making cat5 neutrally buoyant

[MNDeepROV]

I'm working on a cat5e buoyant solution as well (and will compare with fiber solution as I'm gathering that info too!).

Has anyone had any issues with the air inside the cat5e sheathing?...especially for those that have gone to deeper depths? Perhaps it's negligible, but I think it might obviously make the cable actually heavier when deep if the cable is buoyant closer to the surface. I've been looking at outdoor cable that is gel filled (perhaps little to no air...but would be heavier), or maybe even stripping the sheathing off so we have just the 8 wires, then putting them in the nylon floating rope, etc...or having some sort of protector shell that doesn't hold air.

On a side note, after I play with some more cable samples I might try to used some close cell sponge "cord". It is buoyant and under water it does not seem to release any air when compressed. This could be used along side cat5e fed inside of nylon rope to encase everything.

Here is a link: http://www.grainger.com/product/TRIM-LO ... ?$smthumb$

I've got some 3/8" at home and it's very buoyant...maybe too much so. But if I end up choosing a heavier cable, or a smaller size "cord" it could help in getting closer to the neutrally buoyant equation! I'm in contact with some bulk suppliers to see if I can get samples and to see just how much longer rolls would costs... I think the sizes range from 1/8" on up.

[micoma]

MNDeepRov you said you have some 3/8" of the foam. I looked at the link but could not tell if it was similar to this http://www.thefoamfactory.com/closedcel ... ylene.html. If it is have you checked to see how much a foot of the foam will support? I am thinking of using some for my tether but can't decide on 1/4" or 3/8" According to my assumed calculations 1/4" would not be enough for me. http://micomarov.weebly.com/tether.html.

[MNDeepROV]

Hey Micoma,

I double checked my cord and it's actually closer to 1/4"...just slightly over (I was going off the top of my head on the last post). It's not something I ordered but had at home on a Pelican Case. They use it on some of there seals. I'm going to get several sizes of samples of this stuff in short lengths, then I can do some calculations. I haven't done any yet. I took a look at your tether webpage. I like your PET expandable sleeving idea, but if I'm going to order 300-500 feet it's expensive. The cord may end up being too expansive too if I can't find it at a good bulk price, but I'm checking. I'll follow-up once if when get some samples and can make some calculations.

[micoma]

MNDeepROV thanks for checking. I would get some samples for testing but, since I am in Venezuela, it won't do me any good. I have to have everything ready to pack up because when I go back to the States I am only there for a week or two before coming back.

[MNDeepROV]

ok, it's been a couple of months as things got busy for me and put my project on hold...back at it now! Just following-up (as I said I would)...I investigated using closed cell cord and rubber cord as way to use a continuous piece to make a tether streamlined and neutrally buoyant.

My idea of closed cell cord isn't working. I guess I had to see it for my self. Basically closed cell doesn't mean no air, of course. I just didn't know how many pockets exactly. There are thousands of little air pockets as can be seen when cutting the cord under water. They might keep make a buoyant cord for shallow depths, but if I'm taking mine down 300-400 feet then the tether would become quite negatively buoyant. Had to experiment though!

It led me to another idea. How about solid rubber cord?, I thought. I tried several of the options shown here (it's also where I got the closed cell cord):

http://www.mcmaster.com/#standard-rubber-cords/=tlx2jh

There are a few high-temp and high-psi rated options. Some too expensive but I tried the cheaper ones and while in theory they could work, the formula, for using a continuous length to insert into a braided nylon cord with the cat5e, just isn't working out. Some too dense, some too buoyant.

So, as so many others are doing I may have to attach floats at certain distances to make a a proper tether. I was hoping to avoid that to make a more streamlined tether, but some of you have come up with some potentially great float ideas. More to experiment with!

[TigerShark]

I think Rubber will sink or be close. We need something much less dense than water. I am looking into mineral oil but that still isn't going to help much. I am working on a spreadsheet to calculate the effects of the densities of different materials.

It is a mess right now:
1cu mm=1.0 × 10-9 cubic meters

6mm OD, 4mm ID .157" ID .236" OD cat 5e .185" mm3 Conductors total Volume inside 1 meter (4mm) Voulume outside 1 meter (6mm) Volume of poly
wire 0.511 mm diam 205 8 1640 12571.42857 mm3 28285.7 mm3 15714.27143
Each conductor 1mm diameter 0.000012571 m3 0.000028286 cu m 0.000015715
.5mm radius
Volume 785.7 8 conductors 6285cumm kg/meter
For 1 Meter Tubing/tether insulation 580.7 4645.6 6286cumm remaining 0.00182 0.01456
0.000006286 cu m 0.142784824 Newtons
FW SW Mineral Oil Polyurathane Polyolefin Insulation Copper Bouyancy Seawater
Volume mm3 /m length 6286 15714.27143 4645.6 1640
Volume m3 /m length 0.000028286 0.000028286 0.000006286 1.57143E-05 4.6456E-06 0.00000164
Specific Gravity 1 1.025 0.92 1.12-1.24 1 copper
1.12
SG = ρ / ρW
ρ Density kg/m3 1000 1025 920 1200 1000 8940
0.056674576 0.550729032
Bouyancy (Newtons) 0.2772028 0.28413287 0.056674576 0.184799832 0.04552688 0.14368368 0.430684968 -0.146552098
(B) = ρ V g
g=9.8

[MNDeepROV]

Yeah, the rubber was a bit too dense. In order to make it buoyant I had to use a 1/2" piece just to get enough displacement. It was too buoyant though, and not flexible...

Your poly tether sounds interesting. Keep us informed if you find a solution. Meanwhile, I'll begin digesting your mathematics. Something I've thought about trying to use to narrow down my trial and error options...just haven't delved into it yet. Looks like you're well into it!