Strobe Buoyancy Arms (Foam?)

[fmerkel]

@fmerkel
If it's soft; pipe insulation, pool noodle, wetsuit, etc. it simply isn't going to work. Done that. It may float it on the surface but it'll squish like a bug at depth and lose all buoyancy.
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Amazing ! Wet suit wrap worked for me !
Never failed !

Have you tried it ?
I suspect the the answer is NO !

sdm

Tried pool noodles, and pipe insulation. Did not try wetsuit material but I've dove wetsuits. At 60' there isn't much left. It might work, but it would likely be pretty lame compared to rigid foam. Didn't see any point in even trying.
Fisherman's net floats did work. I even found some that fit right over ultralight arms. They ended up being too floaty and the float was in the wrong place. They are cheap and maybe worth a try.
OTOH, the products made for the job aren't too expensive compared to the rest of the photo kit and they are designed to work....and do.

 

[Sam Miller III]

@gummybun
You live in Toronto -- Contact Alex Pierce who now does blogs on diving equipment. He often uses local shops as a studio - He possible has old wet suits or can obtain scraps for you..
Don't be bashful - He and I have been friends for 30 years tell him I sent you

Sam

 

[gummybun]

A kind suggestion, thank you Sam, I may well do that! Not much better than some scraps and not caring what you look like to have some fun!

If that doesn't pan out I will need to shorten my wifes suit a few inches!

 

[Sam Miller III]

@gummybun

A kind suggestion, thank you Sam, I may well do that! Not much better than some scraps and not caring what you look like to have some fun!

If that doesn't pan out I will need to shorten my wifes suit a few inches!
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You are one brave hombre
who knows how to ruin a great vacation !
good luck !

Sam

 

[gummybun]

I still may go with the 1/4" neoprene option as I can travel with that more easily, but looking around the basement I came across a couple of old Yoga Blocks 4"x6"x9" semi solid blocks you (evedently) stand on, but they are soft too. One cork and one foam - the foam one was $6 - never unwrapped. Eco Wise brand I bought at the dollar store a few years ago. "EVA Foam Structure, Durable and Lightweight, Beveled Edges for Extra Comfort, Latex, PVC, Phthalates and Chloride free" so that must please the reef critters - especially the beveled edges!

My first test was to submerge it in fresh water in the kitchen sink - it took 8lbs of lead to bring it to neutral. left it 6" under for one hour, weight prior to dunking was 0.2lbs weight after dunking was 0.2lbs. I observed no bubble being released.
I plan to cut a chip off, 1" x 1" weight it to neutral with some washer, put it into my 100ft home brew pressure pot and see how much water it absorbs, and if it sinks. Upon pressurization it sunk to the bottom and one of two elastics holding on the washers released. Nothing else happened over the following 60 minutes. When I released the pressure the foam block wobble and seemed like it would rise, but did not. On removal the block was weighed as follows...

Foam Block 1"x1"x1"
Damp weight 0.85g Before pressure test, 0.93g After pressure test (100ft, 60min)
Weight Loading to Neutral Buoyancy + 19.95g steel with 1.14g (2) elastic bands.
I put the assembled block back into the kitchen sink and it still floats just below the surface.

Conclusion - this foam appears promising. Pending board member comment.

 

[tursiops]

So, 0.85g of foam soaked up 0.08g of water after 60min at 100ft. It lost 10% of its buoyancy. The questions are, (a) does it dry out and start over at 0.85g? (b) Is it still 1x1x1 or is it a bit smaller than it was, and if so does it recover from that?

The fact that it sank when pressurized means it got smaller, but how much? Maybe you could weight it prior to pressuization so it is (say) 1g buoyant (i.e., use 18.95g steel rather than 19.95), and see if it sinks when pressurized. A little playing like this will tell you how much buoyancy it loses under pressure.

There are two main issues, I think:
(1) does it shrink under pressure.....like a neoprene wetsuit does (no matter with Sam Miller says), and a pool noodle does...and if so, how much buoyancy does it lose? Does it recover its size when depressurized, or is there a permanent deformation? Repeated pressurizations are the issue here....
(2) does it absorb water? Does it dry out again, or stay wet? This can be an issue for air travel following a series of dives...people do not like the STIX floats for this reason. They take forever to dry.

I think (1) is the dominating concern....here is a picture of a standard Styrofoam cup that was submerged to great depth in the ocean. It long ago dried out, and weighs the same as it did initially but it is now about 1.5 inches tall and about 1.2 inches in diam at the mouth. Permanent and major deformation under enough pressure.

