Backplate/Wing selection & Use Questions

[MichaelMc]

Having flexibility in where you put lead/steel is good for trim.

But if you carry enough lead you start just needing spots to put it all. The plate is a good spot for trim. Losing the flexibility for that 3lb. difference is not an issue when you have many more pounds that need homes, and which you can use to address any trim needs.

In the tropics, AL or cutout SS has advantages in giving you more flexibility.

 

[Colliam7]

To a great extent, the answer of individuals will depend on their PERSONAL preferences, regarding weight (added) and the distribution of that weight, as well as the diversity of their diving.

I dive fresh water and salt water, cold water and warm water, using a wetsuit and a drysuit, and carrying single (backmount) cylinders and double (backmount) cylinders. That is not some sort of boast about my diving, simply background on my selections of plates.

Yes, I could dive under all of those conditions with an AL plate, with weight adjusted to accommodate the buoyancy requirements. But, I choose - as a priority - to use the minimum amount of ADDED weight necessary. That is MY personal preference, it doesn't have to be yours, or anyone else's.

So:

If I am diving a wetsuit and a single cylinder in fresh water, I wear a steel BP, and I may or may not add weight. Since my preference is steel cylinders, generally I do not add any weight. My rig is actually balanced, but I do not carry / need 'ditch-able' weight

If I am diving a wetsuit and a single cylinder in salt water, I wear a steel BP, and add some weight.

If I am diving a drysuit with double AL 80s, in salt or fresh water, I wear a steel BP, and add some weight.

If I am diving a drysuit with double steel 100s, in salt or fresh water, I wear a steel BP, and add some weight.

But, if I am diving a wetsuit with double steel 100s, 120s, or 130s, in salt or fresh water, I wear an AL BP, and add no weight.

BUT, all of that nis what works for ME. YOUR results in each of these situations may differ.

My point - YOU decide how you want to configure your rig, for the diversity of diving that YOU do, and YOUR preferences.

If you want to own / use one and only one plate, go with AL, or the steel 'lite' plates that weigh less. There is no problem doing that, and you can then add weight as you need / choose.

If you can own / use both steel and AL plates, and your diving is diverse, set up a steel plate, AND set up an AL plate, and use them according to the conditions in which you are diving.

Therefore, to address your question: yes, you could use an AL plate for every condition, and adjust the added weight. But, you could also use both a steel plate and an AL plate, and adjust weight according to the need. Some would suggest that is inefficient, because now you need to manage two plates. But, for some others (myself included), it is the preferable course. And, both are right.

 

[Doctor Rig]

Great pragmatic feedback and input! Much appreciated!

 

[lexvil]

Don’t mistake dry weight for diving weight, the 3 lb difference dry will be closer to 4 lb wet (salt) given the choice for diving I will always choose SS but for travel where I’m carrying it, aluminum. One of these days Eric will make me a light weight SS freedom plate and I will get rid of the al one.

 

[Doctor Rig]

As an engineer and reflecting on thread input so far, I’d like to share some “theoretical” thoughts that have come to mind. Before I start, I’ll admit to you that I’m not that familiar with BP/W configurations and use, except what I’ve read..... but I’m learning, which is the purpose of this post. Feel free to correct me if any statement basis is incorrect.

It’s logical, that the closer the Back Plate CG is the diver’s CG, the better diver’s stability would be. The CG of a BP depends on the curvature of the BP, the greater the BP curvature the closer it would be to the diver’s CG. With a P-weight added into the BP “V”, yes it would shift the BP CG further away from the diver’s CG. The “V” depth of BPs varies from 1.25 to 1.5 inches.... smaller would be theoretically better. In reality, any lead generated shift of CG from adding a P-weight as discussed, would be significantly less than lead added to tank strap trim pockets.

What does make sense is total backplate weight, with and without lead, is much better than adding trim pocket lead. This supports the keel weight argument, correct?

Overall, maybe the most versatile configuration is likely a Steel Lite BP, which is travel friendly and utilizes a P-weight for both trim & weighting as needed & desired.

 

[saxman242]

I doubt you'd find a noticeable difference in cg movement between a steel plate and an Al plate with a p-weight in the spine.

Personally, I use an Al plate.

In warm water/traveling, I run it, no STA and trim pockets on the upper and lower cam bands. That meets all my weight needs when I'm not wearing a wet suit.

In cold water, I attach a ~6 lbs p weight in the "v" of the plate, add an sta (the p weight blocks the cam band holes in my plate, so I have to use an sta), add ditchable weight pockets, and run the same trim pockets on the cam band. I can get an extra 25ish lbs of lead on the set up that way.


