Question Do round bottom cylinders change your trim?

[The Cosmicist]

Do round bottom cylinders change your trim/weight balance? I was given LP72s to use for my GUE Fundies class last year and I struggled with being "head heavy" the entire class, which I'd never experience before. My trim hasn't had that particular problem when diving with AL80s and HP100s. It just occurred to me that it could be the cylinder type. Does the rounded bottom mean less steel is at the bottom of the cylinder? Does that actually matter?

 

[happy-diver]

Yes!

 

[rx7diver]

Do round bottom cylinders change your trim/weight balance? I was given LP72s to use for my GUE Fundies class last year and I struggled with being "head heavy" the entire class, which I'd never experience before. My trim hasn't had that particular problem when diving with AL80s and HP100s. It just occurred to me that it could be the cylinder type. Does the rounded bottom mean less steel is at the bottom of the cylinder? Does that actually matter?

An HP100 has a round bottom.

rx7diver

 

[Raphus]

Yes bit its not really that big of a difference.
Just mount the tank a timy bit ower and you should be ok.

 

[Raphus]

I am not 100% sure about that, but i think lp72 are more heavy in the water then the bigger tanks. That could be a reason you experienced a different trim.

 

[rjack321]

LP72s have floaty butts and trimwise act a lot like AL80s. But its not due to the rounded bottom. It's mostly due to their light weight and thin walls relative to their displaced water volume

 

[The Cosmicist]

An HP100 has a round bottom.

rx7diver

So that tells me it’s not the round bottom then. I’ve had no issues with HP100s.

Yes bit its not really that big of a difference.
Just mount the tank a timy bit ower and you should be ok.

I had the tank as low as it could be in the cam straps. I’m also somewhat tall with a long torso.

LP72s have floaty butts and trimwise act a lot like AL80s. But its not due to the rounded bottom. It's mostly due to their light weight and thin walls relative to their displaced water volume

Ok, that makes sense. It’s just a peculiarity with the LP72 then. I’ll have to just make a note of that and remember that if I’m diving with that tank, I need to move all of my weight low.

Thanks for the responses!

 

[divad]

You could try negative(r) fins.

 

[broncobowsher]

Yes.

But the round bottom isn't the difference. It is the tank change that what makes a difference. Different brands of AL80s will trim out differently as well. It's minor. but when down to that last little bit of trim it may be noticable.

Sidemounted matched steel 100s. Left = Right.
Do the same with different brands of AL80s. Besides they sit different than the steels, left would always sit a little different than right.

 

[The Cosmicist]

You could try negative(r) fins.

I would do this, but I won't be diving with LP72s regularly. It'll be just something I have to remember to adjust for if the time arises. I was using Dive Rite XTs at the time with a wetsuit.

Yes.

But the round bottom isn't the difference. It is the tank change that what makes a difference. Different brands of AL80s will trim out differently as well. It's minor. but when down to that last little bit of trim it may be noticable.

Sidemounted matched steel 100s. Left = Right.
Do the same with different brands of AL80s. Besides they sit different than the steels, left would always sit a little different than right.

Yeah it was definitely noticeable with me. Never had the problem with other cylinder types.