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[Jack]

Hi Great Forum.

I've just finished building the hull and superstructure of this survey tug. Its 1015mm long and weighs 3.9 kg when loaded up with survey equipment, and will tow a catamaran weighing about 2kg. Running time is to be 1 hour+ at 1 - 3 km/h. Another option will be using a towfish of about 3kg at speeds of about 10km/h

There is no motor, batteries servos prop or rudder. I want to fit a kort nozzle with a brushless motor and lipo batteries. I want to use a brushless motor due to the reduce electrical interference.

I need some help identifying low rpm motors and matching that to a kort nozzle. Also is there a shop where I can find everything I need.

Thanks Stephen Jack


Heres a short video of the first sea trial

http://www.youtube.com/watch?v=9riaVwCqkfk&feature=channel_page

[Martin (Admin)]

Not sure about brushless motors "reduce electrical interference" you might want to check that out with
the particular equipment you are using as I know brushless motors cause havoc with some video cameras.

Also brushless motos don't like slow speeds so you will probably need a "sensored" brushless motor setup or
use a some sort of gear or belt drive reduction. The RC buggy boys might be able to point you in the right
direction with that but be prepared to dig your hand in your pocket quite deep!

Don't know of any one-stop supplier for all the equipment but have a look through the Mayhem 'Traders Directory'
for known suppliers: http://www.modelboatmayhem.co.uk/links/traders.htm

[Jack]

Hi Martin,

That list of shops has been very helpful. I think I've found a suitable motor, the Graupner 720BB, do you have a suggestion for an ESC? I'm considering using Gel Cell batteries but they are probably going to be too large and add too much weight.

Thanks Stephen Jack

[SteamboatPhil]

Contact Dave at Action Electronics ( see traders section) he's got  the very ESC you need   

[catengineman]

May I enquire as to why in an earlier post you gave the impression you want speed for a survey vessel that would be towing?

Most of the work I have done regarding survey was at slow speed and when towing that is possibly the one thing you will not require, lots of power yes, along with good steerage and a good tow point on your build,

if you are towing a *fish* then that would be below the surface, an acoustic air gun is like a small barge towed behind at some distance, CPT's are done from the stern and the vessel is held on station.

Just wanted to find out your views on the above.

R,

[Jack]

May I enquire as to why in an earlier post you gave the impression you want speed for a survey vessel that would be towing?
R,

I have a few ideas on multilayed analysis which can be done at a reasonable cost due to changes which are happening in GPS systems. One layer I want to use is Magnetometer results which I can sample at 0.5m intervals towing in the 10 - 15km range. I will look at towfish, surface vessel designs or a hybrid and see how they fair with regards to drag and quality of results . I know the sensors have to kept horizontal, but I have had no experience in this type of survey works so its a bit of trial and error.  Most of my professional survey work has been on land, this is hobby stuff and I have no preconceptions on what is or is not possible.

[catengineman]

Hi Jack,

Not very sure on how small you will be able to get a transducer but the ones I had dealings with were 500mm X 500mm X 350mm and weighed around the 25kilo mark.

all the sound survey we did was at or around the 2 knot speed and towing was around 5 to 8 knots.

I think you may need a bigger boat

keep us informed as to your progress

R,

[Jack]

This is one of the pieces of equipment I'm considering installing, weight about 3kg in total.

http://users.skynet.be/fa352591/index.htm

I may even have a go at trying it an electric glider, I use these for aerial photography at the moment.

Do you have any information on interpretation of magnetometer results?

If I can find a side scan sonar of similar weight and at a good price I'd love have that rigged up too