?

I bought the Apeks RK3. It doesn't say anything about being the HD variation but last time I checked I think I remember them sinking slightly.

 

[Underwater Tourist]

When I bought my current set I didn't realize there are some that are negative and some positive and apparently bought some negative ones. At least they're negative in fresh water.

Might be a helpful video for you:

 

[Kharon]

Hahaha... I suppose I am dense. I was surprised too. I had been carrying 4 lbs when I did this exercise. I kept dropping my weight until I had none. I tried again picking up just 1 lb and sure enough I descended.

I would try putting 2 - 1# weights very high on the tank and a tiny bit of air in the bc.

 

[The Chairman]

Just because you don't need weight, doesn't mean you can't use weight. Shoulder or tank neck weights might be a great solution for you.

 

[Badger7]

I bought the Apeks RK3. It doesn't say anything about being the HD variation but last time I checked I think I remember them sinking slightly.

They use the same mold, but they do change a little mold key on them for the HD versus the non-HD version. If you look in the foot pocket, there will be a little circle. If the circle is blank they are the ligher non-hd version. If the circle says "70" they are the heavier HD version that sinks in both fresh and salt. Commonly, twinset divers prefer the HD version to offset the extra valves and brass up by their head, and single tank divers might be better off with a lighter fin.

 

[Badger7]

 

[Badger7]

I filled up a barrel with fresh water and used a spring scale to determine my HD super size fins were about 120 grams negative bouyancy (each) in fresh, while non-HD super size were almost exactly neutral in freshwater.