 

[gummybun]

I think...
View attachment 510622

Thanks tursiops. Yes, of course I do not disagree (except it lost 9.4% of it's buoyancy not 10% ) and I think that I have started to aswer some of your thoughts, If I understand them - for instance the cube was measured damp before pressure. and it floated (unpressurized) just below surface as before, after pressure. Detailed dimensions (with calipers) would be somewhat meaningless as the cube was not machined square, and is frankly beyond the sensible scope of a preliminary exercise like this.

Repeated trials or a long overnight dunking would be a good idea; doable and would have measurable results. I could also measure overall displacement rather than use calipers I guess. Not sure I have a big enough test tube with gradients.

By the way, that cup looks way better than I look after a long time in the water - and my 'buoyancy' always seems to return.

Edit - Oh, I see , you are suggesting I play by under-ballasting the bundle to estimate the remaining buoyancy % at 100ft. Yeah, I could try that.

Edit 2 - interesting results, am comparing to pink rigid, cork, will post later.

 

[gummybun]

So thank you tursiops for your suggestion. I did some measurements on various 'round the house' products and I will itemize my findings. I cut approximate 1" cubes of product and measured the dry/damp weight and the weight they support before dipping below the surface (fresh water). Then I pressurized for 1 hour and then fiddled to see what would keep them on the surface of the pressure pot which reached a pressure equal to 108 feet (this weeks max pressure). I also measured the damp weight after but as all materials recovered dimensonally and dried out - I can not see the relevance of this. All products stayed pressurized for one night after to see if they collapsed - all recovered.

Product, : Damp wt. , Surface 'lift' , Post-Pressurized Weight , Pressurized 'lift' @108'
EcoFoam : 0.85g, 19.95g , 0.93g, 3.55g
Cork : 3.25g , 13.52g : 4.05g : 10.3g
Foam Pipe Wrap : 0.61g : 24.25g : 0.86g : 4.85g
Neoprene Pipe Wrap : 1.51g : 21.34g : 1.64g : 3.82g
Blue R6 Foam : 0.46g : 21.3g : 0.78g : 9.29g
Pink R6 Foam : 0.68g : 19g : 1.12g : 8.41g
Crap Neoprene* : 11.52g* : 23.63g* : 13.65g* : 4.03g*

Right off I must say my Neoprene sample was crap - I have no 7mm or 1/4' cut-offs on hand - so this test is highly suspect due to the sample I used. When I get my hads on something better I will edit the list.

Dry weight to lift at depth appears to show that R6 Foam is the clear winner.
Cork gives the best lift at depth but heavy as you go up.
Garden variety Pipe Wrap appears not bad, quite good until you go deep and even then not too shabby.

Caveats and comments.
The relevant measurements will change depending on the diver's needs and circumstance.
I can only test small samples due to my 'pressure chamber'.
I have only tested samples a few times and can not say some products characteristics may change.
This was not by any means considered to be a 'scientific' survey, only some quick testing to establish some comparative observations. Your mileage may differ.

If people have any interest in this list - I will re-test for a second set of results.

 

[tursiops]

I'm tempted to send you a small piece of STIX for comparison. I think the most important measure is buoyancy at depth (pressurized) vs at surface (unpressurized). I think that is your fourth number divided by your second number? By that measure, your cork did the best, followed by the R6 foam. Neoprene sucks, as we already know, since wetsuits lose their insulation at depth.

I'm not sure of the importance of your "dry weight to lift at depth" other than being related to how heavy the rig is to carry around at the surface. That IS important, or course, but secondary to retaining buoyancy with depth.

 

[gummybun]

Only temped eh? I'll need to try harder! But really, and excuse me for saying this, but comparison to top 'existing' foam type standards is useful, or also to Kevlar tube arms, but in itself, this is for me missing more than one point. I know there are primo bits of foam out there, primo arms with primo clamps and primo fiber optic cables, prime housings and tripods, primo freaking everything. This is the DIY thread so give us poor suckers some space! Of course I know you can - I'm just being dramatic.

Regarding your second point, I refer to my first Caveat. Every diver will have his/her own needs profile. I considered some ratio calc's but thought I was getting ahead of myself. I figure people can figure the relevant ratios for their situation. For me - heavy cork or stiff foam (even light) (or presumably STIX that I have never handled) is a problem for travel. I need light soft pliable stuff I can shove inside other stuff for long transcontinental flights with 4 to 6 transfers. Also for me most my shots are in the 30 to 60 ft range - so that means that some of the weaker materials that compress more at depth are less of a problem ( I am thinking - as a novice in this area). The odd shot at 100ft - I'll suffer the weight, or so I figure.

One foam undocumented above - still in the pot tonight, slides discretely up the middle of my Locline stems - does STIX do that? I'm just trying to sandbox here, but do feel free to send me a chip of the good stuff! I enjoy your comments, don't get me wrong.