Question Halcyon aluminium versus carbon BP

[DiveTucson]

I was under impression my STA was aluminum (with a 6lb optional weight when you need it - obviously I removed mine). This was a way it came with Eclipse system. Of course now I will have to see what it actually is. It’s definitely matte and not shiny like stainless steel plate - exactly as shown on Extreme exposure site: Halcyon Convertible 6-lb Weighted Single Tank Adapter Notice it doesn’t say whether it’s Aluminum or Steel but given it’s 6lb and add on weight is 4lb, suppose this STA is 2lbs

It is 100% stainless steel.

 

[andrethediver]

Thank you for clarifying.

Here is a thread that discusses the buoyancy characteristics of a Halcyon carbon fiber plate:

Halcyon Carbon Plate

All else being equal, an aluminum plate and a carbon plate (and a tungsten plate, and a stainless plate, and a uranium plate) will displace identical amounts of water. Displacement is purely based on volume of the object being submerged - mass and/or density have no impact on it. (Edited to add...

scubaboard.com

Given everything you have shared, even though a carbon fiber plate may be slightly less negatively buoyant than an aluminum one, it is not enough to have a material affect on your total buoyancy while diving without any neoprene....you will still be overweighted. Due to this, I still contend that it would be better to keep the weight in your wallet.

-Z

Looks like CF backplate is 1.2 lbs with built in Cinch system and Aluminium plate is 1.7 lbs without. Not sure about cinch weight itself. So there is another half lb weight saving. Not sure if CF has a built in STA also…

 

[andrethediver]

I hope you realize that if you do have the weighted STA you can simply remove the lead insert and buy a couple of SS bolts to attach the STA to the BP. Carriage bolts of 1" and 1.25" will do the trick.

Obviously I removed the lead weight…

 

[justinthedeeps]

Has anyone used these $20 Chinese STAs from Aliexpress with heavier tanks? Halcyon branded are way more $$

I certainly would have given it a shot, if I hadn't already bought a Halcygucci backplate back in 2018 that is still showing zero issues! That includes use with twinsets, JJ rebreather, etc, and no STA with a single tank.

At comparative prices though, the AliEx kit is almost 'free to try!'

Its really not a complicated piece of equipment. If it suddenly cracks or delams on a dive without any prior signs, this alone is still unlikely to kill you. It just needs to be stiff, strong, and impervious to repeated exposure to seawater pressures up to ~200 psi. Presumably, they would be smart enough to know to use 316 or higher grade stainless steel grommets ... ? It's not a 4000 metres submersible

 

[JoeTPhilly]

Just wear a wetsuit. LOL

 

[JoeTPhilly]

I was under impression my STA was aluminum but now that I checked Halcyon doesn’t even offer aluminum STA and one with Eclipse is SS weights around 2lbs without cam bands. Carbon fiber are 0.25 lbs for comparison at $140. Halcyon Dive Systems

It is not that heavy; less than a pound. With the cam bands and bolts it is 2.4 pounds in total. However, you need to compare the 15 ounces of the SS STA to the CF STA since you will still need the bands and bolts.

 

[JoeTPhilly]

Looks like CF backplate is 1.2 lbs with built in Cinch system and Aluminium plate is 1.7 lbs without. Not sure about cinch weight itself. So there is another half lb weight saving. Not sure if CF has a built in STA also…

There new Halcyon CF plate comes with the cinch built in but no longer has the built in STA. In the past there was two version; regular and pro. You might be able to find the discontinued regular CF with no cinch and no built in STA.

As to weight savings, the cinch upgrade is just a delrin plate bolted on the plate; weight would be minimal.

 

[andrethediver]

Is that CF backplate one with built in Cinch? My aluminum BP has additional plastic? Cinch bolted on it so not sure how built in looks like.

 

[Tracy]

Halcyon does not make an Aluminum STA. So you most likely have a stainless STA.

They used to make it. Not sure when they stopped. I have a Halcyon AL STA.

 

[Tracy]

Is that CF backplate one with built in Cinch? My aluminum BP has additional plastic? Cinch bolted on it so not sure how built in looks like.

I have a new CF backplate with the cinch system and integrated STA if you are interested in one. I bought it and never dove it. It seems too short for me.