PLB housing question and also opinion on them.

[OTF]

One thing to consider with PLB housings is how easily they open. Ideally it should never pop open accidentally underwater, but open very easily when needed in an emergency. As in, something you can access reliably even if injured, partially incapacitated, wearing thick gloves, or with near-hypothermic hands. Not something that takes a lot of hard twisting/prying or is liable to get jammed up with corrosion and sand. Keep any threads/orings regularly cleaned and greased. Also consider a tether for the housing and PLB itself, but make sure it's not a string that can get caught in the lid and compromise the seal (ask me how I know about that last one).

 

[TT_Vert]

Have you calculated and taken into account the stresses on the rectangular case at 5 atm? There is a reason pressure vessels are cylindrical......

My software will do that analysis I think. I'll have to spin up a design at some point. You're at about 65 psi at 100 fsw AFAIK.

Nice!! Do you need that design to be square that? Ill probably design a hinge in there so long as I can prevent pinching the oring

 

[tursiops]

At least design them for 130ft with an additional safety factor, like 2x. Anything less than 200 psi is probably a bad idea. Remember the goal is NOT just keeping your PLB dry, you are also protecting it from being crushed.

 

[TT_Vert]

At least design them for 130ft with an additional safety factor, like 2x. Anything less than 200 psi is probably a bad idea. Remember the goal is NOT just keeping your PLB dry, you are also protecting it from being crushed.

Oh I will test well below any depth I will ever go (alive), just illustrating it's not a huge pressure with something with a semi small surface area if selecting the correct aluminum alloy. Likely a 2.0 FoS

 

[OTF]

At least design them for 130ft with an additional safety factor, like 2x. Anything less than 200 psi is probably a bad idea. Remember the goal is NOT just keeping your PLB dry, you are also protecting it from being crushed.

I was about to type essentially the same message; you want significant safety factor on this to withstand impact, exceeded depth, and damage over time.

 

[lairdb]

Have you calculated and taken into account the stresses on the rectangular case at 5 atm? There is a reason pressure vessels are cylindrical......

At least design them for 130ft with an additional safety factor, like 2x. Anything less than 200 psi is probably a bad idea. Remember the goal is NOT just keeping your PLB dry, you are also protecting it from being crushed.

For sure. On the other hand, consider most acrylic camera cases, the InReach case, smartphone cases from many mfr’s, etc. Round distributes stress better — but aluminium is tough, especially the 5000s (e.g. 5083), and ribs can do a lot.

One thing to consider with PLB housings is how easily they open. Ideally it should never pop open accidentally underwater, but open very easily when needed in an emergency. As in, something you can access reliably even if injured, partially incapacitated, wearing thick gloves, or with near-hypothermic hands. Not something that takes a lot of hard twisting/prying or is liable to get jammed up with corrosion and sand. Keep any threads/orings regularly cleaned and greased. Also consider a tether for the housing and PLB itself, but make sure it's not a string that can get caught in the lid and compromise the seal (ask me how I know about that last one).

Yeah, I think that’s actually the biggest challenge with a non-threaded concept. As soon as I finished my sketch, I was looking at it and thinking “if you closed this thing in Denver and flew to Cozumel, you might not get it open.”.

 

[lairdb]

Have you calculated and taken into account the stresses on the rectangular case at 5 atm? There is a reason pressure vessels are cylindrical......

This was quick and dirty, but using AL6061, 2mm wall thickness and no added ribs etc., at 10ATM the maximum wall deflection is 0.3858mm. Now, depending on the sealing area design, that could be enough to cause issues... but deflection at that area where I already built it up shows as only 0.090mm.

 

[TT_Vert]

This was quick and dirty, but using AL6061, 2mm wall thickness and no added ribs etc., at 10ATM the maximum wall deflection is 0.3858mm. Now, depending on the sealing area design, that could be enough to cause issues... but deflection at that area where I already built it up shows as only 0.090mm.

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View attachment 917629

Pretty sure you'd be fine w/ that. Your areas where the oring sealing surface are won't be distorted enough IMO. I wonder what would you would see if you didn't radius the corners

 

[Johnoly]

I'm still a bit leary of using VHF at water level. I'm curious of others opinions on that actually.

I dive with the HX-40 in a McMurdo canister. The reason I chose the HX-40 was it pumps out a FULL 5 WATTS on the HI setting. Most other radios are at only 3 watts. Just before Covid happened, I got lost from my dive boat in West Palm. It was 3-5 waves and current was ripping at 4knots. The boat was outside of the gulf stream wall with a slower current. I had my SMB up but the boat was going away from me, picking up other divers. I waited 20mins to see if they would head north towards my direction, but they were looking too far south. I pulled my radio, channel 78(not 16) and called the captain to come way way north to me, which he did. As I was floating, another dive captain on the Jupiter wreck trek 5 miles north asked me on the radio if I needed help. I talked to him perfectly clear and told him I'm alright. I know different weather conditions can degrade signal strength but I dive with the HX40 because it's the most powerful handheld available. Also I've had other Standard Horizon(SH) handhelds that have flooded and SH gave me an RMA and a new radio with no questions. I have been using my double O-ring McMurdo canister since 2008 and I have flooded it twice, probably from banging it around on charters. No way would I use a single O-ring system as my final rescue plan. Attached is my current dive canister that I dive with Every Dive.

 

[TT_Vert]

my one concern about having all that in there is that it's going to be a disaster trying to use it and keep it dry. you pull one thing and everything is coming out. Granted, you have it all tethered together which is a great idea but if you pull out your radio you have a ton of other stuff likely sitting in the water. You're going to be at the surface best case but not far from the water. How do you manage to keep this stuff dry while open and in use? That laser is a great idea, where did you get that and how would you even aim that unless you had a visual on someone?

Dave