I find the Al plate with p weight an ideal solution for going back and forth, but for long term durability, an Al plate isn't the best option. I already have wear around the holes from galvanic corrosion due to the plate and the fasteners, etc.

Ultimately, plates are pretty cheap. If you do a lot of traveling, it may be worth just getting both.

 

[MichaelMc]

Cutout lite SS is better that AL. Because of aluminum's very low density its (small) land weight is mostly wasted a bit less useful as ballast. Plus SS cutout is likely stronger, and has nice holes you can use to fasten stuff if you want, like lead weights some where along their length.

Yes in terms of front/back trim desirability:
Lead on back side of tank < on side of tank < in weighted STA < in channel < in plate.
Though your spine might like some empty room in the channel, if your suit is thin.

But lead on your front waist is better than all the above in terms of moving back/front trim to the front. Assuming it does not mess up your head/toe trim.

Lead strapped to the back side of the plate, with zip tie and gorilla tape, off to either side is very close to the channel weight in terms of front/back trim. It marginally reduces BC lift, but does not interfere with your spine or with any STA/band bolts.

If you have 10+ or 15+ lb. of total non-tank ballast needs then a solid SS plate tidies up your problems by giving some a nice home. It is a rather obvious choice for those conditions.

If you have 3 lb.:
- cut out SS gives you 1-2 lb. to play with. for trim. Which might help a little.
- solid SS makes you over weighted, though likely not enough to matter. But you have fewer ways to dial in trim. Just playing with the tank or your legs.

If you're between 3 lb. of and 10+ lb?
It's up to you. It depends. Lots of personal preferences. A cut out SS gives you more trim options. A solid SS matches what you want if you have more.

A channel weight vs solid SS is not as big a difference as a cutout SS plate and lead on the front of your body. Most typically on the waist, but it could be a little on the front shoulders or the chest.

 

[saxman242]

Cutout lite SS is better that AL. Because of aluminum's very low density its (small) land weight is mostly wasted as ballast

It's not really that different though... A 2 lbs aluminum plate is about 1.25lbs negative. A 2 lbs cutout lite ss plate is about 1.75lbs negative.

Either way, you're stuck in the noise of the size of the trim weights available.

When you start talking about heavier plates, it makes a much larger difference.

 

[MichaelMc]

Yeah, the SS vs AL density for 2 lb. is in the noise.

For me, the SS cutout is nice as it offers places to more firmly attach trim lead up its length. And is apparently stronger. Plus you do not need to worry about dissimilar metal issues with SS bolts. So a win on all accounts. My lite plate is AL, but if I bought now I'd get cutout SS. I do not dive it enough to spend $100 to switch it out, yet.

 

[Zef]

Between Al plates and cutout SS plates, the main benefit of the AL plate is cost: a cutout SS plate will typically cost more than a standard type AL plate. The main benefit of the cutout SS plate is the design factor if the cutout design appeals to you.

I am not 100% sure because I only have standard SS and AL plates in my arsenal but I doubt that there is strength or stiffness difference between cutout SS and standard AL plates that is material to divers...

...if you look at the Dive Rite cutout SS plate, it is of a thinner gauge than the standard steel plate. I don't think that this design is any more or less durable than a similar weight AL plate. Both are good options for applications where the packable weight of one's kit is of concern such as when traveling by air. In this regard, the AL plate will typically come at a less expensive price but as others have pointed out there could be an issue with galvanic corrosion between hardware and plate with an AL plate...not as much an issue with single tank setup unless one is use metal book screws (sex bolts) to secure the wing in place, or using a STA with steel hardware.

Because of the galvanic corrosion issue cited abovce, if one planned on diving doubles, or planned on using an STA, then I would recommend the cutout SS plate over the AL.

Between SS, cutout SS, and AL, there really is no bad choice, typically one's choice is either price dependent or their perception of which is most appropriate for their application based on their personal analysis (to include packed weight for travel).

For me, I dive locally where the waters do not get warmer than 21c (@ 70f) and the water temp does not stay that warm for very long. I primarily dive in drysuit or semidry and because we don't travel much for diving I have a SS plate. When we purchased my daughters setup a couple years ago we got her an AL plate because she did not need the extra weight the SS plate offered. The benefit to me is that she is now at university so if I was to travel for diving I have the benefit of using her AL plate to cut down on baggage weight (I specifically left her harness uncut for this contingency).

-Z