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SUPER low volume mask modification

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Apneaddict

Well-Known Member
Sep 2, 2010
1,339
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I know that for serious depth work, most freedivers prefer the Aquasphere Sphera, as it is low volume and compresses with depth.

I have a narrow face and the Sphera is too wide for me for a comfortable fit and on me there is quite a decent amount of air volume when on.

I mostly dive in cold water (Canadian lakes), so need the silicone coverage of a mask and fluid goggles just won't cut it.

For safety, I also like the visibility that a mask provides... not to mention the lack of hassle and durability of glass lenses.

Here's what I came up with with this scene as my inspiration:


I took the mask in my collection that had the smallest amount of void space while on. For me, it was the Micromask. My eyelashes touch the lenses but the peripheral edges / sides had 75+% of the air space.

I used a silicone putty product called Sugru to fill the void spaces that I didn't "need" for line diving.


First I cut up a credit card and use as an estimator and electrical taped it in place to verify the amount of peripheral vision vs. remaining volume that I'd end up with (didn't want to screw up a $100 mask).




Once sure, I moulded some Sugru into the voids and fit it behind the seal.

When this thick, the Sugru takes several days to FULLY cure and off-gas... but it makes an awesome bond and is safe on your eyes / skin.

The result is less than 20cc of air space and incredible visibility, because my eyes are so close to the lenses. I've still got 2/3 of the visibility with only 20% of the volume!!

 
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Additional pics:







Yet to be tested at depth, but in a 5m pool its obvious that there isn't any volume really and if you want to equalize the mask, it takes a nostril-full. Very easy to put too much air in it.

If you do the math on the volume (I added 50cc of Sugru), it could save you .5L to .6L of air that you don't have to blow into the mask that you can use for one extra equalization... Which at depth could be a SIGNIFICANT # of meters.

 
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Once I had the Sugru in place and it starts to cure / set (within :10 - :15 mins) I put it on and pressed it into my face to get a custom fit with slight indentations for cheekbones, etc. to ensure a good seal when in the water.
 
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Very nicely and cleverly done... Congrats on a good homemade dive-gear build...

I've been thinking about the concept lately, and I see pro's and con's... this is what I've come up with:

If you equalize your mask all the way down, it's a super trick. Makes things more simple and easy.

Myself however I stop equalize app. 1/3 of the way down pressurewise, because the mask can collapse to 1/3 airspace app... That means that if I go to 50m 6 atm, I equalize at 1/2 atm about 10m. I can even do it at 20m and would be able to take it to 80m theoretically. Now if I put anything inside my mask, it might change the way it can collapse, and if anything stop the mask from collapsing, then I would get my eyes sucked out instead. So if I try it myself, I would have to be really carefull not to change the collapsing properties of the mask.

Another thing I have thought about is this: When doing competition dives it might actually be a good thing to store some fairly fresh air inside the mask, so that when going up, if you manage, you can "re-use" the air, and get that O2 your brain needs in the final seconds before finishing the surface protocol. Also it can be a nice feeling taking in air on the way up.

Last thing is that I think you overestimate the amount of air you spare... If you go to 100 meters, then yes theoretically it would mean you did spare 0.5 L, but two thing have to be added to that calculation: 1) The mask was compressible before modified, so in my mask it would be 1/3 of that number (0.5 / 3 = 0.166 L), unless it's still compressible to some degree (wich it probably is). And 2) What you really want to measure is the airspace it uses AFTER taking mouthfill... because before you got plenty of air, and even if you save a lot, most of it will compress and stay in lungs... You will reach RV a little later, but only a little. So it's true you might save 0.5 L, but it's not the hole picture...

However, if you do equalize it all the way down, I can see how good it is after taking mouthfil...

And if it still compresses to some degree, like to ½ size, it might be very interesting to try out...

Could you possibly test how deep you can take it without equalizing it. Or perhaps like Trux once did, and what you probably also did, push it against your face to see how much it can collapse, and then measure the water content.

I need to make one of those one day, just for the fun of it at least...
 
To me, the micromask never really collapsed / compressed much / well. It's advantage was solely in vision and low volume.

I use a Sporasub Mystic for recreation and non-competition diving and it is much more collapsable. I don't equalize it below about 25 or so and then take a mouthfill.

The Micromask with this modification has almost no air in it when on. My eyebrows, eyelashes and cheeks are all touching glass.

There is maybe 10ccs / MLs of air space when tightened up and compressed against my face.

I don't think this would work great for a sphera, unless you chose to give up compressibility for the sake of micro-volume (10-30ccs total perhaps).

Assuming I equalize the mask at the following depths and I filled in 50ml of void space with silicone, the space that I wouldn't need to equalize would be the following at the approx depths in equivalent surface volume:

3m = 80ml
7.5m = 105ml
15m = 150ml
30m = 240ml

Added up it equals 570ml.

This is the equivalent of having an extra 570ml in my lungs at the surface that I could use exclusively for ear equalization.

I think this type of modification should work for someone who had equalization as their limiting factor. It also would allow a slightly deeper mouthfill.

I'm curious about depth needed before first equalization as well. In theory a pressure gradient is a pressure gradient and it shouldn't matter... But I suspect (based on pool testing) it will be deeper than my more compressible Mystic.
 
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Now, you can't add it up like that. You filled it with 50cc, that means at 30m, or 4 atm, that's 4x50cc=200cc you don't need to equalize...

Those 200cc in the lungs will at 30m also be 50cc, so the change in depth for mouthfill is tiny... And your mouthfill will be the same size...

It's the technical ease on descend, and especially the low volume AFTER the mouthfill that will make this mask really good as I see it...

Btw, do you plan on equalising it all the way down, or let it compress also?
 
