would this work ? an ROV type ?,

lobsterman

lobsterman

Sr. Member
Jan 8, 2005
416
24
Maine
Hi All,

i am curious if this system i'll describe may work to some degree or not ?, any thoughts on it would be appreciated.

i am thinking a lage rov capable of towing the tendering vessel slow speed of course, with a series of cameras and metal detecting coils along the front edge of it, with a sort of vaccume shaped funnel scoup underneath it, with a pair of 4" airlift hoses off the back that would lead up to the back of the boat where it would discharge into a semi-sumerged screen platform that would also double as the retrieval base platform for the ROV, there would be several reels across the midsection of the boat to handle the power,air and suction lines and hoses, the towing line would lead to a bow winch, the airline down for the airlift could also be mounted at the bow and attached to the tow line with tension clips that seperate as the tow line and hose are retrieved by the reels on the fordeck.

i have the concept sketched out on paper, and i have set this all up to be a one man operation, i know it would be a lot for one person to maintain the running operations of all of the systems, navigating, launch and retrievel etc. but it does seem that it is possible that something like this set up could be made so that you would almost feel as though you are simply waking along the bottom surveying areas and picking up interesting targets at your leisure.

i think the limiting factor would be the depth of the airlift recovery hoses, those reels of the 4" corregated drainage tubing would take up some deck space but i think a maximum working depth of 100', would be sufficiant to test the theory and all the processes involved.

if it works it could have a few differnt type of applications where a large scale operation would not be practical, as an example... underwater bridge inspections and video recording, or even small scale dredging, or it could be used contracting for the athorities use in searches, etc.

it is hard for me to describe the set up fully but, i am sure you can picture what i am thinking about. i wish i could include i diagram of what i am describing but at the moment i don't have the capability of doing that at the moment.

let me know what you think, could a set up like this be made to work ?
 

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i forgot to mention that this would be set up for about a 30'-40' forward cabin vessel with a large open back deck set up with a drop down tailgate / retrieval ramp (open stern lobsterboat ).

and the overall dimensions of the ROV would be about 8' wide X 10' long X 3' high ( including the frame, lights, shielding bars, hose attachment points, skids, etc. ).

hummmmh... i wonder if i could use it to vaccum up some lobsters ? ;D
 

You lost me after "curious"! I can't even fathom what you are talking about building. I guess my response would be DOH!! M :dontknow: nty (Forgive me for I know not what I do).
 

I take it you are going to use surface generated power ? batteries would not last long towing a surface vessel too. an rov usually works deeper wrecks, the depth would probably crush the hose or pinch it off making it useless. you could use rov mounted tanks direct to the nozzle but again you would be limited by the size of the tank and rov.

it could be done and I would love to see it in action, but you are going to need alot of engineering and a good reason to build one.

best wishes , tim
 

Monty said:
You lost me after "curious"! I can't even fathom what you are talking about building. I guess my response would be DOH!! M :dontknow: nty (Forgive me for I know not what I do).
Click to expand...
I understand what you are wanting to build and it sounds more like work than fun. However what ever you like to do. Seems like the addition of metal detecting coils on the front of the ORV would be the weakest point. Usually the dredges come into play after a hot spot is found by other means.
 

That might be difficult to deploy & retrieve from a 30-40' vessel.
 

hi,

yes the power would be supplied from the surface, i may run the thrusters with hydraulics, 100' depth is all i'd want for now, yes i have a few prospective targets (but they are not treasure wrecks ), not in the traditional sense anyhow. it's late i gotta go, i'l try to reply back tommorow.
 

