Too heavy strobe?

Hey all

I recently purchased a single Scubalamp D-pro strobe, it's mounted on 2 ULCS 8" buoyancy arms but it's still feels like it's not enough to hold it.

How do you handle heavy strobes out of the water when walking to / from the dive if it's a shore dive or when passing / giving it if it's boat dive?

what can I add to the arms to create even better buoyancy underwater?

D-Pro is specified as 120g negative underwater, which doesn't sound like that much, to be honest. I run dual Retra Pros with superchargers, and those are slightly lighter than D-Pro in air (1150g with batteries, whereas D-Pro is 1080g + battery, which is probably another 150-200g), but considerably heavier underwater (320g vs D-Pro's 120g). The D-Pro is heavy, but somewhat less dense, giving it more intrinsic buoyancy.

Is your rig overall too negative, or is it more of a trim issue, where it's trying to twist in some direction that you don't want it to go? Are you using a plastic or metal housing? What ports/wet lenses?

Outside of water not much can be done about the weight - you can experiment with various ways of folding the arms; for example, with a single strobe mounted on a handle with two arm segments, you can fold them over the housing when not in use, maybe even use a piece of bungee cord to secure the middle joint. Cheap low-quality clamps have a tendency to slip even when tightened down, but you're using ULCS arms, so I presume your clamps are ULCS too, and those are good quality.

If nothing else, you can move to larger diameter buoyancy arms, i.e. 80mm instead of your 50mm, or adjustable ones like Hugyfloats or Weefine equivalents.

As Barmaglot says, there’s not much you can do out of water other than playing around to find a way of folding the arms/strobe to achieve a package that is easier to carry, ie as stable as you can manage. 

Have you checked how negative the system is in-water, perhaps using the luggage scales method?  If it is really negative you could consider adding an arm across the top of the housing and adding, say, Stix foam. This creates a very useful carrying handle (and dive computer mounting point) as well as additional buoyancy. 

I've found that having a carry handle at the joint of the two strobe arms (basically the top of the M that they form with camera and strobes) means that gravity will pull everything into place. You can either use one of the clamps that have an attachment point or use a long clamp and use a carabiner that goes straight onto the joint of the clamp.

4 hours ago, hyp said:

I've found that having a carry handle at the joint of the two strobe arms (basically the top of the M that they form with camera and strobes) means that gravity will pull everything into place. You can either use one of the clamps that have an attachment point or use a long clamp and use a carabiner that goes straight onto the joint of the clamp.

That's what I do, I have long clamps with shackles at the top of the M and it stays in pace.   The OP only has a single strobe though, so might need to get creative to carry it by a similar method, perhaps a lanyard from the middle arm joint across to a handle on the opposite side to the strobe arm?

On buoyancy you really need to weigh the rig in water first, that takes the guesswork out of trying to solve the issue that is being experienced.

On 6/10/2023 at 7:20 PM, TimG said:

Have you checked how negative the system is in-water, perhaps using the luggage scales method?

I'm not familiar with that method

I like it a bit negative underwater, but it felt like the clamps had a hard time keeping the strobe in place.

Maybe consider shorter but larger diameter float arms to get similar or greater buoyancy but put less momentum on joints.

8 hours ago, sarthur1 said:

I'm not familiar with that method

Take a luggage scale (something like this) and suspend the assembled rig from it in a bathtub/bucket/pool/whatever. The scale obviously stays above water. If your rig is negative (which, as I understand it, it is) it will show you exactly how negative it is. Note that in seawater, it will be a couple percent more floaty than in freshwater.

1 hour ago, Barmaglot said:

Maybe consider shorter but larger diameter float arms to get similar or greater buoyancy but put less momentum on joints.

I'll look into it, thank you!

I can't really comment on the weight you guys are experiencing, I use Sea & Sea strobes. But I have something that helps me in carrying my rig. I made a carrying strap that is longer than the ones I've seen the "big DSLR rigs" use. Strap it near the clamp of my 2 arms on each strobe and when I exit the water of a shore dive I have a carabiner on my BC at about chest level that I hang it on. Its also long enough that I can sling my setup over a shoulder and carry it that way. Frees my hands to hold fins and stabilize myself on a deck or shore entry. Its a bit over 15"

On 6/12/2023 at 1:46 PM, sarthur1 said:

I'm not familiar with that method

I like it a bit negative underwater, but it felt like the clamps had a hard time keeping the strobe in place.

@sarthur1

As others have mentioned, your arms/strobe will likely need to be folded a bit for carrying out of the water. You don't want to ratchet down the clamp so much that the arm/strobe won't move as you are carrying it (not necessary and it will be harder to loosen underwater).

Are you saying that your arm & clamp won't hold the strobe still while underwater? That's unlikely, unless one of your clamps is not aligned correctly.

In short, you only should care about the "holding power" underwater, above water it's going to sag/move - that's by design...