Trident ROV side panels

General Discussion
#1

Hello everyone,
I have been wondering about the side panels/ bumpers on the Trident. We are exploring a vertical wall and have got snagged on it a few times resulting in the loss of a side panel. I imagine that this happens when we have to pull on the tether to free the Trident, which then travels backwards and hits some protuberance on the wall, which dislodges the side panel. The wall is very deep, so there is no option to dive down and retrieve it. As you might know the panels are simply snapped on. I am wondering whether I should try and attach them more firmly (glue) or whether it is actually “good” that they dislodge and perhaps assist in freeing the Trident from a snag.
Ideas/ opinions welcome :)))

thank you
best
Petr

#2

Gday petr.myska,

I have also lost side covers in heavy surf and when operating in areas full of snags however I have always been fortunate to retrieve them.

I like to remove the covers when cleaning and drying Trident as part of post-dive maintenance so I use exterior grade waterproof adhesive tape to secure the side covers when needed. The brand I use here in Australia is Gorilla however any high-stick waterproof tape can be used. There is a nominal gap of 1.5mm between the inside of the side covers and the hull and this is perfect for low profile double-sided tape.

I would love to know more about the location you lost your side covers…is retrieval by drone possible? This sounds like a real challenging location.

#3

Hello
Thank you for the tip. I will see if I can get something of that sort here in Mexico.
How big a piece/ pieces do you use? Have you lost any panel since you started using the tape?

Unfortunately, the wall we are exploring is very deep. No one knows for sure, but it can be thousand feet plus. We have found some exciting coral gardens at depths starting at 180 feet and explored down to about 220 feet. We do however need to be careful. Staying close enough to the wall to see something and not getting snagged at the same time is quite difficult. I can see in the footage when the panel detaches and drops, but they just go down to the abyss. I truly don’t think there is any practical way of retrieving them.

best
Petr

#4

Could you attach just enough flotation to the side plates that they float to the surface on their own when detached?

#5

That’s an interesting idea, but that measure would also make the entire ROV more buoyant. So I would have to deal with that. But a good idea … Thanks.
-p-

#6

G’day Petr,

I have not lost any side covers since using tape…but I am also more careful as well so it might not be the tape at all.

I have used a range of high-stick exterior grade waterproof single sided tape and also double sided tape…whatever I have on hand or more often whatever is available at the hardware store. I have used 19mm, 25mm and even 50mm tape cut into approx 100mm long sections. I started with short lengths of tape stuck over the outside of the covers and onto the hull. I also had some 25mm double sided tape that I used and I ran a whole length down each side between the hull and the side covers.

Douglas’ idea has merit as well. If you add some buoyancy to the side covers then you will need to add a corresponding weight to the hull to maintain neutral buoyancy. I would add the buoyancy as strips of self adhesive foam towards the top of the side covers such that the longitudinal centre of any buoyancy strips added is in line with an imaginary transverse line drawn through the sea water ballast screw holes (this is the approx centre of buoyancy for the submerged Trident). I would then add the weight to the underside of the hull such that the centre of gravity for the additional weight is also in line with the sea water ballast screw holes. We get self-adhesive wheel balance weights here in Australia that are easily found at tyre repair shops (often for free or for a small cost) and these work a treat…they come in 5g, 10g, 25g and 50g sizes…the sea water ballasts are 47g each (hint for anyone that loses their ballast weights).

In my case however, I would rather keep the side covers attached.

#7

Thanks for all the info and advice. Last question - do you think the “ability” to lose/ detach the side panels has anything to do with some sort of “anti-snag”/ release mechanism that helps free the Trident in case of it getting hung up on anything? Sort of a sacrificial part of the ROV?
thanks
P

#8

G’day petr,

I have never thought of it that way because Trident is already quite ‘slippery and free of snags’.

I suspect the side covers are removable for another purpose but freeing Trident from a snag might just be a secondary design effect. If freeing Trident from a snag was a primary design element then I would have thought the effect would have been made greater than slightly reduced dimensions and a slightly reduced sliding friction as a result of the side covers and rubber bumpers being removed.

I initially tinkered with mounting payloads such as dive lights to the side covers and this was awesome for rapid payload changes (I have a spare set of side covers) but the covers would come off too easily due to the additional weight and due to the drag/inertia that would pry the covers off when operating (this is another reason for my use of tape). If you try something similar then yes, the side covers could be designed to hold the payloads up to a design limit and then separate if required to free Trident.

One of the Trident designers might be able to provide a more definitive response…

#9

Thank you …
I have read a few posts you wrote about various subjects and understand you are quite involved with the ROV topic. I wasn’t very happy to hear that Tridents might be discontinued. Would you recommend buying a stock of spare parts, especially motors? (I replaced those once already).

Also, as I described in my original post, we have lots of issues with snags of the Trident cable on the wall we are exploring. It is a very exciting area to study, but with lots of hazards.
Any advice is greatly appreciated!

thank you
Petr

#10

G’day Petr,

Your exploration area sounds very interesting, particularly since you know it is risky but you still feel a need to go there. I would love to know more so that I (we) can better understand the challenges you face…do you have any video or photos that you are able to share? Are you operating in fresh water or seawater? Is the wall a cliff or a crevasse and how much clearance do you have to operate? Is the route to the wall a zig-zag and/or is there a significant overhang or swim-through along the route that restricts manoeuvring…

If your greatest challenge is the tether then this may be difficult to solve. I avoid the risk of tether snags by carefully planning my entry/exit points and by routing Trident away from snags including by using Trident to drag the tether away from snags, accumulating free tether in a clear space of water near the target and then doubling back to the target from a safe direction.

This is not always possible due to current and surging but it is a general principle that I try to follow. I have also created a pool based obstacle course to help operators practice tether management and to provide them with experience getting tangled (and subsequently clearing snags and tangles remotely). You might also find this of benefit in your case since you are unable to dive to clear a snag, particularly if you can create a realistic set of obstacles based on the challenges you encounter.

The use of clump weights to submerge the tether and to hold it away from snags may also provide a benefit. This may require you to deploy Trident from a boat or kayak located offshore of the wall.

Oh and yes, I take great care to protect and maintain all of the equipment that I use and I also keep spares for everything. The guys at Sofar do not yet sell spares (except for the accessories like the controller, tether, reel and case) but I am hoping we will soon gain access to critical spare parts. I have replaced all of my motors and I have kept the old motors that still work as spares. I have also been able to partially refurbish some of my motors (there is a growing body of knowledge about motors thanks to posts by others here in the forum). The Trident community might come up with a solution to the spare parts challenge if required.

I hope these ideas help.