First dive. 2.8. West of Scotland


#1

First dive, in a bit of current, 9m depth. It was at the marina where we keep our boat and we were surprised to find how barren the sea bed was. A friend from the marine lab there said it was because the salinity is constantly changing, it’s where a loch meets the sea.
The first hour was taken up with untangling the tether! Should have done it at home, not on the boat!
I found that because of the current taking the ROV away and tensioning the tether it was very difficult to turn.
Here is an hour of fairly boring stuff condensed into a few minutes.
Andrew


#2

Great video Andy… I haven’t had mine out yet but I’m encouraged by what you saw. Where about on the west of Scotland was that? Very happy with the video quality… that was smooth!


#3

Thanks for that (name?)
We’re in Oban and getting very excited about the number of wrecks near here.
Did our second dive yesterday on SS Breda wreck. I’ve just posted the video. Very scary, I don’t know how you ever get the confidence to go into places with the risk of a tangle.
I guess if it all goes pear shaped there are lots of local divers that would retrieve it for a bottle of good Whisky!

I’m thinking about intertwining some very strong fishing line with the tether wire. What are your thoughts?
Andy


#4

Heya (Brian here),

Sorry I’m in crazy busy week mode right now. I teach design in Glasgow which means not a lot of time for outside activities till the end of the month. Been meaning to come up to Oban and check out the SAMS at some point. Will have to let you know when I do. :slight_smile:

The best I’ve seen for making a better tether are the people using hollow polypropylene line and running their tether down the middle. Check out:

https://discourse-cdn-sjc1.com/business6/uploads/openrov/4820/afed1c675ccc1bcb.docx
and
https://discourse-cdn-sjc1.com/business6/uploads/openrov/4821/18e0d8a0969bad8b.docx

Chat soon,

Brian


#5

Hi Brian
Thanks for the links. I would like to do that because the cost of buying neutrally buoyant tether from the store would be huge.
I can’t find hollow polypropylene though, plenty of polyester braid (I use it on the boat all the time) but polypropylene is usually 3 strand (not hollow).
The best would be hollow Dyneema. Very strong, and, but well over £1 per metre.
Let me know if you find anything.
Cheers
Andrew


#6

I was about to ask you something similar… hard to source in the UK… I’ll be in the states this fall (over xmas to visit with the parents). I might have better luck there - will let you know!


#7

I’ve just ordered three of these
http://www.ebay.co.uk/itm/121047022579
I figure it’s going to be easier to thread the wire through 30 metres at a time, then I’ll stitch the joints with whipping twine and cover with heat shrink.
There’s actually quite a few on eBay, but most won’t deliver to Scottish Highlands :frowning:


#8

That looks promising… it would be nice if you could find a good waterproof cable connector solution and then split my cable up. Have you seen these?


http://www.dx.com/p/maitech-2-copper-core-waterproof-connector-terminal-head-black-314033#.Viqls_mrRJ5

Let me know how the threading goes… I like the idea of a few different colours… If I could split my cable into 4 x 25 m sections of different colours… all the better :smile:


#9

Yep, thinking about this a bit more last night, my plan will be to order those 30 m length ropes (assuming they are hollow inside and will work for you), and then split my tether into 25 m lengths with some waterproof connectors at the end of each length, then I can more easily adjust the length of tether I take into the field. In terms of tether management have you come up with a solution yet? There was a very nice over engineered version I saw yesterday that looked pretty good (OPEN ROV 2.6 #1206 and the over-engineered tether management).


#10

I’ve just ordered an extra rope (4 in total) and changed the order from all yellow, to one of each colour, after you mentioned it. I’m not sure I would want to split the tether with connectors, what happens if you need to haul it in, in the event of a power failure or software crash? In my experience, the connectors are always the failure points. I’ll be happy to be convinced otherwise though.


#11

Hi Andy… my thought would be to do something like this:

So the (red) rope would be tight, with the (blue) tether and connectors loose. Ideally thetwo ends of the rope could be attached with small carabiners or the like. This way, even if the connector fails and you loose power, you could still pull it up (and the connects do screw together, so they should be fairly secure I would assume).

  • B

#12

That looks good. I’ll let you know how the threading goes.


#13

Absolutely nothing wrong with what you are suggesting
But you can also consider using

The only thing wrong with them is that they do like to be kept under strain (but I have used sleeving {heat shrink}) to assist in keeping them in place

Maybe you can give some feed back of your experiences when you do it into


#14

Handy links… thanks Scott.

By the way, my office does a lot of laser and photometry work (for heritage sites around the world). I loved your post on SfM, and I have a few places I’m considering using my ROV next year for this sort of thing (Scapa Flow in the Orkneys, if that means anything to you). Will have to get in touch with you when I get set up for that!

Thanks again for the advice,

Brian


#15

No problems its all about sharing our experiences and learning from each other

Adding to the SfM I have also been thinking about a structured light system add on

Where the small portable video projector cold act as both an external light (when not generating light patterns - so just white light) but could also be used to provide the black and white light stripes and use a camera for the 3D scanning mmmmm

Still just tossing it around - have you done any of this style scanning at your work?

Scott


#16

Most of our work is for world heritage sites, so we usually work with laser scanning with some straight up camera photogrammetry thrown in for when we are dealing with something simple. I personally don’t do any of the scanning myself though (I’m more on the 3D visualization side of things).


#17

Sounds like interesting work Brian.