Since this topic comes up again over time, I am opening a thread to discuss it and gather data and ideas in the future. 👴🏽

Stix foam cubes have always been a very good and solid choice for floating arms. Their big advantages are:

• They are made in different base cube sizes, which fit into normal aluminum arms.

• You can get the floatation you want by adding/remove them or even cutting them.

• Because they are modular, you can easily change them quickly between dives depending on the lenses, ports, or lights you are using.

• They also look sleek ☺️

They have somehow, some limit too:

• They are only guaranteed down to 40 meters. This means they cannot be used for technical dives. I tried them myself at 70 meters, they became like marshmallows and the camera was like an anchor.

• They are specifically thought for arms and not for other special uses, like collars for wet lenses or pads to use as a base for a video housing.

• Even though compared to the cost of other parts of underwater camera gear, they are cheap, they are not cheap overall.

Also, many of us have always been interested in the dark side of DIY 😈 So, let's see what a possible alternative could be.

The option most like Stix foam is high density closed-cell PVC foam.

High-density PVC foams are very important materials in making strong, light composite products. They are not just light fillers. They are made to be strong inside materials that are key to how well "sandwich structures" work and stay together. These PVC foams have mostly closed cells and a special connected structure.

These foams are made to be very strong and last a long time. Important features of these materials include that they soak up very little water, can stand up to chemicals very well, and hardly let any moisture in.

The most famous commercial name is Divinycell. Ther are countless types for different markets and uses. I linked directly the most suited and cheap for our use case.

From the datasheet you can download, I'll give you a spoiler right away: for recreational diving, the H45 type is good, while for technical diving, the H60 or even H100 type is good. The codes tell you its density in kg/m3 (I'm a metric guy, good luck to those who use Imperial). The only column we care about is its compression strength. I would use the minimum value. So:

Unit		H45	H60	H100
MPa	Minimum	0.5	0.7	1.15
Bar		5	7	11.5
Depth (meters)		50	70	115

Hence, a material with compressive strength of 0.5 MPa (0.1 MPa = 1 Bar) can theoretically withstand the pressure at 50 meters depth in seawater before starting to deform. Someone would like apply a safety factor in real applications. Personally I would use H100 for everything.

I used Divinycell as an example because it seems to be an industry standard and the more common. But there are other similar products out there. All of them have a similar chart, so the idea is the same. (Corecell, Klegecell, Airex, Termanto, Nidaplast)

It's worth mentioning that there are also partially pre-cut panels of cubes that would be perfect for collars.

Where can you get this material? Is it expensive?

It depends on where you are in the world. The material itself is very cheap, but if you buy from distributors, it's usually sold in panels as big as doors (1 meter by 2 meters). So, the cost becomes quite high, and it's also too much for what we usually need it for.

Again, where you can get it depends on the country you are in. Below, I will share some personal ideas.

• Maybe you are lucky and you live in a part of the world where you can find this material online or hardware stores or model shops.
  

• Distributors are the main place to get it. Try asking for a demo sample, like a piece that is 40x40 cm and 4 or 5 cm thick.
  

• In the sea world, this material is very common for building the main parts of boat decks. It gets covered with resin or wood. So, small and large boatyards have a lot of it, including many leftover pieces from cutting. If you are lucky, it's easy to get some for free.
  

• High-density PVC is the most used material for fishing floats. Specifically, for deep nets, they use floats that are guaranteed to work at depths over 200 meters. Here in Italy, there's a big company that sent me a box full of floats for free. They said these floats didn't pass their quality tests. But actually, they are perfect; they just have tiny cosmetic flaws that I couldn't even see. I specifically chose the large, cylinder-shaped ones. They don't look good as they are, but they can be cut, painted and used as basic blocks for what we need.

You can, of course, also find it through some brands that sell diving and underwater photography gear. But the words "diving/underwater photography," and "cheap" are oxymorons. 😄 Two links:

https://www.easydive.it/en/accessories/arms-and-accessories/floats/floating-square-easy-float.25.html

https://www.adval.it/_eng/galleggiamento.html

One last word on how to work with it: You can easily cut it with a wood saw or a utility knife, and you can sand it just like balsa wood. It can also be spray-painted.

10 years ago I got a demo panel of about 40x40x5 cm. With a pencil, I drew squares the same size as the Jumbo Stix, and the carpenter cut them for me. I also had him make off-center holes, like the Stix, using a hole saw. Hundreds of tech dives with them.

I've got these two pieces of THALAGAL for my monitor, and I guard them like precious jewels, considering they cost an arm and a leg!

My precious treasure of fishing floats is waiting for the next project.

Please feel free to add corrections, links, and suggestions.

Ciao

2 hours ago, Davide DB said:

My precious treasure of fishing floats is waiting for the next project.

