Trim question on BP/W

[cummings66]

I have a DSS BP/W and dive a drysuit with a single AL80, right now we're getting along fine and I have my trim pretty close to where I want it with the only added weight being on my belt.

The issue is I have 16lbs of lead on my belt and I'd like to take some of that off. I've considered the lead plate that goes on the BP which is 8lbs or so and I've got a lead on a steel 100 tank as well. Now if I move that much weight to my BP my trim should change.

I know how to adjust my trim of course, but I don't want to buy the weight plates or the steel tank and then discover that my feet are high. In other words the combination will take ~12 lbs off my belt leaving 4 lbs there, the rest of the weight will be on my back spread out along the plate allowing little variance for trim. Because I'm good now with 16lbs on the belt I'm concerned that moving the weight like that will force me out of trim with the only way back being ankle weights. What do you think? I just don't like ankle weights.

 

[TSandM]

Thank you for asking this question, because I've been wondering the same thing.

 

[BabyDuck]

maybe some of it in cam band pouches?

 

[MSilvia]

Try adjusting the position you hold your legs in while you swim. The more bend there is at your knees (the closer your feet are to your butt), the more "head heavy" you will be, and the straighter you hold them (the further your feet are from your butt), the more your head will pitch upward. Basicly, if you use your body position to adjust your trim, you won't have to worry as much about the change. Just expect it to take a little getting used to. Since the shift in weight is close to your center of gravity though, it shouldn't take much adjustment to get it nailed.

 

[countryboy]

Don't assume the weight change will be pound for pound..

When I switched to BP/W (S. Steel, 6lbs) I took 8 lbs. off my belt.
When I switch from Al. 80 (+4 positive empty) to a LP Steel 108 (neutral empty), I change ~ 8 lbs from my belt.

The only way to positively identify what it will take is to perform a buoyance check post dive w/ nearly empty tanks (less than 500 psi on the Al. 80, less than 400 psi on the LP steel in my case).

This is with single 7mm full suit, hood gloves, etc.

If you can, try to borrow (rent?) a tank that you wish to buy first and try it out. Try using velcro strips (or small weight pouches) in standard weights and move them around your rig to see if you can find the balance you desire. Personally, I did not like the small HP 100 PST tanks, that is why I purchsed the LP 108's instead.. as always.. your mileage may vary..

 

[GreenDiverDown]

Wow! Two excellent tips, already!

I swear by cam band pockets... they make dialing in trim a snap. Changes in leg position can be used to make fine adjustments in trim and in a pinch can be used to trim out when in a setup that isn't already tweaked for a partcular dive.

I think Tobin will be along to help you with the weight plate deal... they're stainless, BTW, not lead.

A simple way to check it out before buying the plates would be to just thread two 2# weights on each cam band and then take 8# of your belt. Dive it and try it. But I suspect that the plates would work well with the Al cylinder and an eight pound weight belt.

If you switch to a steel cylinder things will change, of course. I don't dive steels but just thinking about this I suspect that you would not want to use the weight plates in that kind of set up. Trim issues aside, you'll still want a balanced rig and to do that you MAY need some ditchable weight. For a single E7-100 I would guess that to be around eight pounds. That sorta rules out using the plates.

 

[piikki]

This is no attempt at advice but from a noob to noob I tell what happened when I swapped from Al to steel – maybe it will offer you something. Nobody advised me of what moving weight around the body would do to trim too much, so I did experience a few cackling moments in a process. I have somewhat floaty legs (attached to somewhat of a floaty body) and already in OW with regular Al80s I was prone to wheelies head first (ie if I bent my knees I felt like the legs were going to take me for a ride).

When diving Al80, 20 lbs (originally 30lbs) of lead on belt kept be from wheelbarrowing my way but as soon as I bought a steel tank (and that was soon), and reducing weight to 6lbs on the waist I found myself on my nose again. This was regardless of were my floaty legs were – and it took me considerable time to realize it had basically nothing to do with the steel tank per se BUT the type of steel tank I had. I had bought too short a tank (HP80) for myself and I had no weight on my flying butt. Otherwise it was absolutely great, and that’s why I wanted to pitch in.

Even with a wrong tank tt did not take too many dives to realize what was happening and compensate the best I could for the slight tendency to nose-dive (ie incurable top-heaviness). Considering this was the only steel tank that was available at the time, I’d still choose it over the Al80 any day because what it did otherwise: it placed all the weight on my center of gravity (and lungs), it took all weight off my belt, and it practically gave me half the effect of diving with a plate in my opinion (all the weight is there, dropped it from elsewhere). If I had had correct size tank from the beginning, it would have been perfect. I do admit I don’t dive dry, so I don’t know what that brings with it though! Now I wait with horror what happens every time I need to use rental Al - I strap a fair amount of lead on tank straps to make press my butt down and effectively keep my legs from rising. I can’t believe you would go worse with a steel tank if you don’t make a sizing mistake.

 

[cummings66]

nothing to do with the steel tank per se BUT the type of steel tank I had. I had bought too short a tank (HP80) for myself and I had no weight on my flying butt. Otherwise it was absolutely great, and that’s why I wanted to pitch in.

Buying the wrong tank is one of those things I want to avoid and part of the reason for the question.

I would like to end up with less ditchable weights, ideally the amount needed to offset the air in my tank. By the way, I dive a Viking drysuit.

 

[mmadiver]

Off the topic: What sort of viking suit, and what underwear do you wear?

 

[matt_unique]

.... Because I'm good now with 16lbs on the belt I'm concerned that moving the weight like that will force me out of trim with the only way back being ankle weights....

Heaven Forbid!

--Matt