Interesting idea, sir.
I spent a bit of time thinking about how to implement this sort of system and I think I see some issues that might make this difficult to achieve. My Fluid Mechanics professor would LOVE this one, because there are so many different aspects to this idea. I am going to touch on just a few, due to the fact that while I am typing this I should be doing Fluid Mechanics homework.
1. Assuming that you are planning on attaching the ROV/sled to the front of the boat with a Y-shaped bridle of some sort, the first thing to consider is how much line will have to be between the ROV and the bow of the boat. When the towline gets tight, the ROV is going to want to stay at the surface so we have to drive it down into the water- either with negative buoyancy or downward thrust. Negative buoyancy is not a good thing. If you have sufficient negative buoyancy to hold the ROV down into the water it will want to drop like the proverbial stone if the boat rides up the towline and the tension in the towline is reduced. Therefore you will have to provide downward thrust to achieve and hold your desired depth. We can calculate that by considering the following-
The shorter the towline the steeper the angle between ROV and bow. The steeper the angle, the more energy lost due to two factors: the tendency of the ROV to pull the bow of the boat down into the water, and the loss of efficiency by pulling off-axis. If you pay out a 600' line with your ROV at 100' depth you will have an angle of about 10 degrees. You will lose only about 3-4% in forward thrust and have about 1/2 of your thrust pulling the bow of the boat down and the ROV up. Using a total forward thrust of 150 lbs (arbitrarily chosen because that would be 2 really big trolling motors) you'll have 147 lbs pulling forward and 26 lbs pulling the ROV upwards. With different angles it works out to: 20 degrees-140/51, 30 degrees-129/75, 45 degrees- 106/106. So...a long towline is a necessity, as is having sufficient downward thrust. Keeping the ROV oriented parallel to the bottom is going to require some consideration as well.
I would suggest that it might well be easier to mount some auxiliary propulsion to the boat (maybe a few of those big trolling motors), and slave the ROV and auxiliary boat propulsion controllers together, so the boat can follow the ROV rather than have the ROV tow the boat. This will result in MUCH shorter towline lengths which will allow much greater maneuverability as well as helping with the following:
2. Driving thruster motors with hydraulic is done quite often on work-class ROVs working at depth. The hydraulic system on the ROV is powered by high voltage power sent down that long tether. The Perry Slingsby Company's "kW Hydraulic Power Unit" (datasheet available here: http://www.perryslingsbysystems.com/datasheets.html operates on 2000v 3-phase power. Extremely high voltage is required to be able to feed enough watts of power down a long tether to accommodate this sort of equipment. I do not know what sort of power generation equipment you might have. This could be an option.
The other alternative is to use very long hydraulic lines and put the hydraulic power unit aboard the boat. Very long hose lengths are going to have very high pressure losses due to friction. After you find the requirements of your hydraulic system, this site: http://www.gates.com/industrial/pressure/fluidFlow.cfm?location_id=3044 will help you find just how big the hoses would have to be to flow enough fluid to meet the requirements. It looks to me like assuming 3o gpm and 200 feet of hose
The last consideration having to do with hydraulics might be the steering effect that the hydraulic hoses will have on the ROV. Pressurized to 3000-3500 psi. hoses begin to act more like solid pipes than limber hoses...then there are the effects that currents will have on the lines and...and then there are those 4" dredge lines to add...and then when you turn the suction on the ROV is going to need to counteract the downward force of the dredge lines and...
You might want to get some new batteries for the calculator. This project has a lot of calculating for you to do.

I better go back to work.
Have fun and keep us posted.
:icon_thumright:
 

Hi Ropesfish,

thanks for reply, i appreciate your educated thoughts on this subject, obviously i would need to consider soo many engineering aspects for a project like this, (admittedly,i still have much to learn), but after doing a little research, i learned about a US Navy tethered rov that is somewhat similar, but it is on a much larger scale, in soo many ways (financial, technical, capabilities, depths, etc.), even though my set up would be much smaller in scale and technology, i feel that an airlift assembly/system could be configured for shallow water operations with an approx. 100' max working depth, and the forward operating speed would be very slow (approx. 1--2 knots maximum )

the rov would have i a slight positive bouyancy (for emergencies and ease of recovery), the rov would maintain a steady contact with the bottom in forward working operations, and it could maintain it's position, surface, or attain a neutral bouyancy during stopped operations via the 4 thrusters, the rov will have an sort of flattened down or squatty, bullet or blimp shaped cage around it, with skid plates along the bottom and sides, it will also have small built in wheels or casters on it as well, though not much of the wheels will actually be exposed, it will make shoreside handling much easier.

i doubt that i will ever be able to set it up to be the ideally functioning rov work system, but that doesn't rule out that i could still make one that would be functional. sometimes reducing things to thier simplest forms is best. family just got in, i gotta go.
 

Hi Lobsterman,
It sounds like you are at the beginning of the same trip I took...trying to figure out how the heck to build what you want to build. I took a shortcut that has lasted 6 years...went back to school @ 47.
Let me point you to some sources you might find of use.
Welcome to the club!

Ron's ROV Links-all the things you'd ever want-great site! :http://www.ronsrovlinks.nl/modules/wflinks/
Yahoo Homebuilt ROV site-great stuff in the archives: http://groups.yahoo.com/group/robotrov/
Roper Resources: http://www.roperresources.com/loader.html
Marine Advanced Technology Education Center: Great folks...good info..takes some looking though:
http://www.marinetech.org/home.php

Organizations: Some great information lurks inside-
Oceanic Engineering Society: http://www.oceanicengineering.org/index.cfm
The Marine Technology Society:https://www.mtsociety.org/home.aspx
 

For only 100' why not use a diver with a water dredge? They cost a hell of a lot less than designing an ROV and would be much quicker to deploy without the headaches. That is unless you are looking for the technical challenge of designing an ROV?
 

i usually prefer to work alone, but once specific targets have been located and the area is set to be worked, perhaps a diver could be used, but just to do random searching with divers is impractical.

also, i might be able to eliminate some of the roadblocks for this project by not requiring the rov to pull the surface vessel, but that would create a whole new set of problems... such as piloting the rov, and running the boat at the same time, running them in sequence and tending all the lines and hoses by myself, would be a logistical nightmare. and would be nearly impossible for one person to handle.
 

I'd use a mag to locate targets and divers to check out the hits. Let me know if you need someone to bring up some treasure for you....
 

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