MY PRECIOUSSSSS

I made a lot of things with 3D printing... some was floating arms.
The main problem are to have part where to water don't come in... it works good with epoxy and carbon fiber to have a long life.. otherwise after some dives the arms a leaking or if you go to deep imploded... Bigger wall --> more weight... lighter --> thinger wall --> leak easyer because of the deformation and some time break

A lot of try & error.

A solution I used and probably will reuse are to make a 3d part with thing wall. and fill it with epoxy shaum. Dual wall are also an option

Epoxy Resin PB 250 + Hardener DM 03

I used this solution to repair somme leaking parts.. really easy to use.

The foam is very rigid and waterproof. I used the 250 version but now there is a product that is 170 kg/M3. I allready buy this one nd will made some tests.
The target is to build lighter arms, without losing durability --> they will be smaller

"Work" for the next winter 🤪

I use exactly the same fishing floats as you show in the last photo. I order them here, for 2,20 Euro each (no problem, at least in EU, but you have to order a lot to be in balance with shipping costs (I guess 15-25 Euro within EU, depending on location): https://engelnetze.com/en/float-cd-250g-buoyancy-91x45mm-14mm-center-hole/?_gl=1*1sv2od3*_up*MQ..*_gs*MQ..&gclid=CjwKCAjw4K3DBhBqEiwAYtG_9LUz0wqqiSOspGiHNOOJMt1FDejaZ_UqQt0JOrV_Lkc2fyx0BXNM7BoCbGUQAvD_BwE

Also these here are nice to use (currently 1,79 Euro each): https://engelnetze.com/en/float-y30-270g-buoyancy-67x109mm-14mm-center-hole/?_gl=1*19hzov0*_up*MQ..*_gs*MQ..&gclid=CjwKCAjw4K3DBhBqEiwAYtG_9LUz0wqqiSOspGiHNOOJMt1FDejaZ_UqQt0JOrV_Lkc2fyx0BXNM7BoCbGUQAvD_BwE

They are closed cell foam and hence can also be cut e.g. into two halves and still will not suck water (I also use halves of both types of floats for fine tuning). One can drill a 25mm hole in the middle, for easily putting the flash arm through. With a little force, one can use them also as they are (but sometimes an O-ring of the arm gets loose then and has to be fixed again).

I never had Stix floats, but I think they are at least of the same, if not better, quality since these floats are used in hundreds if not thousands to balance the nets of commercial fishermen.

This type of floats is designed for the surface, but is good enough for recreational scubadiving as well (up to approx. 50m; they will compress a little beyond 30-40, but with the types I have linked this compression is small & reversible (I once ordered bigger ones ("float T"/680g buoancy, but these are too weak and collapse upon pressure and hence cannot be recommended). Lisi and me use them now since years at full satisfaction, little signs of usage until now...

=> For technical diving I would take floats that are made from material that is more robust and tolerates greater depth than PVC, e.g. these here (I did never test them out, so cannot say about real life performance, especially #1 and #2 will have to be tested out whether they withstand the pressure at the depths where you dive):

#1.: PE and PP, more robust than PVC (good for high pressure cleaner, but they do not say up to what depth). Only available up to 100g flotation: https://engelnetze.com/en/solid-pe-and-pp-floats/?_gl=1*4uqk5e*_up*MQ..*_gs*MQ..&gclid=CjwKCAjw4K3DBhBqEiwAYtG_9A5H5eSfHAZdPf3BwBY_HWtA9AYhgVUmAZx7k1p0HSrG3AEtzDdxKhoCI7wQAvD_BwE

#2.: EVA floats. Robust and available between 160-8500g buoancy: https://engelnetze.com/en/eva-floats/?_gl=1*s8r69f*_up*MQ..*_gs*MQ..&gclid=CjwKCAjw4K3DBhBqEiwAYtG_9A5H5eSfHAZdPf3BwBY_HWtA9AYhgVUmAZx7k1p0HSrG3AEtzDdxKhoCI7wQAvD_BwE

#3.: Dedicated Deep Sea Trawl Floats (rated between 400-1800m, depending on type; will do it for you in any case 😋 ). Available 780-17600g, probably they have to be cut into pieces: https://engelnetze.com/en/deep-sea-trawl-floats/?_gl=1*1lck9m3*_up*MQ..*_gs*MQ..&gclid=CjwKCAjw4K3DBhBqEiwAYtG_9A5H5eSfHAZdPf3BwBY_HWtA9AYhgVUmAZx7k1p0HSrG3AEtzDdxKhoCI7wQAvD_BwE

Wolfgang

Edited July 7Jul 7 by Architeuthis

It would be good also to find out the material they use for the styrofoam collars on the WWl and others that seems like it is good to 100m so should have a compressive strength around 10 bar/1000 kPa. The highest compressive strength I found was 700 kPa or so and density up around 50 kg/m3, but most data sheets just put down >100 or something, I think that's a spec value for some common use and if it meets that they just report >spec.

I seem to recall people talking about using yoga blocks which seem quite robust, but I seem to recall people reporting that they collapse at depth.