Obviously my math was bad (copied it from another spreadsheet), but I think the logic holds.

Mask Equalization Depth : Equivalent amount of air needed at the surface to equalize mask

5m = 75ml
10m = 100ml
20m = 150ml
30m = 200ml

Added up it equals 525ml

Meaning: Equalizing the mask without the "spacers" would require an additional 525ml of lung capacity on the surface to equalize the mask at the same intervals as the one with the "spacers" and still have the same amount of air in your lungs at 30m.

I understand that at -30m, this translates into an additional 131ml of air in the lungs. At -40m it's 105ml.

I'm not sure how large my mouthfill is... But I'm figuring approx 175 ml.

It's not a tonne, but I hope it will give me an extra ear equalization (or a more full mouthfill if I do it to late)... And that means more meters.

This game is hard enough - I'll take any advantage I can get!

I plan on equalizing the mask to around -30, then ride it downwards from there.
 
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It tells you exactly what I calculated: That at 30m it equals 200ml... Why would you add it up, it doesn't make any sense whatsoever...

Anyway, the important thing is how it works, and I think it will work just fine...
 
I added it up because I equalize my mask at EACH of those depths.

I don't use a sphera and nothing really collapses like it (except the Flow mask - which I have but doesn't fit me well either and distorts vision like hell and the seal feels questionable). As a result a non-sphera requires earlier and more frequent equalization.

I also think I equalize my mask more frequently than most / many. My eyes an sinuses are just sensitive to pressure I think. Plus... I've sloppily lost my mouthfill before by not equalizing it early enough and the suction of the mask heartbreakingly stole my mouthfill.

The combined (surface-relative) air savings is what I am suggesting the modified mask is like having.

Put another way, it's similar to being able to pack an extra .5 L of air at the surface.

If you don't put that air into your mask at each of those equalization points, you have more air in your lungs available for mouthfill and / or equalization.
 
I give up... Just look at the numbers long enough, and you'l see it doesn't make sense...

What you have in total is 200ml from surface - equivalent to 50ml at 30m - nothing more, nothing less...
 
Did some volume measurements:

Modified Micromask:
= 52 ml when lightly fitted
= 22 ml tightly pressed
= 18.5 ml tightly pressed with nose pinched

The compressibility ratio of 2.8 would suggest no need for equalization before 18m... But don't trust my math!!! LOL

My previous depth mask was the Sporasub Mystic:
= 75 ml when lightly fitted
= 51 ml tightly pressed
 
That's impressive... And "real" water pressure might even squeeze it a bit more around the nose fx... Looks promissing...
 
Apneaddict said:
I added it up because I equalize my mask at EACH of those depths.
Click to expand...

Your maths assumes you are equalising a completely empty (i.e. flooded) mask every time. By that logic, if you equalised every metre you'd need several litres of air.
 
Mullins said:
Your maths assumes you are equalising a completely empty (i.e. flooded) mask every time. By that logic, if you equalised every metre you'd need several litres of air.
Click to expand...

Ding Ding Ding!! Correct.

Assuming the compression figures above (64.5% max compression), the amount of air saved that doesn't have to be put in is 339ml (525 x 64.5%). This is assuming the spacers don't affect compression, which I'm sure they do.

The reality is likely something around 250-300ml saved I think.


Another thing I was considering based on my compression tests... Is that sometimes a softer silicone'd skirt on a glass lensed mask might not be as good as a firmer mask.

Both my Superocchio and this Micromask (firmer than my Mystic) when compressed suck my cheeks into the void space, which acts like a dynamic spacer. I was surprised that my Mystic didn't compress more. Perhaps it would in the water with equal pressure applied, but I think a semi-firm skirt that is firmer than your cheeks could be a factor.
 
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It depends on the time of year and even day of week, as the lakes "flip" to oxegenate and one day can be 10*c colder than the day before!

I'm speaking primarily of Lake Ontario (one of the Great Lakes, which are like freshwater inland seas)

In the summer, maybe 20*c at the surface and as low as 7*c deeper down. We get some pretty strong thermoclines.

It can be 12-15*c at the surface early and late in the season when we are still diving.

Alexei made it down to -90m in a 3mm suit... And I'm sure it was maybe 4 or 5*c down there!

We also dive in colder water up north and quarries which are similar to the lake temps.
 
Another note:

On second thought, Im sure that I've actually increased the compressibility ratio of this mask big-time, by adding the spacers (although the sides of the mask are now less compliant).

Not intuitive, I know!

I've filled the void spaces that were on the sides that were always present and never collapsed much. This was perhaps 2/3 of the volume when on my face. Because of the large volume of this area, it hurt the overall mask compressibility.

Once modified, the only void space left fills in pretty good with pressure, as evidenced in the compressibility ratio.

If you can fill in the majority of void space that never disappears (no matter how hard the mask is compressed) and leave only the space that does compress away / fill in well, you end up with a good compressible mask!

I'll try to find an unmolested micromask at some point (next 6 mos) and do "before" measurements on my face to compare... But I recall the stock micromask requiring an abrupt equalization with little notice, which indicates low compressibility.
 
I think your right, and that's very interesting... I didn't expect that ability to compress...

I wonder if it's possible with the sphera also, perhaps make it 4-5-6 times compressible... Or if it's something that has to do with this particular mask (given the large space in sides)... But theoretically I think it should be possible to fill out at least some parts of a sphera... Of to look at my mask...
 
Looking at the sphera I think it's possible to fill out some empty space, but it's not a lot, and I'd need to stay clear of the skirt, because it looks like it can bend inwards behind the plastic frame...

I plan on doing this some time this year: Cover the plastic-glass with some thin clear plastic, and then put plasticine in it and see how it works...
 
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